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用户:耿淅耀

2024-02-26T17:48:04Z

耿淅耀：个人页更新

<blockquote>大家好～我叫耿淅耀，目前在上海工作。

前两年隐身了快两年，因为发生了许多事，而目前终于风平浪静，我又回来了！

我最喜欢的tag仍然是“复杂系统设计”，但也会时常挂上“脑科学”、“量子计算”、“光芯片”、“植物工厂”这些别的同样浪漫的tags。

能拥有某一个领域成体系的全部知识，能拥有一些世上只有几个人知道的新知识，这是我的愿望。

冬十二变成春三月，如今我更从容地回到这个社区，希望能真正贡献绵薄之力，此致敬礼。

如有闲暇，也可以讨论关于文学、音乐、绘画、神话、手工、编程诸事，我也藏起了许多惊喜。

时常交谈，时常收获，沉溺于人类亘古激情之谜，还有物质构成之梦之欢喜！</blockquote>

pls加微信：'''gengxiyao-seven'''

神经元

2022-04-30T07:36:00Z

耿淅耀：

此词条由神经动力学读书会词条梳理志愿者[[用户:Autumnwolfberry|Autumnwolfberry]]翻译审校，未经专家审核，带来阅读不便，请见谅。

{{short description|Electrically excitable cell that communicates via synapses}}
{{About|the type of cell}}
{{Distinguish|Neutron}}
{{Infobox neuron
|name = Neuron
|image = Blausen 0657 MultipolarNeuron.png
|caption =Anatomy of a [[multipolar neuron]]
|function =
|neurotransmitter =
|morphology =
|afferents =
|efferents =
}}

A '''neuron''' or '''nerve cell''' is an [[membrane potential#Cell excitability|electrically excitable]] [[cell (biology)|cell]] that communicates with other cells via specialized connections called [[synapse]]s. The neuron is the main component of [[nervous tissue]] in all [[Animalia|animals]] except [[sponge]]s and [[placozoa]]. [[Plant]]s and [[fungi]] do not have nerve cells.

神经元或神经细胞是一种可电兴奋的细胞，通过称为突触的专门连接与其他细胞进行交流。神经元是所有动物神经组织的主要组成部分，除了海绵动物门和扁盘动物门。植物和真菌没有神经细胞。

Neurons are typically classified into three types based on their function. [[Sensory neuron]]s respond to [[Stimulus (physiology)|stimuli]] such as touch, sound, or light that affect the cells of the [[Sense|sensory organs]], and they send signals to the spinal cord or brain. [[Motor neuron]]s receive signals from the brain and spinal cord to control everything from [[muscle contraction]]s to [[gland|glandular output]]. [[Interneuron]]s connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together they form what is called a [[neural circuit]].

神经元通常根据其功能被分为三种类型。感觉神经元对影响感觉器官细胞的刺激，如触摸、声音或光线作出反应，并向脊髓或大脑发送信号。运动神经元接收来自大脑和脊髓的信号，控制从肌肉收缩到腺体输出的一切。中间神经元将神经元与大脑或脊髓同一区域内的其他神经元连接起来。当多个神经元连接在一起时，它们形成所谓的神经回路。

A typical neuron consists of a cell body ([[Soma (biology)|soma]]), [[dendrite]]s, and a single [[axon]]. The soma is a compact structure and the axon and dendrites are filaments extruding from the soma. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The axon leaves the soma at a swelling called the [[axon hillock]] and travels for as far as 1 meter in humans or more in other species. It branches but usually maintains a constant diameter. At the farthest tip of the axon's branches are [[axon terminals]], where the neuron can transmit a signal across the [[synapse]] to another cell. Neurons may lack dendrites or have no axon. The term [[neurite]] is used to describe either a dendrite or an axon, particularly when the cell is [[Cellular differentiation|undifferentiated]].

一个典型的神经元由一个细胞体（soma：胞体）、树突和一个轴突组成。胞体是一个紧凑的结构，轴突和树突是从胞体中挤出的丝状物。树突通常有大量的分支，并从胞体中延伸出几百微米。轴突在一个称为轴突丘的肿胀处离开胞体，在人类中最远可达1米，在其他物种中则更远。它有分支，但通常保持一个恒定的直径。在轴突分支的最远端是轴突终端，在那里神经元可以通过突触向另一个细胞传递信号。神经元可能缺乏树突或没有轴突。术语神经突被用来描述树突或轴突，特别是当细胞未分化时。

Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to a dendrite of another. However, synapses can connect an axon to another axon or a dendrite to another dendrite.

大多数神经元通过树突和胞体接收信号，并沿轴突发出信号。在大多数突触中，信号从一个神经元的轴突交叉到另一个神经元的树突。然而，突触可以将一个轴突连接到另一个轴突，或者将一个树突连接到另一个树突。

The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to maintenance of [[voltage]] gradients across their [[Cell membrane|membranes]]. If the voltage changes by a large enough amount over a short interval, the neuron generates an [[All-or-none law|all-or-nothing]] [[electrochemical]] pulse called an [[action potential]]. This potential travels rapidly along the axon and activates synaptic connections as it reaches them. Synaptic signals may be [[Excitatory postsynaptic potential|excitatory]] or [[Inhibitory postsynaptic potential|inhibitory]], increasing or reducing the net voltage that reaches the soma.

信号传递过程部分是电子的，部分是化学的。神经元具有电兴奋性，这是由于其膜上的电压梯度得到了维持。如果电压在短时间内发生足够大的变化，神经元就会产生一个全有或全无的电化学脉冲，称为动作电位。这个电位沿轴突迅速传播，到达突触连接时激活它们。突触信号可能是兴奋性的或抑制性的，增加或减少到达胞体的净电压。

In most cases, neurons are generated by [[neural stem cell]]s during brain development and childhood. [[Neurogenesis]] largely ceases during adulthood in most areas of the brain.

在大多数情况下，神经元是在大脑发育和儿童时期由神经干细胞生成的。在大脑的大多数区域，神经元的生成在成年后基本停止。

{{toclimit|3}}

== Nervous system神经系统 ==

[[File:Anatomy of a Neuron with Synapse.png|thumb|upright=1.15|Schematic of an anatomically accurate single pyramidal neuron, the primary excitatory neuron of cerebral cortex, with a synaptic connection from an incoming axon onto a dendritic spine.解剖学上准确的单个锥体神经元的示意图，大脑皮层的主要兴奋性神经元，具有从传入轴突到树突棘的突触连接。]]
{{unreferenced section|date=December 2020}}

Neurons are the primary components of the nervous system, along with the [[glial cells]] that give them structural and metabolic support. The nervous system is made up of the [[central nervous system]], which includes the [[brain]] and [[spinal cord]], and the [[peripheral nervous system]], which includes the [[autonomic nervous system|autonomic]] and [[somatic nervous system]]s. In vertebrates, the majority of neurons belong to the [[central nervous system]], but some reside in peripheral [[ganglion|ganglia]], and many sensory neurons are situated in sensory organs such as the [[retina]] and [[cochlea]].

神经元是神经系统的主要组成部分，同时还有给予其结构和代谢支持的胶质细胞。神经系统由中枢神经系统和周围神经系统组成，前者包括大脑和脊髓，后者包括自主神经和躯体神经系统。在脊椎动物中，大多数神经元属于中枢神经系统，但也有一些居住在周围神经节中，许多感觉神经元位于感觉器官中，如视网膜和耳蜗。

Axons may bundle into [[nerve fascicle|fascicle]]s that make up the [[nerve]]s in the [[peripheral nervous system]] (like strands of wire make up cables). Bundles of axons in the central nervous system are called [[nerve tract|tracts]].

轴突可以捆绑成束，组成周围神经系统的神经（就像电线股组成的电缆）。中枢神经系统中的轴突束被称为束。

== Anatomy and histology解剖学和组织学 ==

[[File:Components of neuron.jpg|thumb|upright=1.8|Diagram of the components of a neuron]]
Neurons are highly specialized for the processing and transmission of cellular signals. Given their diversity of functions performed in different parts of the nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 [[Micrometre|micrometers]] in diameter.<ref>{{cite web |first = Melissa |last = Davies |title = The Neuron: size comparison |url = https://www.ualberta.ca/~neuro/OnlineIntro/NeuronExample.htm |work = Neuroscience: A journey through the brain |date = 2002-04-09 |access-date = 2009-06-20}}</ref>

神经元对细胞信号的处理和传送是高度专业化。鉴于它们在神经系统的不同部分所执行的功能的多样性，它们的形状、大小和电化学特性也有很大差异。例如，一个神经元的胞体的直径可以从4到100微米不等。<ref>{{cite web |first = Melissa |last = Davies |title = The Neuron: size comparison |url = https://www.ualberta.ca/~neuro/OnlineIntro/NeuronExample.htm |work = Neuroscience: A journey through the brain |date = 2002-04-09 |access-date = 2009-06-20}}</ref>

*The '''[[Soma (biology)|soma]]''' is the body of the neuron. As it contains the [[cell nucleus|nucleus]], most [[protein biosynthesis|protein synthesis]] occurs here. The nucleus can range from 3 to 18 micrometers in diameter.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Brain Facts and Figures |url = http://faculty.washington.edu/chudler/facts.html |work = Neuroscience for Kids |access-date = 2009-06-20 }}</ref>
*细胞体是神经元的主体。由于它含有细胞核，大多数蛋白质合成发生在这里。细胞核的直径可以从3到18微米不等。<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Brain Facts and Figures |url = http://faculty.washington.edu/chudler/facts.html |work = Neuroscience for Kids |access-date = 2009-06-20 }}</ref>

*The '''[[dendrites]]''' of a neuron are cellular extensions with many branches. This overall shape and structure is referred to metaphorically as a dendritic tree. This is where the majority of input to the neuron occurs via the [[dendritic spine]].
*神经元的树突是有许多分支的细胞延伸。这种整体形状和结构被比喻为树突树。神经元的大部分输入是通过树突棘发生的。

*The '''[[axon]]''' is a finer, cable-like projection that can extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length. The axon primarily carries [[nerve signal]]s away from the soma, and carries some types of information back to it. Many neurons have only one axon, but this axon may—and usually will—undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the '''[[axon hillock]]'''. Besides being an anatomical structure, the axon hillock also has the greatest density of [[voltage-dependent sodium channels]]. This makes it the most easily excited part of the neuron and the spike initiation zone for the axon. In electrophysiological terms, it has the most negative [[threshold potential]].
*轴突是一种较细的、像电缆一样的突起，其长度可以是胞体直径的几十倍、几百倍、甚至几万倍。轴突主要携带神经信号离开胞体，并将某些类型的信息带回胞体。许多神经元只有一个轴突，但这个轴突可能--通常也会--发生广泛的分支，从而能够与许多靶细胞进行交流。轴突从胞体中出现的部分被称为轴突丘。除了是一种解剖结构外，轴突丘还具有最大密度的电压依赖性钠离子通道。这使得它成为神经元最容易兴奋的部分和轴突的锋电位触发区。在电生理学方面，它具有最负的阈值电位。

**While the axon and axon hillock are generally involved in information outflow, this region can also receive input from other neurons.
**虽然轴突和轴突丘通常会参与信息外流，但这一区域也能接受来自其他神经元的输入。

*The '''[[axon terminal]]''' is found at the end of the axon farthest from the soma and contains [[synapses]]. Synaptic boutons are specialized structures where [[neurotransmitter]] chemicals are released to communicate with target neurons. In addition to synaptic boutons at the axon terminal, a neuron may have ''en passant'' boutons, which are located along the length of the axon.
*轴突终端位于轴突离胞体最远的一端，包含突触。突触结是专门的结构，神经递质化学物质在此释放，与目标神经元进行交流。除了轴突末端的突触结外，神经元还可能有沿轴突长度方向分布的 "中途结"。

[[File:Neuron Cell Body.png|thumb|Neuron cell body神经元细胞体]]

The accepted view of the neuron attributes dedicated functions to its various anatomical components; however, dendrites and axons often act in ways contrary to their so-called main function.<ref>{{Cite web |date=2021-01-14 |title=16.7: Nervous System |url=https://bio.libretexts.org/Courses/Lumen_Learning/Book%3A_Fundamentals_of_Biology_I_(Lumen)/16%3A_Module_13%3A_Overview_of_Body_Systems/16.7%3A_Nervous_System |access-date=2022-02-28 |website=Biology LibreTexts |language=en}}</ref>

公认的神经元观点将专门的功能归于其各种解剖成分；然而，树突和轴突的作用方式往往与它们所谓的主要功能相反。<ref>{{Cite web |date=2021-01-14 |title=16.7: Nervous System |url=https://bio.libretexts.org/Courses/Lumen_Learning/Book%3A_Fundamentals_of_Biology_I_(Lumen)/16%3A_Module_13%3A_Overview_of_Body_Systems/16.7%3A_Nervous_System |access-date=2022-02-28 |website=Biology LibreTexts |language=en}}</ref>

[[File:Complete neuron cell diagram en.svg|thumb|right|Diagram of a typical myelinated vertebrate motor neuron典型的有髓的脊椎动物运动神经元示意图]]
[[File:BN1 Neurology.webm|thumb|Neurology Video神经病学视频]]

Axons and dendrites in the central nervous system are typically only about one micrometer thick, while some in the peripheral nervous system are much thicker. The soma is usually about 10–25 micrometers in diameter and often is not much larger than the cell nucleus it contains. The longest axon of a human [[motor neuron]] can be over a meter long, reaching from the base of the spine to the toes.

中枢神经系统中的轴突和树突通常只有约1微米厚，而周围神经系统中的一些轴突和树突则要厚得多。胞体的直径通常约为10-25微米，通常不比其包含的细胞核大多少。人类运动神经元最长的轴突可以超过一米长，从脊柱底部一直延伸到脚趾。

Sensory neurons can have axons that run from the toes to the [[posterior column]] of the spinal cord, over 1.5 meters in adults. [[Giraffe]]s have single axons several meters in length running along the entire length of their necks. Much of what is known about axonal function comes from studying the [[squid giant axon]], an ideal experimental preparation because of its relatively immense size (0.5–1 millimeters thick, several centimeters long).

感觉神经元的轴突可以从脚趾一直延伸到脊髓的后柱，成年人的轴突长度超过1.5米。长颈鹿有几米长的单根轴突，沿其脖子的整个长度运行。人们对轴突功能的了解大多来自于对鱿鱼巨型轴突的研究，由于其相对巨大的尺寸（0.5-1毫米厚，数厘米长），这是一种理想的实验准备。

Fully differentiated neurons are permanently [[G0 phase|postmitotic]]<ref>{{cite journal | vauthors = Herrup K, Yang Y | title = Cell cycle regulation in the postmitotic neuron: oxymoron or new biology? | journal = Nature Reviews. Neuroscience | volume = 8 | issue = 5 | pages = 368–78 | date = May 2007 | pmid = 17453017 | doi = 10.1038/nrn2124 | s2cid = 12908713 }}</ref> however, stem cells present in the adult brain may regenerate functional neurons throughout the life of an organism (see [[neurogenesis]]). [[Astrocyte]]s are star-shaped [[glial cell]]s. They have been observed to turn into neurons by virtue of their stem cell-like characteristic of [[pluripotency]].

完全分化的神经元是永久性的有丝分裂后的细胞，<ref>{{cite journal | vauthors = Herrup K, Yang Y | title = Cell cycle regulation in the postmitotic neuron: oxymoron or new biology? | journal = Nature Reviews. Neuroscience | volume = 8 | issue = 5 | pages = 368–78 | date = May 2007 | pmid = 17453017 | doi = 10.1038/nrn2124 | s2cid = 12908713 }}</ref>然而，存在于成人大脑中的干细胞可以在有机体的整个生命过程中再生出功能性神经元（见神经元的生成）。星形胶质细胞是星形的胶质细胞。它们已经被观察到可以凭借其类干细胞的多能性特征而变成神经元。

===Membrane膜结构===

{{unreferenced section|date=December 2020}}
Like all animal cells, the cell body of every neuron is enclosed by a [[plasma membrane]], a bilayer of [[lipid]] molecules with many types of protein structures embedded in it. A lipid bilayer is a powerful electrical [[Insulator (electricity)|insulator]], but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are [[voltage-gated ion channel|voltage gated]], meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The [[ion]] materials include [[sodium]], [[potassium]], [[chloride]], and [[calcium]]. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane.

像所有的动物细胞一样，每个神经元的细胞体都被一个质膜所包围，质膜是由脂质分子组成的双层膜，其中嵌入了许多类型的蛋白质结构。脂质双层是一个强大的电绝缘体，但在神经元中，嵌入膜中的许多蛋白质结构是电活性的。这些结构包括允许带电离子流过膜的离子通道和以化学方式将离子从膜的一侧输送到另一侧的离子泵。大多数离子通道只对特定类型的离子有渗透性。一些离子通道是电压门控的，这意味着它们可以通过改变膜上的电压差在开放和关闭状态之间进行切换。其他的是化学门控，意味着它们可以通过与扩散在细胞外液中的化学物质的相互作用在开放和关闭状态之间切换。离子材料包括钠、钾、氯和钙。离子通道和离子泵之间的相互作用在膜上产生一个电压差，通常在基线上小于1/10伏。这个电压有两个功能：首先，它为嵌入膜中的各种电压依赖性蛋白机械提供了动力源；其次，它为膜的不同部分之间的电信号传输提供了一个基础。

===Histology and internal structure组织学和内部结构===

[[File:Gyrus Dentatus 40x.jpg|thumb|250px|Golgi-stained neurons in human hippocampal tissue高尔基染色神经元在人海马组织]]

[[Image:SUM 110913 Cort Neurons 2.5d in vitro 488 Phalloidin no perm 4 cmle-2.png|thumb|300px|Actin filaments in a mouse cortical neuron in culture培养中的小鼠皮质神经元中的肌动蛋白丝]]

Numerous microscopic clumps called [[Nissl body|Nissl bodies]] (or Nissl substance) are seen when nerve cell bodies are stained with a basophilic ("base-loving") dye. These structures consist of [[Endoplasmic reticulum#Rough endoplasmic reticulum|rough endoplasmic reticulum]] and associated [[ribosomal RNA]]. Named after German psychiatrist and neuropathologist [[Franz Nissl]] (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as [[aniline]] or (weakly) [[haematoxylin]]<ref>{{cite book|title=State Hospitals Bulletin|url={{google books |plainurl=y |id=Wp8CAAAAYAAJ|page=378}}|year=1897|publisher=State Commission in Lunacy.|page=378}}</ref> highlight negatively charged components, and so bind to the phosphate backbone of the ribosomal RNA.

当用嗜碱性（"嗜碱"）染料对神经细胞体进行染色时，可以看到许多称为尼氏体（或尼氏物质）的微观团块。这些结构由粗糙的内质网和相关的核糖体RNA组成。它们以德国精神病学家和神经病理学家弗朗茨-尼斯尔（1860-1919）的名字命名，参与蛋白质的合成，其突出性可以用神经细胞代谢非常活跃的事实来解释。嗜碱性染料如苯胺或（弱）血红蛋白<ref>{{cite book|title=State Hospitals Bulletin|url={{google books |plainurl=y |id=Wp8CAAAAYAAJ|page=378}}|year=1897|publisher=State Commission in Lunacy.|page=378}}</ref>会突出带负电的成分，因此与核糖体RNA的磷酸盐骨架结合。

The cell body of a neuron is supported by a complex mesh of structural proteins called [[neurofilament]]s, which together with neurotubules (neuronal microtubules) are assembled into larger neurofibrils.<ref name="Webster">{{cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |website=www.merriam-webster.com}}</ref> Some neurons also contain pigment granules, such as [[neuromelanin]] (a brownish-black pigment that is byproduct of synthesis of [[catecholamine]]s), and [[lipofuscin]] (a yellowish-brown pigment), both of which accumulate with age.<ref>{{cite journal | vauthors = Zecca L, Gallorini M, Schünemann V, Trautwein AX, Gerlach M, Riederer P, Vezzoni P, Tampellini D | title = Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes | journal = Journal of Neurochemistry | volume = 76 | issue = 6 | pages = 1766–73 | date = March 2001 | pmid = 11259494 | doi = 10.1046/j.1471-4159.2001.00186.x | s2cid = 31301135 }}</ref><ref>{{cite journal | vauthors = Herrero MT, Hirsch EC, Kastner A, Luquin MR, Javoy-Agid F, Gonzalo LM, Obeso JA, Agid Y | title = Neuromelanin accumulation with age in catecholaminergic neurons from Macaca fascicularis brainstem | journal = Developmental Neuroscience | volume = 15 | issue = 1 | pages = 37–48 | date = 1993 | pmid = 7505739 | doi = 10.1159/000111315 }}</ref><ref>{{cite journal | vauthors = Brunk UT, Terman A | title = Lipofuscin: mechanisms of age-related accumulation and influence on cell function | journal = Free Radical Biology & Medicine | volume = 33 | issue = 5 | pages = 611–9 | date = September 2002 | pmid = 12208347 | doi = 10.1016/s0891-5849(02)00959-0 }}</ref> Other structural proteins that are important for neuronal function are [[actin]] and the [[tubulin]] of [[microtubule]]s. [[Class III β-tubulin]] is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule.<ref>{{cite journal | vauthors = Zhao B, Meka DP, Scharrenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F | title = Microtubules Modulate F-actin Dynamics during Neuronal Polarization | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 9583 | date = August 2017 | pmid = 28851982 | pmc = 5575062 | doi = 10.1038/s41598-017-09832-8 | bibcode = 2017NatSR...7.9583Z }}</ref>

神经元的细胞体由称为神经丝的结构蛋白的复杂网状结构支撑，它与神经管（神经元微管）一起被组装成较大的神经纤维。<ref name="Webster">{{cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |website=www.merriam-webster.com}}</ref> 一些神经元还含有色素颗粒，如神经黑色素（一种棕黑色的色素，是儿茶酚胺合成的副产品）和脂褐素（一种黄褐色的色素），这两种物质都会随着年龄的增长而积累。<ref>{{cite journal | vauthors = Zecca L, Gallorini M, Schünemann V, Trautwein AX, Gerlach M, Riederer P, Vezzoni P, Tampellini D | title = Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes | journal = Journal of Neurochemistry | volume = 76 | issue = 6 | pages = 1766–73 | date = March 2001 | pmid = 11259494 | doi = 10.1046/j.1471-4159.2001.00186.x | s2cid = 31301135 }}</ref><ref>{{cite journal | vauthors = Herrero MT, Hirsch EC, Kastner A, Luquin MR, Javoy-Agid F, Gonzalo LM, Obeso JA, Agid Y | title = Neuromelanin accumulation with age in catecholaminergic neurons from Macaca fascicularis brainstem | journal = Developmental Neuroscience | volume = 15 | issue = 1 | pages = 37–48 | date = 1993 | pmid = 7505739 | doi = 10.1159/000111315 }}</ref><ref>{{cite journal | vauthors = Brunk UT, Terman A | title = Lipofuscin: mechanisms of age-related accumulation and influence on cell function | journal = Free Radical Biology & Medicine | volume = 33 | issue = 5 | pages = 611–9 | date = September 2002 | pmid = 12208347 | doi = 10.1016/s0891-5849(02)00959-0 }}</ref> 对神经元功能很重要的其他结构蛋白是肌动蛋白和微管的管蛋白。第三类β-管蛋白几乎只在神经元中发现。在神经元发育过程中，肌动蛋白主要存在于轴突和树突的顶端。在那里，肌动蛋白的动态可以通过与微管的相互作用而被调节。<ref>{{cite journal | vauthors = Zhao B, Meka DP, Scharrenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F | title = Microtubules Modulate F-actin Dynamics during Neuronal Polarization | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 9583 | date = August 2017 | pmid = 28851982 | pmc = 5575062 | doi = 10.1038/s41598-017-09832-8 | bibcode = 2017NatSR...7.9583Z }}</ref>

There are different internal structural characteristics between axons and dendrites. Typical axons almost never contain [[ribosomes]], except some in the initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases.

轴突和树突之间存在着不同的内部结构特征。典型的轴突几乎不含核糖体，除了在初始段有一些。树突含有颗粒状的内质网或核糖体，随着与细胞体距离的增加，其数量逐渐减少。

==Classification分类==

[[File:GFPneuron.png|thumb|250px|right|Image of pyramidal neurons in mouse [[cerebral cortex]] expressing [[green fluorescent protein]]. The red staining indicates [[GABA]]ergic interneurons.<ref>{{cite journal | vauthors = Lee WC, Huang H, Feng G, Sanes JR, Brown EN, So PT, Nedivi E | title = Dynamic remodeling of dendritic arbors in GABAergic interneurons of adult visual cortex | journal = PLOS Biology | volume = 4 | issue = 2 | pages = e29 | date = February 2006 | pmid = 16366735 | pmc = 1318477 | doi = 10.1371/journal.pbio.0040029 |doi-access=free }}</ref>]]

[[File:smi32neuron.jpg|thumb|250px|right|SMI32-stained pyramidal neurons in [[cerebral cortex]]]]

{{See also|List of distinct cell types in the adult human body#Nervous system}}
另见：成人体内不同的细胞类型列表 § 神经系统

Neurons vary in shape and size and can be classified by their [[Morphology (biology)|morphology]] and function.<ref name="Al">{{cite book|last=Al|first=Martini, Frederic Et|title=Anatomy and Physiology' 2007 Ed.2007 Edition|url={{google books |plainurl=y |id=joJb82gVsLoC|page=288}}|publisher=Rex Bookstore, Inc.|isbn=978-971-23-4807-5|pages=288}}</ref> The anatomist [[Camillo Golgi]] grouped neurons into two types; type I with long axons used to move signals over long distances and type II with short axons, which can often be confused with dendrites. Type I cells can be further classified by the location of the soma. The basic morphology of type I neurons, represented by spinal [[motor neurons]], consists of a cell body called the soma and a long thin axon covered by a [[myelin sheath]]. The dendritic tree wraps around the cell body and receives signals from other neurons. The end of the axon has branching [[axon terminal]]s that release neurotransmitters into a gap called the [[synaptic cleft]] between the terminals and the dendrites of the next neuron.

神经元的形状和大小各不相同，可按其形态和功能进行分类。<ref name="Al">{{cite book|last=Al|first=Martini, Frederic Et|title=Anatomy and Physiology' 2007 Ed.2007 Edition|url={{google books |plainurl=y |id=joJb82gVsLoC|page=288}}|publisher=Rex Bookstore, Inc.|isbn=978-971-23-4807-5|pages=288}}</ref> 解剖学家卡米洛-高尔基将神经元分为两类：I型有长轴，用于长距离移动信号；II型有短轴，常与树突相混淆。I型细胞可按胞体的位置进一步分类。以脊髓运动神经元为代表的I型神经元的基本形态包括一个称为胞体的细胞体和一个由髓鞘覆盖的细长轴突。树突树环绕着细胞体，接收来自其他神经元的信号。轴突的末端有分支的轴突终端，将神经递质释放到终端和下一个神经元树突之间的间隙中，称为突触间隙。

===Structural classification结构分类===

====Polarity极性====

[[File:Neurons uni bi multi pseudouni.svg|thumb|Different kinds of neurons不同种类的神经元: 1 [[Unipolar neuron单极神经元]] 2 [[Bipolar neuron双极神经元]] 3 [[Multipolar neuron多极神经元]] 4 [[Pseudounipolar neuron伪单极神经元]] ]]

Most neurons can be anatomically characterized as:
大多数神经元在解剖学上可以被描述为：

*[[Unipolar neuron|Unipolar]]: single process
*[[Bipolar cell|Bipolar]]: 1 axon and 1 dendrite
*[[Multipolar neuron|Multipolar]]: 1 axon and 2 or more dendrites
**[[Golgi I]]: neurons with long-projecting axonal processes; examples are pyramidal cells, Purkinje cells, and anterior horn cells
**[[Golgi II]]: neurons whose axonal process projects locally; the best example is the granule cell
*[[Anaxonic neuron|Anaxonic]]: where the axon cannot be distinguished from the dendrite(s)
*[[Pseudounipolar cells|Pseudounipolar]]: 1 process which then serves as both an axon and a dendrite

* 单极性：单一原生质过程
* 双极性：1个轴突和1个树突
* 多极性：1个轴突和2个或更多的树突
** 高尔基I型：具有长轴突的神经元；比如锥体细胞、浦肯野细胞和前角细胞。
** 高尔基II型：其轴突过程在局部投射的神经元；最好的例子是颗粒细胞
* 无轴性：轴突与树突无法区分的神经元类型。
* 假单极神经元：1个原生质过程，然后既是轴突又是树突。

====Other其他====

Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are:

一些独特的神经元类型可以根据其在神经系统中的位置和独特的形状来识别。一些例子是：

*[[Basket cell]]s, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and [[cerebellum]]
*[[Betz cell]]s, large motor neurons
*[[Lugaro cell]]s, interneurons of the cerebellum
*[[Medium spiny neuron]]s, most neurons in the [[corpus striatum]]
*[[Purkinje cell]]s, huge neurons in the cerebellum, a type of Golgi I multipolar neuron
*[[Pyramidal cell]]s, neurons with triangular soma, a type of Golgi I
*[[Renshaw cell]]s, neurons with both ends linked to [[alpha motor neuron]]s
*[[Unipolar brush cell]]s, interneurons with unique dendrite ending in a brush-like tuft
*[[Granule cell]]s, a type of Golgi II neuron
*[[Anterior horn (spinal cord)|Anterior horn]] cells, [[motoneurons]] located in the spinal cord
*[[Spindle cell]]s, interneurons that connect widely separated areas of the brain

*篮状细胞，在目标细胞的胞体周围形成密集的终端丛，发现于大脑皮层和小脑的中间神经元。
*贝兹细胞，大运动神经元
*卢加洛细胞，小脑的中间神经元
*中型多棘神经元，纹状体中的大多数神经元
*浦肯野细胞，小脑中的巨大神经元，一种高尔基I型多极神经元
*锥体细胞，具有三角形胞体的神经元，是高尔基I型的一种。
*伦肖细胞，两端与α运动神经元相连的神经元
*单极刷细胞，具有独特的树突末端为刷状簇的中间神经元
*颗粒细胞，高尔基II型神经元的一种类型
*前角细胞，位于脊髓中的运动神经元
*纺锤体细胞，连接大脑广泛分布的中间神经元
*纺锤体细胞的运动神经元、连接大脑广泛分离区域的中间神经元

===Functional classification功能分类===

====Direction方向====

*[[Afferent neuron]]s convey information from tissues and organs into the central nervous system and are also called [[sensory neurons]].
*[[Efferent neuron]]s (motor neurons) transmit signals from the central nervous system to the effector cells.
*[[Interneuron]]s connect neurons within specific regions of the central nervous system.

* 传入神经元将信息从组织和器官传入中枢神经系统，也被称为感觉神经元。
* 传出神经元(运动神经元) 将信号从中枢神经系统传递给效应细胞。
* 中间神经元连接中枢神经系统特定区域内的神经元。

Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain.

传入和传出也泛指分别为大脑带来信息或从大脑发出信息的神经元。

====Action on other neurons对其他神经元的影响====

A neuron affects other neurons by releasing a neurotransmitter that binds to [[receptor (biochemistry)|chemical receptor]]s. The effect upon the postsynaptic neuron is determined by the type of receptor that is activated, not by the presynaptic neuron or by the neurotransmitter. A neurotransmitter can be thought of as a key, and a receptor as a lock: the same neurotransmitter can activate multiple types of receptors. Receptors can be classified broadly as ''excitatory'' (causing an increase in firing rate), ''inhibitory'' (causing a decrease in firing rate), or ''modulatory'' (causing long-lasting effects not directly related to firing rate).

一个神经元通过释放一种与化学受体结合的神经递质来影响其他神经元。对突触后神经元的影响是由被激活的受体类型决定的，而不是由突触前神经元或神经递质决定的。可以认为神经递质是一把钥匙，而受体是一把锁：同一神经递质可以激活多种类型的受体。受体可大致分为兴奋性（导致放电率增加）、抑制性（导致放电率下降）或调节性（导致与放电率无直接关系的长期影响）。

The two most common (90%+) neurotransmitters in the brain, [[glutamate]] and [[GABA]], have largely consistent actions. Glutamate acts on several types of receptors, and has effects that are excitatory at [[ionotropic receptor]]s and a modulatory effect at [[metabotropic receptor]]s. Similarly, GABA acts on several types of receptors, but all of them have inhibitory effects (in adult animals, at least). Because of this consistency, it is common for neuroscientists to refer to cells that release glutamate as "excitatory neurons", and cells that release GABA as "inhibitory neurons". Some other types of neurons have consistent effects, for example, "excitatory" motor neurons in the spinal cord that release [[acetylcholine]], and "inhibitory" [[spinal neuron]]s that release [[glycine]].

大脑中最常见的两种（90%以上）神经递质，即谷氨酸和GABA，其作用基本一致。谷氨酸作用于几种类型的受体，在离子型受体上有兴奋作用，在代谢型受体上有调节作用。同样，GABA作用于几种类型的受体，但它们都有抑制作用（至少在成年动物中）。由于这种一致性，神经科学家通常把释放谷氨酸的细胞称为 "兴奋性神经元"，而把释放GABA的细胞称为 "抑制性神经元"。其他一些类型的神经元也有一致的影响，例如，脊髓中释放乙酰胆碱的 "兴奋性 "运动神经元，以及释放甘氨酸的 "抑制性 "脊髓神经元。

The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neuron. In principle, a single neuron, releasing a single neurotransmitter, can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still. For example, [[photoreceptor cell]]s in the retina constantly release the neurotransmitter glutamate in the absence of light. So-called OFF [[retinal bipolar cells|bipolar cells]] are, like most neurons, excited by the released glutamate. However, neighboring target neurons called ON bipolar cells are instead inhibited by glutamate, because they lack typical [[ionotropic receptor|ionotropic]] [[glutamate receptors]] and instead express a class of inhibitory [[metabotropic receptor|metabotropic]] glutamate receptors.<ref>{{cite journal | vauthors = Gerber U | title = Metabotropic glutamate receptors in vertebrate retina | journal = Documenta Ophthalmologica. Advances in Ophthalmology | volume = 106 | issue = 1 | pages = 83–7 | date = January 2003 | pmid = 12675489 | doi = 10.1023/A:1022477203420 | s2cid = 22296630 }}</ref> When light is present, the photoreceptors cease releasing glutamate, which relieves the ON bipolar cells from inhibition, activating them; this simultaneously removes the excitation from the OFF bipolar cells, silencing them.

兴奋性和抑制性神经递质之间的区别不是绝对的。相反，它取决于突触后神经元上存在的化学受体的类别。原则上，一个神经元，释放一种神经递质，可以对某些目标产生兴奋作用，对其他目标产生抑制作用，对其他目标仍有调节作用。例如，视网膜上的感光细胞在没有光的情况下不断释放神经递质谷氨酸。像大多数神经元一样，所谓的关闭双极细胞被释放的谷氨酸所激发。然而，被称为ON双极细胞的邻近目标神经元反而受到谷氨酸的抑制，因为它们缺乏典型的离子型谷氨酸受体，而是表达一类抑制性的代谢型谷氨酸受体。<ref>{{cite journal | vauthors = Gerber U | title = Metabotropic glutamate receptors in vertebrate retina | journal = Documenta Ophthalmologica. Advances in Ophthalmology | volume = 106 | issue = 1 | pages = 83–7 | date = January 2003 | pmid = 12675489 | doi = 10.1023/A:1022477203420 | s2cid = 22296630 }}</ref>当有光时，光感受器停止释放谷氨酸，这解除了ON双极细胞的抑制，激活了它们；这同时消除了OFF双极细胞的兴奋，使它们沉默。

It is possible to identify the type of inhibitory effect a presynaptic neuron will have on a postsynaptic neuron, based on the proteins the presynaptic neuron expresses. [[Parvalbumin]]-expressing neurons typically dampen the output signal of the postsynaptic neuron in the [[visual cortex]], whereas [[somatostatin]]-expressing neurons typically block dendritic inputs to the postsynaptic neuron.<ref name="pmid22878717">{{cite journal | vauthors = Wilson NR, Runyan CA, Wang FL, Sur M | title = Division and subtraction by distinct cortical inhibitory networks in vivo | journal = Nature | volume = 488 | issue = 7411 | pages = 343–8 | date = August 2012 | pmid = 22878717 | pmc = 3653570 | doi = 10.1038/nature11347 | bibcode = 2012Natur.488..343W | hdl = 1721.1/92709 }}</ref>

根据突触前神经元表达的蛋白质，可以确定突触前神经元对突触后神经元的抑制作用的类型。表达副白蛋白的神经元通常会抑制视觉皮层中突触后神经元的输出信号，而表达躯干素的神经元通常会阻断突触后神经元的树突输入。<ref name="pmid22878717">{{cite journal | vauthors = Wilson NR, Runyan CA, Wang FL, Sur M | title = Division and subtraction by distinct cortical inhibitory networks in vivo | journal = Nature | volume = 488 | issue = 7411 | pages = 343–8 | date = August 2012 | pmid = 22878717 | pmc = 3653570 | doi = 10.1038/nature11347 | bibcode = 2012Natur.488..343W | hdl = 1721.1/92709 }}</ref>

====Discharge patterns放电模式====

Neurons have intrinsic electroresponsive properties like intrinsic transmembrane voltage [[Neural oscillation|oscillatory]] patterns.<ref name="llinas2014">{{cite journal | vauthors = Llinás RR | title = Intrinsic electrical properties of mammalian neurons and CNS function: a historical perspective | journal = Frontiers in Cellular Neuroscience | volume = 8 | pages = 320 | date = 2014-01-01 | pmid = 25408634 | pmc = 4219458 | doi = 10.3389/fncel.2014.00320 | doi-access = free }}</ref> So neurons can be classified according to their [[electrophysiology|electrophysiological]] characteristics:

神经元具有内在的电反应特性，如内在的跨膜电压振荡模式。<ref name="llinas2014">{{cite journal | vauthors = Llinás RR | title = Intrinsic electrical properties of mammalian neurons and CNS function: a historical perspective | journal = Frontiers in Cellular Neuroscience | volume = 8 | pages = 320 | date = 2014-01-01 | pmid = 25408634 | pmc = 4219458 | doi = 10.3389/fncel.2014.00320 | doi-access = free }}</ref>因此，可以根据神经元的电生理特性对其进行分类：

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.
*Phasic or bursting. Neurons that fire in bursts are called phasic.
*Fast spiking. Some neurons are notable for their high firing rates, for example some types of cortical inhibitory interneurons, cells in [[globus pallidus]], [[retinal ganglion cells]].<ref>{{cite conference | title = Ion conductances related to shaping the repetitive firing in rat retinal ganglion cells | vauthors = Kolodin YO, Veselovskaia NN, Veselovsky NS, Fedulova SA | conference = Acta Physiologica Congress | url = http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | access-date = 2009-06-20 | archive-url = https://web.archive.org/web/20121007164451/http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | archive-date = 2012-10-07 | url-status = dead }}</ref><ref>{{cite web|url=http://ykolodin.50webs.com/ |title=Ionic conductances underlying excitability in tonically firing retinal ganglion cells of adult rat |publisher=Ykolodin.50webs.com |date=2008-04-27 |access-date=2013-02-16}}</ref>

*紧张性或规律性棘波。一些神经元通常持续（紧张地）活跃，通常以恒定的频率放电。例如：神经干细胞中的interneurons。
*瞬变性或爆发性。爆发性放电的神经元被称为瞬变性的。
*快闪性。一些神经元因其高放电率而引人注目，例如某些类型的皮质抑制性中间神经元、苍白球、视网膜神经节细胞。<ref>{{cite conference | title = Ion conductances related to shaping the repetitive firing in rat retinal ganglion cells | vauthors = Kolodin YO, Veselovskaia NN, Veselovsky NS, Fedulova SA | conference = Acta Physiologica Congress | url = http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | access-date = 2009-06-20 | archive-url = https://web.archive.org/web/20121007164451/http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | archive-date = 2012-10-07 | url-status = dead }}</ref><ref>{{cite web|url=http://ykolodin.50webs.com/ |title=Ionic conductances underlying excitability in tonically firing retinal ganglion cells of adult rat |publisher=Ykolodin.50webs.com |date=2008-04-27 |access-date=2013-02-16}}</ref>

====Neurotransmitter神经递质 ====

[[File:Neurotransmitters.jpg|thumb|Synaptic vesicles containing neurotransmitters含有神经递质的突触小泡。]]
{{Main|Neurotransmitter}}

[[Neurotransmitter]]s are chemical messengers passed from one neuron to another neuron or to a [[muscle cell]] or [[Gland|gland cell]].

神经递质是由一个神经元传递给另一个神经元或肌肉细胞或腺体细胞的化学信使。

*Cholinergic neurons – acetylcholine. [[Acetylcholine]] is released from presynaptic neurons into the synaptic cleft. It acts as a [[ligand]] for both ligand-gated ion channels and [[Metabotropic receptor|metabotropic]] (GPCRs) [[Muscarinic acetylcholine receptor|muscarinic receptors]]. [[Nicotinic receptors]] are pentameric ligand-gated ion channels composed of alpha and beta subunits that bind [[nicotine]]. Ligand binding opens the channel causing influx of [[Sodium|Na+]] depolarization and increases the probability of presynaptic neurotransmitter release. Acetylcholine is synthesized from [[choline]] and [[acetyl coenzyme A]].
*Adrenergic neurons – noradrenaline. [[Noradrenaline]] (norepinephrine) is released from most [[postganglionic]] neurons in the [[sympathetic nervous system]] onto two sets of GPCRs: [[Adrenergic receptor|alpha adrenoceptor]]s and [[beta adrenoceptor]]s. Noradrenaline is one of the three common [[catecholamine]] neurotransmitter, and the most prevalent of them in the [[peripheral nervous system]]; as with other catecholamines, it is synthesised from [[tyrosine]].
*GABAergic neurons – [[gamma aminobutyric acid]]. GABA is one of two neuroinhibitors in the [[central nervous system]] (CNS), along with glycine. GABA has a homologous function to [[Acetylcholine|ACh]], gating anion channels that allow [[Chlorine|Cl−]] ions to enter the post synaptic neuron. Cl− causes hyperpolarization within the neuron, decreasing the probability of an action potential firing as the voltage becomes more negative (for an action potential to fire, a positive voltage threshold must be reached). GABA is synthesized from glutamate neurotransmitters by the enzyme [[glutamate decarboxylase]].
*Glutamatergic neurons – glutamate. [[Glutamate]] is one of two primary excitatory amino acid neurotransmitters, along with [[Aspartic acid|aspartate]]. Glutamate receptors are one of four categories, three of which are ligand-gated ion channels and one of which is a [[G protein|G-protein]] coupled receptor (often referred to as GPCR).

*胆碱能神经元--乙酰胆碱。乙酰胆碱从突触前神经元释放到突触间隙中。它是配体门控离子通道和代谢型（GPCRs：G蛋白耦联受体）毒蕈碱受体的配体。烟碱受体是由结合了尼古丁的α和β亚基组成的五聚体配体门控离子通道。配体结合后打开通道，造成Na+的流入，使其去极化，并增加突触前神经递质释放的概率。乙酰胆碱是由胆碱和乙酰辅酶A合成的。
*肾上腺素能神经元--去甲肾上腺素。去甲肾上腺素（norepinephrine去甲肾上腺素）从交感神经系统的大多数神经节后神经元释放到两组GPCRs上：α肾上腺素受体和β肾上腺素受体。去甲肾上腺素是三种常见的儿茶酚胺神经递质之一，也是周围神经系统中最普遍的一种；与其他儿茶酚胺一样，它是由酪氨酸合成的。
*GABA能神经元--γ氨基丁酸。GABA与甘氨酸一起是中枢神经系统（CNS）中的两种神经抑制剂之一。GABA具有与ACh相同的功能，对允许Cl-离子进入突触后神经元的阴离子通道进行门控。Cl-导致神经元内的超极化，随着电压变得更负，降低了动作电位放电的概率（要引发动作电位，必须达到一个正电压阈值）。GABA是由谷氨酸神经递质通过谷氨酸脱羧酶合成的。
*谷氨酸能神经元--谷氨酸。谷氨酸与天门冬氨酸一起是两种主要的兴奋性氨基酸神经递质之一。谷氨酸受体是四类之一，其中三类是配体门控离子通道，一类是G-蛋白耦联受体（通常称为GPCR）。

:#[[AMPA]] and [[Kainic acid|Kainate]] receptors function as [[Ion|cation]] channels permeable to Na+ cation channels mediating fast excitatory synaptic transmission.
:#[[N-Methyl-D-aspartic acid|NMDA]] receptors are another cation channel that is more permeable to [[Calcium in biology|Ca2+]]. The function of NMDA receptors depend on glycine receptor binding as a co-[[agonist]] within the channel pore. NMDA receptors do not function without both ligands present.
:#Metabotropic receptors, GPCRs modulate synaptic transmission and postsynaptic excitability.
::Glutamate can cause excitotoxicity when blood flow to the brain is interrupted, resulting in [[brain damage]]. When blood flow is suppressed, glutamate is released from presynaptic neurons, causing greater NMDA and AMPA receptor activation than normal outside of stress conditions, leading to elevated Ca2+ and Na+ entering the post synaptic neuron and cell damage. Glutamate is synthesized from the amino acid glutamine by the enzyme [[Glutamine oxoglutarate aminotransferase|glutamate synthase]].

:#AMPA和红藻氨酸受体作为阳离子通道可渗透到Na+阳离子通道，介导快速兴奋性突触传递。
:#NMDA受体是另一个对Ca2+更易渗透的阳离子通道。NMDA受体的功能取决于甘氨酸受体的结合，作为通道孔内的共轭物。如果没有这两种配体存在，NMDA受体就不能发挥作用。
:#促代谢受体，GPCRs调节突触传递和突触后兴奋性。
::当流向大脑的血流被中断时，谷氨酸可引起兴奋性毒性，导致大脑损伤。当血流被抑制时，谷氨酸从突触前的神经元中释放出来，导致NMDA和AMPA受体的激活比压力条件以外的正常情况下更大，导致升高的Ca2+和Na+进入突触后的神经元和细胞损伤。谷氨酸是由谷氨酸合成酶从氨基酸谷氨酰胺中合成的。

*Dopaminergic neurons—[[dopamine]]. [[Dopamine]] is a neurotransmitter that acts on D1 type (D1 and D5) Gs-coupled receptors, which increase cAMP and PKA, and D2 type (D2, D3, and D4) receptors, which activate Gi-coupled receptors that decrease cAMP and PKA. Dopamine is connected to mood and behavior and modulates both pre- and post-synaptic neurotransmission. Loss of dopamine neurons in the [[substantia nigra]] has been linked to [[Parkinson's disease]]. Dopamine is synthesized from the amino acid [[tyrosine]]. Tyrosine is catalyzed into levodopa (or [[L-DOPA]]) by [[Tyrosine hydroxylase|tyrosine hydroxlase]], and levodopa is then converted into dopamine by the aromatic amino acid [[Carboxy-lyases|decarboxylase]].
*Serotonergic neurons—[[serotonin]]. [[Serotonin]] (5-Hydroxytryptamine, 5-HT) can act as excitatory or inhibitory. Of its four 5-HT receptor classes, 3 are GPCR and 1 is a ligand-gated cation channel. Serotonin is synthesized from [[tryptophan]] by [[tryptophan hydroxylase]], and then further by decarboxylase. A lack of 5-HT at postsynaptic neurons has been linked to depression. Drugs that block the presynaptic [[serotonin transporter]] are used for treatment, such as [[Prozac]] and [[Zoloft]].
*Purinergic neurons—ATP. [[Adenosine triphosphate|ATP]] is a neurotransmitter acting at both ligand-gated ion channels ([[P2X]] receptors) and GPCRs ([[P2Y receptor|P2Y]]) receptors. ATP is, however, best known as a [[cotransmitter]]. Such [[purinergic signalling]] can also be mediated by other [[purine]]s like [[adenosine]], which particularly acts at P2Y receptors.
*Histaminergic neurons—[[histamine]]. [[Histamine]] is a [[monoamine neurotransmitter]] and [[neuromodulator]]. Histamine-producing neurons are found in the [[tuberomammillary nucleus]] of the [[hypothalamus]].<ref>{{cite journal | vauthors = Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y | title = Histamine: neural circuits and new medications | journal = Sleep | volume = 42 | issue = 1 | date = January 2019 | pmid = 30239935 | pmc = 6335869 | doi = 10.1093/sleep/zsy183 }}</ref> Histamine is involved in [[arousal]] and regulating sleep/wake behaviors.

*多巴胺能神经元——多巴胺。多巴胺是一种神经递质，作用于D1型（D1和D5）Gs耦联受体，增加cAMP和PKA，以及D2型（D2、D3和D4）受体，激活Gi耦联受体，减少cAMP和PKA。多巴胺与情绪和行为有关，调节突触前和突触后的神经传递。黑质中的多巴胺神经元的丧失与帕金森病有关。多巴胺是由氨基酸酪氨酸合成的。酪氨酸被酪氨酸羟化酶催化为左旋多巴（或L-DOPA），然后左旋多巴被芳香族氨基酸脱羧酶转化为多巴胺。
*羟色胺能神经元——羟色胺。羟色胺（5-Hydroxytryptamine，5-HT）可以起到兴奋性或抑制性作用。在其四个5-HT受体类别中，3个是GPCR，1个是配体门控的阳离子通道。羟色胺由色氨酸经色氨酸羟化酶合成，然后再经脱羧酶进一步合成。突触后神经元缺乏5-HT与抑郁症有关。阻断突触前5-羟色胺转运体的药物被用于治疗，如百忧解和左洛复。
*嘌呤神经元——ATP。ATP是一种同时作用于配体门控离子通道（P2X受体）和GPCRs（P2Y）受体的神经递质。然而，ATP最有名的是作为一种共传导剂。这种嘌呤信号也可以由其他嘌呤介导，如腺苷，它特别作用于P2Y受体。
*组胺能神经元——组胺。组胺是一种单胺类神经递质和神经调节剂。产生组胺的神经元存在于下丘脑的管状乳头核。<ref>{{cite journal | vauthors = Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y | title = Histamine: neural circuits and new medications | journal = Sleep | volume = 42 | issue = 1 | date = January 2019 | pmid = 30239935 | pmc = 6335869 | doi = 10.1093/sleep/zsy183 }}</ref> 组胺参与唤醒和调节睡眠/觉醒行为。

====Multimodel classification多模式分类====

Since 2012 there has been a push from the cellular and computational neuroscience community to come up with a universal classification of neurons that will apply to all neurons in the brain as well as across species. This is done by considering the three essential qualities of all neurons: electrophysiology, morphology, and the individual transcriptome of the cells. Besides being universal this classification has the advantage of being able to classify astrocytes as well. A method called Patch-Seq in which all three qualities can be measured at once is used extensively by the Allen Institute for Brain Science.<ref>{{cite web |url=https://www.news-medical.net/news/20201203/Patch-seq-technique-helps-depict-the-variation-of-neural-cells-in-the-brain.aspx |title=Patch-seq technique helps depict the variation of neural cells in the brain |work=News-medical.net |date=3 December 2020 |access-date=26 August 2021 |url-status=live}}</ref>

自2012年以来，细胞和计算神经科学界一直在推动提出一个通用的神经元分类，该分类将适用于大脑中的所有神经元以及跨物种。这是通过考虑所有神经元的三个基本属性来实现的：电生理学、形态学和细胞的个体转录组。除了具有普遍性之外，这种分类法还有一个优点，就是能够对星形胶质细胞进行分类。艾伦脑科学研究所广泛使用一种叫做Patch-Seq的方法，可以同时测量所有三种属性。<ref>{{cite web |url=https://www.news-medical.net/news/20201203/Patch-seq-technique-helps-depict-the-variation-of-neural-cells-in-the-brain.aspx |title=Patch-seq technique helps depict the variation of neural cells in the brain |work=News-medical.net |date=3 December 2020 |access-date=26 August 2021 |url-status=live}}</ref>

==Connectivity连接性==

{{Main|Synapse|Chemical synapse化学突触}}
[[File:Chemical synapse schema cropped.jpg|thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell沿着轴突传播到下一个细胞的细胞体和树突的一种信号。]]
[[File:Neuro Muscular Junction.png|thumb|Chemical synapse|left]]

Neurons communicate with each other via [[synapses]], where either the [[axon terminal]] of one cell contacts another neuron's dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in the cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the [[supraoptic nucleus]], have only one or two dendrites, each of which receives thousands of synapses.

神经元通过突触相互沟通，一个细胞的轴突终端接触到另一个神经元的树突、胞体，或者更少见的轴突。像小脑中的浦肯野细胞这样的神经元可以有超过1000个树突分支，与成千上万的其他细胞建立连接; 其他的神经元，如视上核的大细胞神经元，只有一个或两个树突，每个树突接收数千个突触。

Synapses can be [[EPSP|excitatory]] or [[IPSP|inhibitory]], either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive [[gap junction|junctions]] between cells.<ref>{{cite book |last1=Macpherson |first1=Gordon |title=Black's Medical Dictionary |date=2002 |publisher=Scarecrow Press |location=Lanham, MD |isbn=0810849844 |pages=431–434 |edition=40 }}</ref>

突触可以是兴奋性的或抑制性的，分别增加或减少目标神经元的活动。一些神经元还通过电突触进行交流，电突触是细胞之间直接的、导电的连接点。<ref>{{cite book |last1=Macpherson |first1=Gordon |title=Black's Medical Dictionary |date=2002 |publisher=Scarecrow Press |location=Lanham, MD |isbn=0810849844 |pages=431–434 |edition=40 }}</ref>

When an action potential reaches the axon terminal, it opens [[Voltage-dependent calcium channel|voltage-gated calcium channels]], allowing [[Calcium in biology|calcium ions]] to enter the terminal. Calcium causes [[synaptic vesicles]] filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the [[axon terminal]] triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial [[energy metabolism]] to produce [[Adenosine triphosphate|ATP]] to support continuous neurotransmission.<ref name="pmid23746507">{{cite journal | vauthors = Ivannikov MV, Macleod GT | title = Mitochondrial free Ca²⁺ levels and their effects on energy metabolism in Drosophila motor nerve terminals | journal = Biophysical Journal | volume = 104 | issue = 11 | pages = 2353–61 | date = June 2013 | pmid = 23746507 | pmc = 3672877 | doi = 10.1016/j.bpj.2013.03.064 | bibcode = 2013BpJ...104.2353I }}</ref>

当动作电位到达轴突末端时，它打开电压门控的钙离子通道，允许钙离子进入末端。钙离子使充满神经递质分子的突触小泡与膜融合，将其内容释放到突触间隙中。神经递质在突触间隙中扩散，激活突触后神经元上的受体。轴突末端的高细胞钙引发线粒体钙吸收，这反过来又激活了线粒体的能量代谢，产生ATP以支持持续的神经传递。<ref name="pmid23746507">{{cite journal | vauthors = Ivannikov MV, Macleod GT | title = Mitochondrial free Ca²⁺ levels and their effects on energy metabolism in Drosophila motor nerve terminals | journal = Biophysical Journal | volume = 104 | issue = 11 | pages = 2353–61 | date = June 2013 | pmid = 23746507 | pmc = 3672877 | doi = 10.1016/j.bpj.2013.03.064 | bibcode = 2013BpJ...104.2353I }}</ref>

An [[autapse]] is a synapse in which a neuron's axon connects to its own dendrites.

自突触是指神经元的轴突与自己的树突相连的突触。

The [[human brain]] has some 8.6 x 1010 (eighty six billion) neurons.<ref>{{ cite journal | vauthors = Herculano-Houzel S | title = The human brain in numbers: a linearly scaled-up primate brain | journal = Frontiers in Human Neuroscience | volume = 3 | pages = 31 | date = November 2009 | pmid = 19915731 | doi = 10.3389/neuro.09.031.2009 | pmc = 2776484 | doi-access = free }}</ref> Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 1015 synapses (1 quadrillion). [[Synaptic pruning|This number declines with age]], stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5 x 1014 synapses (100 to 500 trillion).<ref>{{cite journal | vauthors = Drachman DA | title = Do we have brain to spare? | journal = Neurology | volume = 64 | issue = 12 | pages = 2004–5 | date = June 2005 | pmid = 15985565 | doi = 10.1212/01.WNL.0000166914.38327.BB | s2cid = 38482114 }}</ref>

[[File:Axon Propagation.svg|thumb|563x563px|An annotated diagram of the stages of an action potential propagating down an axon including the role of ion concentration and pump and channel proteins.一个动作电位沿轴突传播的阶段的注释图，包括离子浓度和泵及通道蛋白的作用。]]

人脑有大约8.6 x 1010（86亿）个神经元。<ref>{{ cite journal | vauthors = Herculano-Houzel S | title = The human brain in numbers: a linearly scaled-up primate brain | journal = Frontiers in Human Neuroscience | volume = 3 | pages = 31 | date = November 2009 | pmid = 19915731 | doi = 10.3389/neuro.09.031.2009 | pmc = 2776484 | doi-access = free }}</ref>每个神经元平均有7000个与其他神经元的突触连接。据估计，一个三岁孩子的大脑大约有1015个突触（1万亿）。这个数字随着年龄的增长而下降，到成年后趋于稳定。对成年人的估计有所不同，从1014到5 x 1014个突触（100到500万亿）不等。<ref>{{cite journal | vauthors = Drachman DA | title = Do we have brain to spare? | journal = Neurology | volume = 64 | issue = 12 | pages = 2004–5 | date = June 2005 | pmid = 15985565 | doi = 10.1212/01.WNL.0000166914.38327.BB | s2cid = 38482114 }}</ref>

=== Nonelectrochemical signaling非电化学信号传递 ===

Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through:
* force generated by the enlargement of dendritic spines<ref>{{cite journal |last1=Ucar |first1=Hasan |last2=Watanabe |first2=Satoshi |last3=Noguchi |first3=Jun |last4=Morimoto |first4=Yuichi |last5=Iino |first5=Yusuke |last6=Yagishita |first6=Sho |last7=Takahashi |first7=Noriko |last8=Kasai |first8=Haruo |title=Mechanical actions of dendritic-spine enlargement on presynaptic exocytosis |journal=Nature |date=December 2021 |volume=600 |issue=7890 |pages=686–689 |doi=10.1038/s41586-021-04125-7 |language=en |issn=1476-4687}} Lay summary: {{cite news |title=Forceful synapses reveal mechanical interactions in the brain |url=https://www.nature.com/articles/d41586-021-03516-0 |access-date=21 February 2022 |work=Nature |date=24 November 2021 |language=en |doi=10.1038/d41586-021-03516-0}}</ref>
* the transfer of [[protein]]s – transneuronally transported proteins (TNTPs)<ref>{{cite news |title=Researchers discover new type of cellular communication in the brain |url=https://medicalxpress.com/news/2022-01-cellular-brain.html |access-date=12 February 2022 |work=The Scripps Research Institute |language=en}}</ref><ref>{{cite journal |last1=Schiapparelli |first1=Lucio M. |last2=Sharma |first2=Pranav |last3=He |first3=Hai-Yan |last4=Li |first4=Jianli |last5=Shah |first5=Sahil H. |last6=McClatchy |first6=Daniel B. |last7=Ma |first7=Yuanhui |last8=Liu |first8=Han-Hsuan |last9=Goldberg |first9=Jeffrey L. |last10=Yates |first10=John R. |last11=Cline |first11=Hollis T. |title=Proteomic screen reveals diverse protein transport between connected neurons in the visual system |journal=Cell Reports |date=25 January 2022 |volume=38 |issue=4 |doi=10.1016/j.celrep.2021.110287 |language=English |issn=2211-1247}}</ref>

除了电和化学信号，研究表明健康人脑中的神经元还可以通过以下方式交流：
*树突棘扩大产生的力。<ref>{{cite journal |last1=Ucar |first1=Hasan |last2=Watanabe |first2=Satoshi |last3=Noguchi |first3=Jun |last4=Morimoto |first4=Yuichi |last5=Iino |first5=Yusuke |last6=Yagishita |first6=Sho |last7=Takahashi |first7=Noriko |last8=Kasai |first8=Haruo |title=Mechanical actions of dendritic-spine enlargement on presynaptic exocytosis |journal=Nature |date=December 2021 |volume=600 |issue=7890 |pages=686–689 |doi=10.1038/s41586-021-04125-7 |language=en |issn=1476-4687}} Lay summary: {{cite news |title=Forceful synapses reveal mechanical interactions in the brain |url=https://www.nature.com/articles/d41586-021-03516-0 |access-date=21 February 2022 |work=Nature |date=24 November 2021 |language=en |doi=10.1038/d41586-021-03516-0}}</ref>
*蛋白质的转移--经神经元转运蛋白（TNTPs）。<ref>{{cite news |title=Researchers discover new type of cellular communication in the brain |url=https://medicalxpress.com/news/2022-01-cellular-brain.html |access-date=12 February 2022 |work=The Scripps Research Institute |language=en}}</ref><ref>{{cite journal |last1=Schiapparelli |first1=Lucio M. |last2=Sharma |first2=Pranav |last3=He |first3=Hai-Yan |last4=Li |first4=Jianli |last5=Shah |first5=Sahil H. |last6=McClatchy |first6=Daniel B. |last7=Ma |first7=Yuanhui |last8=Liu |first8=Han-Hsuan |last9=Goldberg |first9=Jeffrey L. |last10=Yates |first10=John R. |last11=Cline |first11=Hollis T. |title=Proteomic screen reveals diverse protein transport between connected neurons in the visual system |journal=Cell Reports |date=25 January 2022 |volume=38 |issue=4 |doi=10.1016/j.celrep.2021.110287 |language=English |issn=2211-1247}}</ref>

They can also get modulated by input from the environment and [[hormone]]s released from other parts of the organism,<ref>{{cite journal |last1=Levitan |first1=Irwin B. |last2=Kaczmarek |first2=Leonard K. |title=Electrical Signaling in Neurons |doi=10.1093/med/9780199773893.001.0001/med-9780199773893-chapter-3 |publisher=Oxford University Press}}</ref> which could be influenced more or less directly by neurons. This also applies to [[neurotrophin]]s such as [[BDNF]]. The [[gut microbiome]] is also connected with the brain.<ref>{{cite journal |last1=O’Leary |first1=Olivia F. |last2=Ogbonnaya |first2=Ebere S. |last3=Felice |first3=Daniela |last4=Levone |first4=Brunno R. |last5=C. Conroy |first5=Lorraine |last6=Fitzgerald |first6=Patrick |last7=Bravo |first7=Javier A. |last8=Forsythe |first8=Paul |last9=Bienenstock |first9=John |last10=Dinan |first10=Timothy G. |last11=Cryan |first11=John F. |title=The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus |journal=European Neuropsychopharmacology |date=1 February 2018 |volume=28 |issue=2 |pages=307–316 |doi=10.1016/j.euroneuro.2017.12.004 |language=en |issn=0924-977X}}</ref>

它们也可以被来自环境的输入和机体其他部分释放的激素所调控，<ref>{{cite journal |last1=Levitan |first1=Irwin B. |last2=Kaczmarek |first2=Leonard K. |title=Electrical Signaling in Neurons |doi=10.1093/med/9780199773893.001.0001/med-9780199773893-chapter-3 |publisher=Oxford University Press}}</ref> 这些都可以或多或少地被神经元直接影响。这也适用于神经营养素，如BDNF。肠道微生物组也与大脑有关。<ref>{{cite journal |last1=O’Leary |first1=Olivia F. |last2=Ogbonnaya |first2=Ebere S. |last3=Felice |first3=Daniela |last4=Levone |first4=Brunno R. |last5=C. Conroy |first5=Lorraine |last6=Fitzgerald |first6=Patrick |last7=Bravo |first7=Javier A. |last8=Forsythe |first8=Paul |last9=Bienenstock |first9=John |last10=Dinan |first10=Timothy G. |last11=Cryan |first11=John F. |title=The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus |journal=European Neuropsychopharmacology |date=1 February 2018 |volume=28 |issue=2 |pages=307–316 |doi=10.1016/j.euroneuro.2017.12.004 |language=en |issn=0924-977X}}</ref>

==Mechanisms for propagating action potentials动作电位的传播机制==
In 1937 [[John Zachary Young]] suggested that the [[squid giant axon]] could be used to study neuronal electrical properties.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Milestones in Neuroscience Research |url = http://faculty.washington.edu/chudler/hist.html |work = Neuroscience for Kids |access-date = 2009-06-20}}</ref> It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the [[membrane potential]].

1937年，约翰-扎卡里-杨提出，乌贼巨大轴突可用于研究神经元的电特性。<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Milestones in Neuroscience Research |url = http://faculty.washington.edu/chudler/hist.html |work = Neuroscience for Kids |access-date = 2009-06-20}}</ref>它比人类神经元大，但与人类神经元相似，因此更容易研究。通过将电极插入乌贼巨轴突，对膜电位进行了精确测量。

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate [[subthreshold membrane potential oscillations]]. These signals are generated and propagated by charge-carrying [[ions]] including sodium (Na+), potassium (K+), chloride (Cl−), and [[Calcium signaling|calcium (Ca2+)]].

轴突和胞体的细胞膜含有电压门控离子通道，使神经元能够产生和传播电信号（动作电位）。一些神经元还产生阈下膜电位振荡。这些信号是由携带电荷的离子产生和传播的，包括钠（Na+）、钾（K+）、氯（Cl-）和钙（Ca2+）。

Several stimuli can activate a neuron leading to electrical activity, including [[Mechanoreceptor|pressure]], stretch, chemical transmitters, and changes of the electric potential across the cell membrane.<ref>{{cite web|first1=Joe |last1=Patlak |first2=Ray |last2=Gibbons | name-list-style = vanc |title=Electrical Activity of Nerves |url=http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |work=Action Potentials in Nerve Cells |date=2000-11-01 |access-date=2009-06-20 |url-status=dead |archive-url=https://web.archive.org/web/20090827220335/http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |archive-date=August 27, 2009 }}</ref> Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.<ref name="Harris-Warrick">{{cite journal |last1=Harris-Warrick |first1=RM |title=Neuromodulation and flexibility in Central Pattern Generator networks. |journal=Current Opinion in Neurobiology |date=October 2011 |volume=21 |issue=5 |pages=685–92 |doi=10.1016/j.conb.2011.05.011 |pmid=21646013|pmc=3171584 }}</ref>

有几种刺激可以激活神经元，导致电活动，包括压力、拉伸、化学传导物和细胞膜上的电势变化。<ref>{{cite web|first1=Joe |last1=Patlak |first2=Ray |last2=Gibbons | name-list-style = vanc |title=Electrical Activity of Nerves |url=http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |work=Action Potentials in Nerve Cells |date=2000-11-01 |access-date=2009-06-20 |url-status=dead |archive-url=https://web.archive.org/web/20090827220335/http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |archive-date=August 27, 2009 }}</ref>刺激导致细胞膜内特定的离子通道打开，使得离子流经细胞膜，改变膜电位。神经元必须保持界定其神经元类型的特定电特性。<ref name="Harris-Warrick">{{cite journal |last1=Harris-Warrick |first1=RM |title=Neuromodulation and flexibility in Central Pattern Generator networks. |journal=Current Opinion in Neurobiology |date=October 2011 |volume=21 |issue=5 |pages=685–92 |doi=10.1016/j.conb.2011.05.011 |pmid=21646013|pmc=3171584 }}</ref>

Thin neurons and axons require less [[metabolism|metabolic]] expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of [[myelin]] around their axons. The sheaths are formed by [[glia]]l cells: [[oligodendrocyte]]s in the central nervous system and [[Schwann cell]]s in the peripheral nervous system. The sheath enables action potentials to travel [[saltatory conduction|faster]] than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed [[node of Ranvier|nodes of Ranvier]], which contain a high density of voltage-gated ion channels. [[Multiple sclerosis]] is a neurological disorder that results from demyelination of axons in the central nervous system.

薄的神经元和轴突需要较少的代谢支出来产生和传导动作电位，但较粗的轴突能更快地传递冲动。为了在保持快速传导的同时尽量减少代谢支出，许多神经元的轴突周围有绝缘的髓鞘。这些髓鞘是由胶质细胞形成的：中枢神经系统的少突胶质细胞和周围神经系统的许旺细胞。髓鞘使得动作电位比相同直径的无髓轴突走得更快，同时消耗更少的能量。周围神经中的髓鞘通常沿着轴突生长，长度约为1毫米，并且点缀着无髓鞘的郎飞氏结，其中包含高密度的电压门控离子通道。多发性硬化症是一种神经系统疾病，由中枢神经系统中轴突的脱髓鞘导致。

Some neurons do not generate action potentials, but instead generate a [[graded potential|graded electrical signal]], which in turn causes graded neurotransmitter release. Such [[non-spiking neurons]] tend to be sensory neurons or interneurons, because they cannot carry signals long distances.

有些神经元不产生动作电位，而是产生一个分级的电信号，反过来引起分级的神经递质释放。这样的非脉冲神经元往往是感觉神经元或中间神经元，因为它们不能长距离携带信号。

==Neural coding神经编码==
[[Neural coding]] is concerned with how sensory and other information is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the [[Stimulus (physiology)|stimulus]] and the individual or [[Neural ensemble|ensemble]] neuronal responses, and the relationships among the electrical activities of the neurons within the ensemble.<ref name="Brown">{{cite journal | vauthors = Brown EN, Kass RE, Mitra PP | title = Multiple neural spike train data analysis: state-of-the-art and future challenges | journal = Nature Neuroscience | volume = 7 | issue = 5 | pages = 456–61 | date = May 2004 | pmid = 15114358 | doi = 10.1038/nn1228 | s2cid = 562815 }}</ref> It is thought that neurons can encode both [[Digital data|digital]] and [[analog signal|analog]] information.<ref>{{cite book | vauthors = Thorpe SJ |chapter=Spike arrival times: A highly efficient coding scheme for neural networks |chapter-url= http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf |pages= 91–94 |title=Parallel processing in neural systems and computers| veditors = Eckmiller R, Hartmann G, Hauske G |date=1990|publisher=North-Holland|isbn=9780444883902 |url={{google books |plainurl=y |id=boBqAAAAMAAJ}}|language=en|archive-url=https://web.archive.org/web/20120215151304/http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf|archive-date=2012-02-15}}</ref>

神经编码关注的是感觉和其他信息如何在大脑中被神经元所表达。研究神经编码的主要目的是描述刺激与单个或集合神经元反应之间的关系，以及集合内神经元电活动之间的关系。<ref name="Brown">{{cite journal | vauthors = Brown EN, Kass RE, Mitra PP | title = Multiple neural spike train data analysis: state-of-the-art and future challenges | journal = Nature Neuroscience | volume = 7 | issue = 5 | pages = 456–61 | date = May 2004 | pmid = 15114358 | doi = 10.1038/nn1228 | s2cid = 562815 }}</ref>人们认为，神经元既可以编码数字信息，也可以编码模拟信息。<ref>{{cite book | vauthors = Thorpe SJ |chapter=Spike arrival times: A highly efficient coding scheme for neural networks |chapter-url= http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf |pages= 91–94 |title=Parallel processing in neural systems and computers| veditors = Eckmiller R, Hartmann G, Hauske G |date=1990|publisher=North-Holland|isbn=9780444883902 |url={{google books |plainurl=y |id=boBqAAAAMAAJ}}|language=en|archive-url=https://web.archive.org/web/20120215151304/http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf|archive-date=2012-02-15}}</ref>

==All-or-none principle全有或全无原则==

[[File:All-or-none_law_en.svg|thumb|318x318px|As long as the stimulus reaches the threshold, the full response would be given. Larger stimulus does not result in a larger response, vice versa.只要刺激达到阈值，就会有充分的反应。较大的刺激不会导致较大的反应，反之亦然。<ref name=":0">{{Cite book|title=Biological psychology|last=Kalat, James W|year=2016|isbn=9781305105409|edition=12|location=Australia|oclc=898154491}}</ref>{{Rp|31}}]]
{{Main|All-or-none law}}

The conduction of nerve impulses is an example of an [[All-or-none law|all-or-none]] response. In other words, if a neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal, but can increase firing frequency.<ref name=":0" />{{Rp|31}} Receptors respond in different ways to stimuli. Slowly adapting or [[tonic (physiology)|tonic receptors]] respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can't become "stronger" for a specific frequency.

神经冲动的传导是一个全有或全无反应的例子。换句话说，如果一个神经元有任何反应，那么它必须完全响应。更大的刺激强度，如更亮的图像/更响的声音，不会产生更强的信号，但可以增加放电频率。<ref name=":0" />{{Rp|31}}受体以不同方式回应刺激。缓慢适应的或紧张性的受体对稳定的刺激作出响应，并产生稳定的放电率。紧张性受体最常通过增加其放电频率对刺激强度的增加作出反应，通常是一个与每秒钟的脉冲相关的刺激的幂函数。这可以比喻为光的内在属性，即一个特定频率（颜色）的更大强度需要更多的光子，因为光子不能对一个特定频率变得 "更强"。

Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with steady stimulus; examples include [[Human skin|skin]] which, when touched causes neurons to fire, but if the object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function.

其他受体类型包括时相性或瞬变性受体，其放电随着稳定的刺激而减少或停止；比如包括皮肤，当被触摸时引起神经元放电，但如果物体保持均匀的压力，神经元就停止放电。对压力和振动有反应的皮肤和肌肉的神经元有过滤的附属结构来帮助它们发挥作用。

The [[pacinian corpuscle]] is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus is transferred to the axon, which fires. If the pressure is steady, stimulus ends; thus, typically these neurons respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of a number of other neurons.<ref>{{cite book | last1 = Eckert | first1 = Roger | last2 = Randall | first2 = David | name-list-style = vanc | title = Animal physiology: mechanisms and adaptations | year = 1983 | publisher = W.H. Freeman | location = San Francisco | isbn = 978-0-7167-1423-1 | page = [https://archive.org/details/animalphysiology0000ecke/page/239 239] | url = https://archive.org/details/animalphysiology0000ecke/page/239 }}</ref>

帕西尼氏小体就是这样一个结构。它有像洋葱一样的同心层，围绕着轴突终端形成。当施加压力使小体变形时，机械刺激被转移到轴突上，轴突就会放电。如果压力是稳定的，刺激就会结束；因此，通常这些神经元在最初的变形过程中会有短暂的去极化反应，而当压力被移除时又会有短暂的去极化反应，从而使小体再次改变形状。其他类型的适应对扩展其他一些神经元的功能很重要。<ref>{{cite book | last1 = Eckert | first1 = Roger | last2 = Randall | first2 = David | name-list-style = vanc | title = Animal physiology: mechanisms and adaptations | year = 1983 | publisher = W.H. Freeman | location = San Francisco | isbn = 978-0-7167-1423-1 | page = [https://archive.org/details/animalphysiology0000ecke/page/239 239] | url = https://archive.org/details/animalphysiology0000ecke/page/239 }}</ref>

==Etymology and spelling词源和拼写==

The German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] introduced the term ''neuron'' in 1891,<ref name="finger"/> based on the [[Greek language|ancient Greek]] νεῦρον ''neuron'' 'sinew, cord, nerve'.<ref name="oed">''[[Oxford English Dictionary]]'', 3rd edition, 2003, ''s.v.''</ref>

德国解剖学家Heinrich Wilhelm Waldeyer于1891年提出了神经元一词，[36]其依据是古希腊语νεῦρον neuron's sinew, cord, nerve'。<ref name="finger"/> based on the [[Greek language|ancient Greek]] νεῦρον ''neuron'' 'sinew, cord, nerve'.<ref name="oed">''[[Oxford English Dictionary]]'', 3rd edition, 2003, ''s.v.''</ref>

The word was adopted in French with the spelling ''neurone''. That spelling was also used by many writers in English,<ref name="mehta">{{cite journal | vauthors = Mehta AR, Mehta PR, Anderson SP, MacKinnon BL, Compston A | title = Grey Matter Etymology and the neuron(e) | journal = Brain | volume = 143 | issue = 1 | pages = 374–379 | date = January 2020 | pmid = 31844876 | pmc = 6935745 | doi = 10.1093/brain/awz367 | url = }}</ref> but has now become rare in American usage and uncommon in British usage.<ref name="ngram">{{cite web |title=Google Books Ngram Viewer |url=https://books.google.com/ngrams/graph?content=neuron%2Cneurone&year_start=1900&year_end=2008&case_insensitive=on&corpus=15&smoothing=3&direct_url=t4%3B%2Cneuron%3B%2Cc0%3B%2Cs0%3B%3Bneuron%3B%2Cc0%3B%3BNeuron%3B%2Cc0%3B%3BNEURON%3B%2Cc0%3B.t4%3B%2Cneurone%3B%2Cc0%3B%2Cs0%3B%3Bneurone%3B%2Cc0%3B%3BNeurone%3B%2Cc0%3B%3BNEURONE%3B%2Cc0 |website=books.google.com |access-date=19 December 2020 |language=en}}</ref><ref name="oed"/>

这个词以前在法语中被采用，拼写为'neurone'。<ref name="mehta">{{cite journal | vauthors = Mehta AR, Mehta PR, Anderson SP, MacKinnon BL, Compston A | title = Grey Matter Etymology and the neuron(e) | journal = Brain | volume = 143 | issue = 1 | pages = 374–379 | date = January 2020 | pmid = 31844876 | pmc = 6935745 | doi = 10.1093/brain/awz367 | url = }}</ref>这种拼法也曾被许多英语作家使用，[38]但现在在美国的用法中已经很少见，在英国的用法中也不常见。<ref name="ngram">{{cite web |title=Google Books Ngram Viewer |url=https://books.google.com/ngrams/graph?content=neuron%2Cneurone&year_start=1900&year_end=2008&case_insensitive=on&corpus=15&smoothing=3&direct_url=t4%3B%2Cneuron%3B%2Cc0%3B%2Cs0%3B%3Bneuron%3B%2Cc0%3B%3BNeuron%3B%2Cc0%3B%3BNEURON%3B%2Cc0%3B.t4%3B%2Cneurone%3B%2Cc0%3B%2Cs0%3B%3Bneurone%3B%2Cc0%3B%3BNeurone%3B%2Cc0%3B%3BNEURONE%3B%2Cc0 |website=books.google.com |access-date=19 December 2020 |language=en}}</ref><ref name="oed"/>

==History历史==
{{Further|History of neuroscience}}
[[File:Golgi Hippocampus.jpg|left|thumb|Drawing by Camillo Golgi of a [[hippocampus]] stained using the [[silver nitrate]] method卡米洛-高尔基绘制的使用硝酸银法染色的海马体。]]
[[File:Purkinje cell by Cajal.png|thumb|Drawing of a Purkinje cell in the [[cerebellar cortex]] done by Santiago Ramón y Cajal, demonstrating the ability of Golgi's staining method to reveal fine detail圣地亚哥-拉蒙-卡亚尔（Santiago Ramón y Cajal）绘制的小脑皮层中的浦肯野细胞图，展示了高尔基染色法揭示精细细节的能力。]]

The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist [[Santiago Ramón y Cajal]].<ref name="López-Muñoz">{{cite journal | vauthors = López-Muñoz F, Boya J, Alamo C | title = Neuron theory, the cornerstone of neuroscience, on the centenary of the Nobel Prize award to Santiago Ramón y Cajal | journal = Brain Research Bulletin | volume = 70 | issue = 4–6 | pages = 391–405 | date = October 2006 | pmid = 17027775 | doi = 10.1016/j.brainresbull.2006.07.010 | s2cid = 11273256 }}</ref>

神经元作为神经系统主要功能单位的地位，在19世纪末通过西班牙解剖学家圣地亚哥-拉蒙-卡亚尔的作品首次得到承认。<ref name="López-Muñoz">{{cite journal | vauthors = López-Muñoz F, Boya J, Alamo C | title = Neuron theory, the cornerstone of neuroscience, on the centenary of the Nobel Prize award to Santiago Ramón y Cajal | journal = Brain Research Bulletin | volume = 70 | issue = 4–6 | pages = 391–405 | date = October 2006 | pmid = 17027775 | doi = 10.1016/j.brainresbull.2006.07.010 | s2cid = 11273256 }}</ref>

To make the structure of individual neurons visible, [[Santiago Ramón y Cajal|Ramón y Cajal]] improved a [[Golgi's method|silver staining process]] that had been developed by [[Camillo Golgi]].<ref name="López-Muñoz" /> The improved process involves a technique called "double impregnation" and is still in use.

为了使单个神经元的结构清晰可见，Ramón y Cajal改进了Camillo Golgi开发的银染工艺。<ref name="López-Muñoz" />改进后的工艺涉及一种称为 "双浸渍 "的技术，现在仍在使用。

In 1888 Ramón y Cajal published a paper about the bird cerebellum. In this paper, he stated that he could not find evidence for [[anastomosis]] between axons and dendrites and called each nervous element "an absolutely autonomous canton."<ref name="López-Muñoz" /><ref name="finger">{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=Ramon y Cajal's first paper on the Golgi stain was on the bird cerebellum, and it appeared in the ''Revista''<nowiki> in 1888. He acknowledged that he found the nerve fibers to be very intricate, but stated that he could find no evidence for either axons or dendrites undergoing anastomosis and forming nets. He called each nervous element 'an absolutely autonomous canton.'</nowiki>}}</ref> This became known as the [[neuron doctrine]], one of the central tenets of modern [[neuroscience]].<ref name="López-Muñoz" />

1888年，Ramón y Cajal发表了一篇关于鸟类小脑的论文。在这篇论文中，他说他找不到轴突和树突之间结合的证据，并称每个神经元素为 "一个绝对自主的州县"<ref name="López-Muñoz" /><ref name="finger">{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=Ramon y Cajal's first paper on the Golgi stain was on the bird cerebellum, and it appeared in the ''Revista''<nowiki> in 1888. He acknowledged that he found the nerve fibers to be very intricate, but stated that he could find no evidence for either axons or dendrites undergoing anastomosis and forming nets. He called each nervous element 'an absolutely autonomous canton.'</nowiki>}}</ref>，这被称为神经元学说，是现代神经科学的核心原则之一。<ref name="López-Muñoz" />

In 1891, the German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] wrote a highly influential review of the neuron doctrine in which he introduced the term ''neuron'' to describe the anatomical and physiological unit of the nervous system.<ref>{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=... a man who would write a highly influential review of the evidence in favor of the neuron doctrine two years later. In his paper, Waldeyer (1891), ... , wrote that nerve cells terminate freely with end arborizations and that the 'neuron' is the anatomical and physiological unit of the nervous system. The word 'neuron' was born this way.}}</ref><ref>{{cite web|url=http://www.whonamedit.com/doctor.cfm/1846.html|title=Whonamedit - dictionary of medical eponyms|website=www.whonamedit.com|quote=Today, Wilhelm von Waldeyer-Hartz is remembered as the founder of the neurone theory, coining the term "neurone" to describe the cellular function unit of the nervous system and enunciating and clarifying that concept in 1891.}}</ref>

1891年，德国解剖学家Heinrich Wilhelm Waldeyer写了一篇对神经元学说有很大影响的综述，他在其中提出了神经元这一术语来描述神经系统的解剖学和生理学单位。<ref>{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=... a man who would write a highly influential review of the evidence in favor of the neuron doctrine two years later. In his paper, Waldeyer (1891), ... , wrote that nerve cells terminate freely with end arborizations and that the 'neuron' is the anatomical and physiological unit of the nervous system. The word 'neuron' was born this way.}}</ref><ref>{{cite web|url=http://www.whonamedit.com/doctor.cfm/1846.html|title=Whonamedit - dictionary of medical eponyms|website=www.whonamedit.com|quote=Today, Wilhelm von Waldeyer-Hartz is remembered as the founder of the neurone theory, coining the term "neurone" to describe the cellular function unit of the nervous system and enunciating and clarifying that concept in 1891.}}</ref>

The silver impregnation stains are a useful method for [[Neuroanatomy|neuroanatomical]] investigations because, for reasons unknown, it stains only a small percentage of cells in a tissue, exposing the complete micro structure of individual neurons without much overlap from other cells.<ref name="Grant">{{cite journal | vauthors = Grant G | title = How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal | journal = Brain Research Reviews | volume = 55 | issue = 2 | pages = 490–8 | date = October 2007 | pmid = 17306375 | doi = 10.1016/j.brainresrev.2006.11.004 | s2cid = 24331507 }}</ref>

银浸渍染色法是神经解剖学研究的有效方法，因为——由于未知的原因——它只会对组织中的一小部分细胞进行染色，暴露出单个神经元的完整微观结构，而不会与其他细胞有太多的重叠。<ref name="Grant">{{cite journal | vauthors = Grant G | title = How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal | journal = Brain Research Reviews | volume = 55 | issue = 2 | pages = 490–8 | date = October 2007 | pmid = 17306375 | doi = 10.1016/j.brainresrev.2006.11.004 | s2cid = 24331507 }}</ref>

===Neuron doctrine神经元学说===
[[File:PurkinjeCell.jpg|thumb|Drawing of neurons in the pigeon [[cerebellum]], by Spanish neuroscientist [[Santiago Ramón y Cajal]] in 1899. (A) denotes [[Purkinje cell]]s and (B) denotes [[granule cells]], both of which are multipolar.鸽子小脑中的神经元图，由西班牙神经科学家圣地亚哥-拉蒙-卡亚尔于1899年绘制。(A）表示浦肯野细胞，（B）表示颗粒细胞，两者都是多极的。]]

The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramón y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in a meshwork), acting as metabolically distinct units.

神经元学说是现在的一个基本观点，即神经元是神经系统的基本结构和功能单位。该理论是由圣地亚哥-拉蒙-卡亚尔在19世纪末提出的。它认为，神经元是离散的细胞（不以网状结构连接），作为新陈代谢的不同单位发挥作用。

Later discoveries yielded refinements to the doctrine. For example, [[Neuroglia|glial cells]], which are non-neuronal, play an essential role in information processing.<ref>{{cite journal | vauthors = Witcher MR, Kirov SA, Harris KM | title = Plasticity of perisynaptic astroglia during synaptogenesis in the mature rat hippocampus | journal = Glia | volume = 55 | issue = 1 | pages = 13–23 | date = January 2007 | pmid = 17001633 | doi = 10.1002/glia.20415 | citeseerx = 10.1.1.598.7002 | s2cid = 10664003 }}</ref> Also, electrical synapses are more common than previously thought,<ref>{{cite journal | vauthors = Connors BW, Long MA | title = Electrical synapses in the mammalian brain | journal = Annual Review of Neuroscience | volume = 27 | issue = 1 | pages = 393–418 | year = 2004 | pmid = 15217338 | doi = 10.1146/annurev.neuro.26.041002.131128 | url = https://zenodo.org/record/894386 }}</ref> comprising direct, cytoplasmic connections between neurons. In fact, neurons can form even tighter couplings: the squid giant axon arises from the fusion of multiple axons.<ref>{{cite journal | vauthors = Guillery RW | title = Observations of synaptic structures: origins of the neuron doctrine and its current status | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 360 | issue = 1458 | pages = 1281–307 | date = June 2005 | pmid = 16147523 | pmc = 1569502 | doi = 10.1098/rstb.2003.1459 }}</ref>

后来的发现使这一学说得到了完善。例如，非神经元的胶质细胞在信息处理中起着至关重要的作用。<ref>{{cite journal | vauthors = Witcher MR, Kirov SA, Harris KM | title = Plasticity of perisynaptic astroglia during synaptogenesis in the mature rat hippocampus | journal = Glia | volume = 55 | issue = 1 | pages = 13–23 | date = January 2007 | pmid = 17001633 | doi = 10.1002/glia.20415 | citeseerx = 10.1.1.598.7002 | s2cid = 10664003 }}</ref>另外，电突触比以前认为得更常见，<ref>{{cite journal | vauthors = Connors BW, Long MA | title = Electrical synapses in the mammalian brain | journal = Annual Review of Neuroscience | volume = 27 | issue = 1 | pages = 393–418 | year = 2004 | pmid = 15217338 | doi = 10.1146/annurev.neuro.26.041002.131128 | url = https://zenodo.org/record/894386 }}</ref>包括神经元之间的直接胞质连接。事实上，神经元可以形成更紧密的耦合：乌贼的巨型轴突来自于多个轴突的融合。<ref>{{cite journal | vauthors = Guillery RW | title = Observations of synaptic structures: origins of the neuron doctrine and its current status | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 360 | issue = 1458 | pages = 1281–307 | date = June 2005 | pmid = 16147523 | pmc = 1569502 | doi = 10.1098/rstb.2003.1459 }}</ref>

Ramón y Cajal also postulated the Law of Dynamic Polarization, which states that a neuron receives signals at its dendrites and cell body and transmits them, as action potentials, along the axon in one direction: away from the cell body.<ref name="sabb">{{cite journal | vauthors = Sabbatini RM | date = April–July 2003 | url = http://www.cerebromente.org.br/n17/history/neurons3_i.htm | title = Neurons and Synapses: The History of Its Discovery | journal = Brain & Mind Magazine | pages = 17 }}</ref> The Law of Dynamic Polarization has important exceptions; dendrites can serve as synaptic output sites of neurons<ref>{{cite journal | vauthors = Djurisic M, Antic S, Chen WR, Zecevic D | title = Voltage imaging from dendrites of mitral cells: EPSP attenuation and spike trigger zones | journal = The Journal of Neuroscience | volume = 24 | issue = 30 | pages = 6703–14 | date = July 2004 | pmid = 15282273 | pmc = 6729725 | doi = 10.1523/JNEUROSCI.0307-04.2004 | hdl = 1912/2958 }}
</ref> and axons can receive synaptic inputs.<ref>{{cite journal | vauthors = Cochilla AJ, Alford S | title = Glutamate receptor-mediated synaptic excitation in axons of the lamprey | journal = The Journal of Physiology | volume = 499 | issue = Pt 2 | pages = 443–57 | date = March 1997 | pmid = 9080373 | pmc = 1159318 | doi = 10.1113/jphysiol.1997.sp021940 }}</ref>

拉蒙-卡哈尔还提出了动态极化定律，即神经元在其树突和细胞体上接收信号，并作为动作电位沿轴突向一个方向传输：离开细胞体。<ref name="sabb">{{cite journal | vauthors = Sabbatini RM | date = April–July 2003 | url = http://www.cerebromente.org.br/n17/history/neurons3_i.htm | title = Neurons and Synapses: The History of Its Discovery | journal = Brain & Mind Magazine | pages = 17 }}</ref> 动态极化定律有重要的例外；树突可以作为神经元的突触输出点<ref>{{cite journal | vauthors = Djurisic M, Antic S, Chen WR, Zecevic D | title = Voltage imaging from dendrites of mitral cells: EPSP attenuation and spike trigger zones | journal = The Journal of Neuroscience | volume = 24 | issue = 30 | pages = 6703–14 | date = July 2004 | pmid = 15282273 | pmc = 6729725 | doi = 10.1523/JNEUROSCI.0307-04.2004 | hdl = 1912/2958 }}
</ref>，轴突可以接受突触输入。<ref>{{cite journal | vauthors = Cochilla AJ, Alford S | title = Glutamate receptor-mediated synaptic excitation in axons of the lamprey | journal = The Journal of Physiology | volume = 499 | issue = Pt 2 | pages = 443–57 | date = March 1997 | pmid = 9080373 | pmc = 1159318 | doi = 10.1113/jphysiol.1997.sp021940 }}</ref>

===Compartmental modelling of neurons 神经元的间室模型===

Although neurons are often described of as "fundamental units" of the brain, they perform internal computations. Neurons integrate input within dendrites, and this complexity is lost in models that assume neurons to be a fundamental unit. Dendritic branches can be modeled as spatial compartments, whose activity is related due to passive membrane properties, but may also be different depending on input from synapses. [[Compartmental modelling of dendrites]] is especially helpful for understanding the behavior of neurons that are too small to record with electrodes, as is the case for ''Drosophila melanogaster''.<ref>{{cite journal | vauthors = Gouwens NW, Wilson RI | title = Signal propagation in Drosophila central neurons | journal = Journal of Neuroscience | volume = 29 | issue = 19 | pages = 6239–6249 | year = 2009 | pmid = 19439602 | pmc = 2709801 | doi = 10.1523/jneurosci.0764-09.2009 | doi-access = free }}</ref>

尽管神经元经常被描述为大脑的 "基本单位"，但它们执行内部计算。神经元在树突内整合输入，这种复杂性在假定神经元是一个基本单位的模型中丢失。树突分支可以被建模为空间隔间，其活性与被动膜特性相关，但也可能因来自突触的输入的差异而有所不同。树突的间室模型对于理解那些太小而无法用电极记录的神经元的行为特别有帮助，黑腹果蝇就是这种情况。<ref>{{cite journal | vauthors = Gouwens NW, Wilson RI | title = Signal propagation in Drosophila central neurons | journal = Journal of Neuroscience | volume = 29 | issue = 19 | pages = 6239–6249 | year = 2009 | pmid = 19439602 | pmc = 2709801 | doi = 10.1523/jneurosci.0764-09.2009 | doi-access = free }}</ref>

==Neurons in the brain大脑中的神经元==

The number of neurons in the brain varies dramatically from species to species.<ref name="nervenet">{{cite journal | vauthors = Williams RW, Herrup K | title = The control of neuron number | journal = Annual Review of Neuroscience | volume = 11 | issue = 1 | pages = 423–53 | year = 1988 | pmid = 3284447 | doi = 10.1146/annurev.ne.11.030188.002231 }}</ref> In a human, there are an estimated 10–20 billion neurons in the [[cerebral cortex]] and 55–70 billion neurons in the [[cerebellum]].<ref name="pmid27187682">{{cite journal | vauthors = von Bartheld CS, Bahney J, Herculano-Houzel S | title = The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting | journal = The Journal of Comparative Neurology | volume = 524 | issue = 18 | pages = 3865–3895 | date = December 2016 | pmid = 27187682 | pmc = 5063692 | doi = 10.1002/cne.24040 }}</ref> By contrast, the [[nematode]] worm ''[[Caenorhabditis elegans]]'' has just 302 neurons, making it an ideal [[model organism]] as scientists have been able to map all of its neurons. The fruit fly ''[[Drosophila melanogaster]]'', a common subject in biological experiments, has around 100,000 neurons and exhibits many complex behaviors. Many properties of neurons, from the type of neurotransmitters used to ion channel composition, are maintained across species, allowing scientists to study processes occurring in more complex organisms in much simpler experimental systems.

大脑中的神经元数量因物种不同而有很大差异。<ref name="nervenet">{{cite journal | vauthors = Williams RW, Herrup K | title = The control of neuron number | journal = Annual Review of Neuroscience | volume = 11 | issue = 1 | pages = 423–53 | year = 1988 | pmid = 3284447 | doi = 10.1146/annurev.ne.11.030188.002231 }}</ref>在人类中，大脑皮层中估计有100-200亿个神经元，小脑中有550-700亿个神经元。<ref name="pmid27187682">{{cite journal | vauthors = von Bartheld CS, Bahney J, Herculano-Houzel S | title = The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting | journal = The Journal of Comparative Neurology | volume = 524 | issue = 18 | pages = 3865–3895 | date = December 2016 | pmid = 27187682 | pmc = 5063692 | doi = 10.1002/cne.24040 }}</ref>相比之下，秀丽隐杆线虫只有302个神经元，使其成为理想的模型生物，因为科学家已经能够绘制其所有的神经元。黑腹果蝇是生物实验中常见的对象，它有大约10万个神经元，表现出许多复杂的行为。神经元的许多特性，从使用的神经递质类型到离子通道组成，在不同的物种中都保持不变，使科学家能够在更简单的实验系统中研究发生在更复杂生物体中的过程。

==Neurological disorders神经系统疾病==
{{Main主要文章|Neurology神经病学}}
{{More citations needed|date=May 2018}}

'''[[Charcot–Marie–Tooth disease]]''' (CMT) is a heterogeneous inherited disorder of nerves ([[neuropathy]]) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs extending to the hands and arms in advanced stages. Presently incurable, this disease is one of the most common inherited neurological disorders, with 36 in 100,000 affected.<ref name=Krajewski>{{cite journal | vauthors = Krajewski KM, Lewis RA, Fuerst DR, Turansky C, Hinderer SR, Garbern J, Kamholz J, Shy ME | title = Neurological dysfunction and axonal degeneration in Charcot-Marie-Tooth disease type 1A | journal = Brain | volume = 123 | issue = 7 | pages = 1516–27 | date = July 2000 | pmid = 10869062 | doi = 10.1093/brain/123.7.1516 | doi-access = free }}</ref>

腓骨肌萎缩症（CMT）是一种异质性的遗传性神经疾病（神经病变），其特点是肌肉组织和触觉的丧失，主要是在脚和腿上，在晚期会延伸到手和胳膊。该病目前无法治愈，是最常见的遗传性神经系统疾病之一，每10万人中会有36人罹患此病。<ref name=Krajewski>{{cite journal | vauthors = Krajewski KM, Lewis RA, Fuerst DR, Turansky C, Hinderer SR, Garbern J, Kamholz J, Shy ME | title = Neurological dysfunction and axonal degeneration in Charcot-Marie-Tooth disease type 1A | journal = Brain | volume = 123 | issue = 7 | pages = 1516–27 | date = July 2000 | pmid = 10869062 | doi = 10.1093/brain/123.7.1516 | doi-access = free }}</ref>

'''[[Alzheimer's disease]]''' (AD), also known simply as ''Alzheimer's'', is a [[neurodegenerative disease]] characterized by progressive [[cognitive]] deterioration, together with declining activities of daily living and [[neuropsychiatric]] symptoms or behavioral changes.<ref name="nihstages">{{cite web|title=About Alzheimer's Disease: Symptoms|url=http://www.nia.nih.gov/alzheimers/topics/symptoms|publisher=National Institute on Aging|access-date=28 December 2011|url-status=live|archive-url=https://web.archive.org/web/20120115201854/http://www.nia.nih.gov/alzheimers/topics/symptoms|archive-date=15 January 2012|df=dmy-all}}</ref> The most striking early symptom is loss of short-term memory ([[amnesia]]), which usually manifests as minor forgetfulness that becomes steadily more pronounced with illness progression, with relative preservation of older memories. As the disorder progresses, cognitive (intellectual) impairment extends to the domains of language ([[aphasia]]), skilled movements ([[apraxia]]), and recognition ([[agnosia]]), and functions such as decision-making and planning become impaired.<ref name="BMJ2009">{{cite journal | vauthors = Burns A, Iliffe S | title = Alzheimer's disease | journal = BMJ | volume = 338 | pages = b158 | date = February 2009 | pmid = 19196745 | doi = 10.1136/bmj.b158 | s2cid = 8570146 | url = https://semanticscholar.org/paper/0fccf0616b35e3bb427c3783a44777e4dc228713 }}</ref><ref name=NEJM2010>{{cite journal | vauthors = Querfurth HW, LaFerla FM | title = Alzheimer's disease | journal = The New England Journal of Medicine | volume = 362 | issue = 4 | pages = 329–44 | date = January 2010 | pmid = 20107219 | doi = 10.1056/NEJMra0909142 | s2cid = 205115756 | url = https://semanticscholar.org/paper/7bc445c5ddf7869b9f71a5390ff9e9e992533ee3 }}</ref>

阿尔茨海默病（AD），也被简单地称为阿尔茨海默病，是一种神经退行性疾病，其特点是认知能力逐渐退化，伴随着日常生活活动能力下降和神经精神症状或行为变化。<ref name="nihstages">{{cite web|title=About Alzheimer's Disease: Symptoms|url=http://www.nia.nih.gov/alzheimers/topics/symptoms|publisher=National Institute on Aging|access-date=28 December 2011|url-status=live|archive-url=https://web.archive.org/web/20120115201854/http://www.nia.nih.gov/alzheimers/topics/symptoms|archive-date=15 January 2012|df=dmy-all}}</ref>最突出的早期症状是短期记忆的丧失（失忆），通常表现为轻微的遗忘，随着病情的发展，遗忘的程度会逐渐加重，但老的记忆却记忆得相对清楚。随着病情的发展，认知（智力）损害扩展到语言（失语）、熟练动作（失用）和识别（失认）等领域，决策和计划等功能也会受到损害。<ref name="BMJ2009">{{cite journal | vauthors = Burns A, Iliffe S | title = Alzheimer's disease | journal = BMJ | volume = 338 | pages = b158 | date = February 2009 | pmid = 19196745 | doi = 10.1136/bmj.b158 | s2cid = 8570146 | url = https://semanticscholar.org/paper/0fccf0616b35e3bb427c3783a44777e4dc228713 }}</ref><ref name=NEJM2010>{{cite journal | vauthors = Querfurth HW, LaFerla FM | title = Alzheimer's disease | journal = The New England Journal of Medicine | volume = 362 | issue = 4 | pages = 329–44 | date = January 2010 | pmid = 20107219 | doi = 10.1056/NEJMra0909142 | s2cid = 205115756 | url = https://semanticscholar.org/paper/7bc445c5ddf7869b9f71a5390ff9e9e992533ee3 }}</ref>

'''[[Parkinson's disease]]''' (PD), also known as ''Parkinson disease'', is a degenerative disorder of the central nervous system that often impairs motor skills and speech.<ref name=NIH2016>{{cite web|title=Parkinson's Disease Information Page|url=https://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|website=NINDS|access-date=18 July 2016|date=30 June 2016|url-status=live|archive-url=https://web.archive.org/web/20170104201403/http://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|archive-date=4 January 2017|df=dmy-all}}</ref> Parkinson's disease belongs to a group of conditions called [[movement disorders]].<ref>{{cite web | title = Movement Disorders| url = http://www.neuromodulation.com/movement-disorders | work = The International Neuromodulation Society }}</ref> It is characterized by muscle rigidity, [[tremor]], a slowing of physical movement ([[bradykinesia]]), and in extreme cases, a loss of physical movement ([[akinesia]]). The primary symptoms are the results of decreased stimulation of the [[motor cortex]] by the [[basal ganglia]], normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level [[cognitive dysfunction]] and subtle language problems. PD is both chronic and progressive.

帕金森病（PD），又称帕金森病，是一种中枢神经系统的退行性疾病，通常会损害运动技能和语言能力。<ref name=NIH2016>{{cite web|title=Parkinson's Disease Information Page|url=https://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|website=NINDS|access-date=18 July 2016|date=30 June 2016|url-status=live|archive-url=https://web.archive.org/web/20170104201403/http://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|archive-date=4 January 2017|df=dmy-all}}</ref> 帕金森病属于一组被称为运动障碍的疾病。<ref>{{cite web | title = Movement Disorders| url = http://www.neuromodulation.com/movement-disorders | work = The International Neuromodulation Society }}</ref>它的特点是肌肉僵硬、震颤、身体运动变慢（运动迟缓），在极端情况下，身体运动丧失（运动不能）。主要症状是基底神经节对运动皮层刺激减少的结果，通常是由于大脑多巴胺能神经元中产生的多巴胺形成和作用不足造成的。次要症状可能包括高水平的认知功能障碍和微妙的语言问题。帕金森病既是慢性的，也是渐进的。

'''[[Myasthenia gravis]]''' is a neuromuscular disease leading to fluctuating [[muscle weakness]] and fatigability during simple activities. Weakness is typically caused by circulating [[antibodies]] that block [[acetylcholine receptors]] at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with [[immunosuppressants]], [[cholinesterase]] inhibitors and, in selected cases, [[thymectomy]].

重症肌无力是一种神经肌肉疾病，导致简单活动时出现波动性的肌肉无力和疲劳。肌无力通常是由阻断突触后神经肌肉接头处的乙酰胆碱受体的循环抗体引起的，它抑制了神经递质乙酰胆碱的刺激作用。肌无力症用免疫抑制剂、胆碱酯酶抑制剂来治疗，在某些情况下还可以进行胸腺切除术。

===Demyelination脱髓鞘症===
{{Further|Demyelinating disease}}
[[File:Guillain-barré syndrome - Nerve Damage.gif|thumb|Guillain–Barré syndrome – demyelination格林-巴利综合征——脱髓鞘症]]

[[Demyelination]] is the act of demyelinating, or the loss of the myelin sheath insulating the nerves. When myelin degrades, conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. This leads to certain neurodegenerative disorders like [[multiple sclerosis]] and [[chronic inflammatory demyelinating polyneuropathy]].

脱髓鞘是指脱髓鞘的行为，或绝缘于神经的髓鞘的丧失。当髓鞘退化时，信号沿神经的传导会受到影响或丧失，神经最终会萎缩。这导致了某些神经退行性疾病，如多发性硬化症和慢性炎症性脱髓鞘多发性神经病。

===Axonal degeneration轴突变性===
Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration, which is the rapid separation of the proximal and distal ends, occurring within 30 minutes of injury. Degeneration follows with swelling of the [[axolemma]], and eventually leads to bead-like formation. Granular disintegration of the axonal [[cytoskeleton]] and inner [[organelle]]s occurs after axolemma degradation. Early changes include accumulation of [[mitochondria]] in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The disintegration is dependent on [[ubiquitin]] and [[calpain]] [[proteases]] (caused by the influx of calcium ion), suggesting that axonal degeneration is an active process that produces complete fragmentation. The process takes about roughly 24 hours in the PNS and longer in the CNS. The signaling pathways leading to axolemma degeneration are unknown.

尽管大多数损伤反应包括钙离子流入信号，以促进断裂部分的重新愈合，但轴突损伤最初会导致急性轴突变性，即在损伤后30分钟内近端和远端迅速分离。退化后，轴突肿胀，最终形成串珠状肿胀。轴索细胞骨架和内部细胞器的颗粒状解体发生在轴索退化之后。早期的变化包括线粒体在损伤部位的结旁区堆积。内质网降解、线粒体膨胀并最终解体。解体依赖于泛素和钙蛋白酶（由钙离子的涌入引起），表明轴突变性是一个完全破碎的活跃过程。这一过程在PNS（周围神经系统）中大约需要24小时，在CNS（中枢神经系统）中则需要更长时间。导致轴突变性的信号传导途径尚不清楚。

==Neurogenesis神经发生==
{{Main|Neurogenesis}}

Neurons are born through the process of [[neurogenesis]], in which [[neural stem cell]]s divide to produce differentiated neurons. Once fully differentiated neurons are formed, they are no longer capable of undergoing [[mitosis]]. Neurogenesis primarily occurs in the embryo of most organisms.

神经元是通过神经发生的过程诞生的，其中神经干细胞分裂产生分化的神经元。一旦完全分化的神经元形成，它们就不再能够进行有丝分裂。神经发生主要发生在大多数生物体的胚胎中。

[[Adult neurogenesis]] can occur and studies of the age of human neurons suggest that this process occurs only for a minority of cells, and that the vast majority of neurons in the [[neocortex]] forms before birth and persists without replacement. The extent to which adult neurogenesis exists in humans, and its contribution to cognition are controversial, with conflicting reports published in 2018.<ref>{{cite journal | vauthors = Kempermann G, Gage FH, Aigner L, Song H, Curtis MA, Thuret S, Kuhn HG, Jessberger S, Frankland PW, Cameron HA, Gould E, Hen R, Abrous DN, Toni N, Schinder AF, Zhao X, Lucassen PJ, Frisén J | title = Human Adult Neurogenesis: Evidence and Remaining Questions | journal = Cell Stem Cell | volume = 23 | issue = 1 | pages = 25–30 | date = July 2018 | pmid = 29681514 | pmc = 6035081 | doi = 10.1016/j.stem.2018.04.004 }}</ref>

成年神经发生能够发生，对人类神经元年龄的研究表明，这一过程只发生在少数细胞中，新皮层中的绝大多数神经元在出生前就已形成，并持续存在而不被替换。人类中成年神经发生存在的程度，以及它对认知的贡献是有争议的，2018年发表的报告相互矛盾。<ref>{{cite journal | vauthors = Kempermann G, Gage FH, Aigner L, Song H, Curtis MA, Thuret S, Kuhn HG, Jessberger S, Frankland PW, Cameron HA, Gould E, Hen R, Abrous DN, Toni N, Schinder AF, Zhao X, Lucassen PJ, Frisén J | title = Human Adult Neurogenesis: Evidence and Remaining Questions | journal = Cell Stem Cell | volume = 23 | issue = 1 | pages = 25–30 | date = July 2018 | pmid = 29681514 | pmc = 6035081 | doi = 10.1016/j.stem.2018.04.004 }}</ref>

The body contains a variety of stem cell types that have the capacity to differentiate into neurons. Researchers found a way to transform human skin cells into nerve cells using [[transdifferentiation]], in which "cells are forced to adopt new identities".<ref name=twsX33>{{Cite journal |doi=10.1038/news.2011.328 | last = Callaway | first = Ewen |title= How to make a human neuron | journal = Nature |quote= By transforming cells from human skin into working nerve cells, researchers may have come up with a model for nervous-system diseases and perhaps even regenerative therapies based on cell transplants. The achievement, reported online today in ''Nature'', is the latest in a fast-moving field called transdifferentiation, in which cells are forced to adopt new identities. In the past year, researchers have converted connective tissue cells found in skin into heart cells, blood cells, and liver cells.
|date= 26 May 2011 }}</ref>

人体含有各种干细胞类型，它们有能力分化为神经元。研究人员发现了一种利用横向分化将人类皮肤细胞转化为神经细胞的方法，其中 "细胞被迫采用新的身份"。<ref name=twsX33>{{Cite journal |doi=10.1038/news.2011.328 | last = Callaway | first = Ewen |title= How to make a human neuron | journal = Nature |quote= By transforming cells from human skin into working nerve cells, researchers may have come up with a model for nervous-system diseases and perhaps even regenerative therapies based on cell transplants. The achievement, reported online today in ''Nature'', is the latest in a fast-moving field called transdifferentiation, in which cells are forced to adopt new identities. In the past year, researchers have converted connective tissue cells found in skin into heart cells, blood cells, and liver cells.
|date= 26 May 2011 }}</ref>

During [[neurogenesis]] in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that populate cortical layers. [[Epigenetics|Epigenetic]] modifications play a key role in regulating [[gene expression]] in differentiating [[neural stem cells]], and are critical for cell fate determination in the developing and adult mammalian brain. Epigenetic modifications include [[DNA methylation|DNA cytosine methylation]] to form [[5-methylcytosine]] and [[DNA demethylation|5-methylcytosine demethylation]].<ref name=Wang2016>{{cite journal | vauthors = Wang Z, Tang B, He Y, Jin P | title = DNA methylation dynamics in neurogenesis | journal = Epigenomics | volume = 8 | issue = 3 | pages = 401–14 | date = March 2016 | pmid = 26950681 | pmc = 4864063 | doi = 10.2217/epi.15.119 }}</ref> These modifications are critical for cell fate determination in the developing and adult mammalian brain. [[DNA methylation|DNA cytosine methylation]] is catalyzed by [[DNA methyltransferase|DNA methyltransferases (DNMTs)]]. Methylcytosine demethylation is catalyzed in several stages by [[TET enzymes]] that carry out oxidative reactions (e.g. [[5-methylcytosine]] to [[5-hydroxymethylcytosine]]) and enzymes of the DNA [[base excision repair]] (BER) pathway.<ref name=Wang2016/>

在哺乳动物大脑的神经发生过程中，祖细胞和干细胞从增殖性分裂发展到分化性分裂。这一进展导致了皮层中的神经元和胶质细胞的出现。表观遗传学修饰在调节分化中的神经干细胞的基因表达方面起着关键作用，对发育中和成年哺乳动物大脑中的细胞命运决定至关重要。表观遗传修饰包括DNA胞嘧啶甲基化形成5-甲基胞嘧啶和5-甲基胞嘧啶去甲基化。<ref name=Wang2016>{{cite journal | vauthors = Wang Z, Tang B, He Y, Jin P | title = DNA methylation dynamics in neurogenesis | journal = Epigenomics | volume = 8 | issue = 3 | pages = 401–14 | date = March 2016 | pmid = 26950681 | pmc = 4864063 | doi = 10.2217/epi.15.119 }}</ref>这些修饰对于发育中和成年哺乳动物大脑的细胞命运决定至关重要。DNA胞嘧啶甲基化是由DNA甲基转移酶（DNMTs）催化的。甲基胞嘧啶去甲基化是由进行氧化反应（如5-甲基胞嘧啶到5-羟甲基胞嘧啶）的TET酶和DNA碱基切除修复（BER）途径的酶分几个阶段催化的。<ref name=Wang2016/>

At different stages of mammalian nervous system development two DNA repair processes are employed in the repair of DNA double-strand breaks. These pathways are [[homologous recombination]]al repair used in proliferating neural precursor cells, and [[non-homologous end joining]] used mainly at later developmental stages<ref>{{cite journal | vauthors = Orii KE, Lee Y, Kondo N, McKinnon PJ | title = Selective utilization of nonhomologous end-joining and homologous recombination DNA repair pathways during nervous system development | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 26 | pages = 10017–22 | date = June 2006 | pmid = 16777961 | pmc = 1502498 | doi = 10.1073/pnas.0602436103 | bibcode = 2006PNAS..10310017O | doi-access = free }}</ref>

在哺乳动物神经系统发育的不同阶段，有两种DNA修复过程被用于修复DNA双链断裂。这些途径是用于增殖期神经前体细胞的同源重组修复，以及主要用于后期发育阶段的非同源末端连接。<ref>{{cite journal | vauthors = Orii KE, Lee Y, Kondo N, McKinnon PJ | title = Selective utilization of nonhomologous end-joining and homologous recombination DNA repair pathways during nervous system development | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 26 | pages = 10017–22 | date = June 2006 | pmid = 16777961 | pmc = 1502498 | doi = 10.1073/pnas.0602436103 | bibcode = 2006PNAS..10310017O | doi-access = free }}</ref>

==Nerve regeneration神经再生==
{{Main|Neuroregeneration}}
Peripheral axons can regrow if they are severed,<ref name="Yiu_2006">{{cite journal | vauthors = Yiu G, He Z | title = Glial inhibition of CNS axon regeneration | journal = Nature Reviews. Neuroscience | volume = 7 | issue = 8 | pages = 617–27 | date = August 2006 | pmid = 16858390 | pmc = 2693386 | doi = 10.1038/nrn1956 }}</ref> but one neuron cannot be functionally replaced by one of another type ([[Llinás' law]]).<ref name="llinas2014"/>

外围轴突如果被切断，可以重新生长，<ref name="Yiu_2006">{{cite journal | vauthors = Yiu G, He Z | title = Glial inhibition of CNS axon regeneration | journal = Nature Reviews. Neuroscience | volume = 7 | issue = 8 | pages = 617–27 | date = August 2006 | pmid = 16858390 | pmc = 2693386 | doi = 10.1038/nrn1956 }}</ref>但一个神经元在功能上不能被另一种类型的神经元取代（Llinás法则）。<ref name="llinas2014"/>

== See also ==
{{Div col|colwidth=20em}}
* [[Artificial neuron]]
* [[Bidirectional cell]]
* [[Biological neuron model]]
* [[Compartmental neuron models]]
* [[Connectome]]
* [[Dogiel cell]]
* [[List of animals by number of neurons]]
* [[List of neuroscience databases]]
* [[Neuronal galvanotropism]]
* [[Neuroplasticity]]
* [[Growth cone]]
* [[Sholl analysis]]
{{Div col end}}

*人工神经元
*双向细胞
*生物神经元模型
*间室神经元模型
*连接组
*锥体细胞
*按神经元数量排列的动物名单
*神经科学数据库列表
*神经元向电性
*神经可塑性
*生长锥
*肖尔分析

== References参考文献 ==

{{Reflist}}

== Further reading进一步阅读 ==
{{refbegin}}
* {{cite journal | vauthors = Bullock TH, Bennett MV, Johnston D, Josephson R, Marder E, Fields RD | title = Neuroscience. The neuron doctrine, redux | journal = Science | volume = 310 | issue = 5749 | pages = 791–3 | date = November 2005 | pmid = 16272104 | doi = 10.1126/science.1114394 | s2cid = 170670241 }}
* {{Cite book | vauthors = Kandel ER, Schwartz JH, Jessell TM |year=2000 |title=Principles of Neural Science |edition=4th |publisher=McGraw-Hill |location=New York |isbn=0-8385-7701-6 }}
* {{Cite book | vauthors = Peters A, Palay SL, Webster HS |year=1991 |title=The Fine Structure of the Nervous System |edition=3rd |location=New York |publisher=Oxford University Press |isbn=0-19-506571-9 }}
* {{Cite book | vauthors = Ramón y Cajal S |year=1933 |title=Histology |edition=10th |publisher=Wood |location=Baltimore }}
* {{Cite book | vauthors = Roberts A, Bush BM |year=1981 |title=Neurones without Impulses |publisher=Cambridge University Press |location=Cambridge |isbn=0-521-29935-7 }}
* {{Cite book |title=Clinical Neuroanatomy | vauthors = Snell RS |date=2010 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-9427-5 |language=en |url=https://www.google.com/books/edition/_/ABPmvroyrD0C }}
{{refend}}

== External links外部链接 ==
{{sisterlinks|d=Q43054|n=no|b=Human_Anatomy/The_Neuron|v=no|voy=no|wikt=neuron|m=no|mw=no|s=no|species=no}}
*{{Curlie|Science/Biology/Neurobiology/|Neurobiology}}
* [https://web.archive.org/web/20130425202653/http://ibro.info/ IBRO (International Brain Research Organization)]. Fostering neuroscience research especially in less well-funded countries.
* [http://NeuronBank.org NeuronBank] an online neuromics tool for cataloging neuronal types and synaptic connectivity.
* [https://web.archive.org/web/20190621124504/http://brainmaps.org/ High Resolution Neuroanatomical Images of Primate and Non-Primate Brains].
* The [[v:Topic:Neuroscience|Department of Neuroscience]] at [[v:|Wikiversity]], which presently offers two courses: [[v:Fundamentals of Neuroscience|Fundamentals of Neuroscience]] and [[v:Comparative Neuroscience|Comparative Neuroscience]].
* [https://www.neuinfo.org/mynif/search.php?q=Neuron&t=data&s=cover&b=0&r=20 NIF Search – Neuron] via the [[Neuroscience Information Framework]]
* [https://web.archive.org/web/20110813070057/http://ccdb.ucsd.edu/sand/main?event=showMPByType&typeid=0&start=1&pl=y Cell Centered Database – Neuron]
* [http://neurolex.org/wiki/Category:Neuron Complete list of neuron types] according to the Petilla convention, at [[NeuroLex]].
* [http://NeuroMorpho.org NeuroMorpho.Org] an online database of digital reconstructions of neuronal morphology.
* [https://web.archive.org/web/20111008142032/http://www.immunoportal.com/modules.php?name=gallery2&g2_view=keyalbum.KeywordAlbum&g2_keyword=Neuron Immunohistochemistry Image Gallery: Neuron]
* [https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/v/anatomy-of-a-neuron Khan Academy: Anatomy of a neuron]
* [http://www.histology-world.com/photoalbum/thumbnails.php?album=96 Neuron images]

* IBRO (国际大脑研究组织)。促进神经科学研究，尤其是在资金不足的国家。
* NeuronBank 是一个在线神经病学工具，用于编目神经元类型和突触连接。
* 灵长类动物和非灵长类动物大脑的高分辨率神经解剖图像。
* 维基大学神经科学系，目前提供两门课程: 神经科学基础和比较神经科学。
* NIF 搜索-神经元通过神经科学信息框架
* 细胞中心数据库-神经元
* 完整的神经元类型清单根据 Petilla 公约，在 NeuroLex。
* NeuroMorpho. Org，一个神经形态学数字重建的在线数据库。
* Immunohistochemistry Image Gallery: Neuron
* Khan Academy: Anatomy of a neuron
* Neuron images

{{Nervous system tumors}}
{{Nervous tissue}}
{{Portal bar|Biology|Medicine}}
{{Authority control}}

[[Category:Neurons| ]]
[[Category:Medical terminology]]

Category:Medical terminology

类别: 医学术语

<noinclude>

This page was moved from [[wikipedia:en:Neuron]]. Its edit history can be viewed at [[神经元/edithistory]]</noinclude>

[[Category:待整理页面]]

神经元

2022-04-30T06:59:32Z

耿淅耀：

此词条由神经动力学读书会词条梳理志愿者[[用户:Autumnwolfberry|Autumnwolfberry]]翻译审校，未经专家审核，带来阅读不便，请见谅。

{{short description|Electrically excitable cell that communicates via synapses}}
{{About|the type of cell}}
{{Distinguish|Neutron}}
{{Infobox neuron
|name = Neuron
|image = Blausen 0657 MultipolarNeuron.png
|caption =Anatomy of a [[multipolar neuron]]
|function =
|neurotransmitter =
|morphology =
|afferents =
|efferents =
}}

A '''neuron''' or '''nerve cell''' is an [[membrane potential#Cell excitability|electrically excitable]] [[cell (biology)|cell]] that communicates with other cells via specialized connections called [[synapse]]s. The neuron is the main component of [[nervous tissue]] in all [[Animalia|animals]] except [[sponge]]s and [[placozoa]]. [[Plant]]s and [[fungi]] do not have nerve cells.

神经元或神经细胞是一种可电兴奋的细胞，通过称为突触的专门连接与其他细胞进行交流。神经元是所有动物神经组织的主要组成部分，除了海绵动物门和扁盘动物门。植物和真菌没有神经细胞。

Neurons are typically classified into three types based on their function. [[Sensory neuron]]s respond to [[Stimulus (physiology)|stimuli]] such as touch, sound, or light that affect the cells of the [[Sense|sensory organs]], and they send signals to the spinal cord or brain. [[Motor neuron]]s receive signals from the brain and spinal cord to control everything from [[muscle contraction]]s to [[gland|glandular output]]. [[Interneuron]]s connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together they form what is called a [[neural circuit]].

神经元通常根据其功能被分为三种类型。感觉神经元对影响感觉器官细胞的刺激，如触摸、声音或光线作出反应，并向脊髓或大脑发送信号。运动神经元接收来自大脑和脊髓的信号，控制从肌肉收缩到腺体输出的一切。中间神经元将神经元与大脑或脊髓同一区域内的其他神经元连接起来。当多个神经元连接在一起时，它们形成所谓的神经回路。

A typical neuron consists of a cell body ([[Soma (biology)|soma]]), [[dendrite]]s, and a single [[axon]]. The soma is a compact structure and the axon and dendrites are filaments extruding from the soma. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The axon leaves the soma at a swelling called the [[axon hillock]] and travels for as far as 1 meter in humans or more in other species. It branches but usually maintains a constant diameter. At the farthest tip of the axon's branches are [[axon terminals]], where the neuron can transmit a signal across the [[synapse]] to another cell. Neurons may lack dendrites or have no axon. The term [[neurite]] is used to describe either a dendrite or an axon, particularly when the cell is [[Cellular differentiation|undifferentiated]].

一个典型的神经元由一个细胞体（soma：胞体）、树突和一个轴突组成。胞体是一个紧凑的结构，轴突和树突是从胞体中挤出的丝状物。树突通常有大量的分支，并从胞体中延伸出几百微米。轴突在一个称为轴突丘的肿胀处离开胞体，在人类中最远可达1米，在其他物种中则更远。它有分支，但通常保持一个恒定的直径。在轴突分支的最远端是轴突终端，在那里神经元可以通过突触向另一个细胞传递信号。神经元可能缺乏树突或没有轴突。术语神经突被用来描述树突或轴突，特别是当细胞未分化时。

Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to a dendrite of another. However, synapses can connect an axon to another axon or a dendrite to another dendrite.

大多数神经元通过树突和胞体接收信号，并沿轴突发出信号。在大多数突触中，信号从一个神经元的轴突交叉到另一个神经元的树突。然而，突触可以将一个轴突连接到另一个轴突，或者将一个树突连接到另一个树突。

The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to maintenance of [[voltage]] gradients across their [[Cell membrane|membranes]]. If the voltage changes by a large enough amount over a short interval, the neuron generates an [[All-or-none law|all-or-nothing]] [[electrochemical]] pulse called an [[action potential]]. This potential travels rapidly along the axon and activates synaptic connections as it reaches them. Synaptic signals may be [[Excitatory postsynaptic potential|excitatory]] or [[Inhibitory postsynaptic potential|inhibitory]], increasing or reducing the net voltage that reaches the soma.

信号传递过程部分是电子的，部分是化学的。神经元具有电兴奋性，这是由于其膜上的电压梯度得到了维持。如果电压在短时间内发生足够大的变化，神经元就会产生一个全有或全无的电化学脉冲，称为动作电位。这个电位沿轴突迅速传播，到达突触连接时激活它们。突触信号可能是兴奋性的或抑制性的，增加或减少到达胞体的净电压。

In most cases, neurons are generated by [[neural stem cell]]s during brain development and childhood. [[Neurogenesis]] largely ceases during adulthood in most areas of the brain.

在大多数情况下，神经元是在大脑发育和儿童时期由神经干细胞生成的。在大脑的大多数区域，神经元的生成在成年后基本停止。

{{toclimit|3}}

== Nervous system神经系统 ==

[[File:Anatomy of a Neuron with Synapse.png|thumb|upright=1.15|Schematic of an anatomically accurate single pyramidal neuron, the primary excitatory neuron of cerebral cortex, with a synaptic connection from an incoming axon onto a dendritic spine.解剖学上准确的单个锥体神经元的示意图，大脑皮层的主要兴奋性神经元，具有从传入轴突到树突棘的突触连接。]]
{{unreferenced section|date=December 2020}}

Neurons are the primary components of the nervous system, along with the [[glial cells]] that give them structural and metabolic support. The nervous system is made up of the [[central nervous system]], which includes the [[brain]] and [[spinal cord]], and the [[peripheral nervous system]], which includes the [[autonomic nervous system|autonomic]] and [[somatic nervous system]]s. In vertebrates, the majority of neurons belong to the [[central nervous system]], but some reside in peripheral [[ganglion|ganglia]], and many sensory neurons are situated in sensory organs such as the [[retina]] and [[cochlea]].

神经元是神经系统的主要组成部分，同时还有给予其结构和代谢支持的胶质细胞。神经系统由中枢神经系统和周围神经系统组成，前者包括大脑和脊髓，后者包括自主神经和躯体神经系统。在脊椎动物中，大多数神经元属于中枢神经系统，但也有一些居住在周围神经节中，许多感觉神经元位于感觉器官中，如视网膜和耳蜗。

Axons may bundle into [[nerve fascicle|fascicle]]s that make up the [[nerve]]s in the [[peripheral nervous system]] (like strands of wire make up cables). Bundles of axons in the central nervous system are called [[nerve tract|tracts]].

轴突可以捆绑成束，组成周围神经系统的神经（就像电线股组成的电缆）。中枢神经系统中的轴突束被称为束。

== Anatomy and histology解剖学和组织学 ==

[[File:Components of neuron.jpg|thumb|upright=1.8|Diagram of the components of a neuron]]
Neurons are highly specialized for the processing and transmission of cellular signals. Given their diversity of functions performed in different parts of the nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 [[Micrometre|micrometers]] in diameter.<ref>{{cite web |first = Melissa |last = Davies |title = The Neuron: size comparison |url = https://www.ualberta.ca/~neuro/OnlineIntro/NeuronExample.htm |work = Neuroscience: A journey through the brain |date = 2002-04-09 |access-date = 2009-06-20}}</ref>

神经元对细胞信号的处理和传送是高度专业化。鉴于它们在神经系统的不同部分所执行的功能的多样性，它们的形状、大小和电化学特性也有很大差异。例如，一个神经元的胞体的直径可以从4到100微米不等。 <ref>{{cite web |first = Melissa |last = Davies |title = The Neuron: size comparison |url = https://www.ualberta.ca/~neuro/OnlineIntro/NeuronExample.htm |work = Neuroscience: A journey through the brain |date = 2002-04-09 |access-date = 2009-06-20}}</ref>

*The '''[[Soma (biology)|soma]]''' is the body of the neuron. As it contains the [[cell nucleus|nucleus]], most [[protein biosynthesis|protein synthesis]] occurs here. The nucleus can range from 3 to 18 micrometers in diameter.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Brain Facts and Figures |url = http://faculty.washington.edu/chudler/facts.html |work = Neuroscience for Kids |access-date = 2009-06-20 }}</ref>
*细胞体是神经元的主体。由于它含有细胞核，大多数蛋白质合成发生在这里。细胞核的直径可以从3到18微米不等。

*The '''[[dendrites]]''' of a neuron are cellular extensions with many branches. This overall shape and structure is referred to metaphorically as a dendritic tree. This is where the majority of input to the neuron occurs via the [[dendritic spine]].
*神经元的树突是有许多分支的细胞延伸。这种整体形状和结构被比喻为树突树。神经元的大部分输入是通过树突棘发生的。

*The '''[[axon]]''' is a finer, cable-like projection that can extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length. The axon primarily carries [[nerve signal]]s away from the soma, and carries some types of information back to it. Many neurons have only one axon, but this axon may—and usually will—undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the '''[[axon hillock]]'''. Besides being an anatomical structure, the axon hillock also has the greatest density of [[voltage-dependent sodium channels]]. This makes it the most easily excited part of the neuron and the spike initiation zone for the axon. In electrophysiological terms, it has the most negative [[threshold potential]].
*轴突是一种较细的、像电缆一样的突起，其长度可以是胞体直径的几十倍、几百倍、甚至几万倍。轴突主要携带神经信号离开胞体，并将某些类型的信息带回胞体。许多神经元只有一个轴突，但这个轴突可能--通常也会--发生广泛的分支，从而能够与许多靶细胞进行交流。轴突从胞体中出现的部分被称为轴突丘。除了是一种解剖结构外，轴突丘还具有最大密度的电压依赖性钠离子通道。这使得它成为神经元最容易兴奋的部分和轴突的锋电位触发区。在电生理学方面，它具有最负的阈值电位。

**While the axon and axon hillock are generally involved in information outflow, this region can also receive input from other neurons.
**虽然轴突和轴突丘通常会参与信息外流，但这一区域也能接受来自其他神经元的输入。

*The '''[[axon terminal]]''' is found at the end of the axon farthest from the soma and contains [[synapses]]. Synaptic boutons are specialized structures where [[neurotransmitter]] chemicals are released to communicate with target neurons. In addition to synaptic boutons at the axon terminal, a neuron may have ''en passant'' boutons, which are located along the length of the axon.
*轴突终端位于轴突离胞体最远的一端，包含突触。突触结是专门的结构，神经递质化学物质在此释放，与目标神经元进行交流。除了轴突末端的突触结外，神经元还可能有沿轴突长度方向分布的 "中途结"。

[[File:Neuron Cell Body.png|thumb|Neuron cell body神经元细胞体]]

The accepted view of the neuron attributes dedicated functions to its various anatomical components; however, dendrites and axons often act in ways contrary to their so-called main function.<ref>{{Cite web |date=2021-01-14 |title=16.7: Nervous System |url=https://bio.libretexts.org/Courses/Lumen_Learning/Book%3A_Fundamentals_of_Biology_I_(Lumen)/16%3A_Module_13%3A_Overview_of_Body_Systems/16.7%3A_Nervous_System |access-date=2022-02-28 |website=Biology LibreTexts |language=en}}</ref>

公认的神经元观点将专门的功能归于其各种解剖成分；然而，树突和轴突的作用方式往往与它们所谓的主要功能相反。

[[File:Complete neuron cell diagram en.svg|thumb|right|Diagram of a typical myelinated vertebrate motor neuron典型的有髓的脊椎动物运动神经元示意图]]
[[File:BN1 Neurology.webm|thumb|Neurology Video神经病学视频]]

Axons and dendrites in the central nervous system are typically only about one micrometer thick, while some in the peripheral nervous system are much thicker. The soma is usually about 10–25 micrometers in diameter and often is not much larger than the cell nucleus it contains. The longest axon of a human [[motor neuron]] can be over a meter long, reaching from the base of the spine to the toes.

中枢神经系统中的轴突和树突通常只有约1微米厚，而周围神经系统中的一些轴突和树突则要厚得多。胞体的直径通常约为10-25微米，通常不比其包含的细胞核大多少。人类运动神经元最长的轴突可以超过一米长，从脊柱底部一直延伸到脚趾。

Sensory neurons can have axons that run from the toes to the [[posterior column]] of the spinal cord, over 1.5 meters in adults. [[Giraffe]]s have single axons several meters in length running along the entire length of their necks. Much of what is known about axonal function comes from studying the [[squid giant axon]], an ideal experimental preparation because of its relatively immense size (0.5–1 millimeters thick, several centimeters long).

感觉神经元的轴突可以从脚趾一直延伸到脊髓的后柱，成年人的轴突长度超过1.5米。长颈鹿有几米长的单根轴突，沿其脖子的整个长度运行。人们对轴突功能的了解大多来自于对鱿鱼巨型轴突的研究，由于其相对巨大的尺寸（0.5-1毫米厚，数厘米长），这是一种理想的实验准备。

Fully differentiated neurons are permanently [[G0 phase|postmitotic]]<ref>{{cite journal | vauthors = Herrup K, Yang Y | title = Cell cycle regulation in the postmitotic neuron: oxymoron or new biology? | journal = Nature Reviews. Neuroscience | volume = 8 | issue = 5 | pages = 368–78 | date = May 2007 | pmid = 17453017 | doi = 10.1038/nrn2124 | s2cid = 12908713 }}</ref> however, stem cells present in the adult brain may regenerate functional neurons throughout the life of an organism (see [[neurogenesis]]). [[Astrocyte]]s are star-shaped [[glial cell]]s. They have been observed to turn into neurons by virtue of their stem cell-like characteristic of [[pluripotency]].

完全分化的神经元是永久性的有丝分裂后的细胞，然而，存在于成人大脑中的干细胞可以在有机体的整个生命过程中再生出功能性神经元（见神经元的生成）。星形胶质细胞是星形的胶质细胞。它们已经被观察到可以凭借其类干细胞的多能性特征而变成神经元。

===Membrane膜结构===

{{unreferenced section|date=December 2020}}
Like all animal cells, the cell body of every neuron is enclosed by a [[plasma membrane]], a bilayer of [[lipid]] molecules with many types of protein structures embedded in it. A lipid bilayer is a powerful electrical [[Insulator (electricity)|insulator]], but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are [[voltage-gated ion channel|voltage gated]], meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The [[ion]] materials include [[sodium]], [[potassium]], [[chloride]], and [[calcium]]. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane.

像所有的动物细胞一样，每个神经元的细胞体都被一个质膜所包围，质膜是由脂质分子组成的双层膜，其中嵌入了许多类型的蛋白质结构。脂质双层是一个强大的电绝缘体，但在神经元中，嵌入膜中的许多蛋白质结构是电活性的。这些结构包括允许带电离子流过膜的离子通道和以化学方式将离子从膜的一侧输送到另一侧的离子泵。大多数离子通道只对特定类型的离子有渗透性。一些离子通道是电压门控的，这意味着它们可以通过改变膜上的电压差在开放和关闭状态之间进行切换。其他的是化学门控，意味着它们可以通过与扩散在细胞外液中的化学物质的相互作用在开放和关闭状态之间切换。离子材料包括钠、钾、氯和钙。离子通道和离子泵之间的相互作用在膜上产生一个电压差，通常在基线上小于1/10伏。这个电压有两个功能：首先，它为嵌入膜中的各种电压依赖性蛋白机械提供了动力源；其次，它为膜的不同部分之间的电信号传输提供了一个基础。

===Histology and internal structure组织学和内部结构===

[[File:Gyrus Dentatus 40x.jpg|thumb|250px|Golgi-stained neurons in human hippocampal tissue高尔基染色神经元在人海马组织]]

[[Image:SUM 110913 Cort Neurons 2.5d in vitro 488 Phalloidin no perm 4 cmle-2.png|thumb|300px|Actin filaments in a mouse cortical neuron in culture培养中的小鼠皮质神经元中的肌动蛋白丝]]

Numerous microscopic clumps called [[Nissl body|Nissl bodies]] (or Nissl substance) are seen when nerve cell bodies are stained with a basophilic ("base-loving") dye. These structures consist of [[Endoplasmic reticulum#Rough endoplasmic reticulum|rough endoplasmic reticulum]] and associated [[ribosomal RNA]]. Named after German psychiatrist and neuropathologist [[Franz Nissl]] (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as [[aniline]] or (weakly) [[haematoxylin]]<ref>{{cite book|title=State Hospitals Bulletin|url={{google books |plainurl=y |id=Wp8CAAAAYAAJ|page=378}}|year=1897|publisher=State Commission in Lunacy.|page=378}}</ref> highlight negatively charged components, and so bind to the phosphate backbone of the ribosomal RNA.

当用嗜碱性（"嗜碱"）染料对神经细胞体进行染色时，可以看到许多称为尼氏体（或尼氏物质）的微观团块。这些结构由粗糙的内质网和相关的核糖体RNA组成。它们以德国精神病学家和神经病理学家弗朗茨-尼斯尔（1860-1919）的名字命名，参与蛋白质的合成，其突出性可以用神经细胞代谢非常活跃的事实来解释。嗜碱性染料如苯胺或（弱）血红蛋白会突出带负电的成分，因此与核糖体RNA的磷酸盐骨架结合。

The cell body of a neuron is supported by a complex mesh of structural proteins called [[neurofilament]]s, which together with neurotubules (neuronal microtubules) are assembled into larger neurofibrils.<ref name="Webster">{{cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |website=www.merriam-webster.com}}</ref> Some neurons also contain pigment granules, such as [[neuromelanin]] (a brownish-black pigment that is byproduct of synthesis of [[catecholamine]]s), and [[lipofuscin]] (a yellowish-brown pigment), both of which accumulate with age.<ref>{{cite journal | vauthors = Zecca L, Gallorini M, Schünemann V, Trautwein AX, Gerlach M, Riederer P, Vezzoni P, Tampellini D | title = Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes | journal = Journal of Neurochemistry | volume = 76 | issue = 6 | pages = 1766–73 | date = March 2001 | pmid = 11259494 | doi = 10.1046/j.1471-4159.2001.00186.x | s2cid = 31301135 }}</ref><ref>{{cite journal | vauthors = Herrero MT, Hirsch EC, Kastner A, Luquin MR, Javoy-Agid F, Gonzalo LM, Obeso JA, Agid Y | title = Neuromelanin accumulation with age in catecholaminergic neurons from Macaca fascicularis brainstem | journal = Developmental Neuroscience | volume = 15 | issue = 1 | pages = 37–48 | date = 1993 | pmid = 7505739 | doi = 10.1159/000111315 }}</ref><ref>{{cite journal | vauthors = Brunk UT, Terman A | title = Lipofuscin: mechanisms of age-related accumulation and influence on cell function | journal = Free Radical Biology & Medicine | volume = 33 | issue = 5 | pages = 611–9 | date = September 2002 | pmid = 12208347 | doi = 10.1016/s0891-5849(02)00959-0 }}</ref> Other structural proteins that are important for neuronal function are [[actin]] and the [[tubulin]] of [[microtubule]]s. [[Class III β-tubulin]] is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule.<ref>{{cite journal | vauthors = Zhao B, Meka DP, Scharrenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F | title = Microtubules Modulate F-actin Dynamics during Neuronal Polarization | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 9583 | date = August 2017 | pmid = 28851982 | pmc = 5575062 | doi = 10.1038/s41598-017-09832-8 | bibcode = 2017NatSR...7.9583Z }}</ref>

神经元的细胞体由称为神经丝的结构蛋白的复杂网状结构支撑，它与神经管（神经元微管）一起被组装成较大的神经纤维。一些神经元还含有色素颗粒，如神经黑色素（一种棕黑色的色素，是儿茶酚胺合成的副产品）和脂褐素（一种黄褐色的色素），这两种物质都会随着年龄的增长而积累。对神经元功能很重要的其他结构蛋白是肌动蛋白和微管的管蛋白。第三类β-管蛋白几乎只在神经元中发现。在神经元发育过程中，肌动蛋白主要存在于轴突和树突的顶端。在那里，肌动蛋白的动态可以通过与微管的相互作用而被调节。

There are different internal structural characteristics between axons and dendrites. Typical axons almost never contain [[ribosomes]], except some in the initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases.

轴突和树突之间存在着不同的内部结构特征。典型的轴突几乎不含核糖体，除了在初始段有一些。树突含有颗粒状的内质网或核糖体，随着与细胞体距离的增加，其数量逐渐减少。

==Classification分类==

[[File:GFPneuron.png|thumb|250px|right|Image of pyramidal neurons in mouse [[cerebral cortex]] expressing [[green fluorescent protein]]. The red staining indicates [[GABA]]ergic interneurons.<ref>{{cite journal | vauthors = Lee WC, Huang H, Feng G, Sanes JR, Brown EN, So PT, Nedivi E | title = Dynamic remodeling of dendritic arbors in GABAergic interneurons of adult visual cortex | journal = PLOS Biology | volume = 4 | issue = 2 | pages = e29 | date = February 2006 | pmid = 16366735 | pmc = 1318477 | doi = 10.1371/journal.pbio.0040029 |doi-access=free }}</ref>]]

[[File:smi32neuron.jpg|thumb|250px|right|SMI32-stained pyramidal neurons in [[cerebral cortex]]]]

{{See also|List of distinct cell types in the adult human body#Nervous system}}
另见：成人体内不同的细胞类型列表 § 神经系统

Neurons vary in shape and size and can be classified by their [[Morphology (biology)|morphology]] and function.<ref name="Al">{{cite book|last=Al|first=Martini, Frederic Et|title=Anatomy and Physiology' 2007 Ed.2007 Edition|url={{google books |plainurl=y |id=joJb82gVsLoC|page=288}}|publisher=Rex Bookstore, Inc.|isbn=978-971-23-4807-5|pages=288}}</ref> The anatomist [[Camillo Golgi]] grouped neurons into two types; type I with long axons used to move signals over long distances and type II with short axons, which can often be confused with dendrites. Type I cells can be further classified by the location of the soma. The basic morphology of type I neurons, represented by spinal [[motor neurons]], consists of a cell body called the soma and a long thin axon covered by a [[myelin sheath]]. The dendritic tree wraps around the cell body and receives signals from other neurons. The end of the axon has branching [[axon terminal]]s that release neurotransmitters into a gap called the [[synaptic cleft]] between the terminals and the dendrites of the next neuron.

神经元的形状和大小各不相同，可按其形态和功能进行分类。解剖学家卡米洛-高尔基将神经元分为两类；I型有长轴，用于长距离移动信号；II型有短轴，常与树突相混淆。I型细胞可按胞体的位置进一步分类。以脊髓运动神经元为代表的I型神经元的基本形态包括一个称为胞体的细胞体和一个由髓鞘覆盖的细长轴突。树突树环绕着细胞体，接收来自其他神经元的信号。轴突的末端有分支的轴突终端，将神经递质释放到终端和下一个神经元树突之间的间隙中，称为突触间隙。

===Structural classification结构分类===

====Polarity极性====

[[File:Neurons uni bi multi pseudouni.svg|thumb|Different kinds of neurons不同种类的神经元: 1 [[Unipolar neuron单极神经元]] 2 [[Bipolar neuron双极神经元]] 3 [[Multipolar neuron多极神经元]] 4 [[Pseudounipolar neuron伪单极神经元]] ]]

Most neurons can be anatomically characterized as:
大多数神经元在解剖学上可以被描述为：

*[[Unipolar neuron|Unipolar]]: single process
*[[Bipolar cell|Bipolar]]: 1 axon and 1 dendrite
*[[Multipolar neuron|Multipolar]]: 1 axon and 2 or more dendrites
**[[Golgi I]]: neurons with long-projecting axonal processes; examples are pyramidal cells, Purkinje cells, and anterior horn cells
**[[Golgi II]]: neurons whose axonal process projects locally; the best example is the granule cell
*[[Anaxonic neuron|Anaxonic]]: where the axon cannot be distinguished from the dendrite(s)
*[[Pseudounipolar cells|Pseudounipolar]]: 1 process which then serves as both an axon and a dendrite

* 单极性：单一原生质过程
* 双极性：1个轴突和1个树突
* 多极性：1个轴突和2个或更多的树突
** 高尔基I型：具有长轴突的神经元；比如锥体细胞、浦肯野细胞和前角细胞。
** 高尔基II型：其轴突过程在局部投射的神经元；最好的例子是颗粒细胞
* 无轴性：轴突与树突无法区分的神经元类型。
* 假单极神经元：1个原生质过程，然后既是轴突又是树突。

====Other其他====

Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are:

一些独特的神经元类型可以根据其在神经系统中的位置和独特的形状来识别。一些例子是：

*[[Basket cell]]s, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and [[cerebellum]]
*[[Betz cell]]s, large motor neurons
*[[Lugaro cell]]s, interneurons of the cerebellum
*[[Medium spiny neuron]]s, most neurons in the [[corpus striatum]]
*[[Purkinje cell]]s, huge neurons in the cerebellum, a type of Golgi I multipolar neuron
*[[Pyramidal cell]]s, neurons with triangular soma, a type of Golgi I
*[[Renshaw cell]]s, neurons with both ends linked to [[alpha motor neuron]]s
*[[Unipolar brush cell]]s, interneurons with unique dendrite ending in a brush-like tuft
*[[Granule cell]]s, a type of Golgi II neuron
*[[Anterior horn (spinal cord)|Anterior horn]] cells, [[motoneurons]] located in the spinal cord
*[[Spindle cell]]s, interneurons that connect widely separated areas of the brain

*篮状细胞，在目标细胞的胞体周围形成密集的终端丛，发现于大脑皮层和小脑的中间神经元。
*贝兹细胞，大运动神经元
*卢加洛细胞，小脑的中间神经元
*中型多棘神经元，纹状体中的大多数神经元
*浦肯野细胞，小脑中的巨大神经元，一种高尔基I型多极神经元
*锥体细胞，具有三角形胞体的神经元，是高尔基I型的一种。
*伦肖细胞，两端与α运动神经元相连的神经元
*单极刷细胞，具有独特的树突末端为刷状簇的中间神经元
*颗粒细胞，高尔基II型神经元的一种类型
*前角细胞，位于脊髓中的运动神经元
*纺锤体细胞，连接大脑广泛分布的中间神经元
*纺锤体细胞的运动神经元、连接大脑广泛分离区域的中间神经元

===Functional classification功能分类===

====Direction方向====

*[[Afferent neuron]]s convey information from tissues and organs into the central nervous system and are also called [[sensory neurons]].
*[[Efferent neuron]]s (motor neurons) transmit signals from the central nervous system to the effector cells.
*[[Interneuron]]s connect neurons within specific regions of the central nervous system.

* 传入神经元将信息从组织和器官传入中枢神经系统，也被称为感觉神经元。
* 传出神经元(运动神经元) 将信号从中枢神经系统传递给效应细胞。
* 中间神经元连接中枢神经系统特定区域内的神经元。

Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain.

传入和传出也泛指分别为大脑带来信息或从大脑发出信息的神经元。

====Action on other neurons对其他神经元的影响====

A neuron affects other neurons by releasing a neurotransmitter that binds to [[receptor (biochemistry)|chemical receptor]]s. The effect upon the postsynaptic neuron is determined by the type of receptor that is activated, not by the presynaptic neuron or by the neurotransmitter. A neurotransmitter can be thought of as a key, and a receptor as a lock: the same neurotransmitter can activate multiple types of receptors. Receptors can be classified broadly as ''excitatory'' (causing an increase in firing rate), ''inhibitory'' (causing a decrease in firing rate), or ''modulatory'' (causing long-lasting effects not directly related to firing rate).

一个神经元通过释放一种与化学受体结合的神经递质来影响其他神经元。对突触后神经元的影响是由被激活的受体类型决定的，而不是由突触前神经元或神经递质决定的。可以认为神经递质是一把钥匙，而受体是一把锁：同一神经递质可以激活多种类型的受体。受体可大致分为兴奋性（导致放电率增加）、抑制性（导致放电率下降）或调节性（导致与放电率无直接关系的长期影响）。

The two most common (90%+) neurotransmitters in the brain, [[glutamate]] and [[GABA]], have largely consistent actions. Glutamate acts on several types of receptors, and has effects that are excitatory at [[ionotropic receptor]]s and a modulatory effect at [[metabotropic receptor]]s. Similarly, GABA acts on several types of receptors, but all of them have inhibitory effects (in adult animals, at least). Because of this consistency, it is common for neuroscientists to refer to cells that release glutamate as "excitatory neurons", and cells that release GABA as "inhibitory neurons". Some other types of neurons have consistent effects, for example, "excitatory" motor neurons in the spinal cord that release [[acetylcholine]], and "inhibitory" [[spinal neuron]]s that release [[glycine]].

大脑中最常见的两种（90%以上）神经递质，即谷氨酸和GABA，其作用基本一致。谷氨酸作用于几种类型的受体，在离子型受体上有兴奋作用，在代谢型受体上有调节作用。同样，GABA作用于几种类型的受体，但它们都有抑制作用（至少在成年动物中）。由于这种一致性，神经科学家通常把释放谷氨酸的细胞称为 "兴奋性神经元"，而把释放GABA的细胞称为 "抑制性神经元"。其他一些类型的神经元也有一致的影响，例如，脊髓中释放乙酰胆碱的 "兴奋性 "运动神经元，以及释放甘氨酸的 "抑制性 "脊髓神经元。

The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neuron. In principle, a single neuron, releasing a single neurotransmitter, can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still. For example, [[photoreceptor cell]]s in the retina constantly release the neurotransmitter glutamate in the absence of light. So-called OFF [[retinal bipolar cells|bipolar cells]] are, like most neurons, excited by the released glutamate. However, neighboring target neurons called ON bipolar cells are instead inhibited by glutamate, because they lack typical [[ionotropic receptor|ionotropic]] [[glutamate receptors]] and instead express a class of inhibitory [[metabotropic receptor|metabotropic]] glutamate receptors.<ref>{{cite journal | vauthors = Gerber U | title = Metabotropic glutamate receptors in vertebrate retina | journal = Documenta Ophthalmologica. Advances in Ophthalmology | volume = 106 | issue = 1 | pages = 83–7 | date = January 2003 | pmid = 12675489 | doi = 10.1023/A:1022477203420 | s2cid = 22296630 }}</ref> When light is present, the photoreceptors cease releasing glutamate, which relieves the ON bipolar cells from inhibition, activating them; this simultaneously removes the excitation from the OFF bipolar cells, silencing them.

兴奋性和抑制性神经递质之间的区别不是绝对的。相反，它取决于突触后神经元上存在的化学受体的类别。原则上，一个神经元，释放一种神经递质，可以对某些目标产生兴奋作用，对其他目标产生抑制作用，对其他目标仍有调节作用。例如，视网膜上的感光细胞在没有光的情况下不断释放神经递质谷氨酸。像大多数神经元一样，所谓的关闭双极细胞被释放的谷氨酸所激发。然而，被称为ON双极细胞的邻近目标神经元反而受到谷氨酸的抑制，因为它们缺乏典型的离子型谷氨酸受体，而是表达一类抑制性的代谢型谷氨酸受体。当有光时，光感受器停止释放谷氨酸，这解除了ON双极细胞的抑制，激活了它们；这同时消除了OFF双极细胞的兴奋，使它们沉默。

It is possible to identify the type of inhibitory effect a presynaptic neuron will have on a postsynaptic neuron, based on the proteins the presynaptic neuron expresses. [[Parvalbumin]]-expressing neurons typically dampen the output signal of the postsynaptic neuron in the [[visual cortex]], whereas [[somatostatin]]-expressing neurons typically block dendritic inputs to the postsynaptic neuron.<ref name="pmid22878717">{{cite journal | vauthors = Wilson NR, Runyan CA, Wang FL, Sur M | title = Division and subtraction by distinct cortical inhibitory networks in vivo | journal = Nature | volume = 488 | issue = 7411 | pages = 343–8 | date = August 2012 | pmid = 22878717 | pmc = 3653570 | doi = 10.1038/nature11347 | bibcode = 2012Natur.488..343W | hdl = 1721.1/92709 }}</ref>

根据突触前神经元表达的蛋白质，可以确定突触前神经元对突触后神经元的抑制作用的类型。表达副白蛋白的神经元通常会抑制视觉皮层中突触后神经元的输出信号，而表达躯干素的神经元通常会阻断突触后神经元的树突输入。

====Discharge patterns放电模式====

Neurons have intrinsic electroresponsive properties like intrinsic transmembrane voltage [[Neural oscillation|oscillatory]] patterns.<ref name="llinas2014">{{cite journal | vauthors = Llinás RR | title = Intrinsic electrical properties of mammalian neurons and CNS function: a historical perspective | journal = Frontiers in Cellular Neuroscience | volume = 8 | pages = 320 | date = 2014-01-01 | pmid = 25408634 | pmc = 4219458 | doi = 10.3389/fncel.2014.00320 | doi-access = free }}</ref> So neurons can be classified according to their [[electrophysiology|electrophysiological]] characteristics:

神经元具有内在的电反应特性，如内在的跨膜电压振荡模式。因此，可以根据神经元的电生理特性对其进行分类：

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.
*Phasic or bursting. Neurons that fire in bursts are called phasic.
*Fast spiking. Some neurons are notable for their high firing rates, for example some types of cortical inhibitory interneurons, cells in [[globus pallidus]], [[retinal ganglion cells]].<ref>{{cite conference | title = Ion conductances related to shaping the repetitive firing in rat retinal ganglion cells | vauthors = Kolodin YO, Veselovskaia NN, Veselovsky NS, Fedulova SA | conference = Acta Physiologica Congress | url = http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | access-date = 2009-06-20 | archive-url = https://web.archive.org/web/20121007164451/http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | archive-date = 2012-10-07 | url-status = dead }}</ref><ref>{{cite web|url=http://ykolodin.50webs.com/ |title=Ionic conductances underlying excitability in tonically firing retinal ganglion cells of adult rat |publisher=Ykolodin.50webs.com |date=2008-04-27 |access-date=2013-02-16}}</ref>

*紧张性或规律性棘波。一些神经元通常持续（紧张地）活跃，通常以恒定的频率放电。例如：神经干细胞中的interneurons。
*瞬变性或爆发性。爆发性放电的神经元被称为瞬变性的。
*快闪性。一些神经元因其高放电率而引人注目，例如某些类型的皮质抑制性中间神经元、苍白球、视网膜神经节细胞。

====Neurotransmitter神经递质 ====

[[File:Neurotransmitters.jpg|thumb|Synaptic vesicles containing neurotransmitters含有神经递质的突触小泡。]]
{{Main|Neurotransmitter}}

[[Neurotransmitter]]s are chemical messengers passed from one neuron to another neuron or to a [[muscle cell]] or [[Gland|gland cell]].

神经递质是由一个神经元传递给另一个神经元或肌肉细胞或腺体细胞的化学信使。

*Cholinergic neurons – acetylcholine. [[Acetylcholine]] is released from presynaptic neurons into the synaptic cleft. It acts as a [[ligand]] for both ligand-gated ion channels and [[Metabotropic receptor|metabotropic]] (GPCRs) [[Muscarinic acetylcholine receptor|muscarinic receptors]]. [[Nicotinic receptors]] are pentameric ligand-gated ion channels composed of alpha and beta subunits that bind [[nicotine]]. Ligand binding opens the channel causing influx of [[Sodium|Na+]] depolarization and increases the probability of presynaptic neurotransmitter release. Acetylcholine is synthesized from [[choline]] and [[acetyl coenzyme A]].
*Adrenergic neurons – noradrenaline. [[Noradrenaline]] (norepinephrine) is released from most [[postganglionic]] neurons in the [[sympathetic nervous system]] onto two sets of GPCRs: [[Adrenergic receptor|alpha adrenoceptor]]s and [[beta adrenoceptor]]s. Noradrenaline is one of the three common [[catecholamine]] neurotransmitter, and the most prevalent of them in the [[peripheral nervous system]]; as with other catecholamines, it is synthesised from [[tyrosine]].
*GABAergic neurons – [[gamma aminobutyric acid]]. GABA is one of two neuroinhibitors in the [[central nervous system]] (CNS), along with glycine. GABA has a homologous function to [[Acetylcholine|ACh]], gating anion channels that allow [[Chlorine|Cl−]] ions to enter the post synaptic neuron. Cl− causes hyperpolarization within the neuron, decreasing the probability of an action potential firing as the voltage becomes more negative (for an action potential to fire, a positive voltage threshold must be reached). GABA is synthesized from glutamate neurotransmitters by the enzyme [[glutamate decarboxylase]].
*Glutamatergic neurons – glutamate. [[Glutamate]] is one of two primary excitatory amino acid neurotransmitters, along with [[Aspartic acid|aspartate]]. Glutamate receptors are one of four categories, three of which are ligand-gated ion channels and one of which is a [[G protein|G-protein]] coupled receptor (often referred to as GPCR).

*胆碱能神经元--乙酰胆碱。乙酰胆碱从突触前神经元释放到突触间隙中。它是配体门控离子通道和代谢型（GPCRs：G蛋白耦联受体）毒蕈碱受体的配体。烟碱受体是由结合了尼古丁的α和β亚基组成的五聚体配体门控离子通道。配体结合后打开通道，造成Na+的流入，使其去极化，并增加突触前神经递质释放的概率。乙酰胆碱是由胆碱和乙酰辅酶A合成的。
*肾上腺素能神经元--去甲肾上腺素。去甲肾上腺素（norepinephrine去甲肾上腺素）从交感神经系统的大多数神经节后神经元释放到两组GPCRs上：α肾上腺素受体和β肾上腺素受体。去甲肾上腺素是三种常见的儿茶酚胺神经递质之一，也是周围神经系统中最普遍的一种；与其他儿茶酚胺一样，它是由酪氨酸合成的。
*GABA能神经元--γ氨基丁酸。GABA与甘氨酸一起是中枢神经系统（CNS）中的两种神经抑制剂之一。GABA具有与ACh相同的功能，对允许Cl-离子进入突触后神经元的阴离子通道进行门控。Cl-导致神经元内的超极化，随着电压变得更负，降低了动作电位放电的概率（要引发动作电位，必须达到一个正电压阈值）。GABA是由谷氨酸神经递质通过谷氨酸脱羧酶合成的。
*谷氨酸能神经元--谷氨酸。谷氨酸与天门冬氨酸一起是两种主要的兴奋性氨基酸神经递质之一。谷氨酸受体是四类之一，其中三类是配体门控离子通道，一类是G-蛋白耦联受体（通常称为GPCR）。

:#[[AMPA]] and [[Kainic acid|Kainate]] receptors function as [[Ion|cation]] channels permeable to Na+ cation channels mediating fast excitatory synaptic transmission.
:#[[N-Methyl-D-aspartic acid|NMDA]] receptors are another cation channel that is more permeable to [[Calcium in biology|Ca2+]]. The function of NMDA receptors depend on glycine receptor binding as a co-[[agonist]] within the channel pore. NMDA receptors do not function without both ligands present.
:#Metabotropic receptors, GPCRs modulate synaptic transmission and postsynaptic excitability.
::Glutamate can cause excitotoxicity when blood flow to the brain is interrupted, resulting in [[brain damage]]. When blood flow is suppressed, glutamate is released from presynaptic neurons, causing greater NMDA and AMPA receptor activation than normal outside of stress conditions, leading to elevated Ca2+ and Na+ entering the post synaptic neuron and cell damage. Glutamate is synthesized from the amino acid glutamine by the enzyme [[Glutamine oxoglutarate aminotransferase|glutamate synthase]].

:#AMPA和红藻氨酸受体作为阳离子通道可渗透到Na+阳离子通道，介导快速兴奋性突触传递。
:#NMDA受体是另一个对Ca2+更易渗透的阳离子通道。NMDA受体的功能取决于甘氨酸受体的结合，作为通道孔内的共轭物。如果没有这两种配体存在，NMDA受体就不能发挥作用。
:#促代谢受体，GPCRs调节突触传递和突触后兴奋性。
::当流向大脑的血流被中断时，谷氨酸可引起兴奋性毒性，导致大脑损伤。当血流被抑制时，谷氨酸从突触前的神经元中释放出来，导致NMDA和AMPA受体的激活比压力条件以外的正常情况下更大，导致升高的Ca2+和Na+进入突触后的神经元和细胞损伤。谷氨酸是由谷氨酸合成酶从氨基酸谷氨酰胺中合成的。

*Dopaminergic neurons—[[dopamine]]. [[Dopamine]] is a neurotransmitter that acts on D1 type (D1 and D5) Gs-coupled receptors, which increase cAMP and PKA, and D2 type (D2, D3, and D4) receptors, which activate Gi-coupled receptors that decrease cAMP and PKA. Dopamine is connected to mood and behavior and modulates both pre- and post-synaptic neurotransmission. Loss of dopamine neurons in the [[substantia nigra]] has been linked to [[Parkinson's disease]]. Dopamine is synthesized from the amino acid [[tyrosine]]. Tyrosine is catalyzed into levodopa (or [[L-DOPA]]) by [[Tyrosine hydroxylase|tyrosine hydroxlase]], and levodopa is then converted into dopamine by the aromatic amino acid [[Carboxy-lyases|decarboxylase]].
*Serotonergic neurons—[[serotonin]]. [[Serotonin]] (5-Hydroxytryptamine, 5-HT) can act as excitatory or inhibitory. Of its four 5-HT receptor classes, 3 are GPCR and 1 is a ligand-gated cation channel. Serotonin is synthesized from [[tryptophan]] by [[tryptophan hydroxylase]], and then further by decarboxylase. A lack of 5-HT at postsynaptic neurons has been linked to depression. Drugs that block the presynaptic [[serotonin transporter]] are used for treatment, such as [[Prozac]] and [[Zoloft]].
*Purinergic neurons—ATP. [[Adenosine triphosphate|ATP]] is a neurotransmitter acting at both ligand-gated ion channels ([[P2X]] receptors) and GPCRs ([[P2Y receptor|P2Y]]) receptors. ATP is, however, best known as a [[cotransmitter]]. Such [[purinergic signalling]] can also be mediated by other [[purine]]s like [[adenosine]], which particularly acts at P2Y receptors.
*Histaminergic neurons—[[histamine]]. [[Histamine]] is a [[monoamine neurotransmitter]] and [[neuromodulator]]. Histamine-producing neurons are found in the [[tuberomammillary nucleus]] of the [[hypothalamus]].<ref>{{cite journal | vauthors = Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y | title = Histamine: neural circuits and new medications | journal = Sleep | volume = 42 | issue = 1 | date = January 2019 | pmid = 30239935 | pmc = 6335869 | doi = 10.1093/sleep/zsy183 }}</ref> Histamine is involved in [[arousal]] and regulating sleep/wake behaviors.

*多巴胺能神经元——多巴胺。多巴胺是一种神经递质，作用于D1型（D1和D5）Gs耦联受体，增加cAMP和PKA，以及D2型（D2、D3和D4）受体，激活Gi耦联受体，减少cAMP和PKA。多巴胺与情绪和行为有关，调节突触前和突触后的神经传递。黑质中的多巴胺神经元的丧失与帕金森病有关。多巴胺是由氨基酸酪氨酸合成的。酪氨酸被酪氨酸羟化酶催化为左旋多巴（或L-DOPA），然后左旋多巴被芳香族氨基酸脱羧酶转化为多巴胺。
*羟色胺能神经元——羟色胺。羟色胺（5-Hydroxytryptamine，5-HT）可以起到兴奋性或抑制性作用。在其四个5-HT受体类别中，3个是GPCR，1个是配体门控的阳离子通道。羟色胺由色氨酸经色氨酸羟化酶合成，然后再经脱羧酶进一步合成。突触后神经元缺乏5-HT与抑郁症有关。阻断突触前5-羟色胺转运体的药物被用于治疗，如百忧解和左洛复。
*嘌呤神经元——ATP。ATP是一种同时作用于配体门控离子通道（P2X受体）和GPCRs（P2Y）受体的神经递质。然而，ATP最有名的是作为一种共传导剂。这种嘌呤信号也可以由其他嘌呤介导，如腺苷，它特别作用于P2Y受体。
*组胺能神经元——组胺。组胺是一种单胺类神经递质和神经调节剂。产生组胺的神经元存在于下丘脑的管状乳头核。组胺参与唤醒和调节睡眠/觉醒行为。

====Multimodel classification多模式分类====

Since 2012 there has been a push from the cellular and computational neuroscience community to come up with a universal classification of neurons that will apply to all neurons in the brain as well as across species. This is done by considering the three essential qualities of all neurons: electrophysiology, morphology, and the individual transcriptome of the cells. Besides being universal this classification has the advantage of being able to classify astrocytes as well. A method called Patch-Seq in which all three qualities can be measured at once is used extensively by the Allen Institute for Brain Science.<ref>{{cite web |url=https://www.news-medical.net/news/20201203/Patch-seq-technique-helps-depict-the-variation-of-neural-cells-in-the-brain.aspx |title=Patch-seq technique helps depict the variation of neural cells in the brain |work=News-medical.net |date=3 December 2020 |access-date=26 August 2021 |url-status=live}}</ref>

自2012年以来，细胞和计算神经科学界一直在推动提出一个通用的神经元分类，该分类将适用于大脑中的所有神经元以及跨物种。这是通过考虑所有神经元的三个基本属性来实现的：电生理学、形态学和细胞的个体转录组。除了具有普遍性之外，这种分类法还有一个优点，就是能够对星形胶质细胞进行分类。艾伦脑科学研究所广泛使用一种叫做Patch-Seq的方法，可以同时测量所有三种属性。

==Connectivity连接性==

{{Main|Synapse|Chemical synapse化学突触}}
[[File:Chemical synapse schema cropped.jpg|thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell沿着轴突传播到下一个细胞的细胞体和树突的一种信号。]]
[[File:Neuro Muscular Junction.png|thumb|Chemical synapse|left]]

Neurons communicate with each other via [[synapses]], where either the [[axon terminal]] of one cell contacts another neuron's dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in the cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the [[supraoptic nucleus]], have only one or two dendrites, each of which receives thousands of synapses.

神经元通过突触相互沟通，一个细胞的轴突终端接触到另一个神经元的树突、胞体，或者更少见的轴突。像小脑中的浦肯野细胞这样的神经元可以有超过1000个树突分支，与成千上万的其他细胞建立连接; 其他的神经元，如视上核的大细胞神经元，只有一个或两个树突，每个树突接收数千个突触。

Synapses can be [[EPSP|excitatory]] or [[IPSP|inhibitory]], either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive [[gap junction|junctions]] between cells.<ref>{{cite book |last1=Macpherson |first1=Gordon |title=Black's Medical Dictionary |date=2002 |publisher=Scarecrow Press |location=Lanham, MD |isbn=0810849844 |pages=431–434 |edition=40 }}</ref>

突触可以是兴奋性的或抑制性的，分别增加或减少目标神经元的活动。一些神经元还通过电突触进行交流，电突触是细胞之间直接的、导电的连接点。

When an action potential reaches the axon terminal, it opens [[Voltage-dependent calcium channel|voltage-gated calcium channels]], allowing [[Calcium in biology|calcium ions]] to enter the terminal. Calcium causes [[synaptic vesicles]] filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the [[axon terminal]] triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial [[energy metabolism]] to produce [[Adenosine triphosphate|ATP]] to support continuous neurotransmission.<ref name="pmid23746507">{{cite journal | vauthors = Ivannikov MV, Macleod GT | title = Mitochondrial free Ca²⁺ levels and their effects on energy metabolism in Drosophila motor nerve terminals | journal = Biophysical Journal | volume = 104 | issue = 11 | pages = 2353–61 | date = June 2013 | pmid = 23746507 | pmc = 3672877 | doi = 10.1016/j.bpj.2013.03.064 | bibcode = 2013BpJ...104.2353I }}</ref>

当动作电位到达轴突末端时，它打开电压门控的钙离子通道，允许钙离子进入末端。钙离子使充满神经递质分子的突触小泡与膜融合，将其内容释放到突触间隙中。神经递质在突触间隙中扩散，激活突触后神经元上的受体。轴突末端的高细胞钙引发线粒体钙吸收，这反过来又激活了线粒体的能量代谢，产生ATP以支持持续的神经传递。

An [[autapse]] is a synapse in which a neuron's axon connects to its own dendrites.

自突触是指神经元的轴突与自己的树突相连的突触。

The [[human brain]] has some 8.6 x 1010 (eighty six billion) neurons.<ref>{{ cite journal | vauthors = Herculano-Houzel S | title = The human brain in numbers: a linearly scaled-up primate brain | journal = Frontiers in Human Neuroscience | volume = 3 | pages = 31 | date = November 2009 | pmid = 19915731 | doi = 10.3389/neuro.09.031.2009 | pmc = 2776484 | doi-access = free }}</ref> Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 1015 synapses (1 quadrillion). [[Synaptic pruning|This number declines with age]], stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5 x 1014 synapses (100 to 500 trillion).<ref>{{cite journal | vauthors = Drachman DA | title = Do we have brain to spare? | journal = Neurology | volume = 64 | issue = 12 | pages = 2004–5 | date = June 2005 | pmid = 15985565 | doi = 10.1212/01.WNL.0000166914.38327.BB | s2cid = 38482114 }}</ref>

[[File:Axon Propagation.svg|thumb|563x563px|An annotated diagram of the stages of an action potential propagating down an axon including the role of ion concentration and pump and channel proteins.一个动作电位沿轴突传播的阶段的注释图，包括离子浓度和泵及通道蛋白的作用。]]

人脑有大约8.6 x 1010（86亿）个神经元。每个神经元平均有7000个与其他神经元的突触连接。据估计，一个三岁孩子的大脑大约有1015个突触（1万亿）。这个数字随着年龄的增长而下降，到成年后趋于稳定。对成年人的估计有所不同，从1014到5 x 1014个突触（100到500万亿）不等。

=== Nonelectrochemical signaling非电化学信号传递 ===

Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through:
* force generated by the enlargement of dendritic spines<ref>{{cite journal |last1=Ucar |first1=Hasan |last2=Watanabe |first2=Satoshi |last3=Noguchi |first3=Jun |last4=Morimoto |first4=Yuichi |last5=Iino |first5=Yusuke |last6=Yagishita |first6=Sho |last7=Takahashi |first7=Noriko |last8=Kasai |first8=Haruo |title=Mechanical actions of dendritic-spine enlargement on presynaptic exocytosis |journal=Nature |date=December 2021 |volume=600 |issue=7890 |pages=686–689 |doi=10.1038/s41586-021-04125-7 |language=en |issn=1476-4687}} Lay summary: {{cite news |title=Forceful synapses reveal mechanical interactions in the brain |url=https://www.nature.com/articles/d41586-021-03516-0 |access-date=21 February 2022 |work=Nature |date=24 November 2021 |language=en |doi=10.1038/d41586-021-03516-0}}</ref>
* the transfer of [[protein]]s – transneuronally transported proteins (TNTPs)<ref>{{cite news |title=Researchers discover new type of cellular communication in the brain |url=https://medicalxpress.com/news/2022-01-cellular-brain.html |access-date=12 February 2022 |work=The Scripps Research Institute |language=en}}</ref><ref>{{cite journal |last1=Schiapparelli |first1=Lucio M. |last2=Sharma |first2=Pranav |last3=He |first3=Hai-Yan |last4=Li |first4=Jianli |last5=Shah |first5=Sahil H. |last6=McClatchy |first6=Daniel B. |last7=Ma |first7=Yuanhui |last8=Liu |first8=Han-Hsuan |last9=Goldberg |first9=Jeffrey L. |last10=Yates |first10=John R. |last11=Cline |first11=Hollis T. |title=Proteomic screen reveals diverse protein transport between connected neurons in the visual system |journal=Cell Reports |date=25 January 2022 |volume=38 |issue=4 |doi=10.1016/j.celrep.2021.110287 |language=English |issn=2211-1247}}</ref>

除了电和化学信号，研究表明健康人脑中的神经元还可以通过以下方式交流：
*树突棘扩大产生的力
*蛋白质的转移--经神经元转运蛋白（TNTPs）。

They can also get modulated by input from the environment and [[hormone]]s released from other parts of the organism,<ref>{{cite journal |last1=Levitan |first1=Irwin B. |last2=Kaczmarek |first2=Leonard K. |title=Electrical Signaling in Neurons |doi=10.1093/med/9780199773893.001.0001/med-9780199773893-chapter-3 |publisher=Oxford University Press}}</ref> which could be influenced more or less directly by neurons. This also applies to [[neurotrophin]]s such as [[BDNF]]. The [[gut microbiome]] is also connected with the brain.<ref>{{cite journal |last1=O’Leary |first1=Olivia F. |last2=Ogbonnaya |first2=Ebere S. |last3=Felice |first3=Daniela |last4=Levone |first4=Brunno R. |last5=C. Conroy |first5=Lorraine |last6=Fitzgerald |first6=Patrick |last7=Bravo |first7=Javier A. |last8=Forsythe |first8=Paul |last9=Bienenstock |first9=John |last10=Dinan |first10=Timothy G. |last11=Cryan |first11=John F. |title=The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus |journal=European Neuropsychopharmacology |date=1 February 2018 |volume=28 |issue=2 |pages=307–316 |doi=10.1016/j.euroneuro.2017.12.004 |language=en |issn=0924-977X}}</ref>

它们也可以被来自环境的输入和机体其他部分释放的激素所调控，这些都可以或多或少地被神经元直接影响。这也适用于神经营养素，如BDNF。肠道微生物组也与大脑有关。

==Mechanisms for propagating action potentials动作电位的传播机制==
In 1937 [[John Zachary Young]] suggested that the [[squid giant axon]] could be used to study neuronal electrical properties.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Milestones in Neuroscience Research |url = http://faculty.washington.edu/chudler/hist.html |work = Neuroscience for Kids |access-date = 2009-06-20}}</ref> It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the [[membrane potential]].

1937年，约翰-扎卡里-杨提出，乌贼巨大轴突可用于研究神经元的电特性。它比人类神经元大，但与人类神经元相似，因此更容易研究。通过将电极插入乌贼巨轴突，对膜电位进行了精确测量。

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate [[subthreshold membrane potential oscillations]]. These signals are generated and propagated by charge-carrying [[ions]] including sodium (Na+), potassium (K+), chloride (Cl−), and [[Calcium signaling|calcium (Ca2+)]].

轴突和胞体的细胞膜含有电压门控离子通道，使神经元能够产生和传播电信号（动作电位）。一些神经元还产生阈下膜电位振荡。这些信号是由携带电荷的离子产生和传播的，包括钠（Na+）、钾（K+）、氯（Cl-）和钙（Ca2+）。

Several stimuli can activate a neuron leading to electrical activity, including [[Mechanoreceptor|pressure]], stretch, chemical transmitters, and changes of the electric potential across the cell membrane.<ref>{{cite web|first1=Joe |last1=Patlak |first2=Ray |last2=Gibbons | name-list-style = vanc |title=Electrical Activity of Nerves |url=http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |work=Action Potentials in Nerve Cells |date=2000-11-01 |access-date=2009-06-20 |url-status=dead |archive-url=https://web.archive.org/web/20090827220335/http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |archive-date=August 27, 2009 }}</ref> Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.<ref name="Harris-Warrick">{{cite journal |last1=Harris-Warrick |first1=RM |title=Neuromodulation and flexibility in Central Pattern Generator networks. |journal=Current Opinion in Neurobiology |date=October 2011 |volume=21 |issue=5 |pages=685–92 |doi=10.1016/j.conb.2011.05.011 |pmid=21646013|pmc=3171584 }}</ref>

有几种刺激可以激活神经元，导致电活动，包括压力、拉伸、化学传导物和细胞膜上的电势变化。刺激导致细胞膜内特定的离子通道打开，使得离子流经细胞膜，改变膜电位。神经元必须保持界定其神经元类型的特定电特性。

Thin neurons and axons require less [[metabolism|metabolic]] expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of [[myelin]] around their axons. The sheaths are formed by [[glia]]l cells: [[oligodendrocyte]]s in the central nervous system and [[Schwann cell]]s in the peripheral nervous system. The sheath enables action potentials to travel [[saltatory conduction|faster]] than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed [[node of Ranvier|nodes of Ranvier]], which contain a high density of voltage-gated ion channels. [[Multiple sclerosis]] is a neurological disorder that results from demyelination of axons in the central nervous system.

薄的神经元和轴突需要较少的代谢支出来产生和传导动作电位，但较粗的轴突能更快地传递冲动。为了在保持快速传导的同时尽量减少代谢支出，许多神经元的轴突周围有绝缘的髓鞘。这些髓鞘是由胶质细胞形成的：中枢神经系统的少突胶质细胞和周围神经系统的许旺细胞。髓鞘使得动作电位比相同直径的无髓轴突走得更快，同时消耗更少的能量。周围神经中的髓鞘通常沿着轴突生长，长度约为1毫米，并且点缀着无髓鞘的郎飞氏结，其中包含高密度的电压门控离子通道。多发性硬化症是一种神经系统疾病，由中枢神经系统中轴突的脱髓鞘导致。

Some neurons do not generate action potentials, but instead generate a [[graded potential|graded electrical signal]], which in turn causes graded neurotransmitter release. Such [[non-spiking neurons]] tend to be sensory neurons or interneurons, because they cannot carry signals long distances.

有些神经元不产生动作电位，而是产生一个分级的电信号，反过来引起分级的神经递质释放。这样的非脉冲神经元往往是感觉神经元或中间神经元，因为它们不能长距离携带信号。

==Neural coding神经编码==
[[Neural coding]] is concerned with how sensory and other information is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the [[Stimulus (physiology)|stimulus]] and the individual or [[Neural ensemble|ensemble]] neuronal responses, and the relationships among the electrical activities of the neurons within the ensemble.<ref name="Brown">{{cite journal | vauthors = Brown EN, Kass RE, Mitra PP | title = Multiple neural spike train data analysis: state-of-the-art and future challenges | journal = Nature Neuroscience | volume = 7 | issue = 5 | pages = 456–61 | date = May 2004 | pmid = 15114358 | doi = 10.1038/nn1228 | s2cid = 562815 }}</ref> It is thought that neurons can encode both [[Digital data|digital]] and [[analog signal|analog]] information.<ref>{{cite book | vauthors = Thorpe SJ |chapter=Spike arrival times: A highly efficient coding scheme for neural networks |chapter-url= http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf |pages= 91–94 |title=Parallel processing in neural systems and computers| veditors = Eckmiller R, Hartmann G, Hauske G |date=1990|publisher=North-Holland|isbn=9780444883902 |url={{google books |plainurl=y |id=boBqAAAAMAAJ}}|language=en|archive-url=https://web.archive.org/web/20120215151304/http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf|archive-date=2012-02-15}}</ref>

神经编码关注的是感觉和其他信息如何在大脑中被神经元所表达。研究神经编码的主要目的是描述刺激与单个或集合神经元反应之间的关系，以及集合内神经元电活动之间的关系。人们认为，神经元既可以编码数字信息，也可以编码模拟信息。

==All-or-none principle全有或全无原则==

[[File:All-or-none_law_en.svg|thumb|318x318px|As long as the stimulus reaches the threshold, the full response would be given. Larger stimulus does not result in a larger response, vice versa.只要刺激达到阈值，就会有充分的反应。较大的刺激不会导致较大的反应，反之亦然。<ref name=":0">{{Cite book|title=Biological psychology|last=Kalat, James W|year=2016|isbn=9781305105409|edition=12|location=Australia|oclc=898154491}}</ref>{{Rp|31}}]]
{{Main|All-or-none law}}

The conduction of nerve impulses is an example of an [[All-or-none law|all-or-none]] response. In other words, if a neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal, but can increase firing frequency.<ref name=":0" />{{Rp|31}} Receptors respond in different ways to stimuli. Slowly adapting or [[tonic (physiology)|tonic receptors]] respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can't become "stronger" for a specific frequency.

神经冲动的传导是一个全有或全无反应的例子。换句话说，如果一个神经元有任何反应，那么它必须完全响应。更大的刺激强度，如更亮的图像/更响的声音，不会产生更强的信号，但可以增加放电频率。[34]：31受体以不同方式回应刺激。缓慢适应的或紧张性的受体对稳定的刺激作出响应，并产生稳定的放电率。紧张性受体最常通过增加其放电频率对刺激强度的增加作出反应，通常是一个与每秒钟的脉冲相关的刺激的幂函数。这可以比喻为光的内在属性，即一个特定频率（颜色）的更大强度需要更多的光子，因为光子不能对一个特定频率变得 "更强"。

Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with steady stimulus; examples include [[Human skin|skin]] which, when touched causes neurons to fire, but if the object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function.

其他受体类型包括时相性或瞬变性受体，其放电随着稳定的刺激而减少或停止；比如包括皮肤，当被触摸时引起神经元放电，但如果物体保持均匀的压力，神经元就停止放电。对压力和振动有反应的皮肤和肌肉的神经元有过滤的附属结构来帮助它们发挥作用。

The [[pacinian corpuscle]] is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus is transferred to the axon, which fires. If the pressure is steady, stimulus ends; thus, typically these neurons respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of a number of other neurons.<ref>{{cite book | last1 = Eckert | first1 = Roger | last2 = Randall | first2 = David | name-list-style = vanc | title = Animal physiology: mechanisms and adaptations | year = 1983 | publisher = W.H. Freeman | location = San Francisco | isbn = 978-0-7167-1423-1 | page = [https://archive.org/details/animalphysiology0000ecke/page/239 239] | url = https://archive.org/details/animalphysiology0000ecke/page/239 }}</ref>

帕西尼氏小体就是这样一个结构。它有像洋葱一样的同心层，围绕着轴突终端形成。当施加压力使小体变形时，机械刺激被转移到轴突上，轴突就会放电。如果压力是稳定的，刺激就会结束；因此，通常这些神经元在最初的变形过程中会有短暂的去极化反应，而当压力被移除时又会有短暂的去极化反应，从而使小体再次改变形状。其他类型的适应对扩展其他一些神经元的功能很重要。[35]

==Etymology and spelling词源和拼写==

The German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] introduced the term ''neuron'' in 1891,<ref name="finger"/> based on the [[Greek language|ancient Greek]] νεῦρον ''neuron'' 'sinew, cord, nerve'.<ref name="oed">''[[Oxford English Dictionary]]'', 3rd edition, 2003, ''s.v.''</ref>

德国解剖学家Heinrich Wilhelm Waldeyer于1891年提出了神经元一词，[36]其依据是古希腊语νεῦρον neuron's sinew, cord, nerve'。[37]

The word was adopted in French with the spelling ''neurone''. That spelling was also used by many writers in English,<ref name="mehta">{{cite journal | vauthors = Mehta AR, Mehta PR, Anderson SP, MacKinnon BL, Compston A | title = Grey Matter Etymology and the neuron(e) | journal = Brain | volume = 143 | issue = 1 | pages = 374–379 | date = January 2020 | pmid = 31844876 | pmc = 6935745 | doi = 10.1093/brain/awz367 | url = }}</ref> but has now become rare in American usage and uncommon in British usage.<ref name="ngram">{{cite web |title=Google Books Ngram Viewer |url=https://books.google.com/ngrams/graph?content=neuron%2Cneurone&year_start=1900&year_end=2008&case_insensitive=on&corpus=15&smoothing=3&direct_url=t4%3B%2Cneuron%3B%2Cc0%3B%2Cs0%3B%3Bneuron%3B%2Cc0%3B%3BNeuron%3B%2Cc0%3B%3BNEURON%3B%2Cc0%3B.t4%3B%2Cneurone%3B%2Cc0%3B%2Cs0%3B%3Bneurone%3B%2Cc0%3B%3BNeurone%3B%2Cc0%3B%3BNEURONE%3B%2Cc0 |website=books.google.com |access-date=19 December 2020 |language=en}}</ref><ref name="oed"/>

这个词以前在法语中被采用，拼写为neurone。这种拼法也曾被许多英语作家使用，[38]但现在在美国的用法中已经很少见，在英国的用法中也不常见。[39] [37]

==History历史==
{{Further|History of neuroscience}}
[[File:Golgi Hippocampus.jpg|left|thumb|Drawing by Camillo Golgi of a [[hippocampus]] stained using the [[silver nitrate]] method卡米洛-高尔基绘制的使用硝酸银法染色的海马体。]]
[[File:Purkinje cell by Cajal.png|thumb|Drawing of a Purkinje cell in the [[cerebellar cortex]] done by Santiago Ramón y Cajal, demonstrating the ability of Golgi's staining method to reveal fine detail圣地亚哥-拉蒙-卡亚尔（Santiago Ramón y Cajal）绘制的小脑皮层中的浦肯野细胞图，展示了高尔基染色法揭示精细细节的能力。]]

The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist [[Santiago Ramón y Cajal]].<ref name="López-Muñoz">{{cite journal | vauthors = López-Muñoz F, Boya J, Alamo C | title = Neuron theory, the cornerstone of neuroscience, on the centenary of the Nobel Prize award to Santiago Ramón y Cajal | journal = Brain Research Bulletin | volume = 70 | issue = 4–6 | pages = 391–405 | date = October 2006 | pmid = 17027775 | doi = 10.1016/j.brainresbull.2006.07.010 | s2cid = 11273256 }}</ref>

神经元作为神经系统主要功能单位的地位，在19世纪末通过西班牙解剖学家圣地亚哥-拉蒙-卡亚尔的作品首次得到承认。[40]

To make the structure of individual neurons visible, [[Santiago Ramón y Cajal|Ramón y Cajal]] improved a [[Golgi's method|silver staining process]] that had been developed by [[Camillo Golgi]].<ref name="López-Muñoz" /> The improved process involves a technique called "double impregnation" and is still in use.

为了使单个神经元的结构清晰可见，Ramón y Cajal改进了Camillo Golgi开发的银染工艺。[40]改进后的工艺涉及一种称为 "双浸渍 "的技术，现在仍在使用。

In 1888 Ramón y Cajal published a paper about the bird cerebellum. In this paper, he stated that he could not find evidence for [[anastomosis]] between axons and dendrites and called each nervous element "an absolutely autonomous canton."<ref name="López-Muñoz" /><ref name="finger">{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=Ramon y Cajal's first paper on the Golgi stain was on the bird cerebellum, and it appeared in the ''Revista''<nowiki> in 1888. He acknowledged that he found the nerve fibers to be very intricate, but stated that he could find no evidence for either axons or dendrites undergoing anastomosis and forming nets. He called each nervous element 'an absolutely autonomous canton.'</nowiki>}}</ref> This became known as the [[neuron doctrine]], one of the central tenets of modern [[neuroscience]].<ref name="López-Muñoz" />

1888年，Ramón y Cajal发表了一篇关于鸟类小脑的论文。在这篇论文中，他说他找不到轴突和树突之间结合的证据，并称每个神经元素为 "一个绝对自主的州县"[40] [36]，这被称为神经元学说，是现代神经科学的核心原则之一。[40]

In 1891, the German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] wrote a highly influential review of the neuron doctrine in which he introduced the term ''neuron'' to describe the anatomical and physiological unit of the nervous system.<ref>{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=... a man who would write a highly influential review of the evidence in favor of the neuron doctrine two years later. In his paper, Waldeyer (1891), ... , wrote that nerve cells terminate freely with end arborizations and that the 'neuron' is the anatomical and physiological unit of the nervous system. The word 'neuron' was born this way.}}</ref><ref>{{cite web|url=http://www.whonamedit.com/doctor.cfm/1846.html|title=Whonamedit - dictionary of medical eponyms|website=www.whonamedit.com|quote=Today, Wilhelm von Waldeyer-Hartz is remembered as the founder of the neurone theory, coining the term "neurone" to describe the cellular function unit of the nervous system and enunciating and clarifying that concept in 1891.}}</ref>

1891年，德国解剖学家Heinrich Wilhelm Waldeyer写了一篇对神经元学说有很大影响的综述，他在其中提出了神经元这一术语来描述神经系统的解剖学和生理学单位。[41] [42]

The silver impregnation stains are a useful method for [[Neuroanatomy|neuroanatomical]] investigations because, for reasons unknown, it stains only a small percentage of cells in a tissue, exposing the complete micro structure of individual neurons without much overlap from other cells.<ref name="Grant">{{cite journal | vauthors = Grant G | title = How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal | journal = Brain Research Reviews | volume = 55 | issue = 2 | pages = 490–8 | date = October 2007 | pmid = 17306375 | doi = 10.1016/j.brainresrev.2006.11.004 | s2cid = 24331507 }}</ref>

银浸渍染色法是神经解剖学研究的有效方法，因为——由于未知的原因——它只会对组织中的一小部分细胞进行染色，暴露出单个神经元的完整微观结构，而不会与其他细胞有太多的重叠。[43]

===Neuron doctrine神经元学说===
[[File:PurkinjeCell.jpg|thumb|Drawing of neurons in the pigeon [[cerebellum]], by Spanish neuroscientist [[Santiago Ramón y Cajal]] in 1899. (A) denotes [[Purkinje cell]]s and (B) denotes [[granule cells]], both of which are multipolar.鸽子小脑中的神经元图，由西班牙神经科学家圣地亚哥-拉蒙-卡亚尔于1899年绘制。(A）表示浦肯野细胞，（B）表示颗粒细胞，两者都是多极的。]]

The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramón y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in a meshwork), acting as metabolically distinct units.

神经元学说是现在的一个基本观点，即神经元是神经系统的基本结构和功能单位。该理论是由圣地亚哥-拉蒙-卡亚尔在19世纪末提出的。它认为，神经元是离散的细胞（不以网状结构连接），作为新陈代谢的不同单位发挥作用。

Later discoveries yielded refinements to the doctrine. For example, [[Neuroglia|glial cells]], which are non-neuronal, play an essential role in information processing.<ref>{{cite journal | vauthors = Witcher MR, Kirov SA, Harris KM | title = Plasticity of perisynaptic astroglia during synaptogenesis in the mature rat hippocampus | journal = Glia | volume = 55 | issue = 1 | pages = 13–23 | date = January 2007 | pmid = 17001633 | doi = 10.1002/glia.20415 | citeseerx = 10.1.1.598.7002 | s2cid = 10664003 }}</ref> Also, electrical synapses are more common than previously thought,<ref>{{cite journal | vauthors = Connors BW, Long MA | title = Electrical synapses in the mammalian brain | journal = Annual Review of Neuroscience | volume = 27 | issue = 1 | pages = 393–418 | year = 2004 | pmid = 15217338 | doi = 10.1146/annurev.neuro.26.041002.131128 | url = https://zenodo.org/record/894386 }}</ref> comprising direct, cytoplasmic connections between neurons. In fact, neurons can form even tighter couplings: the squid giant axon arises from the fusion of multiple axons.<ref>{{cite journal | vauthors = Guillery RW | title = Observations of synaptic structures: origins of the neuron doctrine and its current status | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 360 | issue = 1458 | pages = 1281–307 | date = June 2005 | pmid = 16147523 | pmc = 1569502 | doi = 10.1098/rstb.2003.1459 }}</ref>

后来的发现使这一学说得到了完善。例如，非神经元的胶质细胞在信息处理中起着至关重要的作用。[44] 另外，电突触比以前认为得更常见，[45] 包括神经元之间的直接胞质连接。事实上，神经元可以形成更紧密的耦合：乌贼的巨型轴突来自于多个轴突的融合。[46]

Ramón y Cajal also postulated the Law of Dynamic Polarization, which states that a neuron receives signals at its dendrites and cell body and transmits them, as action potentials, along the axon in one direction: away from the cell body.<ref name="sabb">{{cite journal | vauthors = Sabbatini RM | date = April–July 2003 | url = http://www.cerebromente.org.br/n17/history/neurons3_i.htm | title = Neurons and Synapses: The History of Its Discovery | journal = Brain & Mind Magazine | pages = 17 }}</ref> The Law of Dynamic Polarization has important exceptions; dendrites can serve as synaptic output sites of neurons<ref>{{cite journal | vauthors = Djurisic M, Antic S, Chen WR, Zecevic D | title = Voltage imaging from dendrites of mitral cells: EPSP attenuation and spike trigger zones | journal = The Journal of Neuroscience | volume = 24 | issue = 30 | pages = 6703–14 | date = July 2004 | pmid = 15282273 | pmc = 6729725 | doi = 10.1523/JNEUROSCI.0307-04.2004 | hdl = 1912/2958 }}
</ref> and axons can receive synaptic inputs.<ref>{{cite journal | vauthors = Cochilla AJ, Alford S | title = Glutamate receptor-mediated synaptic excitation in axons of the lamprey | journal = The Journal of Physiology | volume = 499 | issue = Pt 2 | pages = 443–57 | date = March 1997 | pmid = 9080373 | pmc = 1159318 | doi = 10.1113/jphysiol.1997.sp021940 }}</ref>

拉蒙-卡哈尔还提出了动态极化定律，即神经元在其树突和细胞体上接收信号，并作为动作电位沿轴突向一个方向传输：离开细胞体。[47] 动态极化定律有重要的例外；树突可以作为神经元的突触输出点[48] ，轴突可以接受突触输入。[49]

===Compartmental modelling of neurons 神经元的间室模型===

Although neurons are often described of as "fundamental units" of the brain, they perform internal computations. Neurons integrate input within dendrites, and this complexity is lost in models that assume neurons to be a fundamental unit. Dendritic branches can be modeled as spatial compartments, whose activity is related due to passive membrane properties, but may also be different depending on input from synapses. [[Compartmental modelling of dendrites]] is especially helpful for understanding the behavior of neurons that are too small to record with electrodes, as is the case for ''Drosophila melanogaster''.<ref>{{cite journal | vauthors = Gouwens NW, Wilson RI | title = Signal propagation in Drosophila central neurons | journal = Journal of Neuroscience | volume = 29 | issue = 19 | pages = 6239–6249 | year = 2009 | pmid = 19439602 | pmc = 2709801 | doi = 10.1523/jneurosci.0764-09.2009 | doi-access = free }}</ref>

尽管神经元经常被描述为大脑的 "基本单位"，但它们执行内部计算。神经元在树突内整合输入，这种复杂性在假定神经元是一个基本单位的模型中丢失。树突分支可以被建模为空间隔间，其活性与被动膜特性相关，但也可能因来自突触的输入的差异而有所不同。树突的间室模型对于理解那些太小而无法用电极记录的神经元的行为特别有帮助，黑腹果蝇就是这种情况。[50]

==Neurons in the brain大脑中的神经元==

The number of neurons in the brain varies dramatically from species to species.<ref name="nervenet">{{cite journal | vauthors = Williams RW, Herrup K | title = The control of neuron number | journal = Annual Review of Neuroscience | volume = 11 | issue = 1 | pages = 423–53 | year = 1988 | pmid = 3284447 | doi = 10.1146/annurev.ne.11.030188.002231 }}</ref> In a human, there are an estimated 10–20 billion neurons in the [[cerebral cortex]] and 55–70 billion neurons in the [[cerebellum]].<ref name="pmid27187682">{{cite journal | vauthors = von Bartheld CS, Bahney J, Herculano-Houzel S | title = The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting | journal = The Journal of Comparative Neurology | volume = 524 | issue = 18 | pages = 3865–3895 | date = December 2016 | pmid = 27187682 | pmc = 5063692 | doi = 10.1002/cne.24040 }}</ref> By contrast, the [[nematode]] worm ''[[Caenorhabditis elegans]]'' has just 302 neurons, making it an ideal [[model organism]] as scientists have been able to map all of its neurons. The fruit fly ''[[Drosophila melanogaster]]'', a common subject in biological experiments, has around 100,000 neurons and exhibits many complex behaviors. Many properties of neurons, from the type of neurotransmitters used to ion channel composition, are maintained across species, allowing scientists to study processes occurring in more complex organisms in much simpler experimental systems.

大脑中的神经元数量因物种不同而有很大差异。[51] 在人类中，大脑皮层中估计有100-200亿个神经元，小脑中有550-700亿个神经元。[52] 相比之下，秀丽隐杆线虫只有302个神经元，使其成为理想的模型生物，因为科学家已经能够绘制其所有的神经元。黑腹果蝇是生物实验中常见的对象，它有大约10万个神经元，表现出许多复杂的行为。神经元的许多特性，从使用的神经递质类型到离子通道组成，在不同的物种中都保持不变，使科学家能够在更简单的实验系统中研究发生在更复杂生物体中的过程。

==Neurological disorders神经系统疾病==
{{Main主要文章|Neurology神经病学}}
{{More citations needed|date=May 2018}}

'''[[Charcot–Marie–Tooth disease]]''' (CMT) is a heterogeneous inherited disorder of nerves ([[neuropathy]]) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs extending to the hands and arms in advanced stages. Presently incurable, this disease is one of the most common inherited neurological disorders, with 36 in 100,000 affected.<ref name=Krajewski>{{cite journal | vauthors = Krajewski KM, Lewis RA, Fuerst DR, Turansky C, Hinderer SR, Garbern J, Kamholz J, Shy ME | title = Neurological dysfunction and axonal degeneration in Charcot-Marie-Tooth disease type 1A | journal = Brain | volume = 123 | issue = 7 | pages = 1516–27 | date = July 2000 | pmid = 10869062 | doi = 10.1093/brain/123.7.1516 | doi-access = free }}</ref>

腓骨肌萎缩症（CMT）是一种异质性的遗传性神经疾病（神经病变），其特点是肌肉组织和触觉的丧失，主要是在脚和腿上，在晚期会延伸到手和胳膊。该病目前无法治愈，是最常见的遗传性神经系统疾病之一，每10万人中会有36人罹患此病。[53]

'''[[Alzheimer's disease]]''' (AD), also known simply as ''Alzheimer's'', is a [[neurodegenerative disease]] characterized by progressive [[cognitive]] deterioration, together with declining activities of daily living and [[neuropsychiatric]] symptoms or behavioral changes.<ref name="nihstages">{{cite web|title=About Alzheimer's Disease: Symptoms|url=http://www.nia.nih.gov/alzheimers/topics/symptoms|publisher=National Institute on Aging|access-date=28 December 2011|url-status=live|archive-url=https://web.archive.org/web/20120115201854/http://www.nia.nih.gov/alzheimers/topics/symptoms|archive-date=15 January 2012|df=dmy-all}}</ref> The most striking early symptom is loss of short-term memory ([[amnesia]]), which usually manifests as minor forgetfulness that becomes steadily more pronounced with illness progression, with relative preservation of older memories. As the disorder progresses, cognitive (intellectual) impairment extends to the domains of language ([[aphasia]]), skilled movements ([[apraxia]]), and recognition ([[agnosia]]), and functions such as decision-making and planning become impaired.<ref name="BMJ2009">{{cite journal | vauthors = Burns A, Iliffe S | title = Alzheimer's disease | journal = BMJ | volume = 338 | pages = b158 | date = February 2009 | pmid = 19196745 | doi = 10.1136/bmj.b158 | s2cid = 8570146 | url = https://semanticscholar.org/paper/0fccf0616b35e3bb427c3783a44777e4dc228713 }}</ref><ref name=NEJM2010>{{cite journal | vauthors = Querfurth HW, LaFerla FM | title = Alzheimer's disease | journal = The New England Journal of Medicine | volume = 362 | issue = 4 | pages = 329–44 | date = January 2010 | pmid = 20107219 | doi = 10.1056/NEJMra0909142 | s2cid = 205115756 | url = https://semanticscholar.org/paper/7bc445c5ddf7869b9f71a5390ff9e9e992533ee3 }}</ref>

阿尔茨海默病（AD），也被简单地称为阿尔茨海默病，是一种神经退行性疾病，其特点是认知能力逐渐退化，伴随着日常生活活动能力下降和神经精神症状或行为变化。[54] 最突出的早期症状是短期记忆的丧失（失忆），通常表现为轻微的遗忘，随着病情的发展，遗忘的程度会逐渐加重，但老的记忆却记忆得相对清楚。随着病情的发展，认知（智力）损害扩展到语言（失语）、熟练动作（失用）和识别（失认）等领域，决策和计划等功能也会受到损害[55][56] 。

'''[[Parkinson's disease]]''' (PD), also known as ''Parkinson disease'', is a degenerative disorder of the central nervous system that often impairs motor skills and speech.<ref name=NIH2016>{{cite web|title=Parkinson's Disease Information Page|url=https://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|website=NINDS|access-date=18 July 2016|date=30 June 2016|url-status=live|archive-url=https://web.archive.org/web/20170104201403/http://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|archive-date=4 January 2017|df=dmy-all}}</ref> Parkinson's disease belongs to a group of conditions called [[movement disorders]].<ref>{{cite web | title = Movement Disorders| url = http://www.neuromodulation.com/movement-disorders | work = The International Neuromodulation Society }}</ref> It is characterized by muscle rigidity, [[tremor]], a slowing of physical movement ([[bradykinesia]]), and in extreme cases, a loss of physical movement ([[akinesia]]). The primary symptoms are the results of decreased stimulation of the [[motor cortex]] by the [[basal ganglia]], normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level [[cognitive dysfunction]] and subtle language problems. PD is both chronic and progressive.

帕金森病（PD），又称帕金森病，是一种中枢神经系统的退行性疾病，通常会损害运动技能和语言能力。[57] 帕金森病属于一组被称为运动障碍的疾病。[58] 它的特点是肌肉僵硬、震颤、身体运动变慢（运动迟缓），在极端情况下，身体运动丧失（运动不能）。主要症状是基底神经节对运动皮层刺激减少的结果，通常是由于大脑多巴胺能神经元中产生的多巴胺形成和作用不足造成的。次要症状可能包括高水平的认知功能障碍和微妙的语言问题。帕金森病既是慢性的，也是渐进的。

'''[[Myasthenia gravis]]''' is a neuromuscular disease leading to fluctuating [[muscle weakness]] and fatigability during simple activities. Weakness is typically caused by circulating [[antibodies]] that block [[acetylcholine receptors]] at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with [[immunosuppressants]], [[cholinesterase]] inhibitors and, in selected cases, [[thymectomy]].

重症肌无力是一种神经肌肉疾病，导致简单活动时出现波动性的肌肉无力和疲劳。肌无力通常是由阻断突触后神经肌肉接头处的乙酰胆碱受体的循环抗体引起的，它抑制了神经递质乙酰胆碱的刺激作用。肌无力症用免疫抑制剂、胆碱酯酶抑制剂来治疗，在某些情况下还可以进行胸腺切除术。

===Demyelination脱髓鞘症===
{{Further|Demyelinating disease}}
[[File:Guillain-barré syndrome - Nerve Damage.gif|thumb|Guillain–Barré syndrome – demyelination格林-巴利综合征——脱髓鞘症]]

[[Demyelination]] is the act of demyelinating, or the loss of the myelin sheath insulating the nerves. When myelin degrades, conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. This leads to certain neurodegenerative disorders like [[multiple sclerosis]] and [[chronic inflammatory demyelinating polyneuropathy]].

脱髓鞘是指脱髓鞘的行为，或绝缘于神经的髓鞘的丧失。当髓鞘退化时，信号沿神经的传导会受到影响或丧失，神经最终会萎缩。这导致了某些神经退行性疾病，如多发性硬化症和慢性炎症性脱髓鞘多发性神经病。

===Axonal degeneration轴突变性===
Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration, which is the rapid separation of the proximal and distal ends, occurring within 30 minutes of injury. Degeneration follows with swelling of the [[axolemma]], and eventually leads to bead-like formation. Granular disintegration of the axonal [[cytoskeleton]] and inner [[organelle]]s occurs after axolemma degradation. Early changes include accumulation of [[mitochondria]] in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The disintegration is dependent on [[ubiquitin]] and [[calpain]] [[proteases]] (caused by the influx of calcium ion), suggesting that axonal degeneration is an active process that produces complete fragmentation. The process takes about roughly 24 hours in the PNS and longer in the CNS. The signaling pathways leading to axolemma degeneration are unknown.

尽管大多数损伤反应包括钙离子流入信号，以促进断裂部分的重新愈合，但轴突损伤最初会导致急性轴突变性，即在损伤后30分钟内近端和远端迅速分离。退化后，轴突肿胀，最终形成串珠状肿胀。轴索细胞骨架和内部细胞器的颗粒状解体发生在轴索退化之后。早期的变化包括线粒体在损伤部位的结旁区堆积。内质网降解、线粒体膨胀并最终解体。解体依赖于泛素和钙蛋白酶（由钙离子的涌入引起），表明轴突变性是一个完全破碎的活跃过程。这一过程在PNS（周围神经系统）中大约需要24小时，在CNS（中枢神经系统）中则需要更长时间。导致轴突变性的信号传导途径尚不清楚。

==Neurogenesis神经发生==
{{Main|Neurogenesis}}

Neurons are born through the process of [[neurogenesis]], in which [[neural stem cell]]s divide to produce differentiated neurons. Once fully differentiated neurons are formed, they are no longer capable of undergoing [[mitosis]]. Neurogenesis primarily occurs in the embryo of most organisms.

神经元是通过神经发生的过程诞生的，其中神经干细胞分裂产生分化的神经元。一旦完全分化的神经元形成，它们就不再能够进行有丝分裂。神经发生主要发生在大多数生物体的胚胎中。

[[Adult neurogenesis]] can occur and studies of the age of human neurons suggest that this process occurs only for a minority of cells, and that the vast majority of neurons in the [[neocortex]] forms before birth and persists without replacement. The extent to which adult neurogenesis exists in humans, and its contribution to cognition are controversial, with conflicting reports published in 2018.<ref>{{cite journal | vauthors = Kempermann G, Gage FH, Aigner L, Song H, Curtis MA, Thuret S, Kuhn HG, Jessberger S, Frankland PW, Cameron HA, Gould E, Hen R, Abrous DN, Toni N, Schinder AF, Zhao X, Lucassen PJ, Frisén J | title = Human Adult Neurogenesis: Evidence and Remaining Questions | journal = Cell Stem Cell | volume = 23 | issue = 1 | pages = 25–30 | date = July 2018 | pmid = 29681514 | pmc = 6035081 | doi = 10.1016/j.stem.2018.04.004 }}</ref>

成年神经发生能够发生，对人类神经元年龄的研究表明，这一过程只发生在少数细胞中，新皮层中的绝大多数神经元在出生前就已形成，并持续存在而不被替换。人类中成年神经发生存在的程度，以及它对认知的贡献是有争议的，2018年发表的报告相互矛盾。[59]

The body contains a variety of stem cell types that have the capacity to differentiate into neurons. Researchers found a way to transform human skin cells into nerve cells using [[transdifferentiation]], in which "cells are forced to adopt new identities".<ref name=twsX33>{{Cite journal |doi=10.1038/news.2011.328 | last = Callaway | first = Ewen |title= How to make a human neuron | journal = Nature |quote= By transforming cells from human skin into working nerve cells, researchers may have come up with a model for nervous-system diseases and perhaps even regenerative therapies based on cell transplants. The achievement, reported online today in ''Nature'', is the latest in a fast-moving field called transdifferentiation, in which cells are forced to adopt new identities. In the past year, researchers have converted connective tissue cells found in skin into heart cells, blood cells, and liver cells.
|date= 26 May 2011 }}</ref>

人体含有各种干细胞类型，它们有能力分化为神经元。研究人员发现了一种利用横向分化将人类皮肤细胞转化为神经细胞的方法，其中 "细胞被迫采用新的身份"。[60]

During [[neurogenesis]] in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that populate cortical layers. [[Epigenetics|Epigenetic]] modifications play a key role in regulating [[gene expression]] in differentiating [[neural stem cells]], and are critical for cell fate determination in the developing and adult mammalian brain. Epigenetic modifications include [[DNA methylation|DNA cytosine methylation]] to form [[5-methylcytosine]] and [[DNA demethylation|5-methylcytosine demethylation]].<ref name=Wang2016>{{cite journal | vauthors = Wang Z, Tang B, He Y, Jin P | title = DNA methylation dynamics in neurogenesis | journal = Epigenomics | volume = 8 | issue = 3 | pages = 401–14 | date = March 2016 | pmid = 26950681 | pmc = 4864063 | doi = 10.2217/epi.15.119 }}</ref> These modifications are critical for cell fate determination in the developing and adult mammalian brain. [[DNA methylation|DNA cytosine methylation]] is catalyzed by [[DNA methyltransferase|DNA methyltransferases (DNMTs)]]. Methylcytosine demethylation is catalyzed in several stages by [[TET enzymes]] that carry out oxidative reactions (e.g. [[5-methylcytosine]] to [[5-hydroxymethylcytosine]]) and enzymes of the DNA [[base excision repair]] (BER) pathway.<ref name=Wang2016/>

在哺乳动物大脑的神经发生过程中，祖细胞和干细胞从增殖性分裂发展到分化性分裂。这一进展导致了皮层中的神经元和胶质细胞的出现。表观遗传学修饰在调节分化中的神经干细胞的基因表达方面起着关键作用，对发育中和成年哺乳动物大脑中的细胞命运决定至关重要。表观遗传修饰包括DNA胞嘧啶甲基化形成5-甲基胞嘧啶和5-甲基胞嘧啶去甲基化。[61] 这些修饰对于发育中和成年哺乳动物大脑的细胞命运决定至关重要。DNA胞嘧啶甲基化是由DNA甲基转移酶（DNMTs）催化的。甲基胞嘧啶去甲基化是由进行氧化反应（如5-甲基胞嘧啶到5-羟甲基胞嘧啶）的TET酶和DNA碱基切除修复（BER）途径的酶分几个阶段催化的[61] 。

At different stages of mammalian nervous system development two DNA repair processes are employed in the repair of DNA double-strand breaks. These pathways are [[homologous recombination]]al repair used in proliferating neural precursor cells, and [[non-homologous end joining]] used mainly at later developmental stages<ref>{{cite journal | vauthors = Orii KE, Lee Y, Kondo N, McKinnon PJ | title = Selective utilization of nonhomologous end-joining and homologous recombination DNA repair pathways during nervous system development | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 26 | pages = 10017–22 | date = June 2006 | pmid = 16777961 | pmc = 1502498 | doi = 10.1073/pnas.0602436103 | bibcode = 2006PNAS..10310017O | doi-access = free }}</ref>

在哺乳动物神经系统发育的不同阶段，有两种DNA修复过程被用于修复DNA双链断裂。这些途径是用于增殖期神经前体细胞的同源重组修复，以及主要用于后期发育阶段的非同源末端连接[62] 。

==Nerve regeneration神经再生==
{{Main|Neuroregeneration}}
Peripheral axons can regrow if they are severed,<ref name="Yiu_2006">{{cite journal | vauthors = Yiu G, He Z | title = Glial inhibition of CNS axon regeneration | journal = Nature Reviews. Neuroscience | volume = 7 | issue = 8 | pages = 617–27 | date = August 2006 | pmid = 16858390 | pmc = 2693386 | doi = 10.1038/nrn1956 }}</ref> but one neuron cannot be functionally replaced by one of another type ([[Llinás' law]]).<ref name="llinas2014"/>

外围轴突如果被切断，可以重新生长，[63]但一个神经元在功能上不能被另一种类型的神经元取代（Llinás法则）[15]。

== See also ==
{{Div col|colwidth=20em}}
* [[Artificial neuron]]
* [[Bidirectional cell]]
* [[Biological neuron model]]
* [[Compartmental neuron models]]
* [[Connectome]]
* [[Dogiel cell]]
* [[List of animals by number of neurons]]
* [[List of neuroscience databases]]
* [[Neuronal galvanotropism]]
* [[Neuroplasticity]]
* [[Growth cone]]
* [[Sholl analysis]]
{{Div col end}}

*人工神经元
*双向细胞
*生物神经元模型
*间室神经元模型
*连接组
*锥体细胞
*按神经元数量排列的动物名单
*神经科学数据库列表
*神经元向电性
*神经可塑性
*生长锥
*肖尔分析

== References参考文献 ==

{{Reflist}}

== Further reading进一步阅读 ==
{{refbegin}}
* {{cite journal | vauthors = Bullock TH, Bennett MV, Johnston D, Josephson R, Marder E, Fields RD | title = Neuroscience. The neuron doctrine, redux | journal = Science | volume = 310 | issue = 5749 | pages = 791–3 | date = November 2005 | pmid = 16272104 | doi = 10.1126/science.1114394 | s2cid = 170670241 }}
* {{Cite book | vauthors = Kandel ER, Schwartz JH, Jessell TM |year=2000 |title=Principles of Neural Science |edition=4th |publisher=McGraw-Hill |location=New York |isbn=0-8385-7701-6 }}
* {{Cite book | vauthors = Peters A, Palay SL, Webster HS |year=1991 |title=The Fine Structure of the Nervous System |edition=3rd |location=New York |publisher=Oxford University Press |isbn=0-19-506571-9 }}
* {{Cite book | vauthors = Ramón y Cajal S |year=1933 |title=Histology |edition=10th |publisher=Wood |location=Baltimore }}
* {{Cite book | vauthors = Roberts A, Bush BM |year=1981 |title=Neurones without Impulses |publisher=Cambridge University Press |location=Cambridge |isbn=0-521-29935-7 }}
* {{Cite book |title=Clinical Neuroanatomy | vauthors = Snell RS |date=2010 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-9427-5 |language=en |url=https://www.google.com/books/edition/_/ABPmvroyrD0C }}
{{refend}}

== External links外部链接 ==
{{sisterlinks|d=Q43054|n=no|b=Human_Anatomy/The_Neuron|v=no|voy=no|wikt=neuron|m=no|mw=no|s=no|species=no}}
*{{Curlie|Science/Biology/Neurobiology/|Neurobiology}}
* [https://web.archive.org/web/20130425202653/http://ibro.info/ IBRO (International Brain Research Organization)]. Fostering neuroscience research especially in less well-funded countries.
* [http://NeuronBank.org NeuronBank] an online neuromics tool for cataloging neuronal types and synaptic connectivity.
* [https://web.archive.org/web/20190621124504/http://brainmaps.org/ High Resolution Neuroanatomical Images of Primate and Non-Primate Brains].
* The [[v:Topic:Neuroscience|Department of Neuroscience]] at [[v:|Wikiversity]], which presently offers two courses: [[v:Fundamentals of Neuroscience|Fundamentals of Neuroscience]] and [[v:Comparative Neuroscience|Comparative Neuroscience]].
* [https://www.neuinfo.org/mynif/search.php?q=Neuron&t=data&s=cover&b=0&r=20 NIF Search – Neuron] via the [[Neuroscience Information Framework]]
* [https://web.archive.org/web/20110813070057/http://ccdb.ucsd.edu/sand/main?event=showMPByType&typeid=0&start=1&pl=y Cell Centered Database – Neuron]
* [http://neurolex.org/wiki/Category:Neuron Complete list of neuron types] according to the Petilla convention, at [[NeuroLex]].
* [http://NeuroMorpho.org NeuroMorpho.Org] an online database of digital reconstructions of neuronal morphology.
* [https://web.archive.org/web/20111008142032/http://www.immunoportal.com/modules.php?name=gallery2&g2_view=keyalbum.KeywordAlbum&g2_keyword=Neuron Immunohistochemistry Image Gallery: Neuron]
* [https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/v/anatomy-of-a-neuron Khan Academy: Anatomy of a neuron]
* [http://www.histology-world.com/photoalbum/thumbnails.php?album=96 Neuron images]

* IBRO (国际大脑研究组织)。促进神经科学研究，尤其是在资金不足的国家。
* NeuronBank 是一个在线神经病学工具，用于编目神经元类型和突触连接。
* 灵长类动物和非灵长类动物大脑的高分辨率神经解剖图像。
* 维基大学神经科学系，目前提供两门课程: 神经科学基础和比较神经科学。
* NIF 搜索-神经元通过神经科学信息框架
* 细胞中心数据库-神经元
* 完整的神经元类型清单根据 Petilla 公约，在 NeuroLex。
* NeuroMorpho. Org，一个神经形态学数字重建的在线数据库。
* Immunohistochemistry Image Gallery: Neuron
* Khan Academy: Anatomy of a neuron
* Neuron images

{{Nervous system tumors}}
{{Nervous tissue}}
{{Portal bar|Biology|Medicine}}
{{Authority control}}

[[Category:Neurons| ]]
[[Category:Medical terminology]]

Category:Medical terminology

类别: 医学术语

<noinclude>

This page was moved from [[wikipedia:en:Neuron]]. Its edit history can be viewed at [[神经元/edithistory]]</noinclude>

[[Category:待整理页面]]

神经元

2022-04-30T06:38:53Z

耿淅耀：/* Nervous system神经系统 */

此词条由神经动力学读书会词条梳理志愿者[[用户:Autumnwolfberry|Autumnwolfberry]]翻译审校，未经专家审核，带来阅读不便，请见谅。

{{short description|Electrically excitable cell that communicates via synapses}}
{{About|the type of cell}}
{{Distinguish|Neutron}}
{{Infobox neuron
|name = Neuron
|image = Blausen 0657 MultipolarNeuron.png
|caption =Anatomy of a [[multipolar neuron]]
|function =
|neurotransmitter =
|morphology =
|afferents =
|efferents =
}}

A '''neuron''' or '''nerve cell''' is an [[membrane potential#Cell excitability|electrically excitable]] [[cell (biology)|cell]] that communicates with other cells via specialized connections called [[synapse]]s. The neuron is the main component of [[nervous tissue]] in all [[Animalia|animals]] except [[sponge]]s and [[placozoa]]. [[Plant]]s and [[fungi]] do not have nerve cells.

神经元或神经细胞是一种可电兴奋的细胞，通过称为突触的专门连接与其他细胞进行交流。神经元是所有动物神经组织的主要组成部分，除了海绵动物门和扁盘动物门。植物和真菌没有神经细胞。

Neurons are typically classified into three types based on their function. [[Sensory neuron]]s respond to [[Stimulus (physiology)|stimuli]] such as touch, sound, or light that affect the cells of the [[Sense|sensory organs]], and they send signals to the spinal cord or brain. [[Motor neuron]]s receive signals from the brain and spinal cord to control everything from [[muscle contraction]]s to [[gland|glandular output]]. [[Interneuron]]s connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together they form what is called a [[neural circuit]].

神经元通常根据其功能被分为三种类型。感觉神经元对影响感觉器官细胞的刺激，如触摸、声音或光线作出反应，并向脊髓或大脑发送信号。运动神经元接收来自大脑和脊髓的信号，控制从肌肉收缩到腺体输出的一切。中间神经元将神经元与大脑或脊髓同一区域内的其他神经元连接起来。当多个神经元连接在一起时，它们形成所谓的神经回路。

A typical neuron consists of a cell body ([[Soma (biology)|soma]]), [[dendrite]]s, and a single [[axon]]. The soma is a compact structure and the axon and dendrites are filaments extruding from the soma. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The axon leaves the soma at a swelling called the [[axon hillock]] and travels for as far as 1 meter in humans or more in other species. It branches but usually maintains a constant diameter. At the farthest tip of the axon's branches are [[axon terminals]], where the neuron can transmit a signal across the [[synapse]] to another cell. Neurons may lack dendrites or have no axon. The term [[neurite]] is used to describe either a dendrite or an axon, particularly when the cell is [[Cellular differentiation|undifferentiated]].

一个典型的神经元由一个细胞体（soma：胞体）、树突和一个轴突组成。胞体是一个紧凑的结构，轴突和树突是从胞体中挤出的丝状物。树突通常有大量的分支，并从胞体中延伸出几百微米。轴突在一个称为轴突丘的肿胀处离开胞体，在人类中最远可达1米，在其他物种中则更远。它有分支，但通常保持一个恒定的直径。在轴突分支的最远端是轴突终端，在那里神经元可以通过突触向另一个细胞传递信号。神经元可能缺乏树突或没有轴突。术语神经突被用来描述树突或轴突，特别是当细胞未分化时。

Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to a dendrite of another. However, synapses can connect an axon to another axon or a dendrite to another dendrite.

大多数神经元通过树突和胞体接收信号，并沿轴突发出信号。在大多数突触中，信号从一个神经元的轴突交叉到另一个神经元的树突。然而，突触可以将一个轴突连接到另一个轴突，或者将一个树突连接到另一个树突。

The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to maintenance of [[voltage]] gradients across their [[Cell membrane|membranes]]. If the voltage changes by a large enough amount over a short interval, the neuron generates an [[All-or-none law|all-or-nothing]] [[electrochemical]] pulse called an [[action potential]]. This potential travels rapidly along the axon and activates synaptic connections as it reaches them. Synaptic signals may be [[Excitatory postsynaptic potential|excitatory]] or [[Inhibitory postsynaptic potential|inhibitory]], increasing or reducing the net voltage that reaches the soma.

信号传递过程部分是电子的，部分是化学的。神经元具有电兴奋性，这是由于其膜上的电压梯度得到了维持。如果电压在短时间内发生足够大的变化，神经元就会产生一个全有或全无的电化学脉冲，称为动作电位。这个电位沿轴突迅速传播，到达突触连接时激活它们。突触信号可能是兴奋性的或抑制性的，增加或减少到达胞体的净电压。

In most cases, neurons are generated by [[neural stem cell]]s during brain development and childhood. [[Neurogenesis]] largely ceases during adulthood in most areas of the brain.

在大多数情况下，神经元是在大脑发育和儿童时期由神经干细胞生成的。在大脑的大多数区域，神经元的生成在成年后基本停止。

{{toclimit|3}}

== Nervous system神经系统 ==

[[File:Anatomy of a Neuron with Synapse.png|thumb|upright=1.15|Schematic of an anatomically accurate single pyramidal neuron, the primary excitatory neuron of cerebral cortex, with a synaptic connection from an incoming axon onto a dendritic spine.解剖学上准确的单个锥体神经元的示意图，大脑皮层的主要兴奋性神经元，具有从传入轴突到树突棘的突触连接。]]
{{unreferenced section|date=December 2020}}

Neurons are the primary components of the nervous system, along with the [[glial cells]] that give them structural and metabolic support. The nervous system is made up of the [[central nervous system]], which includes the [[brain]] and [[spinal cord]], and the [[peripheral nervous system]], which includes the [[autonomic nervous system|autonomic]] and [[somatic nervous system]]s. In vertebrates, the majority of neurons belong to the [[central nervous system]], but some reside in peripheral [[ganglion|ganglia]], and many sensory neurons are situated in sensory organs such as the [[retina]] and [[cochlea]].

神经元是神经系统的主要组成部分，同时还有给予其结构和代谢支持的胶质细胞。神经系统由中枢神经系统和周围神经系统组成，前者包括大脑和脊髓，后者包括自主神经和躯体神经系统。在脊椎动物中，大多数神经元属于中枢神经系统，但也有一些居住在周围神经节中，许多感觉神经元位于感觉器官中，如视网膜和耳蜗。

Axons may bundle into [[nerve fascicle|fascicle]]s that make up the [[nerve]]s in the [[peripheral nervous system]] (like strands of wire make up cables). Bundles of axons in the central nervous system are called [[nerve tract|tracts]].

轴突可以捆绑成束，组成周围神经系统的神经（就像电线股组成的电缆）。中枢神经系统中的轴突束被称为束。

== Anatomy and histology解剖学和组织学 ==

[[File:Components of neuron.jpg|thumb|upright=1.8|Diagram of the components of a neuron]]
Neurons are highly specialized for the processing and transmission of cellular signals. Given their diversity of functions performed in different parts of the nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 [[Micrometre|micrometers]] in diameter.<ref>{{cite web |first = Melissa |last = Davies |title = The Neuron: size comparison |url = https://www.ualberta.ca/~neuro/OnlineIntro/NeuronExample.htm |work = Neuroscience: A journey through the brain |date = 2002-04-09 |access-date = 2009-06-20}}</ref>

神经元对细胞信号的处理和传送是高度专业化。鉴于它们在神经系统的不同部分所执行的功能的多样性，它们的形状、大小和电化学特性也有很大差异。例如，一个神经元的胞体的直径可以从4到100微米不等。

*The '''[[Soma (biology)|soma]]''' is the body of the neuron. As it contains the [[cell nucleus|nucleus]], most [[protein biosynthesis|protein synthesis]] occurs here. The nucleus can range from 3 to 18 micrometers in diameter.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Brain Facts and Figures |url = http://faculty.washington.edu/chudler/facts.html |work = Neuroscience for Kids |access-date = 2009-06-20 }}</ref>
*细胞体是神经元的主体。由于它含有细胞核，大多数蛋白质合成发生在这里。细胞核的直径可以从3到18微米不等。

*The '''[[dendrites]]''' of a neuron are cellular extensions with many branches. This overall shape and structure is referred to metaphorically as a dendritic tree. This is where the majority of input to the neuron occurs via the [[dendritic spine]].
*神经元的树突是有许多分支的细胞延伸。这种整体形状和结构被比喻为树突树。神经元的大部分输入是通过树突棘发生的。

*The '''[[axon]]''' is a finer, cable-like projection that can extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length. The axon primarily carries [[nerve signal]]s away from the soma, and carries some types of information back to it. Many neurons have only one axon, but this axon may—and usually will—undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the '''[[axon hillock]]'''. Besides being an anatomical structure, the axon hillock also has the greatest density of [[voltage-dependent sodium channels]]. This makes it the most easily excited part of the neuron and the spike initiation zone for the axon. In electrophysiological terms, it has the most negative [[threshold potential]].
*轴突是一种较细的、像电缆一样的突起，其长度可以是胞体直径的几十倍、几百倍、甚至几万倍。轴突主要携带神经信号离开胞体，并将某些类型的信息带回胞体。许多神经元只有一个轴突，但这个轴突可能--通常也会--发生广泛的分支，从而能够与许多靶细胞进行交流。轴突从胞体中出现的部分被称为轴突丘。除了是一种解剖结构外，轴突丘还具有最大密度的电压依赖性钠离子通道。这使得它成为神经元最容易兴奋的部分和轴突的锋电位触发区。在电生理学方面，它具有最负的阈值电位。

**While the axon and axon hillock are generally involved in information outflow, this region can also receive input from other neurons.
**虽然轴突和轴突丘通常会参与信息外流，但这一区域也能接受来自其他神经元的输入。

*The '''[[axon terminal]]''' is found at the end of the axon farthest from the soma and contains [[synapses]]. Synaptic boutons are specialized structures where [[neurotransmitter]] chemicals are released to communicate with target neurons. In addition to synaptic boutons at the axon terminal, a neuron may have ''en passant'' boutons, which are located along the length of the axon.
*轴突终端位于轴突离胞体最远的一端，包含突触。突触结是专门的结构，神经递质化学物质在此释放，与目标神经元进行交流。除了轴突末端的突触结外，神经元还可能有沿轴突长度方向分布的 "中途结"。

[[File:Neuron Cell Body.png|thumb|Neuron cell body神经元细胞体]]

The accepted view of the neuron attributes dedicated functions to its various anatomical components; however, dendrites and axons often act in ways contrary to their so-called main function.<ref>{{Cite web |date=2021-01-14 |title=16.7: Nervous System |url=https://bio.libretexts.org/Courses/Lumen_Learning/Book%3A_Fundamentals_of_Biology_I_(Lumen)/16%3A_Module_13%3A_Overview_of_Body_Systems/16.7%3A_Nervous_System |access-date=2022-02-28 |website=Biology LibreTexts |language=en}}</ref>

公认的神经元观点将专门的功能归于其各种解剖成分；然而，树突和轴突的作用方式往往与它们所谓的主要功能相反。

[[File:Complete neuron cell diagram en.svg|thumb|right|Diagram of a typical myelinated vertebrate motor neuron典型的有髓的脊椎动物运动神经元示意图]]
[[File:BN1 Neurology.webm|thumb|Neurology Video神经病学视频]]

Axons and dendrites in the central nervous system are typically only about one micrometer thick, while some in the peripheral nervous system are much thicker. The soma is usually about 10–25 micrometers in diameter and often is not much larger than the cell nucleus it contains. The longest axon of a human [[motor neuron]] can be over a meter long, reaching from the base of the spine to the toes.

中枢神经系统中的轴突和树突通常只有约1微米厚，而周围神经系统中的一些轴突和树突则要厚得多。胞体的直径通常约为10-25微米，通常不比其包含的细胞核大多少。人类运动神经元最长的轴突可以超过一米长，从脊柱底部一直延伸到脚趾。

Sensory neurons can have axons that run from the toes to the [[posterior column]] of the spinal cord, over 1.5 meters in adults. [[Giraffe]]s have single axons several meters in length running along the entire length of their necks. Much of what is known about axonal function comes from studying the [[squid giant axon]], an ideal experimental preparation because of its relatively immense size (0.5–1 millimeters thick, several centimeters long).

感觉神经元的轴突可以从脚趾一直延伸到脊髓的后柱，成年人的轴突长度超过1.5米。长颈鹿有几米长的单根轴突，沿其脖子的整个长度运行。人们对轴突功能的了解大多来自于对鱿鱼巨型轴突的研究，由于其相对巨大的尺寸（0.5-1毫米厚，数厘米长），这是一种理想的实验准备。

Fully differentiated neurons are permanently [[G0 phase|postmitotic]]<ref>{{cite journal | vauthors = Herrup K, Yang Y | title = Cell cycle regulation in the postmitotic neuron: oxymoron or new biology? | journal = Nature Reviews. Neuroscience | volume = 8 | issue = 5 | pages = 368–78 | date = May 2007 | pmid = 17453017 | doi = 10.1038/nrn2124 | s2cid = 12908713 }}</ref> however, stem cells present in the adult brain may regenerate functional neurons throughout the life of an organism (see [[neurogenesis]]). [[Astrocyte]]s are star-shaped [[glial cell]]s. They have been observed to turn into neurons by virtue of their stem cell-like characteristic of [[pluripotency]].

完全分化的神经元是永久性的有丝分裂后的细胞，然而，存在于成人大脑中的干细胞可以在有机体的整个生命过程中再生出功能性神经元（见神经元的生成）。星形胶质细胞是星形的胶质细胞。它们已经被观察到可以凭借其类干细胞的多能性特征而变成神经元。

===Membrane膜结构===

{{unreferenced section|date=December 2020}}
Like all animal cells, the cell body of every neuron is enclosed by a [[plasma membrane]], a bilayer of [[lipid]] molecules with many types of protein structures embedded in it. A lipid bilayer is a powerful electrical [[Insulator (electricity)|insulator]], but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are [[voltage-gated ion channel|voltage gated]], meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The [[ion]] materials include [[sodium]], [[potassium]], [[chloride]], and [[calcium]]. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane.

像所有的动物细胞一样，每个神经元的细胞体都被一个质膜所包围，质膜是由脂质分子组成的双层膜，其中嵌入了许多类型的蛋白质结构。脂质双层是一个强大的电绝缘体，但在神经元中，嵌入膜中的许多蛋白质结构是电活性的。这些结构包括允许带电离子流过膜的离子通道和以化学方式将离子从膜的一侧输送到另一侧的离子泵。大多数离子通道只对特定类型的离子有渗透性。一些离子通道是电压门控的，这意味着它们可以通过改变膜上的电压差在开放和关闭状态之间进行切换。其他的是化学门控，意味着它们可以通过与扩散在细胞外液中的化学物质的相互作用在开放和关闭状态之间切换。离子材料包括钠、钾、氯和钙。离子通道和离子泵之间的相互作用在膜上产生一个电压差，通常在基线上小于1/10伏。这个电压有两个功能：首先，它为嵌入膜中的各种电压依赖性蛋白机械提供了动力源；其次，它为膜的不同部分之间的电信号传输提供了一个基础。

===Histology and internal structure组织学和内部结构===

[[File:Gyrus Dentatus 40x.jpg|thumb|250px|Golgi-stained neurons in human hippocampal tissue高尔基染色神经元在人海马组织]]

[[Image:SUM 110913 Cort Neurons 2.5d in vitro 488 Phalloidin no perm 4 cmle-2.png|thumb|300px|Actin filaments in a mouse cortical neuron in culture培养中的小鼠皮质神经元中的肌动蛋白丝]]

Numerous microscopic clumps called [[Nissl body|Nissl bodies]] (or Nissl substance) are seen when nerve cell bodies are stained with a basophilic ("base-loving") dye. These structures consist of [[Endoplasmic reticulum#Rough endoplasmic reticulum|rough endoplasmic reticulum]] and associated [[ribosomal RNA]]. Named after German psychiatrist and neuropathologist [[Franz Nissl]] (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as [[aniline]] or (weakly) [[haematoxylin]]<ref>{{cite book|title=State Hospitals Bulletin|url={{google books |plainurl=y |id=Wp8CAAAAYAAJ|page=378}}|year=1897|publisher=State Commission in Lunacy.|page=378}}</ref> highlight negatively charged components, and so bind to the phosphate backbone of the ribosomal RNA.

当用嗜碱性（"嗜碱"）染料对神经细胞体进行染色时，可以看到许多称为尼氏体（或尼氏物质）的微观团块。这些结构由粗糙的内质网和相关的核糖体RNA组成。它们以德国精神病学家和神经病理学家弗朗茨-尼斯尔（1860-1919）的名字命名，参与蛋白质的合成，其突出性可以用神经细胞代谢非常活跃的事实来解释。嗜碱性染料如苯胺或（弱）血红蛋白会突出带负电的成分，因此与核糖体RNA的磷酸盐骨架结合。

The cell body of a neuron is supported by a complex mesh of structural proteins called [[neurofilament]]s, which together with neurotubules (neuronal microtubules) are assembled into larger neurofibrils.<ref name="Webster">{{cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |website=www.merriam-webster.com}}</ref> Some neurons also contain pigment granules, such as [[neuromelanin]] (a brownish-black pigment that is byproduct of synthesis of [[catecholamine]]s), and [[lipofuscin]] (a yellowish-brown pigment), both of which accumulate with age.<ref>{{cite journal | vauthors = Zecca L, Gallorini M, Schünemann V, Trautwein AX, Gerlach M, Riederer P, Vezzoni P, Tampellini D | title = Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes | journal = Journal of Neurochemistry | volume = 76 | issue = 6 | pages = 1766–73 | date = March 2001 | pmid = 11259494 | doi = 10.1046/j.1471-4159.2001.00186.x | s2cid = 31301135 }}</ref><ref>{{cite journal | vauthors = Herrero MT, Hirsch EC, Kastner A, Luquin MR, Javoy-Agid F, Gonzalo LM, Obeso JA, Agid Y | title = Neuromelanin accumulation with age in catecholaminergic neurons from Macaca fascicularis brainstem | journal = Developmental Neuroscience | volume = 15 | issue = 1 | pages = 37–48 | date = 1993 | pmid = 7505739 | doi = 10.1159/000111315 }}</ref><ref>{{cite journal | vauthors = Brunk UT, Terman A | title = Lipofuscin: mechanisms of age-related accumulation and influence on cell function | journal = Free Radical Biology & Medicine | volume = 33 | issue = 5 | pages = 611–9 | date = September 2002 | pmid = 12208347 | doi = 10.1016/s0891-5849(02)00959-0 }}</ref> Other structural proteins that are important for neuronal function are [[actin]] and the [[tubulin]] of [[microtubule]]s. [[Class III β-tubulin]] is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule.<ref>{{cite journal | vauthors = Zhao B, Meka DP, Scharrenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F | title = Microtubules Modulate F-actin Dynamics during Neuronal Polarization | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 9583 | date = August 2017 | pmid = 28851982 | pmc = 5575062 | doi = 10.1038/s41598-017-09832-8 | bibcode = 2017NatSR...7.9583Z }}</ref>

神经元的细胞体由称为神经丝的结构蛋白的复杂网状结构支撑，它与神经管（神经元微管）一起被组装成较大的神经纤维。一些神经元还含有色素颗粒，如神经黑色素（一种棕黑色的色素，是儿茶酚胺合成的副产品）和脂褐素（一种黄褐色的色素），这两种物质都会随着年龄的增长而积累。对神经元功能很重要的其他结构蛋白是肌动蛋白和微管的管蛋白。第三类β-管蛋白几乎只在神经元中发现。在神经元发育过程中，肌动蛋白主要存在于轴突和树突的顶端。在那里，肌动蛋白的动态可以通过与微管的相互作用而被调节。

There are different internal structural characteristics between axons and dendrites. Typical axons almost never contain [[ribosomes]], except some in the initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases.

轴突和树突之间存在着不同的内部结构特征。典型的轴突几乎不含核糖体，除了在初始段有一些。树突含有颗粒状的内质网或核糖体，随着与细胞体距离的增加，其数量逐渐减少。

==Classification分类==

[[File:GFPneuron.png|thumb|250px|right|Image of pyramidal neurons in mouse [[cerebral cortex]] expressing [[green fluorescent protein]]. The red staining indicates [[GABA]]ergic interneurons.<ref>{{cite journal | vauthors = Lee WC, Huang H, Feng G, Sanes JR, Brown EN, So PT, Nedivi E | title = Dynamic remodeling of dendritic arbors in GABAergic interneurons of adult visual cortex | journal = PLOS Biology | volume = 4 | issue = 2 | pages = e29 | date = February 2006 | pmid = 16366735 | pmc = 1318477 | doi = 10.1371/journal.pbio.0040029 |doi-access=free }}</ref>]]

[[File:smi32neuron.jpg|thumb|250px|right|SMI32-stained pyramidal neurons in [[cerebral cortex]]]]

{{See also|List of distinct cell types in the adult human body#Nervous system}}
另见：成人体内不同的细胞类型列表 § 神经系统

Neurons vary in shape and size and can be classified by their [[Morphology (biology)|morphology]] and function.<ref name="Al">{{cite book|last=Al|first=Martini, Frederic Et|title=Anatomy and Physiology' 2007 Ed.2007 Edition|url={{google books |plainurl=y |id=joJb82gVsLoC|page=288}}|publisher=Rex Bookstore, Inc.|isbn=978-971-23-4807-5|pages=288}}</ref> The anatomist [[Camillo Golgi]] grouped neurons into two types; type I with long axons used to move signals over long distances and type II with short axons, which can often be confused with dendrites. Type I cells can be further classified by the location of the soma. The basic morphology of type I neurons, represented by spinal [[motor neurons]], consists of a cell body called the soma and a long thin axon covered by a [[myelin sheath]]. The dendritic tree wraps around the cell body and receives signals from other neurons. The end of the axon has branching [[axon terminal]]s that release neurotransmitters into a gap called the [[synaptic cleft]] between the terminals and the dendrites of the next neuron.

神经元的形状和大小各不相同，可按其形态和功能进行分类。解剖学家卡米洛-高尔基将神经元分为两类；I型有长轴，用于长距离移动信号；II型有短轴，常与树突相混淆。I型细胞可按胞体的位置进一步分类。以脊髓运动神经元为代表的I型神经元的基本形态包括一个称为胞体的细胞体和一个由髓鞘覆盖的细长轴突。树突树环绕着细胞体，接收来自其他神经元的信号。轴突的末端有分支的轴突终端，将神经递质释放到终端和下一个神经元树突之间的间隙中，称为突触间隙。

===Structural classification结构分类===

====Polarity极性====

[[File:Neurons uni bi multi pseudouni.svg|thumb|Different kinds of neurons不同种类的神经元: 1 [[Unipolar neuron单极神经元]] 2 [[Bipolar neuron双极神经元]] 3 [[Multipolar neuron多极神经元]] 4 [[Pseudounipolar neuron伪单极神经元]] ]]

Most neurons can be anatomically characterized as:
大多数神经元在解剖学上可以被描述为：

*[[Unipolar neuron|Unipolar]]: single process
*[[Bipolar cell|Bipolar]]: 1 axon and 1 dendrite
*[[Multipolar neuron|Multipolar]]: 1 axon and 2 or more dendrites
**[[Golgi I]]: neurons with long-projecting axonal processes; examples are pyramidal cells, Purkinje cells, and anterior horn cells
**[[Golgi II]]: neurons whose axonal process projects locally; the best example is the granule cell
*[[Anaxonic neuron|Anaxonic]]: where the axon cannot be distinguished from the dendrite(s)
*[[Pseudounipolar cells|Pseudounipolar]]: 1 process which then serves as both an axon and a dendrite

* 单极性：单一原生质过程
* 双极性：1个轴突和1个树突
* 多极性：1个轴突和2个或更多的树突
** 高尔基I型：具有长轴突的神经元；比如锥体细胞、浦肯野细胞和前角细胞。
** 高尔基II型：其轴突过程在局部投射的神经元；最好的例子是颗粒细胞
* 无轴性：轴突与树突无法区分的神经元类型。
* 假单极神经元：1个原生质过程，然后既是轴突又是树突。

====Other其他====

Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are:

一些独特的神经元类型可以根据其在神经系统中的位置和独特的形状来识别。一些例子是：

*[[Basket cell]]s, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and [[cerebellum]]
*[[Betz cell]]s, large motor neurons
*[[Lugaro cell]]s, interneurons of the cerebellum
*[[Medium spiny neuron]]s, most neurons in the [[corpus striatum]]
*[[Purkinje cell]]s, huge neurons in the cerebellum, a type of Golgi I multipolar neuron
*[[Pyramidal cell]]s, neurons with triangular soma, a type of Golgi I
*[[Renshaw cell]]s, neurons with both ends linked to [[alpha motor neuron]]s
*[[Unipolar brush cell]]s, interneurons with unique dendrite ending in a brush-like tuft
*[[Granule cell]]s, a type of Golgi II neuron
*[[Anterior horn (spinal cord)|Anterior horn]] cells, [[motoneurons]] located in the spinal cord
*[[Spindle cell]]s, interneurons that connect widely separated areas of the brain

*篮状细胞，在目标细胞的胞体周围形成密集的终端丛，发现于大脑皮层和小脑的中间神经元。
*贝兹细胞，大运动神经元
*卢加洛细胞，小脑的中间神经元
*中型多棘神经元，纹状体中的大多数神经元
*浦肯野细胞，小脑中的巨大神经元，一种高尔基I型多极神经元
*锥体细胞，具有三角形胞体的神经元，是高尔基I型的一种。
*伦肖细胞，两端与α运动神经元相连的神经元
*单极刷细胞，具有独特的树突末端为刷状簇的中间神经元
*颗粒细胞，高尔基II型神经元的一种类型
*前角细胞，位于脊髓中的运动神经元
*纺锤体细胞，连接大脑广泛分布的中间神经元
*纺锤体细胞的运动神经元、连接大脑广泛分离区域的中间神经元

===Functional classification功能分类===

====Direction方向====

*[[Afferent neuron]]s convey information from tissues and organs into the central nervous system and are also called [[sensory neurons]].
*[[Efferent neuron]]s (motor neurons) transmit signals from the central nervous system to the effector cells.
*[[Interneuron]]s connect neurons within specific regions of the central nervous system.

* 传入神经元将信息从组织和器官传入中枢神经系统，也被称为感觉神经元。
* 传出神经元(运动神经元) 将信号从中枢神经系统传递给效应细胞。
* 中间神经元连接中枢神经系统特定区域内的神经元。

Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain.

传入和传出也泛指分别为大脑带来信息或从大脑发出信息的神经元。

====Action on other neurons对其他神经元的影响====

A neuron affects other neurons by releasing a neurotransmitter that binds to [[receptor (biochemistry)|chemical receptor]]s. The effect upon the postsynaptic neuron is determined by the type of receptor that is activated, not by the presynaptic neuron or by the neurotransmitter. A neurotransmitter can be thought of as a key, and a receptor as a lock: the same neurotransmitter can activate multiple types of receptors. Receptors can be classified broadly as ''excitatory'' (causing an increase in firing rate), ''inhibitory'' (causing a decrease in firing rate), or ''modulatory'' (causing long-lasting effects not directly related to firing rate).

一个神经元通过释放一种与化学受体结合的神经递质来影响其他神经元。对突触后神经元的影响是由被激活的受体类型决定的，而不是由突触前神经元或神经递质决定的。可以认为神经递质是一把钥匙，而受体是一把锁：同一神经递质可以激活多种类型的受体。受体可大致分为兴奋性（导致放电率增加）、抑制性（导致放电率下降）或调节性（导致与放电率无直接关系的长期影响）。

The two most common (90%+) neurotransmitters in the brain, [[glutamate]] and [[GABA]], have largely consistent actions. Glutamate acts on several types of receptors, and has effects that are excitatory at [[ionotropic receptor]]s and a modulatory effect at [[metabotropic receptor]]s. Similarly, GABA acts on several types of receptors, but all of them have inhibitory effects (in adult animals, at least). Because of this consistency, it is common for neuroscientists to refer to cells that release glutamate as "excitatory neurons", and cells that release GABA as "inhibitory neurons". Some other types of neurons have consistent effects, for example, "excitatory" motor neurons in the spinal cord that release [[acetylcholine]], and "inhibitory" [[spinal neuron]]s that release [[glycine]].

大脑中最常见的两种（90%以上）神经递质，即谷氨酸和GABA，其作用基本一致。谷氨酸作用于几种类型的受体，在离子型受体上有兴奋作用，在代谢型受体上有调节作用。同样，GABA作用于几种类型的受体，但它们都有抑制作用（至少在成年动物中）。由于这种一致性，神经科学家通常把释放谷氨酸的细胞称为 "兴奋性神经元"，而把释放GABA的细胞称为 "抑制性神经元"。其他一些类型的神经元也有一致的影响，例如，脊髓中释放乙酰胆碱的 "兴奋性 "运动神经元，以及释放甘氨酸的 "抑制性 "脊髓神经元。

The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neuron. In principle, a single neuron, releasing a single neurotransmitter, can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still. For example, [[photoreceptor cell]]s in the retina constantly release the neurotransmitter glutamate in the absence of light. So-called OFF [[retinal bipolar cells|bipolar cells]] are, like most neurons, excited by the released glutamate. However, neighboring target neurons called ON bipolar cells are instead inhibited by glutamate, because they lack typical [[ionotropic receptor|ionotropic]] [[glutamate receptors]] and instead express a class of inhibitory [[metabotropic receptor|metabotropic]] glutamate receptors.<ref>{{cite journal | vauthors = Gerber U | title = Metabotropic glutamate receptors in vertebrate retina | journal = Documenta Ophthalmologica. Advances in Ophthalmology | volume = 106 | issue = 1 | pages = 83–7 | date = January 2003 | pmid = 12675489 | doi = 10.1023/A:1022477203420 | s2cid = 22296630 }}</ref> When light is present, the photoreceptors cease releasing glutamate, which relieves the ON bipolar cells from inhibition, activating them; this simultaneously removes the excitation from the OFF bipolar cells, silencing them.

兴奋性和抑制性神经递质之间的区别不是绝对的。相反，它取决于突触后神经元上存在的化学受体的类别。原则上，一个神经元，释放一种神经递质，可以对某些目标产生兴奋作用，对其他目标产生抑制作用，对其他目标仍有调节作用。例如，视网膜上的感光细胞在没有光的情况下不断释放神经递质谷氨酸。像大多数神经元一样，所谓的关闭双极细胞被释放的谷氨酸所激发。然而，被称为ON双极细胞的邻近目标神经元反而受到谷氨酸的抑制，因为它们缺乏典型的离子型谷氨酸受体，而是表达一类抑制性的代谢型谷氨酸受体。当有光时，光感受器停止释放谷氨酸，这解除了ON双极细胞的抑制，激活了它们；这同时消除了OFF双极细胞的兴奋，使它们沉默。

It is possible to identify the type of inhibitory effect a presynaptic neuron will have on a postsynaptic neuron, based on the proteins the presynaptic neuron expresses. [[Parvalbumin]]-expressing neurons typically dampen the output signal of the postsynaptic neuron in the [[visual cortex]], whereas [[somatostatin]]-expressing neurons typically block dendritic inputs to the postsynaptic neuron.<ref name="pmid22878717">{{cite journal | vauthors = Wilson NR, Runyan CA, Wang FL, Sur M | title = Division and subtraction by distinct cortical inhibitory networks in vivo | journal = Nature | volume = 488 | issue = 7411 | pages = 343–8 | date = August 2012 | pmid = 22878717 | pmc = 3653570 | doi = 10.1038/nature11347 | bibcode = 2012Natur.488..343W | hdl = 1721.1/92709 }}</ref>

根据突触前神经元表达的蛋白质，可以确定突触前神经元对突触后神经元的抑制作用的类型。表达副白蛋白的神经元通常会抑制视觉皮层中突触后神经元的输出信号，而表达躯干素的神经元通常会阻断突触后神经元的树突输入。

====Discharge patterns放电模式====

Neurons have intrinsic electroresponsive properties like intrinsic transmembrane voltage [[Neural oscillation|oscillatory]] patterns.<ref name="llinas2014">{{cite journal | vauthors = Llinás RR | title = Intrinsic electrical properties of mammalian neurons and CNS function: a historical perspective | journal = Frontiers in Cellular Neuroscience | volume = 8 | pages = 320 | date = 2014-01-01 | pmid = 25408634 | pmc = 4219458 | doi = 10.3389/fncel.2014.00320 | doi-access = free }}</ref> So neurons can be classified according to their [[electrophysiology|electrophysiological]] characteristics:

神经元具有内在的电反应特性，如内在的跨膜电压振荡模式。因此，可以根据神经元的电生理特性对其进行分类：

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.
*Phasic or bursting. Neurons that fire in bursts are called phasic.
*Fast spiking. Some neurons are notable for their high firing rates, for example some types of cortical inhibitory interneurons, cells in [[globus pallidus]], [[retinal ganglion cells]].<ref>{{cite conference | title = Ion conductances related to shaping the repetitive firing in rat retinal ganglion cells | vauthors = Kolodin YO, Veselovskaia NN, Veselovsky NS, Fedulova SA | conference = Acta Physiologica Congress | url = http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | access-date = 2009-06-20 | archive-url = https://web.archive.org/web/20121007164451/http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | archive-date = 2012-10-07 | url-status = dead }}</ref><ref>{{cite web|url=http://ykolodin.50webs.com/ |title=Ionic conductances underlying excitability in tonically firing retinal ganglion cells of adult rat |publisher=Ykolodin.50webs.com |date=2008-04-27 |access-date=2013-02-16}}</ref>

*紧张性或规律性棘波。一些神经元通常持续（紧张地）活跃，通常以恒定的频率放电。例如：神经干细胞中的interneurons。
*瞬变性或爆发性。爆发性放电的神经元被称为瞬变性的。
*快闪性。一些神经元因其高放电率而引人注目，例如某些类型的皮质抑制性中间神经元、苍白球、视网膜神经节细胞。

====Neurotransmitter神经递质 ====

[[File:Neurotransmitters.jpg|thumb|Synaptic vesicles containing neurotransmitters含有神经递质的突触小泡。]]
{{Main|Neurotransmitter}}

[[Neurotransmitter]]s are chemical messengers passed from one neuron to another neuron or to a [[muscle cell]] or [[Gland|gland cell]].

神经递质是由一个神经元传递给另一个神经元或肌肉细胞或腺体细胞的化学信使。

*Cholinergic neurons – acetylcholine. [[Acetylcholine]] is released from presynaptic neurons into the synaptic cleft. It acts as a [[ligand]] for both ligand-gated ion channels and [[Metabotropic receptor|metabotropic]] (GPCRs) [[Muscarinic acetylcholine receptor|muscarinic receptors]]. [[Nicotinic receptors]] are pentameric ligand-gated ion channels composed of alpha and beta subunits that bind [[nicotine]]. Ligand binding opens the channel causing influx of [[Sodium|Na+]] depolarization and increases the probability of presynaptic neurotransmitter release. Acetylcholine is synthesized from [[choline]] and [[acetyl coenzyme A]].
*Adrenergic neurons – noradrenaline. [[Noradrenaline]] (norepinephrine) is released from most [[postganglionic]] neurons in the [[sympathetic nervous system]] onto two sets of GPCRs: [[Adrenergic receptor|alpha adrenoceptor]]s and [[beta adrenoceptor]]s. Noradrenaline is one of the three common [[catecholamine]] neurotransmitter, and the most prevalent of them in the [[peripheral nervous system]]; as with other catecholamines, it is synthesised from [[tyrosine]].
*GABAergic neurons – [[gamma aminobutyric acid]]. GABA is one of two neuroinhibitors in the [[central nervous system]] (CNS), along with glycine. GABA has a homologous function to [[Acetylcholine|ACh]], gating anion channels that allow [[Chlorine|Cl−]] ions to enter the post synaptic neuron. Cl− causes hyperpolarization within the neuron, decreasing the probability of an action potential firing as the voltage becomes more negative (for an action potential to fire, a positive voltage threshold must be reached). GABA is synthesized from glutamate neurotransmitters by the enzyme [[glutamate decarboxylase]].
*Glutamatergic neurons – glutamate. [[Glutamate]] is one of two primary excitatory amino acid neurotransmitters, along with [[Aspartic acid|aspartate]]. Glutamate receptors are one of four categories, three of which are ligand-gated ion channels and one of which is a [[G protein|G-protein]] coupled receptor (often referred to as GPCR).

*胆碱能神经元--乙酰胆碱。乙酰胆碱从突触前神经元释放到突触间隙中。它是配体门控离子通道和代谢型（GPCRs：G蛋白耦联受体）毒蕈碱受体的配体。烟碱受体是由结合了尼古丁的α和β亚基组成的五聚体配体门控离子通道。配体结合后打开通道，造成Na+的流入，使其去极化，并增加突触前神经递质释放的概率。乙酰胆碱是由胆碱和乙酰辅酶A合成的。
*肾上腺素能神经元--去甲肾上腺素。去甲肾上腺素（norepinephrine去甲肾上腺素）从交感神经系统的大多数神经节后神经元释放到两组GPCRs上：α肾上腺素受体和β肾上腺素受体。去甲肾上腺素是三种常见的儿茶酚胺神经递质之一，也是周围神经系统中最普遍的一种；与其他儿茶酚胺一样，它是由酪氨酸合成的。
*GABA能神经元--γ氨基丁酸。GABA与甘氨酸一起是中枢神经系统（CNS）中的两种神经抑制剂之一。GABA具有与ACh相同的功能，对允许Cl-离子进入突触后神经元的阴离子通道进行门控。Cl-导致神经元内的超极化，随着电压变得更负，降低了动作电位放电的概率（要引发动作电位，必须达到一个正电压阈值）。GABA是由谷氨酸神经递质通过谷氨酸脱羧酶合成的。
*谷氨酸能神经元--谷氨酸。谷氨酸与天门冬氨酸一起是两种主要的兴奋性氨基酸神经递质之一。谷氨酸受体是四类之一，其中三类是配体门控离子通道，一类是G-蛋白耦联受体（通常称为GPCR）。

:#[[AMPA]] and [[Kainic acid|Kainate]] receptors function as [[Ion|cation]] channels permeable to Na+ cation channels mediating fast excitatory synaptic transmission.
:#[[N-Methyl-D-aspartic acid|NMDA]] receptors are another cation channel that is more permeable to [[Calcium in biology|Ca2+]]. The function of NMDA receptors depend on glycine receptor binding as a co-[[agonist]] within the channel pore. NMDA receptors do not function without both ligands present.
:#Metabotropic receptors, GPCRs modulate synaptic transmission and postsynaptic excitability.
::Glutamate can cause excitotoxicity when blood flow to the brain is interrupted, resulting in [[brain damage]]. When blood flow is suppressed, glutamate is released from presynaptic neurons, causing greater NMDA and AMPA receptor activation than normal outside of stress conditions, leading to elevated Ca2+ and Na+ entering the post synaptic neuron and cell damage. Glutamate is synthesized from the amino acid glutamine by the enzyme [[Glutamine oxoglutarate aminotransferase|glutamate synthase]].

:#AMPA和红藻氨酸受体作为阳离子通道可渗透到Na+阳离子通道，介导快速兴奋性突触传递。
:#NMDA受体是另一个对Ca2+更易渗透的阳离子通道。NMDA受体的功能取决于甘氨酸受体的结合，作为通道孔内的共轭物。如果没有这两种配体存在，NMDA受体就不能发挥作用。
:#促代谢受体，GPCRs调节突触传递和突触后兴奋性。
::当流向大脑的血流被中断时，谷氨酸可引起兴奋性毒性，导致大脑损伤。当血流被抑制时，谷氨酸从突触前的神经元中释放出来，导致NMDA和AMPA受体的激活比压力条件以外的正常情况下更大，导致升高的Ca2+和Na+进入突触后的神经元和细胞损伤。谷氨酸是由谷氨酸合成酶从氨基酸谷氨酰胺中合成的。

*Dopaminergic neurons—[[dopamine]]. [[Dopamine]] is a neurotransmitter that acts on D1 type (D1 and D5) Gs-coupled receptors, which increase cAMP and PKA, and D2 type (D2, D3, and D4) receptors, which activate Gi-coupled receptors that decrease cAMP and PKA. Dopamine is connected to mood and behavior and modulates both pre- and post-synaptic neurotransmission. Loss of dopamine neurons in the [[substantia nigra]] has been linked to [[Parkinson's disease]]. Dopamine is synthesized from the amino acid [[tyrosine]]. Tyrosine is catalyzed into levodopa (or [[L-DOPA]]) by [[Tyrosine hydroxylase|tyrosine hydroxlase]], and levodopa is then converted into dopamine by the aromatic amino acid [[Carboxy-lyases|decarboxylase]].
*Serotonergic neurons—[[serotonin]]. [[Serotonin]] (5-Hydroxytryptamine, 5-HT) can act as excitatory or inhibitory. Of its four 5-HT receptor classes, 3 are GPCR and 1 is a ligand-gated cation channel. Serotonin is synthesized from [[tryptophan]] by [[tryptophan hydroxylase]], and then further by decarboxylase. A lack of 5-HT at postsynaptic neurons has been linked to depression. Drugs that block the presynaptic [[serotonin transporter]] are used for treatment, such as [[Prozac]] and [[Zoloft]].
*Purinergic neurons—ATP. [[Adenosine triphosphate|ATP]] is a neurotransmitter acting at both ligand-gated ion channels ([[P2X]] receptors) and GPCRs ([[P2Y receptor|P2Y]]) receptors. ATP is, however, best known as a [[cotransmitter]]. Such [[purinergic signalling]] can also be mediated by other [[purine]]s like [[adenosine]], which particularly acts at P2Y receptors.
*Histaminergic neurons—[[histamine]]. [[Histamine]] is a [[monoamine neurotransmitter]] and [[neuromodulator]]. Histamine-producing neurons are found in the [[tuberomammillary nucleus]] of the [[hypothalamus]].<ref>{{cite journal | vauthors = Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y | title = Histamine: neural circuits and new medications | journal = Sleep | volume = 42 | issue = 1 | date = January 2019 | pmid = 30239935 | pmc = 6335869 | doi = 10.1093/sleep/zsy183 }}</ref> Histamine is involved in [[arousal]] and regulating sleep/wake behaviors.

*多巴胺能神经元——多巴胺。多巴胺是一种神经递质，作用于D1型（D1和D5）Gs耦联受体，增加cAMP和PKA，以及D2型（D2、D3和D4）受体，激活Gi耦联受体，减少cAMP和PKA。多巴胺与情绪和行为有关，调节突触前和突触后的神经传递。黑质中的多巴胺神经元的丧失与帕金森病有关。多巴胺是由氨基酸酪氨酸合成的。酪氨酸被酪氨酸羟化酶催化为左旋多巴（或L-DOPA），然后左旋多巴被芳香族氨基酸脱羧酶转化为多巴胺。
*羟色胺能神经元——羟色胺。羟色胺（5-Hydroxytryptamine，5-HT）可以起到兴奋性或抑制性作用。在其四个5-HT受体类别中，3个是GPCR，1个是配体门控的阳离子通道。羟色胺由色氨酸经色氨酸羟化酶合成，然后再经脱羧酶进一步合成。突触后神经元缺乏5-HT与抑郁症有关。阻断突触前5-羟色胺转运体的药物被用于治疗，如百忧解和左洛复。
*嘌呤神经元——ATP。ATP是一种同时作用于配体门控离子通道（P2X受体）和GPCRs（P2Y）受体的神经递质。然而，ATP最有名的是作为一种共传导剂。这种嘌呤信号也可以由其他嘌呤介导，如腺苷，它特别作用于P2Y受体。
*组胺能神经元——组胺。组胺是一种单胺类神经递质和神经调节剂。产生组胺的神经元存在于下丘脑的管状乳头核。组胺参与唤醒和调节睡眠/觉醒行为。

====Multimodel classification多模式分类====

Since 2012 there has been a push from the cellular and computational neuroscience community to come up with a universal classification of neurons that will apply to all neurons in the brain as well as across species. This is done by considering the three essential qualities of all neurons: electrophysiology, morphology, and the individual transcriptome of the cells. Besides being universal this classification has the advantage of being able to classify astrocytes as well. A method called Patch-Seq in which all three qualities can be measured at once is used extensively by the Allen Institute for Brain Science.<ref>{{cite web |url=https://www.news-medical.net/news/20201203/Patch-seq-technique-helps-depict-the-variation-of-neural-cells-in-the-brain.aspx |title=Patch-seq technique helps depict the variation of neural cells in the brain |work=News-medical.net |date=3 December 2020 |access-date=26 August 2021 |url-status=live}}</ref>

自2012年以来，细胞和计算神经科学界一直在推动提出一个通用的神经元分类，该分类将适用于大脑中的所有神经元以及跨物种。这是通过考虑所有神经元的三个基本属性来实现的：电生理学、形态学和细胞的个体转录组。除了具有普遍性之外，这种分类法还有一个优点，就是能够对星形胶质细胞进行分类。艾伦脑科学研究所广泛使用一种叫做Patch-Seq的方法，可以同时测量所有三种属性。

==Connectivity连接性==

{{Main|Synapse|Chemical synapse化学突触}}
[[File:Chemical synapse schema cropped.jpg|thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell沿着轴突传播到下一个细胞的细胞体和树突的一种信号。]]
[[File:Neuro Muscular Junction.png|thumb|Chemical synapse|left]]

Neurons communicate with each other via [[synapses]], where either the [[axon terminal]] of one cell contacts another neuron's dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in the cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the [[supraoptic nucleus]], have only one or two dendrites, each of which receives thousands of synapses.

神经元通过突触相互沟通，一个细胞的轴突终端接触到另一个神经元的树突、胞体，或者更少见的轴突。像小脑中的浦肯野细胞这样的神经元可以有超过1000个树突分支，与成千上万的其他细胞建立连接; 其他的神经元，如视上核的大细胞神经元，只有一个或两个树突，每个树突接收数千个突触。

Synapses can be [[EPSP|excitatory]] or [[IPSP|inhibitory]], either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive [[gap junction|junctions]] between cells.<ref>{{cite book |last1=Macpherson |first1=Gordon |title=Black's Medical Dictionary |date=2002 |publisher=Scarecrow Press |location=Lanham, MD |isbn=0810849844 |pages=431–434 |edition=40 }}</ref>

突触可以是兴奋性的或抑制性的，分别增加或减少目标神经元的活动。一些神经元还通过电突触进行交流，电突触是细胞之间直接的、导电的连接点。

When an action potential reaches the axon terminal, it opens [[Voltage-dependent calcium channel|voltage-gated calcium channels]], allowing [[Calcium in biology|calcium ions]] to enter the terminal. Calcium causes [[synaptic vesicles]] filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the [[axon terminal]] triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial [[energy metabolism]] to produce [[Adenosine triphosphate|ATP]] to support continuous neurotransmission.<ref name="pmid23746507">{{cite journal | vauthors = Ivannikov MV, Macleod GT | title = Mitochondrial free Ca²⁺ levels and their effects on energy metabolism in Drosophila motor nerve terminals | journal = Biophysical Journal | volume = 104 | issue = 11 | pages = 2353–61 | date = June 2013 | pmid = 23746507 | pmc = 3672877 | doi = 10.1016/j.bpj.2013.03.064 | bibcode = 2013BpJ...104.2353I }}</ref>

当动作电位到达轴突末端时，它打开电压门控的钙离子通道，允许钙离子进入末端。钙离子使充满神经递质分子的突触小泡与膜融合，将其内容释放到突触间隙中。神经递质在突触间隙中扩散，激活突触后神经元上的受体。轴突末端的高细胞钙引发线粒体钙吸收，这反过来又激活了线粒体的能量代谢，产生ATP以支持持续的神经传递。

An [[autapse]] is a synapse in which a neuron's axon connects to its own dendrites.

自突触是指神经元的轴突与自己的树突相连的突触。

The [[human brain]] has some 8.6 x 1010 (eighty six billion) neurons.<ref>{{ cite journal | vauthors = Herculano-Houzel S | title = The human brain in numbers: a linearly scaled-up primate brain | journal = Frontiers in Human Neuroscience | volume = 3 | pages = 31 | date = November 2009 | pmid = 19915731 | doi = 10.3389/neuro.09.031.2009 | pmc = 2776484 | doi-access = free }}</ref> Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 1015 synapses (1 quadrillion). [[Synaptic pruning|This number declines with age]], stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5 x 1014 synapses (100 to 500 trillion).<ref>{{cite journal | vauthors = Drachman DA | title = Do we have brain to spare? | journal = Neurology | volume = 64 | issue = 12 | pages = 2004–5 | date = June 2005 | pmid = 15985565 | doi = 10.1212/01.WNL.0000166914.38327.BB | s2cid = 38482114 }}</ref>

[[File:Axon Propagation.svg|thumb|563x563px|An annotated diagram of the stages of an action potential propagating down an axon including the role of ion concentration and pump and channel proteins.一个动作电位沿轴突传播的阶段的注释图，包括离子浓度和泵及通道蛋白的作用。]]

人脑有大约8.6 x 1010（86亿）个神经元。每个神经元平均有7000个与其他神经元的突触连接。据估计，一个三岁孩子的大脑大约有1015个突触（1万亿）。这个数字随着年龄的增长而下降，到成年后趋于稳定。对成年人的估计有所不同，从1014到5 x 1014个突触（100到500万亿）不等。

=== Nonelectrochemical signaling非电化学信号传递 ===

Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through:
* force generated by the enlargement of dendritic spines<ref>{{cite journal |last1=Ucar |first1=Hasan |last2=Watanabe |first2=Satoshi |last3=Noguchi |first3=Jun |last4=Morimoto |first4=Yuichi |last5=Iino |first5=Yusuke |last6=Yagishita |first6=Sho |last7=Takahashi |first7=Noriko |last8=Kasai |first8=Haruo |title=Mechanical actions of dendritic-spine enlargement on presynaptic exocytosis |journal=Nature |date=December 2021 |volume=600 |issue=7890 |pages=686–689 |doi=10.1038/s41586-021-04125-7 |language=en |issn=1476-4687}} Lay summary: {{cite news |title=Forceful synapses reveal mechanical interactions in the brain |url=https://www.nature.com/articles/d41586-021-03516-0 |access-date=21 February 2022 |work=Nature |date=24 November 2021 |language=en |doi=10.1038/d41586-021-03516-0}}</ref>
* the transfer of [[protein]]s – transneuronally transported proteins (TNTPs)<ref>{{cite news |title=Researchers discover new type of cellular communication in the brain |url=https://medicalxpress.com/news/2022-01-cellular-brain.html |access-date=12 February 2022 |work=The Scripps Research Institute |language=en}}</ref><ref>{{cite journal |last1=Schiapparelli |first1=Lucio M. |last2=Sharma |first2=Pranav |last3=He |first3=Hai-Yan |last4=Li |first4=Jianli |last5=Shah |first5=Sahil H. |last6=McClatchy |first6=Daniel B. |last7=Ma |first7=Yuanhui |last8=Liu |first8=Han-Hsuan |last9=Goldberg |first9=Jeffrey L. |last10=Yates |first10=John R. |last11=Cline |first11=Hollis T. |title=Proteomic screen reveals diverse protein transport between connected neurons in the visual system |journal=Cell Reports |date=25 January 2022 |volume=38 |issue=4 |doi=10.1016/j.celrep.2021.110287 |language=English |issn=2211-1247}}</ref>

除了电和化学信号，研究表明健康人脑中的神经元还可以通过以下方式交流：
*树突棘扩大产生的力
*蛋白质的转移--经神经元转运蛋白（TNTPs）。

They can also get modulated by input from the environment and [[hormone]]s released from other parts of the organism,<ref>{{cite journal |last1=Levitan |first1=Irwin B. |last2=Kaczmarek |first2=Leonard K. |title=Electrical Signaling in Neurons |doi=10.1093/med/9780199773893.001.0001/med-9780199773893-chapter-3 |publisher=Oxford University Press}}</ref> which could be influenced more or less directly by neurons. This also applies to [[neurotrophin]]s such as [[BDNF]]. The [[gut microbiome]] is also connected with the brain.<ref>{{cite journal |last1=O’Leary |first1=Olivia F. |last2=Ogbonnaya |first2=Ebere S. |last3=Felice |first3=Daniela |last4=Levone |first4=Brunno R. |last5=C. Conroy |first5=Lorraine |last6=Fitzgerald |first6=Patrick |last7=Bravo |first7=Javier A. |last8=Forsythe |first8=Paul |last9=Bienenstock |first9=John |last10=Dinan |first10=Timothy G. |last11=Cryan |first11=John F. |title=The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus |journal=European Neuropsychopharmacology |date=1 February 2018 |volume=28 |issue=2 |pages=307–316 |doi=10.1016/j.euroneuro.2017.12.004 |language=en |issn=0924-977X}}</ref>

它们也可以被来自环境的输入和机体其他部分释放的激素所调控，这些都可以或多或少地被神经元直接影响。这也适用于神经营养素，如BDNF。肠道微生物组也与大脑有关。

==Mechanisms for propagating action potentials动作电位的传播机制==
In 1937 [[John Zachary Young]] suggested that the [[squid giant axon]] could be used to study neuronal electrical properties.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Milestones in Neuroscience Research |url = http://faculty.washington.edu/chudler/hist.html |work = Neuroscience for Kids |access-date = 2009-06-20}}</ref> It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the [[membrane potential]].

1937年，约翰-扎卡里-杨提出，乌贼巨大轴突可用于研究神经元的电特性。它比人类神经元大，但与人类神经元相似，因此更容易研究。通过将电极插入乌贼巨轴突，对膜电位进行了精确测量。

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate [[subthreshold membrane potential oscillations]]. These signals are generated and propagated by charge-carrying [[ions]] including sodium (Na+), potassium (K+), chloride (Cl−), and [[Calcium signaling|calcium (Ca2+)]].

轴突和胞体的细胞膜含有电压门控离子通道，使神经元能够产生和传播电信号（动作电位）。一些神经元还产生阈下膜电位振荡。这些信号是由携带电荷的离子产生和传播的，包括钠（Na+）、钾（K+）、氯（Cl-）和钙（Ca2+）。

Several stimuli can activate a neuron leading to electrical activity, including [[Mechanoreceptor|pressure]], stretch, chemical transmitters, and changes of the electric potential across the cell membrane.<ref>{{cite web|first1=Joe |last1=Patlak |first2=Ray |last2=Gibbons | name-list-style = vanc |title=Electrical Activity of Nerves |url=http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |work=Action Potentials in Nerve Cells |date=2000-11-01 |access-date=2009-06-20 |url-status=dead |archive-url=https://web.archive.org/web/20090827220335/http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |archive-date=August 27, 2009 }}</ref> Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.<ref name="Harris-Warrick">{{cite journal |last1=Harris-Warrick |first1=RM |title=Neuromodulation and flexibility in Central Pattern Generator networks. |journal=Current Opinion in Neurobiology |date=October 2011 |volume=21 |issue=5 |pages=685–92 |doi=10.1016/j.conb.2011.05.011 |pmid=21646013|pmc=3171584 }}</ref>

有几种刺激可以激活神经元，导致电活动，包括压力、拉伸、化学传导物和细胞膜上的电势变化。刺激导致细胞膜内特定的离子通道打开，使得离子流经细胞膜，改变膜电位。神经元必须保持界定其神经元类型的特定电特性。

Thin neurons and axons require less [[metabolism|metabolic]] expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of [[myelin]] around their axons. The sheaths are formed by [[glia]]l cells: [[oligodendrocyte]]s in the central nervous system and [[Schwann cell]]s in the peripheral nervous system. The sheath enables action potentials to travel [[saltatory conduction|faster]] than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed [[node of Ranvier|nodes of Ranvier]], which contain a high density of voltage-gated ion channels. [[Multiple sclerosis]] is a neurological disorder that results from demyelination of axons in the central nervous system.

薄的神经元和轴突需要较少的代谢支出来产生和传导动作电位，但较粗的轴突能更快地传递冲动。为了在保持快速传导的同时尽量减少代谢支出，许多神经元的轴突周围有绝缘的髓鞘。这些髓鞘是由胶质细胞形成的：中枢神经系统的少突胶质细胞和周围神经系统的许旺细胞。髓鞘使得动作电位比相同直径的无髓轴突走得更快，同时消耗更少的能量。周围神经中的髓鞘通常沿着轴突生长，长度约为1毫米，并且点缀着无髓鞘的郎飞氏结，其中包含高密度的电压门控离子通道。多发性硬化症是一种神经系统疾病，由中枢神经系统中轴突的脱髓鞘导致。

Some neurons do not generate action potentials, but instead generate a [[graded potential|graded electrical signal]], which in turn causes graded neurotransmitter release. Such [[non-spiking neurons]] tend to be sensory neurons or interneurons, because they cannot carry signals long distances.

有些神经元不产生动作电位，而是产生一个分级的电信号，反过来引起分级的神经递质释放。这样的非脉冲神经元往往是感觉神经元或中间神经元，因为它们不能长距离携带信号。

==Neural coding神经编码==
[[Neural coding]] is concerned with how sensory and other information is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the [[Stimulus (physiology)|stimulus]] and the individual or [[Neural ensemble|ensemble]] neuronal responses, and the relationships among the electrical activities of the neurons within the ensemble.<ref name="Brown">{{cite journal | vauthors = Brown EN, Kass RE, Mitra PP | title = Multiple neural spike train data analysis: state-of-the-art and future challenges | journal = Nature Neuroscience | volume = 7 | issue = 5 | pages = 456–61 | date = May 2004 | pmid = 15114358 | doi = 10.1038/nn1228 | s2cid = 562815 }}</ref> It is thought that neurons can encode both [[Digital data|digital]] and [[analog signal|analog]] information.<ref>{{cite book | vauthors = Thorpe SJ |chapter=Spike arrival times: A highly efficient coding scheme for neural networks |chapter-url= http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf |pages= 91–94 |title=Parallel processing in neural systems and computers| veditors = Eckmiller R, Hartmann G, Hauske G |date=1990|publisher=North-Holland|isbn=9780444883902 |url={{google books |plainurl=y |id=boBqAAAAMAAJ}}|language=en|archive-url=https://web.archive.org/web/20120215151304/http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf|archive-date=2012-02-15}}</ref>

神经编码关注的是感觉和其他信息如何在大脑中被神经元所表达。研究神经编码的主要目的是描述刺激与单个或集合神经元反应之间的关系，以及集合内神经元电活动之间的关系。人们认为，神经元既可以编码数字信息，也可以编码模拟信息。

==All-or-none principle全有或全无原则==

[[File:All-or-none_law_en.svg|thumb|318x318px|As long as the stimulus reaches the threshold, the full response would be given. Larger stimulus does not result in a larger response, vice versa.只要刺激达到阈值，就会有充分的反应。较大的刺激不会导致较大的反应，反之亦然。<ref name=":0">{{Cite book|title=Biological psychology|last=Kalat, James W|year=2016|isbn=9781305105409|edition=12|location=Australia|oclc=898154491}}</ref>{{Rp|31}}]]
{{Main|All-or-none law}}

The conduction of nerve impulses is an example of an [[All-or-none law|all-or-none]] response. In other words, if a neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal, but can increase firing frequency.<ref name=":0" />{{Rp|31}} Receptors respond in different ways to stimuli. Slowly adapting or [[tonic (physiology)|tonic receptors]] respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can't become "stronger" for a specific frequency.

神经冲动的传导是一个全有或全无反应的例子。换句话说，如果一个神经元有任何反应，那么它必须完全响应。更大的刺激强度，如更亮的图像/更响的声音，不会产生更强的信号，但可以增加放电频率。[34]：31受体以不同方式回应刺激。缓慢适应的或紧张性的受体对稳定的刺激作出响应，并产生稳定的放电率。紧张性受体最常通过增加其放电频率对刺激强度的增加作出反应，通常是一个与每秒钟的脉冲相关的刺激的幂函数。这可以比喻为光的内在属性，即一个特定频率（颜色）的更大强度需要更多的光子，因为光子不能对一个特定频率变得 "更强"。

Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with steady stimulus; examples include [[Human skin|skin]] which, when touched causes neurons to fire, but if the object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function.

其他受体类型包括时相性或瞬变性受体，其放电随着稳定的刺激而减少或停止；比如包括皮肤，当被触摸时引起神经元放电，但如果物体保持均匀的压力，神经元就停止放电。对压力和振动有反应的皮肤和肌肉的神经元有过滤的附属结构来帮助它们发挥作用。

The [[pacinian corpuscle]] is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus is transferred to the axon, which fires. If the pressure is steady, stimulus ends; thus, typically these neurons respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of a number of other neurons.<ref>{{cite book | last1 = Eckert | first1 = Roger | last2 = Randall | first2 = David | name-list-style = vanc | title = Animal physiology: mechanisms and adaptations | year = 1983 | publisher = W.H. Freeman | location = San Francisco | isbn = 978-0-7167-1423-1 | page = [https://archive.org/details/animalphysiology0000ecke/page/239 239] | url = https://archive.org/details/animalphysiology0000ecke/page/239 }}</ref>

帕西尼氏小体就是这样一个结构。它有像洋葱一样的同心层，围绕着轴突终端形成。当施加压力使小体变形时，机械刺激被转移到轴突上，轴突就会放电。如果压力是稳定的，刺激就会结束；因此，通常这些神经元在最初的变形过程中会有短暂的去极化反应，而当压力被移除时又会有短暂的去极化反应，从而使小体再次改变形状。其他类型的适应对扩展其他一些神经元的功能很重要。[35]

==Etymology and spelling词源和拼写==

The German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] introduced the term ''neuron'' in 1891,<ref name="finger"/> based on the [[Greek language|ancient Greek]] νεῦρον ''neuron'' 'sinew, cord, nerve'.<ref name="oed">''[[Oxford English Dictionary]]'', 3rd edition, 2003, ''s.v.''</ref>

德国解剖学家Heinrich Wilhelm Waldeyer于1891年提出了神经元一词，[36]其依据是古希腊语νεῦρον neuron's sinew, cord, nerve'。[37]

The word was adopted in French with the spelling ''neurone''. That spelling was also used by many writers in English,<ref name="mehta">{{cite journal | vauthors = Mehta AR, Mehta PR, Anderson SP, MacKinnon BL, Compston A | title = Grey Matter Etymology and the neuron(e) | journal = Brain | volume = 143 | issue = 1 | pages = 374–379 | date = January 2020 | pmid = 31844876 | pmc = 6935745 | doi = 10.1093/brain/awz367 | url = }}</ref> but has now become rare in American usage and uncommon in British usage.<ref name="ngram">{{cite web |title=Google Books Ngram Viewer |url=https://books.google.com/ngrams/graph?content=neuron%2Cneurone&year_start=1900&year_end=2008&case_insensitive=on&corpus=15&smoothing=3&direct_url=t4%3B%2Cneuron%3B%2Cc0%3B%2Cs0%3B%3Bneuron%3B%2Cc0%3B%3BNeuron%3B%2Cc0%3B%3BNEURON%3B%2Cc0%3B.t4%3B%2Cneurone%3B%2Cc0%3B%2Cs0%3B%3Bneurone%3B%2Cc0%3B%3BNeurone%3B%2Cc0%3B%3BNEURONE%3B%2Cc0 |website=books.google.com |access-date=19 December 2020 |language=en}}</ref><ref name="oed"/>

这个词以前在法语中被采用，拼写为neurone。这种拼法也曾被许多英语作家使用，[38]但现在在美国的用法中已经很少见，在英国的用法中也不常见。[39] [37]

==History历史==
{{Further|History of neuroscience}}
[[File:Golgi Hippocampus.jpg|left|thumb|Drawing by Camillo Golgi of a [[hippocampus]] stained using the [[silver nitrate]] method卡米洛-高尔基绘制的使用硝酸银法染色的海马体。]]
[[File:Purkinje cell by Cajal.png|thumb|Drawing of a Purkinje cell in the [[cerebellar cortex]] done by Santiago Ramón y Cajal, demonstrating the ability of Golgi's staining method to reveal fine detail圣地亚哥-拉蒙-卡亚尔（Santiago Ramón y Cajal）绘制的小脑皮层中的浦肯野细胞图，展示了高尔基染色法揭示精细细节的能力。]]

The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist [[Santiago Ramón y Cajal]].<ref name="López-Muñoz">{{cite journal | vauthors = López-Muñoz F, Boya J, Alamo C | title = Neuron theory, the cornerstone of neuroscience, on the centenary of the Nobel Prize award to Santiago Ramón y Cajal | journal = Brain Research Bulletin | volume = 70 | issue = 4–6 | pages = 391–405 | date = October 2006 | pmid = 17027775 | doi = 10.1016/j.brainresbull.2006.07.010 | s2cid = 11273256 }}</ref>

神经元作为神经系统主要功能单位的地位，在19世纪末通过西班牙解剖学家圣地亚哥-拉蒙-卡亚尔的作品首次得到承认。[40]

To make the structure of individual neurons visible, [[Santiago Ramón y Cajal|Ramón y Cajal]] improved a [[Golgi's method|silver staining process]] that had been developed by [[Camillo Golgi]].<ref name="López-Muñoz" /> The improved process involves a technique called "double impregnation" and is still in use.

为了使单个神经元的结构清晰可见，Ramón y Cajal改进了Camillo Golgi开发的银染工艺。[40]改进后的工艺涉及一种称为 "双浸渍 "的技术，现在仍在使用。

In 1888 Ramón y Cajal published a paper about the bird cerebellum. In this paper, he stated that he could not find evidence for [[anastomosis]] between axons and dendrites and called each nervous element "an absolutely autonomous canton."<ref name="López-Muñoz" /><ref name="finger">{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=Ramon y Cajal's first paper on the Golgi stain was on the bird cerebellum, and it appeared in the ''Revista''<nowiki> in 1888. He acknowledged that he found the nerve fibers to be very intricate, but stated that he could find no evidence for either axons or dendrites undergoing anastomosis and forming nets. He called each nervous element 'an absolutely autonomous canton.'</nowiki>}}</ref> This became known as the [[neuron doctrine]], one of the central tenets of modern [[neuroscience]].<ref name="López-Muñoz" />

1888年，Ramón y Cajal发表了一篇关于鸟类小脑的论文。在这篇论文中，他说他找不到轴突和树突之间结合的证据，并称每个神经元素为 "一个绝对自主的州县"[40] [36]，这被称为神经元学说，是现代神经科学的核心原则之一。[40]

In 1891, the German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] wrote a highly influential review of the neuron doctrine in which he introduced the term ''neuron'' to describe the anatomical and physiological unit of the nervous system.<ref>{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=... a man who would write a highly influential review of the evidence in favor of the neuron doctrine two years later. In his paper, Waldeyer (1891), ... , wrote that nerve cells terminate freely with end arborizations and that the 'neuron' is the anatomical and physiological unit of the nervous system. The word 'neuron' was born this way.}}</ref><ref>{{cite web|url=http://www.whonamedit.com/doctor.cfm/1846.html|title=Whonamedit - dictionary of medical eponyms|website=www.whonamedit.com|quote=Today, Wilhelm von Waldeyer-Hartz is remembered as the founder of the neurone theory, coining the term "neurone" to describe the cellular function unit of the nervous system and enunciating and clarifying that concept in 1891.}}</ref>

1891年，德国解剖学家Heinrich Wilhelm Waldeyer写了一篇对神经元学说有很大影响的综述，他在其中提出了神经元这一术语来描述神经系统的解剖学和生理学单位。[41] [42]

The silver impregnation stains are a useful method for [[Neuroanatomy|neuroanatomical]] investigations because, for reasons unknown, it stains only a small percentage of cells in a tissue, exposing the complete micro structure of individual neurons without much overlap from other cells.<ref name="Grant">{{cite journal | vauthors = Grant G | title = How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal | journal = Brain Research Reviews | volume = 55 | issue = 2 | pages = 490–8 | date = October 2007 | pmid = 17306375 | doi = 10.1016/j.brainresrev.2006.11.004 | s2cid = 24331507 }}</ref>

银浸渍染色法是神经解剖学研究的有效方法，因为——由于未知的原因——它只会对组织中的一小部分细胞进行染色，暴露出单个神经元的完整微观结构，而不会与其他细胞有太多的重叠。[43]

===Neuron doctrine神经元学说===
[[File:PurkinjeCell.jpg|thumb|Drawing of neurons in the pigeon [[cerebellum]], by Spanish neuroscientist [[Santiago Ramón y Cajal]] in 1899. (A) denotes [[Purkinje cell]]s and (B) denotes [[granule cells]], both of which are multipolar.鸽子小脑中的神经元图，由西班牙神经科学家圣地亚哥-拉蒙-卡亚尔于1899年绘制。(A）表示浦肯野细胞，（B）表示颗粒细胞，两者都是多极的。]]

The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramón y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in a meshwork), acting as metabolically distinct units.

神经元学说是现在的一个基本观点，即神经元是神经系统的基本结构和功能单位。该理论是由圣地亚哥-拉蒙-卡亚尔在19世纪末提出的。它认为，神经元是离散的细胞（不以网状结构连接），作为新陈代谢的不同单位发挥作用。

Later discoveries yielded refinements to the doctrine. For example, [[Neuroglia|glial cells]], which are non-neuronal, play an essential role in information processing.<ref>{{cite journal | vauthors = Witcher MR, Kirov SA, Harris KM | title = Plasticity of perisynaptic astroglia during synaptogenesis in the mature rat hippocampus | journal = Glia | volume = 55 | issue = 1 | pages = 13–23 | date = January 2007 | pmid = 17001633 | doi = 10.1002/glia.20415 | citeseerx = 10.1.1.598.7002 | s2cid = 10664003 }}</ref> Also, electrical synapses are more common than previously thought,<ref>{{cite journal | vauthors = Connors BW, Long MA | title = Electrical synapses in the mammalian brain | journal = Annual Review of Neuroscience | volume = 27 | issue = 1 | pages = 393–418 | year = 2004 | pmid = 15217338 | doi = 10.1146/annurev.neuro.26.041002.131128 | url = https://zenodo.org/record/894386 }}</ref> comprising direct, cytoplasmic connections between neurons. In fact, neurons can form even tighter couplings: the squid giant axon arises from the fusion of multiple axons.<ref>{{cite journal | vauthors = Guillery RW | title = Observations of synaptic structures: origins of the neuron doctrine and its current status | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 360 | issue = 1458 | pages = 1281–307 | date = June 2005 | pmid = 16147523 | pmc = 1569502 | doi = 10.1098/rstb.2003.1459 }}</ref>

后来的发现使这一学说得到了完善。例如，非神经元的胶质细胞在信息处理中起着至关重要的作用。[44] 另外，电突触比以前认为得更常见，[45] 包括神经元之间的直接胞质连接。事实上，神经元可以形成更紧密的耦合：乌贼的巨型轴突来自于多个轴突的融合。[46]

Ramón y Cajal also postulated the Law of Dynamic Polarization, which states that a neuron receives signals at its dendrites and cell body and transmits them, as action potentials, along the axon in one direction: away from the cell body.<ref name="sabb">{{cite journal | vauthors = Sabbatini RM | date = April–July 2003 | url = http://www.cerebromente.org.br/n17/history/neurons3_i.htm | title = Neurons and Synapses: The History of Its Discovery | journal = Brain & Mind Magazine | pages = 17 }}</ref> The Law of Dynamic Polarization has important exceptions; dendrites can serve as synaptic output sites of neurons<ref>{{cite journal | vauthors = Djurisic M, Antic S, Chen WR, Zecevic D | title = Voltage imaging from dendrites of mitral cells: EPSP attenuation and spike trigger zones | journal = The Journal of Neuroscience | volume = 24 | issue = 30 | pages = 6703–14 | date = July 2004 | pmid = 15282273 | pmc = 6729725 | doi = 10.1523/JNEUROSCI.0307-04.2004 | hdl = 1912/2958 }}
</ref> and axons can receive synaptic inputs.<ref>{{cite journal | vauthors = Cochilla AJ, Alford S | title = Glutamate receptor-mediated synaptic excitation in axons of the lamprey | journal = The Journal of Physiology | volume = 499 | issue = Pt 2 | pages = 443–57 | date = March 1997 | pmid = 9080373 | pmc = 1159318 | doi = 10.1113/jphysiol.1997.sp021940 }}</ref>

拉蒙-卡哈尔还提出了动态极化定律，即神经元在其树突和细胞体上接收信号，并作为动作电位沿轴突向一个方向传输：离开细胞体。[47] 动态极化定律有重要的例外；树突可以作为神经元的突触输出点[48] ，轴突可以接受突触输入。[49]

===Compartmental modelling of neurons 神经元的间室模型===

Although neurons are often described of as "fundamental units" of the brain, they perform internal computations. Neurons integrate input within dendrites, and this complexity is lost in models that assume neurons to be a fundamental unit. Dendritic branches can be modeled as spatial compartments, whose activity is related due to passive membrane properties, but may also be different depending on input from synapses. [[Compartmental modelling of dendrites]] is especially helpful for understanding the behavior of neurons that are too small to record with electrodes, as is the case for ''Drosophila melanogaster''.<ref>{{cite journal | vauthors = Gouwens NW, Wilson RI | title = Signal propagation in Drosophila central neurons | journal = Journal of Neuroscience | volume = 29 | issue = 19 | pages = 6239–6249 | year = 2009 | pmid = 19439602 | pmc = 2709801 | doi = 10.1523/jneurosci.0764-09.2009 | doi-access = free }}</ref>

尽管神经元经常被描述为大脑的 "基本单位"，但它们执行内部计算。神经元在树突内整合输入，这种复杂性在假定神经元是一个基本单位的模型中丢失。树突分支可以被建模为空间隔间，其活性与被动膜特性相关，但也可能因来自突触的输入的差异而有所不同。树突的间室模型对于理解那些太小而无法用电极记录的神经元的行为特别有帮助，黑腹果蝇就是这种情况。[50]

==Neurons in the brain大脑中的神经元==

The number of neurons in the brain varies dramatically from species to species.<ref name="nervenet">{{cite journal | vauthors = Williams RW, Herrup K | title = The control of neuron number | journal = Annual Review of Neuroscience | volume = 11 | issue = 1 | pages = 423–53 | year = 1988 | pmid = 3284447 | doi = 10.1146/annurev.ne.11.030188.002231 }}</ref> In a human, there are an estimated 10–20 billion neurons in the [[cerebral cortex]] and 55–70 billion neurons in the [[cerebellum]].<ref name="pmid27187682">{{cite journal | vauthors = von Bartheld CS, Bahney J, Herculano-Houzel S | title = The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting | journal = The Journal of Comparative Neurology | volume = 524 | issue = 18 | pages = 3865–3895 | date = December 2016 | pmid = 27187682 | pmc = 5063692 | doi = 10.1002/cne.24040 }}</ref> By contrast, the [[nematode]] worm ''[[Caenorhabditis elegans]]'' has just 302 neurons, making it an ideal [[model organism]] as scientists have been able to map all of its neurons. The fruit fly ''[[Drosophila melanogaster]]'', a common subject in biological experiments, has around 100,000 neurons and exhibits many complex behaviors. Many properties of neurons, from the type of neurotransmitters used to ion channel composition, are maintained across species, allowing scientists to study processes occurring in more complex organisms in much simpler experimental systems.

大脑中的神经元数量因物种不同而有很大差异。[51] 在人类中，大脑皮层中估计有100-200亿个神经元，小脑中有550-700亿个神经元。[52] 相比之下，秀丽隐杆线虫只有302个神经元，使其成为理想的模型生物，因为科学家已经能够绘制其所有的神经元。黑腹果蝇是生物实验中常见的对象，它有大约10万个神经元，表现出许多复杂的行为。神经元的许多特性，从使用的神经递质类型到离子通道组成，在不同的物种中都保持不变，使科学家能够在更简单的实验系统中研究发生在更复杂生物体中的过程。

==Neurological disorders神经系统疾病==
{{Main主要文章|Neurology神经病学}}
{{More citations needed|date=May 2018}}

'''[[Charcot–Marie–Tooth disease]]''' (CMT) is a heterogeneous inherited disorder of nerves ([[neuropathy]]) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs extending to the hands and arms in advanced stages. Presently incurable, this disease is one of the most common inherited neurological disorders, with 36 in 100,000 affected.<ref name=Krajewski>{{cite journal | vauthors = Krajewski KM, Lewis RA, Fuerst DR, Turansky C, Hinderer SR, Garbern J, Kamholz J, Shy ME | title = Neurological dysfunction and axonal degeneration in Charcot-Marie-Tooth disease type 1A | journal = Brain | volume = 123 | issue = 7 | pages = 1516–27 | date = July 2000 | pmid = 10869062 | doi = 10.1093/brain/123.7.1516 | doi-access = free }}</ref>

腓骨肌萎缩症（CMT）是一种异质性的遗传性神经疾病（神经病变），其特点是肌肉组织和触觉的丧失，主要是在脚和腿上，在晚期会延伸到手和胳膊。该病目前无法治愈，是最常见的遗传性神经系统疾病之一，每10万人中会有36人罹患此病。[53]

'''[[Alzheimer's disease]]''' (AD), also known simply as ''Alzheimer's'', is a [[neurodegenerative disease]] characterized by progressive [[cognitive]] deterioration, together with declining activities of daily living and [[neuropsychiatric]] symptoms or behavioral changes.<ref name="nihstages">{{cite web|title=About Alzheimer's Disease: Symptoms|url=http://www.nia.nih.gov/alzheimers/topics/symptoms|publisher=National Institute on Aging|access-date=28 December 2011|url-status=live|archive-url=https://web.archive.org/web/20120115201854/http://www.nia.nih.gov/alzheimers/topics/symptoms|archive-date=15 January 2012|df=dmy-all}}</ref> The most striking early symptom is loss of short-term memory ([[amnesia]]), which usually manifests as minor forgetfulness that becomes steadily more pronounced with illness progression, with relative preservation of older memories. As the disorder progresses, cognitive (intellectual) impairment extends to the domains of language ([[aphasia]]), skilled movements ([[apraxia]]), and recognition ([[agnosia]]), and functions such as decision-making and planning become impaired.<ref name="BMJ2009">{{cite journal | vauthors = Burns A, Iliffe S | title = Alzheimer's disease | journal = BMJ | volume = 338 | pages = b158 | date = February 2009 | pmid = 19196745 | doi = 10.1136/bmj.b158 | s2cid = 8570146 | url = https://semanticscholar.org/paper/0fccf0616b35e3bb427c3783a44777e4dc228713 }}</ref><ref name=NEJM2010>{{cite journal | vauthors = Querfurth HW, LaFerla FM | title = Alzheimer's disease | journal = The New England Journal of Medicine | volume = 362 | issue = 4 | pages = 329–44 | date = January 2010 | pmid = 20107219 | doi = 10.1056/NEJMra0909142 | s2cid = 205115756 | url = https://semanticscholar.org/paper/7bc445c5ddf7869b9f71a5390ff9e9e992533ee3 }}</ref>

阿尔茨海默病（AD），也被简单地称为阿尔茨海默病，是一种神经退行性疾病，其特点是认知能力逐渐退化，伴随着日常生活活动能力下降和神经精神症状或行为变化。[54] 最突出的早期症状是短期记忆的丧失（失忆），通常表现为轻微的遗忘，随着病情的发展，遗忘的程度会逐渐加重，但老的记忆却记忆得相对清楚。随着病情的发展，认知（智力）损害扩展到语言（失语）、熟练动作（失用）和识别（失认）等领域，决策和计划等功能也会受到损害[55][56] 。

'''[[Parkinson's disease]]''' (PD), also known as ''Parkinson disease'', is a degenerative disorder of the central nervous system that often impairs motor skills and speech.<ref name=NIH2016>{{cite web|title=Parkinson's Disease Information Page|url=https://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|website=NINDS|access-date=18 July 2016|date=30 June 2016|url-status=live|archive-url=https://web.archive.org/web/20170104201403/http://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|archive-date=4 January 2017|df=dmy-all}}</ref> Parkinson's disease belongs to a group of conditions called [[movement disorders]].<ref>{{cite web | title = Movement Disorders| url = http://www.neuromodulation.com/movement-disorders | work = The International Neuromodulation Society }}</ref> It is characterized by muscle rigidity, [[tremor]], a slowing of physical movement ([[bradykinesia]]), and in extreme cases, a loss of physical movement ([[akinesia]]). The primary symptoms are the results of decreased stimulation of the [[motor cortex]] by the [[basal ganglia]], normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level [[cognitive dysfunction]] and subtle language problems. PD is both chronic and progressive.

帕金森病（PD），又称帕金森病，是一种中枢神经系统的退行性疾病，通常会损害运动技能和语言能力。[57] 帕金森病属于一组被称为运动障碍的疾病。[58] 它的特点是肌肉僵硬、震颤、身体运动变慢（运动迟缓），在极端情况下，身体运动丧失（运动不能）。主要症状是基底神经节对运动皮层刺激减少的结果，通常是由于大脑多巴胺能神经元中产生的多巴胺形成和作用不足造成的。次要症状可能包括高水平的认知功能障碍和微妙的语言问题。帕金森病既是慢性的，也是渐进的。

'''[[Myasthenia gravis]]''' is a neuromuscular disease leading to fluctuating [[muscle weakness]] and fatigability during simple activities. Weakness is typically caused by circulating [[antibodies]] that block [[acetylcholine receptors]] at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with [[immunosuppressants]], [[cholinesterase]] inhibitors and, in selected cases, [[thymectomy]].

重症肌无力是一种神经肌肉疾病，导致简单活动时出现波动性的肌肉无力和疲劳。肌无力通常是由阻断突触后神经肌肉接头处的乙酰胆碱受体的循环抗体引起的，它抑制了神经递质乙酰胆碱的刺激作用。肌无力症用免疫抑制剂、胆碱酯酶抑制剂来治疗，在某些情况下还可以进行胸腺切除术。

===Demyelination脱髓鞘症===
{{Further|Demyelinating disease}}
[[File:Guillain-barré syndrome - Nerve Damage.gif|thumb|Guillain–Barré syndrome – demyelination格林-巴利综合征——脱髓鞘症]]

[[Demyelination]] is the act of demyelinating, or the loss of the myelin sheath insulating the nerves. When myelin degrades, conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. This leads to certain neurodegenerative disorders like [[multiple sclerosis]] and [[chronic inflammatory demyelinating polyneuropathy]].

脱髓鞘是指脱髓鞘的行为，或绝缘于神经的髓鞘的丧失。当髓鞘退化时，信号沿神经的传导会受到影响或丧失，神经最终会萎缩。这导致了某些神经退行性疾病，如多发性硬化症和慢性炎症性脱髓鞘多发性神经病。

===Axonal degeneration轴突变性===
Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration, which is the rapid separation of the proximal and distal ends, occurring within 30 minutes of injury. Degeneration follows with swelling of the [[axolemma]], and eventually leads to bead-like formation. Granular disintegration of the axonal [[cytoskeleton]] and inner [[organelle]]s occurs after axolemma degradation. Early changes include accumulation of [[mitochondria]] in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The disintegration is dependent on [[ubiquitin]] and [[calpain]] [[proteases]] (caused by the influx of calcium ion), suggesting that axonal degeneration is an active process that produces complete fragmentation. The process takes about roughly 24 hours in the PNS and longer in the CNS. The signaling pathways leading to axolemma degeneration are unknown.

尽管大多数损伤反应包括钙离子流入信号，以促进断裂部分的重新愈合，但轴突损伤最初会导致急性轴突变性，即在损伤后30分钟内近端和远端迅速分离。退化后，轴突肿胀，最终形成串珠状肿胀。轴索细胞骨架和内部细胞器的颗粒状解体发生在轴索退化之后。早期的变化包括线粒体在损伤部位的结旁区堆积。内质网降解、线粒体膨胀并最终解体。解体依赖于泛素和钙蛋白酶（由钙离子的涌入引起），表明轴突变性是一个完全破碎的活跃过程。这一过程在PNS（周围神经系统）中大约需要24小时，在CNS（中枢神经系统）中则需要更长时间。导致轴突变性的信号传导途径尚不清楚。

==Neurogenesis神经发生==
{{Main|Neurogenesis}}

Neurons are born through the process of [[neurogenesis]], in which [[neural stem cell]]s divide to produce differentiated neurons. Once fully differentiated neurons are formed, they are no longer capable of undergoing [[mitosis]]. Neurogenesis primarily occurs in the embryo of most organisms.

神经元是通过神经发生的过程诞生的，其中神经干细胞分裂产生分化的神经元。一旦完全分化的神经元形成，它们就不再能够进行有丝分裂。神经发生主要发生在大多数生物体的胚胎中。

[[Adult neurogenesis]] can occur and studies of the age of human neurons suggest that this process occurs only for a minority of cells, and that the vast majority of neurons in the [[neocortex]] forms before birth and persists without replacement. The extent to which adult neurogenesis exists in humans, and its contribution to cognition are controversial, with conflicting reports published in 2018.<ref>{{cite journal | vauthors = Kempermann G, Gage FH, Aigner L, Song H, Curtis MA, Thuret S, Kuhn HG, Jessberger S, Frankland PW, Cameron HA, Gould E, Hen R, Abrous DN, Toni N, Schinder AF, Zhao X, Lucassen PJ, Frisén J | title = Human Adult Neurogenesis: Evidence and Remaining Questions | journal = Cell Stem Cell | volume = 23 | issue = 1 | pages = 25–30 | date = July 2018 | pmid = 29681514 | pmc = 6035081 | doi = 10.1016/j.stem.2018.04.004 }}</ref>

成年神经发生能够发生，对人类神经元年龄的研究表明，这一过程只发生在少数细胞中，新皮层中的绝大多数神经元在出生前就已形成，并持续存在而不被替换。人类中成年神经发生存在的程度，以及它对认知的贡献是有争议的，2018年发表的报告相互矛盾。[59]

The body contains a variety of stem cell types that have the capacity to differentiate into neurons. Researchers found a way to transform human skin cells into nerve cells using [[transdifferentiation]], in which "cells are forced to adopt new identities".<ref name=twsX33>{{Cite journal |doi=10.1038/news.2011.328 | last = Callaway | first = Ewen |title= How to make a human neuron | journal = Nature |quote= By transforming cells from human skin into working nerve cells, researchers may have come up with a model for nervous-system diseases and perhaps even regenerative therapies based on cell transplants. The achievement, reported online today in ''Nature'', is the latest in a fast-moving field called transdifferentiation, in which cells are forced to adopt new identities. In the past year, researchers have converted connective tissue cells found in skin into heart cells, blood cells, and liver cells.
|date= 26 May 2011 }}</ref>

人体含有各种干细胞类型，它们有能力分化为神经元。研究人员发现了一种利用横向分化将人类皮肤细胞转化为神经细胞的方法，其中 "细胞被迫采用新的身份"。[60]

During [[neurogenesis]] in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that populate cortical layers. [[Epigenetics|Epigenetic]] modifications play a key role in regulating [[gene expression]] in differentiating [[neural stem cells]], and are critical for cell fate determination in the developing and adult mammalian brain. Epigenetic modifications include [[DNA methylation|DNA cytosine methylation]] to form [[5-methylcytosine]] and [[DNA demethylation|5-methylcytosine demethylation]].<ref name=Wang2016>{{cite journal | vauthors = Wang Z, Tang B, He Y, Jin P | title = DNA methylation dynamics in neurogenesis | journal = Epigenomics | volume = 8 | issue = 3 | pages = 401–14 | date = March 2016 | pmid = 26950681 | pmc = 4864063 | doi = 10.2217/epi.15.119 }}</ref> These modifications are critical for cell fate determination in the developing and adult mammalian brain. [[DNA methylation|DNA cytosine methylation]] is catalyzed by [[DNA methyltransferase|DNA methyltransferases (DNMTs)]]. Methylcytosine demethylation is catalyzed in several stages by [[TET enzymes]] that carry out oxidative reactions (e.g. [[5-methylcytosine]] to [[5-hydroxymethylcytosine]]) and enzymes of the DNA [[base excision repair]] (BER) pathway.<ref name=Wang2016/>

在哺乳动物大脑的神经发生过程中，祖细胞和干细胞从增殖性分裂发展到分化性分裂。这一进展导致了皮层中的神经元和胶质细胞的出现。表观遗传学修饰在调节分化中的神经干细胞的基因表达方面起着关键作用，对发育中和成年哺乳动物大脑中的细胞命运决定至关重要。表观遗传修饰包括DNA胞嘧啶甲基化形成5-甲基胞嘧啶和5-甲基胞嘧啶去甲基化。[61] 这些修饰对于发育中和成年哺乳动物大脑的细胞命运决定至关重要。DNA胞嘧啶甲基化是由DNA甲基转移酶（DNMTs）催化的。甲基胞嘧啶去甲基化是由进行氧化反应（如5-甲基胞嘧啶到5-羟甲基胞嘧啶）的TET酶和DNA碱基切除修复（BER）途径的酶分几个阶段催化的[61] 。

At different stages of mammalian nervous system development two DNA repair processes are employed in the repair of DNA double-strand breaks. These pathways are [[homologous recombination]]al repair used in proliferating neural precursor cells, and [[non-homologous end joining]] used mainly at later developmental stages<ref>{{cite journal | vauthors = Orii KE, Lee Y, Kondo N, McKinnon PJ | title = Selective utilization of nonhomologous end-joining and homologous recombination DNA repair pathways during nervous system development | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 26 | pages = 10017–22 | date = June 2006 | pmid = 16777961 | pmc = 1502498 | doi = 10.1073/pnas.0602436103 | bibcode = 2006PNAS..10310017O | doi-access = free }}</ref>

在哺乳动物神经系统发育的不同阶段，有两种DNA修复过程被用于修复DNA双链断裂。这些途径是用于增殖期神经前体细胞的同源重组修复，以及主要用于后期发育阶段的非同源末端连接[62] 。

==Nerve regeneration神经再生==
{{Main|Neuroregeneration}}
Peripheral axons can regrow if they are severed,<ref name="Yiu_2006">{{cite journal | vauthors = Yiu G, He Z | title = Glial inhibition of CNS axon regeneration | journal = Nature Reviews. Neuroscience | volume = 7 | issue = 8 | pages = 617–27 | date = August 2006 | pmid = 16858390 | pmc = 2693386 | doi = 10.1038/nrn1956 }}</ref> but one neuron cannot be functionally replaced by one of another type ([[Llinás' law]]).<ref name="llinas2014"/>

外围轴突如果被切断，可以重新生长，[63]但一个神经元在功能上不能被另一种类型的神经元取代（Llinás法则）[15]。

== See also ==
{{Div col|colwidth=20em}}
* [[Artificial neuron]]
* [[Bidirectional cell]]
* [[Biological neuron model]]
* [[Compartmental neuron models]]
* [[Connectome]]
* [[Dogiel cell]]
* [[List of animals by number of neurons]]
* [[List of neuroscience databases]]
* [[Neuronal galvanotropism]]
* [[Neuroplasticity]]
* [[Growth cone]]
* [[Sholl analysis]]
{{Div col end}}

*人工神经元
*双向细胞
*生物神经元模型
*间室神经元模型
*连接组
*锥体细胞
*按神经元数量排列的动物名单
*神经科学数据库列表
*神经元向电性
*神经可塑性
*生长锥
*肖尔分析

== References参考文献 ==

{{Reflist}}

== Further reading进一步阅读 ==
{{refbegin}}
* {{cite journal | vauthors = Bullock TH, Bennett MV, Johnston D, Josephson R, Marder E, Fields RD | title = Neuroscience. The neuron doctrine, redux | journal = Science | volume = 310 | issue = 5749 | pages = 791–3 | date = November 2005 | pmid = 16272104 | doi = 10.1126/science.1114394 | s2cid = 170670241 }}
* {{Cite book | vauthors = Kandel ER, Schwartz JH, Jessell TM |year=2000 |title=Principles of Neural Science |edition=4th |publisher=McGraw-Hill |location=New York |isbn=0-8385-7701-6 }}
* {{Cite book | vauthors = Peters A, Palay SL, Webster HS |year=1991 |title=The Fine Structure of the Nervous System |edition=3rd |location=New York |publisher=Oxford University Press |isbn=0-19-506571-9 }}
* {{Cite book | vauthors = Ramón y Cajal S |year=1933 |title=Histology |edition=10th |publisher=Wood |location=Baltimore }}
* {{Cite book | vauthors = Roberts A, Bush BM |year=1981 |title=Neurones without Impulses |publisher=Cambridge University Press |location=Cambridge |isbn=0-521-29935-7 }}
* {{Cite book |title=Clinical Neuroanatomy | vauthors = Snell RS |date=2010 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-9427-5 |language=en |url=https://www.google.com/books/edition/_/ABPmvroyrD0C }}
{{refend}}

== External links外部链接 ==
{{sisterlinks|d=Q43054|n=no|b=Human_Anatomy/The_Neuron|v=no|voy=no|wikt=neuron|m=no|mw=no|s=no|species=no}}
*{{Curlie|Science/Biology/Neurobiology/|Neurobiology}}
* [https://web.archive.org/web/20130425202653/http://ibro.info/ IBRO (International Brain Research Organization)]. Fostering neuroscience research especially in less well-funded countries.
* [http://NeuronBank.org NeuronBank] an online neuromics tool for cataloging neuronal types and synaptic connectivity.
* [https://web.archive.org/web/20190621124504/http://brainmaps.org/ High Resolution Neuroanatomical Images of Primate and Non-Primate Brains].
* The [[v:Topic:Neuroscience|Department of Neuroscience]] at [[v:|Wikiversity]], which presently offers two courses: [[v:Fundamentals of Neuroscience|Fundamentals of Neuroscience]] and [[v:Comparative Neuroscience|Comparative Neuroscience]].
* [https://www.neuinfo.org/mynif/search.php?q=Neuron&t=data&s=cover&b=0&r=20 NIF Search – Neuron] via the [[Neuroscience Information Framework]]
* [https://web.archive.org/web/20110813070057/http://ccdb.ucsd.edu/sand/main?event=showMPByType&typeid=0&start=1&pl=y Cell Centered Database – Neuron]
* [http://neurolex.org/wiki/Category:Neuron Complete list of neuron types] according to the Petilla convention, at [[NeuroLex]].
* [http://NeuroMorpho.org NeuroMorpho.Org] an online database of digital reconstructions of neuronal morphology.
* [https://web.archive.org/web/20111008142032/http://www.immunoportal.com/modules.php?name=gallery2&g2_view=keyalbum.KeywordAlbum&g2_keyword=Neuron Immunohistochemistry Image Gallery: Neuron]
* [https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/v/anatomy-of-a-neuron Khan Academy: Anatomy of a neuron]
* [http://www.histology-world.com/photoalbum/thumbnails.php?album=96 Neuron images]

* IBRO (国际大脑研究组织)。促进神经科学研究，尤其是在资金不足的国家。
* NeuronBank 是一个在线神经病学工具，用于编目神经元类型和突触连接。
* 灵长类动物和非灵长类动物大脑的高分辨率神经解剖图像。
* 维基大学神经科学系，目前提供两门课程: 神经科学基础和比较神经科学。
* NIF 搜索-神经元通过神经科学信息框架
* 细胞中心数据库-神经元
* 完整的神经元类型清单根据 Petilla 公约，在 NeuroLex。
* NeuroMorpho. Org，一个神经形态学数字重建的在线数据库。
* Immunohistochemistry Image Gallery: Neuron
* Khan Academy: Anatomy of a neuron
* Neuron images

{{Nervous system tumors}}
{{Nervous tissue}}
{{Portal bar|Biology|Medicine}}
{{Authority control}}

[[Category:Neurons| ]]
[[Category:Medical terminology]]

Category:Medical terminology

类别: 医学术语

<noinclude>

This page was moved from [[wikipedia:en:Neuron]]. Its edit history can be viewed at [[神经元/edithistory]]</noinclude>

[[Category:待整理页面]]

神经元

2022-04-30T06:35:11Z

耿淅耀：

此词条由神经动力学读书会词条梳理志愿者[[用户:Autumnwolfberry|Autumnwolfberry]]翻译审校，未经专家审核，带来阅读不便，请见谅。

{{short description|Electrically excitable cell that communicates via synapses}}
{{About|the type of cell}}
{{Distinguish|Neutron}}
{{Infobox neuron
|name = Neuron
|image = Blausen 0657 MultipolarNeuron.png
|caption =Anatomy of a [[multipolar neuron]]
|function =
|neurotransmitter =
|morphology =
|afferents =
|efferents =
}}

A '''neuron''' or '''nerve cell''' is an [[membrane potential#Cell excitability|electrically excitable]] [[cell (biology)|cell]] that communicates with other cells via specialized connections called [[synapse]]s. The neuron is the main component of [[nervous tissue]] in all [[Animalia|animals]] except [[sponge]]s and [[placozoa]]. [[Plant]]s and [[fungi]] do not have nerve cells.

神经元或神经细胞是一种可电兴奋的细胞，通过称为突触的专门连接与其他细胞进行交流。神经元是所有动物神经组织的主要组成部分，除了海绵动物门和扁盘动物门。植物和真菌没有神经细胞。

Neurons are typically classified into three types based on their function. [[Sensory neuron]]s respond to [[Stimulus (physiology)|stimuli]] such as touch, sound, or light that affect the cells of the [[Sense|sensory organs]], and they send signals to the spinal cord or brain. [[Motor neuron]]s receive signals from the brain and spinal cord to control everything from [[muscle contraction]]s to [[gland|glandular output]]. [[Interneuron]]s connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together they form what is called a [[neural circuit]].

神经元通常根据其功能被分为三种类型。感觉神经元对影响感觉器官细胞的刺激，如触摸、声音或光线作出反应，并向脊髓或大脑发送信号。运动神经元接收来自大脑和脊髓的信号，控制从肌肉收缩到腺体输出的一切。中间神经元将神经元与大脑或脊髓同一区域内的其他神经元连接起来。当多个神经元连接在一起时，它们形成所谓的神经回路。

A typical neuron consists of a cell body ([[Soma (biology)|soma]]), [[dendrite]]s, and a single [[axon]]. The soma is a compact structure and the axon and dendrites are filaments extruding from the soma. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The axon leaves the soma at a swelling called the [[axon hillock]] and travels for as far as 1 meter in humans or more in other species. It branches but usually maintains a constant diameter. At the farthest tip of the axon's branches are [[axon terminals]], where the neuron can transmit a signal across the [[synapse]] to another cell. Neurons may lack dendrites or have no axon. The term [[neurite]] is used to describe either a dendrite or an axon, particularly when the cell is [[Cellular differentiation|undifferentiated]].

一个典型的神经元由一个细胞体（soma：胞体）、树突和一个轴突组成。胞体是一个紧凑的结构，轴突和树突是从胞体中挤出的丝状物。树突通常有大量的分支，并从胞体中延伸出几百微米。轴突在一个称为轴突丘的肿胀处离开胞体，在人类中最远可达1米，在其他物种中则更远。它有分支，但通常保持一个恒定的直径。在轴突分支的最远端是轴突终端，在那里神经元可以通过突触向另一个细胞传递信号。神经元可能缺乏树突或没有轴突。术语神经突被用来描述树突或轴突，特别是当细胞未分化时。

Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to a dendrite of another. However, synapses can connect an axon to another axon or a dendrite to another dendrite.

大多数神经元通过树突和胞体接收信号，并沿轴突发出信号。在大多数突触中，信号从一个神经元的轴突交叉到另一个神经元的树突。然而，突触可以将一个轴突连接到另一个轴突，或者将一个树突连接到另一个树突。

The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to maintenance of [[voltage]] gradients across their [[Cell membrane|membranes]]. If the voltage changes by a large enough amount over a short interval, the neuron generates an [[All-or-none law|all-or-nothing]] [[electrochemical]] pulse called an [[action potential]]. This potential travels rapidly along the axon and activates synaptic connections as it reaches them. Synaptic signals may be [[Excitatory postsynaptic potential|excitatory]] or [[Inhibitory postsynaptic potential|inhibitory]], increasing or reducing the net voltage that reaches the soma.

信号传递过程部分是电子的，部分是化学的。神经元具有电兴奋性，这是由于其膜上的电压梯度得到了维持。如果电压在短时间内发生足够大的变化，神经元就会产生一个全有或全无的电化学脉冲，称为动作电位。这个电位沿轴突迅速传播，到达突触连接时激活它们。突触信号可能是兴奋性的或抑制性的，增加或减少到达胞体的净电压。

In most cases, neurons are generated by [[neural stem cell]]s during brain development and childhood. [[Neurogenesis]] largely ceases during adulthood in most areas of the brain.

在大多数情况下，神经元是在大脑发育和儿童时期由神经干细胞生成的。在大脑的大多数区域，神经元的生成在成年后基本停止。

{{toclimit|3}}

== Nervous system神经系统 ==

[[File:Anatomy of a Neuron with Synapse.png|thumb|upright=1.15|Schematic of an anatomically accurate single pyramidal neuron, the primary excitatory neuron of cerebral cortex, with a synaptic connection from an incoming axon onto a dendritic spine.]]
{{unreferenced section|date=December 2020}}

解剖学上准确的单个锥体神经元的示意图，大脑皮层的主要兴奋性神经元，具有从传入轴突到树突棘的突触连接。

Neurons are the primary components of the nervous system, along with the [[glial cells]] that give them structural and metabolic support. The nervous system is made up of the [[central nervous system]], which includes the [[brain]] and [[spinal cord]], and the [[peripheral nervous system]], which includes the [[autonomic nervous system|autonomic]] and [[somatic nervous system]]s. In vertebrates, the majority of neurons belong to the [[central nervous system]], but some reside in peripheral [[ganglion|ganglia]], and many sensory neurons are situated in sensory organs such as the [[retina]] and [[cochlea]].

神经元是神经系统的主要组成部分，同时还有给予其结构和代谢支持的胶质细胞。神经系统由中枢神经系统和周围神经系统组成，前者包括大脑和脊髓，后者包括自主神经和躯体神经系统。在脊椎动物中，大多数神经元属于中枢神经系统，但也有一些居住在周围神经节中，许多感觉神经元位于感觉器官中，如视网膜和耳蜗。

Axons may bundle into [[nerve fascicle|fascicle]]s that make up the [[nerve]]s in the [[peripheral nervous system]] (like strands of wire make up cables). Bundles of axons in the central nervous system are called [[nerve tract|tracts]].

轴突可以捆绑成束，组成周围神经系统的神经（就像电线股组成的电缆）。中枢神经系统中的轴突束被称为束。

== Anatomy and histology解剖学和组织学 ==

[[File:Components of neuron.jpg|thumb|upright=1.8|Diagram of the components of a neuron]]
Neurons are highly specialized for the processing and transmission of cellular signals. Given their diversity of functions performed in different parts of the nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 [[Micrometre|micrometers]] in diameter.<ref>{{cite web |first = Melissa |last = Davies |title = The Neuron: size comparison |url = https://www.ualberta.ca/~neuro/OnlineIntro/NeuronExample.htm |work = Neuroscience: A journey through the brain |date = 2002-04-09 |access-date = 2009-06-20}}</ref>

神经元对细胞信号的处理和传送是高度专业化。鉴于它们在神经系统的不同部分所执行的功能的多样性，它们的形状、大小和电化学特性也有很大差异。例如，一个神经元的胞体的直径可以从4到100微米不等。

*The '''[[Soma (biology)|soma]]''' is the body of the neuron. As it contains the [[cell nucleus|nucleus]], most [[protein biosynthesis|protein synthesis]] occurs here. The nucleus can range from 3 to 18 micrometers in diameter.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Brain Facts and Figures |url = http://faculty.washington.edu/chudler/facts.html |work = Neuroscience for Kids |access-date = 2009-06-20 }}</ref>
*细胞体是神经元的主体。由于它含有细胞核，大多数蛋白质合成发生在这里。细胞核的直径可以从3到18微米不等。

*The '''[[dendrites]]''' of a neuron are cellular extensions with many branches. This overall shape and structure is referred to metaphorically as a dendritic tree. This is where the majority of input to the neuron occurs via the [[dendritic spine]].
*神经元的树突是有许多分支的细胞延伸。这种整体形状和结构被比喻为树突树。神经元的大部分输入是通过树突棘发生的。

*The '''[[axon]]''' is a finer, cable-like projection that can extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length. The axon primarily carries [[nerve signal]]s away from the soma, and carries some types of information back to it. Many neurons have only one axon, but this axon may—and usually will—undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the '''[[axon hillock]]'''. Besides being an anatomical structure, the axon hillock also has the greatest density of [[voltage-dependent sodium channels]]. This makes it the most easily excited part of the neuron and the spike initiation zone for the axon. In electrophysiological terms, it has the most negative [[threshold potential]].
*轴突是一种较细的、像电缆一样的突起，其长度可以是胞体直径的几十倍、几百倍、甚至几万倍。轴突主要携带神经信号离开胞体，并将某些类型的信息带回胞体。许多神经元只有一个轴突，但这个轴突可能--通常也会--发生广泛的分支，从而能够与许多靶细胞进行交流。轴突从胞体中出现的部分被称为轴突丘。除了是一种解剖结构外，轴突丘还具有最大密度的电压依赖性钠离子通道。这使得它成为神经元最容易兴奋的部分和轴突的锋电位触发区。在电生理学方面，它具有最负的阈值电位。

**While the axon and axon hillock are generally involved in information outflow, this region can also receive input from other neurons.
**虽然轴突和轴突丘通常会参与信息外流，但这一区域也能接受来自其他神经元的输入。

*The '''[[axon terminal]]''' is found at the end of the axon farthest from the soma and contains [[synapses]]. Synaptic boutons are specialized structures where [[neurotransmitter]] chemicals are released to communicate with target neurons. In addition to synaptic boutons at the axon terminal, a neuron may have ''en passant'' boutons, which are located along the length of the axon.
*轴突终端位于轴突离胞体最远的一端，包含突触。突触结是专门的结构，神经递质化学物质在此释放，与目标神经元进行交流。除了轴突末端的突触结外，神经元还可能有沿轴突长度方向分布的 "中途结"。

[[File:Neuron Cell Body.png|thumb|Neuron cell body神经元细胞体]]

The accepted view of the neuron attributes dedicated functions to its various anatomical components; however, dendrites and axons often act in ways contrary to their so-called main function.<ref>{{Cite web |date=2021-01-14 |title=16.7: Nervous System |url=https://bio.libretexts.org/Courses/Lumen_Learning/Book%3A_Fundamentals_of_Biology_I_(Lumen)/16%3A_Module_13%3A_Overview_of_Body_Systems/16.7%3A_Nervous_System |access-date=2022-02-28 |website=Biology LibreTexts |language=en}}</ref>

公认的神经元观点将专门的功能归于其各种解剖成分；然而，树突和轴突的作用方式往往与它们所谓的主要功能相反。

[[File:Complete neuron cell diagram en.svg|thumb|right|Diagram of a typical myelinated vertebrate motor neuron典型的有髓的脊椎动物运动神经元示意图]]
[[File:BN1 Neurology.webm|thumb|Neurology Video神经病学视频]]

Axons and dendrites in the central nervous system are typically only about one micrometer thick, while some in the peripheral nervous system are much thicker. The soma is usually about 10–25 micrometers in diameter and often is not much larger than the cell nucleus it contains. The longest axon of a human [[motor neuron]] can be over a meter long, reaching from the base of the spine to the toes.

中枢神经系统中的轴突和树突通常只有约1微米厚，而周围神经系统中的一些轴突和树突则要厚得多。胞体的直径通常约为10-25微米，通常不比其包含的细胞核大多少。人类运动神经元最长的轴突可以超过一米长，从脊柱底部一直延伸到脚趾。

Sensory neurons can have axons that run from the toes to the [[posterior column]] of the spinal cord, over 1.5 meters in adults. [[Giraffe]]s have single axons several meters in length running along the entire length of their necks. Much of what is known about axonal function comes from studying the [[squid giant axon]], an ideal experimental preparation because of its relatively immense size (0.5–1 millimeters thick, several centimeters long).

感觉神经元的轴突可以从脚趾一直延伸到脊髓的后柱，成年人的轴突长度超过1.5米。长颈鹿有几米长的单根轴突，沿其脖子的整个长度运行。人们对轴突功能的了解大多来自于对鱿鱼巨型轴突的研究，由于其相对巨大的尺寸（0.5-1毫米厚，数厘米长），这是一种理想的实验准备。

Fully differentiated neurons are permanently [[G0 phase|postmitotic]]<ref>{{cite journal | vauthors = Herrup K, Yang Y | title = Cell cycle regulation in the postmitotic neuron: oxymoron or new biology? | journal = Nature Reviews. Neuroscience | volume = 8 | issue = 5 | pages = 368–78 | date = May 2007 | pmid = 17453017 | doi = 10.1038/nrn2124 | s2cid = 12908713 }}</ref> however, stem cells present in the adult brain may regenerate functional neurons throughout the life of an organism (see [[neurogenesis]]). [[Astrocyte]]s are star-shaped [[glial cell]]s. They have been observed to turn into neurons by virtue of their stem cell-like characteristic of [[pluripotency]].

完全分化的神经元是永久性的有丝分裂后的细胞，然而，存在于成人大脑中的干细胞可以在有机体的整个生命过程中再生出功能性神经元（见神经元的生成）。星形胶质细胞是星形的胶质细胞。它们已经被观察到可以凭借其类干细胞的多能性特征而变成神经元。

===Membrane膜结构===

{{unreferenced section|date=December 2020}}
Like all animal cells, the cell body of every neuron is enclosed by a [[plasma membrane]], a bilayer of [[lipid]] molecules with many types of protein structures embedded in it. A lipid bilayer is a powerful electrical [[Insulator (electricity)|insulator]], but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are [[voltage-gated ion channel|voltage gated]], meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The [[ion]] materials include [[sodium]], [[potassium]], [[chloride]], and [[calcium]]. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane.

像所有的动物细胞一样，每个神经元的细胞体都被一个质膜所包围，质膜是由脂质分子组成的双层膜，其中嵌入了许多类型的蛋白质结构。脂质双层是一个强大的电绝缘体，但在神经元中，嵌入膜中的许多蛋白质结构是电活性的。这些结构包括允许带电离子流过膜的离子通道和以化学方式将离子从膜的一侧输送到另一侧的离子泵。大多数离子通道只对特定类型的离子有渗透性。一些离子通道是电压门控的，这意味着它们可以通过改变膜上的电压差在开放和关闭状态之间进行切换。其他的是化学门控，意味着它们可以通过与扩散在细胞外液中的化学物质的相互作用在开放和关闭状态之间切换。离子材料包括钠、钾、氯和钙。离子通道和离子泵之间的相互作用在膜上产生一个电压差，通常在基线上小于1/10伏。这个电压有两个功能：首先，它为嵌入膜中的各种电压依赖性蛋白机械提供了动力源；其次，它为膜的不同部分之间的电信号传输提供了一个基础。

===Histology and internal structure组织学和内部结构===

[[File:Gyrus Dentatus 40x.jpg|thumb|250px|Golgi-stained neurons in human hippocampal tissue高尔基染色神经元在人海马组织]]

[[Image:SUM 110913 Cort Neurons 2.5d in vitro 488 Phalloidin no perm 4 cmle-2.png|thumb|300px|Actin filaments in a mouse cortical neuron in culture培养中的小鼠皮质神经元中的肌动蛋白丝]]

Numerous microscopic clumps called [[Nissl body|Nissl bodies]] (or Nissl substance) are seen when nerve cell bodies are stained with a basophilic ("base-loving") dye. These structures consist of [[Endoplasmic reticulum#Rough endoplasmic reticulum|rough endoplasmic reticulum]] and associated [[ribosomal RNA]]. Named after German psychiatrist and neuropathologist [[Franz Nissl]] (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as [[aniline]] or (weakly) [[haematoxylin]]<ref>{{cite book|title=State Hospitals Bulletin|url={{google books |plainurl=y |id=Wp8CAAAAYAAJ|page=378}}|year=1897|publisher=State Commission in Lunacy.|page=378}}</ref> highlight negatively charged components, and so bind to the phosphate backbone of the ribosomal RNA.

当用嗜碱性（"嗜碱"）染料对神经细胞体进行染色时，可以看到许多称为尼氏体（或尼氏物质）的微观团块。这些结构由粗糙的内质网和相关的核糖体RNA组成。它们以德国精神病学家和神经病理学家弗朗茨-尼斯尔（1860-1919）的名字命名，参与蛋白质的合成，其突出性可以用神经细胞代谢非常活跃的事实来解释。嗜碱性染料如苯胺或（弱）血红蛋白会突出带负电的成分，因此与核糖体RNA的磷酸盐骨架结合。

The cell body of a neuron is supported by a complex mesh of structural proteins called [[neurofilament]]s, which together with neurotubules (neuronal microtubules) are assembled into larger neurofibrils.<ref name="Webster">{{cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |website=www.merriam-webster.com}}</ref> Some neurons also contain pigment granules, such as [[neuromelanin]] (a brownish-black pigment that is byproduct of synthesis of [[catecholamine]]s), and [[lipofuscin]] (a yellowish-brown pigment), both of which accumulate with age.<ref>{{cite journal | vauthors = Zecca L, Gallorini M, Schünemann V, Trautwein AX, Gerlach M, Riederer P, Vezzoni P, Tampellini D | title = Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes | journal = Journal of Neurochemistry | volume = 76 | issue = 6 | pages = 1766–73 | date = March 2001 | pmid = 11259494 | doi = 10.1046/j.1471-4159.2001.00186.x | s2cid = 31301135 }}</ref><ref>{{cite journal | vauthors = Herrero MT, Hirsch EC, Kastner A, Luquin MR, Javoy-Agid F, Gonzalo LM, Obeso JA, Agid Y | title = Neuromelanin accumulation with age in catecholaminergic neurons from Macaca fascicularis brainstem | journal = Developmental Neuroscience | volume = 15 | issue = 1 | pages = 37–48 | date = 1993 | pmid = 7505739 | doi = 10.1159/000111315 }}</ref><ref>{{cite journal | vauthors = Brunk UT, Terman A | title = Lipofuscin: mechanisms of age-related accumulation and influence on cell function | journal = Free Radical Biology & Medicine | volume = 33 | issue = 5 | pages = 611–9 | date = September 2002 | pmid = 12208347 | doi = 10.1016/s0891-5849(02)00959-0 }}</ref> Other structural proteins that are important for neuronal function are [[actin]] and the [[tubulin]] of [[microtubule]]s. [[Class III β-tubulin]] is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule.<ref>{{cite journal | vauthors = Zhao B, Meka DP, Scharrenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F | title = Microtubules Modulate F-actin Dynamics during Neuronal Polarization | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 9583 | date = August 2017 | pmid = 28851982 | pmc = 5575062 | doi = 10.1038/s41598-017-09832-8 | bibcode = 2017NatSR...7.9583Z }}</ref>

神经元的细胞体由称为神经丝的结构蛋白的复杂网状结构支撑，它与神经管（神经元微管）一起被组装成较大的神经纤维。一些神经元还含有色素颗粒，如神经黑色素（一种棕黑色的色素，是儿茶酚胺合成的副产品）和脂褐素（一种黄褐色的色素），这两种物质都会随着年龄的增长而积累。对神经元功能很重要的其他结构蛋白是肌动蛋白和微管的管蛋白。第三类β-管蛋白几乎只在神经元中发现。在神经元发育过程中，肌动蛋白主要存在于轴突和树突的顶端。在那里，肌动蛋白的动态可以通过与微管的相互作用而被调节。

There are different internal structural characteristics between axons and dendrites. Typical axons almost never contain [[ribosomes]], except some in the initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases.

轴突和树突之间存在着不同的内部结构特征。典型的轴突几乎不含核糖体，除了在初始段有一些。树突含有颗粒状的内质网或核糖体，随着与细胞体距离的增加，其数量逐渐减少。

==Classification分类==

[[File:GFPneuron.png|thumb|250px|right|Image of pyramidal neurons in mouse [[cerebral cortex]] expressing [[green fluorescent protein]]. The red staining indicates [[GABA]]ergic interneurons.<ref>{{cite journal | vauthors = Lee WC, Huang H, Feng G, Sanes JR, Brown EN, So PT, Nedivi E | title = Dynamic remodeling of dendritic arbors in GABAergic interneurons of adult visual cortex | journal = PLOS Biology | volume = 4 | issue = 2 | pages = e29 | date = February 2006 | pmid = 16366735 | pmc = 1318477 | doi = 10.1371/journal.pbio.0040029 |doi-access=free }}</ref>]]

[[File:smi32neuron.jpg|thumb|250px|right|SMI32-stained pyramidal neurons in [[cerebral cortex]]]]

{{See also|List of distinct cell types in the adult human body#Nervous system}}
另见：成人体内不同的细胞类型列表 § 神经系统

Neurons vary in shape and size and can be classified by their [[Morphology (biology)|morphology]] and function.<ref name="Al">{{cite book|last=Al|first=Martini, Frederic Et|title=Anatomy and Physiology' 2007 Ed.2007 Edition|url={{google books |plainurl=y |id=joJb82gVsLoC|page=288}}|publisher=Rex Bookstore, Inc.|isbn=978-971-23-4807-5|pages=288}}</ref> The anatomist [[Camillo Golgi]] grouped neurons into two types; type I with long axons used to move signals over long distances and type II with short axons, which can often be confused with dendrites. Type I cells can be further classified by the location of the soma. The basic morphology of type I neurons, represented by spinal [[motor neurons]], consists of a cell body called the soma and a long thin axon covered by a [[myelin sheath]]. The dendritic tree wraps around the cell body and receives signals from other neurons. The end of the axon has branching [[axon terminal]]s that release neurotransmitters into a gap called the [[synaptic cleft]] between the terminals and the dendrites of the next neuron.

神经元的形状和大小各不相同，可按其形态和功能进行分类。解剖学家卡米洛-高尔基将神经元分为两类；I型有长轴，用于长距离移动信号；II型有短轴，常与树突相混淆。I型细胞可按胞体的位置进一步分类。以脊髓运动神经元为代表的I型神经元的基本形态包括一个称为胞体的细胞体和一个由髓鞘覆盖的细长轴突。树突树环绕着细胞体，接收来自其他神经元的信号。轴突的末端有分支的轴突终端，将神经递质释放到终端和下一个神经元树突之间的间隙中，称为突触间隙。

===Structural classification结构分类===

====Polarity极性====

[[File:Neurons uni bi multi pseudouni.svg|thumb|Different kinds of neurons不同种类的神经元: 1 [[Unipolar neuron单极神经元]] 2 [[Bipolar neuron双极神经元]] 3 [[Multipolar neuron多极神经元]] 4 [[Pseudounipolar neuron伪单极神经元]] ]]

Most neurons can be anatomically characterized as:
大多数神经元在解剖学上可以被描述为：

*[[Unipolar neuron|Unipolar]]: single process
*[[Bipolar cell|Bipolar]]: 1 axon and 1 dendrite
*[[Multipolar neuron|Multipolar]]: 1 axon and 2 or more dendrites
**[[Golgi I]]: neurons with long-projecting axonal processes; examples are pyramidal cells, Purkinje cells, and anterior horn cells
**[[Golgi II]]: neurons whose axonal process projects locally; the best example is the granule cell
*[[Anaxonic neuron|Anaxonic]]: where the axon cannot be distinguished from the dendrite(s)
*[[Pseudounipolar cells|Pseudounipolar]]: 1 process which then serves as both an axon and a dendrite

* 单极性：单一原生质过程
* 双极性：1个轴突和1个树突
* 多极性：1个轴突和2个或更多的树突
** 高尔基I型：具有长轴突的神经元；比如锥体细胞、浦肯野细胞和前角细胞。
** 高尔基II型：其轴突过程在局部投射的神经元；最好的例子是颗粒细胞
* 无轴性：轴突与树突无法区分的神经元类型。
* 假单极神经元：1个原生质过程，然后既是轴突又是树突。

====Other其他====

Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are:

一些独特的神经元类型可以根据其在神经系统中的位置和独特的形状来识别。一些例子是：

*[[Basket cell]]s, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and [[cerebellum]]
*[[Betz cell]]s, large motor neurons
*[[Lugaro cell]]s, interneurons of the cerebellum
*[[Medium spiny neuron]]s, most neurons in the [[corpus striatum]]
*[[Purkinje cell]]s, huge neurons in the cerebellum, a type of Golgi I multipolar neuron
*[[Pyramidal cell]]s, neurons with triangular soma, a type of Golgi I
*[[Renshaw cell]]s, neurons with both ends linked to [[alpha motor neuron]]s
*[[Unipolar brush cell]]s, interneurons with unique dendrite ending in a brush-like tuft
*[[Granule cell]]s, a type of Golgi II neuron
*[[Anterior horn (spinal cord)|Anterior horn]] cells, [[motoneurons]] located in the spinal cord
*[[Spindle cell]]s, interneurons that connect widely separated areas of the brain

*篮状细胞，在目标细胞的胞体周围形成密集的终端丛，发现于大脑皮层和小脑的中间神经元。
*贝兹细胞，大运动神经元
*卢加洛细胞，小脑的中间神经元
*中型多棘神经元，纹状体中的大多数神经元
*浦肯野细胞，小脑中的巨大神经元，一种高尔基I型多极神经元
*锥体细胞，具有三角形胞体的神经元，是高尔基I型的一种。
*伦肖细胞，两端与α运动神经元相连的神经元
*单极刷细胞，具有独特的树突末端为刷状簇的中间神经元
*颗粒细胞，高尔基II型神经元的一种类型
*前角细胞，位于脊髓中的运动神经元
*纺锤体细胞，连接大脑广泛分布的中间神经元
*纺锤体细胞的运动神经元、连接大脑广泛分离区域的中间神经元

===Functional classification功能分类===

====Direction方向====

*[[Afferent neuron]]s convey information from tissues and organs into the central nervous system and are also called [[sensory neurons]].
*[[Efferent neuron]]s (motor neurons) transmit signals from the central nervous system to the effector cells.
*[[Interneuron]]s connect neurons within specific regions of the central nervous system.

* 传入神经元将信息从组织和器官传入中枢神经系统，也被称为感觉神经元。
* 传出神经元(运动神经元) 将信号从中枢神经系统传递给效应细胞。
* 中间神经元连接中枢神经系统特定区域内的神经元。

Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain.

传入和传出也泛指分别为大脑带来信息或从大脑发出信息的神经元。

====Action on other neurons对其他神经元的影响====

A neuron affects other neurons by releasing a neurotransmitter that binds to [[receptor (biochemistry)|chemical receptor]]s. The effect upon the postsynaptic neuron is determined by the type of receptor that is activated, not by the presynaptic neuron or by the neurotransmitter. A neurotransmitter can be thought of as a key, and a receptor as a lock: the same neurotransmitter can activate multiple types of receptors. Receptors can be classified broadly as ''excitatory'' (causing an increase in firing rate), ''inhibitory'' (causing a decrease in firing rate), or ''modulatory'' (causing long-lasting effects not directly related to firing rate).

一个神经元通过释放一种与化学受体结合的神经递质来影响其他神经元。对突触后神经元的影响是由被激活的受体类型决定的，而不是由突触前神经元或神经递质决定的。可以认为神经递质是一把钥匙，而受体是一把锁：同一神经递质可以激活多种类型的受体。受体可大致分为兴奋性（导致放电率增加）、抑制性（导致放电率下降）或调节性（导致与放电率无直接关系的长期影响）。

The two most common (90%+) neurotransmitters in the brain, [[glutamate]] and [[GABA]], have largely consistent actions. Glutamate acts on several types of receptors, and has effects that are excitatory at [[ionotropic receptor]]s and a modulatory effect at [[metabotropic receptor]]s. Similarly, GABA acts on several types of receptors, but all of them have inhibitory effects (in adult animals, at least). Because of this consistency, it is common for neuroscientists to refer to cells that release glutamate as "excitatory neurons", and cells that release GABA as "inhibitory neurons". Some other types of neurons have consistent effects, for example, "excitatory" motor neurons in the spinal cord that release [[acetylcholine]], and "inhibitory" [[spinal neuron]]s that release [[glycine]].

大脑中最常见的两种（90%以上）神经递质，即谷氨酸和GABA，其作用基本一致。谷氨酸作用于几种类型的受体，在离子型受体上有兴奋作用，在代谢型受体上有调节作用。同样，GABA作用于几种类型的受体，但它们都有抑制作用（至少在成年动物中）。由于这种一致性，神经科学家通常把释放谷氨酸的细胞称为 "兴奋性神经元"，而把释放GABA的细胞称为 "抑制性神经元"。其他一些类型的神经元也有一致的影响，例如，脊髓中释放乙酰胆碱的 "兴奋性 "运动神经元，以及释放甘氨酸的 "抑制性 "脊髓神经元。

The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neuron. In principle, a single neuron, releasing a single neurotransmitter, can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still. For example, [[photoreceptor cell]]s in the retina constantly release the neurotransmitter glutamate in the absence of light. So-called OFF [[retinal bipolar cells|bipolar cells]] are, like most neurons, excited by the released glutamate. However, neighboring target neurons called ON bipolar cells are instead inhibited by glutamate, because they lack typical [[ionotropic receptor|ionotropic]] [[glutamate receptors]] and instead express a class of inhibitory [[metabotropic receptor|metabotropic]] glutamate receptors.<ref>{{cite journal | vauthors = Gerber U | title = Metabotropic glutamate receptors in vertebrate retina | journal = Documenta Ophthalmologica. Advances in Ophthalmology | volume = 106 | issue = 1 | pages = 83–7 | date = January 2003 | pmid = 12675489 | doi = 10.1023/A:1022477203420 | s2cid = 22296630 }}</ref> When light is present, the photoreceptors cease releasing glutamate, which relieves the ON bipolar cells from inhibition, activating them; this simultaneously removes the excitation from the OFF bipolar cells, silencing them.

兴奋性和抑制性神经递质之间的区别不是绝对的。相反，它取决于突触后神经元上存在的化学受体的类别。原则上，一个神经元，释放一种神经递质，可以对某些目标产生兴奋作用，对其他目标产生抑制作用，对其他目标仍有调节作用。例如，视网膜上的感光细胞在没有光的情况下不断释放神经递质谷氨酸。像大多数神经元一样，所谓的关闭双极细胞被释放的谷氨酸所激发。然而，被称为ON双极细胞的邻近目标神经元反而受到谷氨酸的抑制，因为它们缺乏典型的离子型谷氨酸受体，而是表达一类抑制性的代谢型谷氨酸受体。当有光时，光感受器停止释放谷氨酸，这解除了ON双极细胞的抑制，激活了它们；这同时消除了OFF双极细胞的兴奋，使它们沉默。

It is possible to identify the type of inhibitory effect a presynaptic neuron will have on a postsynaptic neuron, based on the proteins the presynaptic neuron expresses. [[Parvalbumin]]-expressing neurons typically dampen the output signal of the postsynaptic neuron in the [[visual cortex]], whereas [[somatostatin]]-expressing neurons typically block dendritic inputs to the postsynaptic neuron.<ref name="pmid22878717">{{cite journal | vauthors = Wilson NR, Runyan CA, Wang FL, Sur M | title = Division and subtraction by distinct cortical inhibitory networks in vivo | journal = Nature | volume = 488 | issue = 7411 | pages = 343–8 | date = August 2012 | pmid = 22878717 | pmc = 3653570 | doi = 10.1038/nature11347 | bibcode = 2012Natur.488..343W | hdl = 1721.1/92709 }}</ref>

根据突触前神经元表达的蛋白质，可以确定突触前神经元对突触后神经元的抑制作用的类型。表达副白蛋白的神经元通常会抑制视觉皮层中突触后神经元的输出信号，而表达躯干素的神经元通常会阻断突触后神经元的树突输入。

====Discharge patterns放电模式====

Neurons have intrinsic electroresponsive properties like intrinsic transmembrane voltage [[Neural oscillation|oscillatory]] patterns.<ref name="llinas2014">{{cite journal | vauthors = Llinás RR | title = Intrinsic electrical properties of mammalian neurons and CNS function: a historical perspective | journal = Frontiers in Cellular Neuroscience | volume = 8 | pages = 320 | date = 2014-01-01 | pmid = 25408634 | pmc = 4219458 | doi = 10.3389/fncel.2014.00320 | doi-access = free }}</ref> So neurons can be classified according to their [[electrophysiology|electrophysiological]] characteristics:

神经元具有内在的电反应特性，如内在的跨膜电压振荡模式。因此，可以根据神经元的电生理特性对其进行分类：

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.
*Phasic or bursting. Neurons that fire in bursts are called phasic.
*Fast spiking. Some neurons are notable for their high firing rates, for example some types of cortical inhibitory interneurons, cells in [[globus pallidus]], [[retinal ganglion cells]].<ref>{{cite conference | title = Ion conductances related to shaping the repetitive firing in rat retinal ganglion cells | vauthors = Kolodin YO, Veselovskaia NN, Veselovsky NS, Fedulova SA | conference = Acta Physiologica Congress | url = http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | access-date = 2009-06-20 | archive-url = https://web.archive.org/web/20121007164451/http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | archive-date = 2012-10-07 | url-status = dead }}</ref><ref>{{cite web|url=http://ykolodin.50webs.com/ |title=Ionic conductances underlying excitability in tonically firing retinal ganglion cells of adult rat |publisher=Ykolodin.50webs.com |date=2008-04-27 |access-date=2013-02-16}}</ref>

*紧张性或规律性棘波。一些神经元通常持续（紧张地）活跃，通常以恒定的频率放电。例如：神经干细胞中的interneurons。
*瞬变性或爆发性。爆发性放电的神经元被称为瞬变性的。
*快闪性。一些神经元因其高放电率而引人注目，例如某些类型的皮质抑制性中间神经元、苍白球、视网膜神经节细胞。

====Neurotransmitter神经递质 ====

[[File:Neurotransmitters.jpg|thumb|Synaptic vesicles containing neurotransmitters含有神经递质的突触小泡。]]
{{Main|Neurotransmitter}}

[[Neurotransmitter]]s are chemical messengers passed from one neuron to another neuron or to a [[muscle cell]] or [[Gland|gland cell]].

神经递质是由一个神经元传递给另一个神经元或肌肉细胞或腺体细胞的化学信使。

*Cholinergic neurons – acetylcholine. [[Acetylcholine]] is released from presynaptic neurons into the synaptic cleft. It acts as a [[ligand]] for both ligand-gated ion channels and [[Metabotropic receptor|metabotropic]] (GPCRs) [[Muscarinic acetylcholine receptor|muscarinic receptors]]. [[Nicotinic receptors]] are pentameric ligand-gated ion channels composed of alpha and beta subunits that bind [[nicotine]]. Ligand binding opens the channel causing influx of [[Sodium|Na+]] depolarization and increases the probability of presynaptic neurotransmitter release. Acetylcholine is synthesized from [[choline]] and [[acetyl coenzyme A]].
*Adrenergic neurons – noradrenaline. [[Noradrenaline]] (norepinephrine) is released from most [[postganglionic]] neurons in the [[sympathetic nervous system]] onto two sets of GPCRs: [[Adrenergic receptor|alpha adrenoceptor]]s and [[beta adrenoceptor]]s. Noradrenaline is one of the three common [[catecholamine]] neurotransmitter, and the most prevalent of them in the [[peripheral nervous system]]; as with other catecholamines, it is synthesised from [[tyrosine]].
*GABAergic neurons – [[gamma aminobutyric acid]]. GABA is one of two neuroinhibitors in the [[central nervous system]] (CNS), along with glycine. GABA has a homologous function to [[Acetylcholine|ACh]], gating anion channels that allow [[Chlorine|Cl−]] ions to enter the post synaptic neuron. Cl− causes hyperpolarization within the neuron, decreasing the probability of an action potential firing as the voltage becomes more negative (for an action potential to fire, a positive voltage threshold must be reached). GABA is synthesized from glutamate neurotransmitters by the enzyme [[glutamate decarboxylase]].
*Glutamatergic neurons – glutamate. [[Glutamate]] is one of two primary excitatory amino acid neurotransmitters, along with [[Aspartic acid|aspartate]]. Glutamate receptors are one of four categories, three of which are ligand-gated ion channels and one of which is a [[G protein|G-protein]] coupled receptor (often referred to as GPCR).

*胆碱能神经元--乙酰胆碱。乙酰胆碱从突触前神经元释放到突触间隙中。它是配体门控离子通道和代谢型（GPCRs：G蛋白耦联受体）毒蕈碱受体的配体。烟碱受体是由结合了尼古丁的α和β亚基组成的五聚体配体门控离子通道。配体结合后打开通道，造成Na+的流入，使其去极化，并增加突触前神经递质释放的概率。乙酰胆碱是由胆碱和乙酰辅酶A合成的。
*肾上腺素能神经元--去甲肾上腺素。去甲肾上腺素（norepinephrine去甲肾上腺素）从交感神经系统的大多数神经节后神经元释放到两组GPCRs上：α肾上腺素受体和β肾上腺素受体。去甲肾上腺素是三种常见的儿茶酚胺神经递质之一，也是周围神经系统中最普遍的一种；与其他儿茶酚胺一样，它是由酪氨酸合成的。
*GABA能神经元--γ氨基丁酸。GABA与甘氨酸一起是中枢神经系统（CNS）中的两种神经抑制剂之一。GABA具有与ACh相同的功能，对允许Cl-离子进入突触后神经元的阴离子通道进行门控。Cl-导致神经元内的超极化，随着电压变得更负，降低了动作电位放电的概率（要引发动作电位，必须达到一个正电压阈值）。GABA是由谷氨酸神经递质通过谷氨酸脱羧酶合成的。
*谷氨酸能神经元--谷氨酸。谷氨酸与天门冬氨酸一起是两种主要的兴奋性氨基酸神经递质之一。谷氨酸受体是四类之一，其中三类是配体门控离子通道，一类是G-蛋白耦联受体（通常称为GPCR）。

:#[[AMPA]] and [[Kainic acid|Kainate]] receptors function as [[Ion|cation]] channels permeable to Na+ cation channels mediating fast excitatory synaptic transmission.
:#[[N-Methyl-D-aspartic acid|NMDA]] receptors are another cation channel that is more permeable to [[Calcium in biology|Ca2+]]. The function of NMDA receptors depend on glycine receptor binding as a co-[[agonist]] within the channel pore. NMDA receptors do not function without both ligands present.
:#Metabotropic receptors, GPCRs modulate synaptic transmission and postsynaptic excitability.
::Glutamate can cause excitotoxicity when blood flow to the brain is interrupted, resulting in [[brain damage]]. When blood flow is suppressed, glutamate is released from presynaptic neurons, causing greater NMDA and AMPA receptor activation than normal outside of stress conditions, leading to elevated Ca2+ and Na+ entering the post synaptic neuron and cell damage. Glutamate is synthesized from the amino acid glutamine by the enzyme [[Glutamine oxoglutarate aminotransferase|glutamate synthase]].

:#AMPA和红藻氨酸受体作为阳离子通道可渗透到Na+阳离子通道，介导快速兴奋性突触传递。
:#NMDA受体是另一个对Ca2+更易渗透的阳离子通道。NMDA受体的功能取决于甘氨酸受体的结合，作为通道孔内的共轭物。如果没有这两种配体存在，NMDA受体就不能发挥作用。
:#促代谢受体，GPCRs调节突触传递和突触后兴奋性。
::当流向大脑的血流被中断时，谷氨酸可引起兴奋性毒性，导致大脑损伤。当血流被抑制时，谷氨酸从突触前的神经元中释放出来，导致NMDA和AMPA受体的激活比压力条件以外的正常情况下更大，导致升高的Ca2+和Na+进入突触后的神经元和细胞损伤。谷氨酸是由谷氨酸合成酶从氨基酸谷氨酰胺中合成的。

*Dopaminergic neurons—[[dopamine]]. [[Dopamine]] is a neurotransmitter that acts on D1 type (D1 and D5) Gs-coupled receptors, which increase cAMP and PKA, and D2 type (D2, D3, and D4) receptors, which activate Gi-coupled receptors that decrease cAMP and PKA. Dopamine is connected to mood and behavior and modulates both pre- and post-synaptic neurotransmission. Loss of dopamine neurons in the [[substantia nigra]] has been linked to [[Parkinson's disease]]. Dopamine is synthesized from the amino acid [[tyrosine]]. Tyrosine is catalyzed into levodopa (or [[L-DOPA]]) by [[Tyrosine hydroxylase|tyrosine hydroxlase]], and levodopa is then converted into dopamine by the aromatic amino acid [[Carboxy-lyases|decarboxylase]].
*Serotonergic neurons—[[serotonin]]. [[Serotonin]] (5-Hydroxytryptamine, 5-HT) can act as excitatory or inhibitory. Of its four 5-HT receptor classes, 3 are GPCR and 1 is a ligand-gated cation channel. Serotonin is synthesized from [[tryptophan]] by [[tryptophan hydroxylase]], and then further by decarboxylase. A lack of 5-HT at postsynaptic neurons has been linked to depression. Drugs that block the presynaptic [[serotonin transporter]] are used for treatment, such as [[Prozac]] and [[Zoloft]].
*Purinergic neurons—ATP. [[Adenosine triphosphate|ATP]] is a neurotransmitter acting at both ligand-gated ion channels ([[P2X]] receptors) and GPCRs ([[P2Y receptor|P2Y]]) receptors. ATP is, however, best known as a [[cotransmitter]]. Such [[purinergic signalling]] can also be mediated by other [[purine]]s like [[adenosine]], which particularly acts at P2Y receptors.
*Histaminergic neurons—[[histamine]]. [[Histamine]] is a [[monoamine neurotransmitter]] and [[neuromodulator]]. Histamine-producing neurons are found in the [[tuberomammillary nucleus]] of the [[hypothalamus]].<ref>{{cite journal | vauthors = Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y | title = Histamine: neural circuits and new medications | journal = Sleep | volume = 42 | issue = 1 | date = January 2019 | pmid = 30239935 | pmc = 6335869 | doi = 10.1093/sleep/zsy183 }}</ref> Histamine is involved in [[arousal]] and regulating sleep/wake behaviors.

*多巴胺能神经元——多巴胺。多巴胺是一种神经递质，作用于D1型（D1和D5）Gs耦联受体，增加cAMP和PKA，以及D2型（D2、D3和D4）受体，激活Gi耦联受体，减少cAMP和PKA。多巴胺与情绪和行为有关，调节突触前和突触后的神经传递。黑质中的多巴胺神经元的丧失与帕金森病有关。多巴胺是由氨基酸酪氨酸合成的。酪氨酸被酪氨酸羟化酶催化为左旋多巴（或L-DOPA），然后左旋多巴被芳香族氨基酸脱羧酶转化为多巴胺。
*羟色胺能神经元——羟色胺。羟色胺（5-Hydroxytryptamine，5-HT）可以起到兴奋性或抑制性作用。在其四个5-HT受体类别中，3个是GPCR，1个是配体门控的阳离子通道。羟色胺由色氨酸经色氨酸羟化酶合成，然后再经脱羧酶进一步合成。突触后神经元缺乏5-HT与抑郁症有关。阻断突触前5-羟色胺转运体的药物被用于治疗，如百忧解和左洛复。
*嘌呤神经元——ATP。ATP是一种同时作用于配体门控离子通道（P2X受体）和GPCRs（P2Y）受体的神经递质。然而，ATP最有名的是作为一种共传导剂。这种嘌呤信号也可以由其他嘌呤介导，如腺苷，它特别作用于P2Y受体。
*组胺能神经元——组胺。组胺是一种单胺类神经递质和神经调节剂。产生组胺的神经元存在于下丘脑的管状乳头核。组胺参与唤醒和调节睡眠/觉醒行为。

====Multimodel classification多模式分类====

Since 2012 there has been a push from the cellular and computational neuroscience community to come up with a universal classification of neurons that will apply to all neurons in the brain as well as across species. This is done by considering the three essential qualities of all neurons: electrophysiology, morphology, and the individual transcriptome of the cells. Besides being universal this classification has the advantage of being able to classify astrocytes as well. A method called Patch-Seq in which all three qualities can be measured at once is used extensively by the Allen Institute for Brain Science.<ref>{{cite web |url=https://www.news-medical.net/news/20201203/Patch-seq-technique-helps-depict-the-variation-of-neural-cells-in-the-brain.aspx |title=Patch-seq technique helps depict the variation of neural cells in the brain |work=News-medical.net |date=3 December 2020 |access-date=26 August 2021 |url-status=live}}</ref>

自2012年以来，细胞和计算神经科学界一直在推动提出一个通用的神经元分类，该分类将适用于大脑中的所有神经元以及跨物种。这是通过考虑所有神经元的三个基本属性来实现的：电生理学、形态学和细胞的个体转录组。除了具有普遍性之外，这种分类法还有一个优点，就是能够对星形胶质细胞进行分类。艾伦脑科学研究所广泛使用一种叫做Patch-Seq的方法，可以同时测量所有三种属性。

==Connectivity连接性==

{{Main|Synapse|Chemical synapse化学突触}}
[[File:Chemical synapse schema cropped.jpg|thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell沿着轴突传播到下一个细胞的细胞体和树突的一种信号。]]
[[File:Neuro Muscular Junction.png|thumb|Chemical synapse|left]]

Neurons communicate with each other via [[synapses]], where either the [[axon terminal]] of one cell contacts another neuron's dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in the cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the [[supraoptic nucleus]], have only one or two dendrites, each of which receives thousands of synapses.

神经元通过突触相互沟通，一个细胞的轴突终端接触到另一个神经元的树突、胞体，或者更少见的轴突。像小脑中的浦肯野细胞这样的神经元可以有超过1000个树突分支，与成千上万的其他细胞建立连接; 其他的神经元，如视上核的大细胞神经元，只有一个或两个树突，每个树突接收数千个突触。

Synapses can be [[EPSP|excitatory]] or [[IPSP|inhibitory]], either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive [[gap junction|junctions]] between cells.<ref>{{cite book |last1=Macpherson |first1=Gordon |title=Black's Medical Dictionary |date=2002 |publisher=Scarecrow Press |location=Lanham, MD |isbn=0810849844 |pages=431–434 |edition=40 }}</ref>

突触可以是兴奋性的或抑制性的，分别增加或减少目标神经元的活动。一些神经元还通过电突触进行交流，电突触是细胞之间直接的、导电的连接点。

When an action potential reaches the axon terminal, it opens [[Voltage-dependent calcium channel|voltage-gated calcium channels]], allowing [[Calcium in biology|calcium ions]] to enter the terminal. Calcium causes [[synaptic vesicles]] filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the [[axon terminal]] triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial [[energy metabolism]] to produce [[Adenosine triphosphate|ATP]] to support continuous neurotransmission.<ref name="pmid23746507">{{cite journal | vauthors = Ivannikov MV, Macleod GT | title = Mitochondrial free Ca²⁺ levels and their effects on energy metabolism in Drosophila motor nerve terminals | journal = Biophysical Journal | volume = 104 | issue = 11 | pages = 2353–61 | date = June 2013 | pmid = 23746507 | pmc = 3672877 | doi = 10.1016/j.bpj.2013.03.064 | bibcode = 2013BpJ...104.2353I }}</ref>

当动作电位到达轴突末端时，它打开电压门控的钙离子通道，允许钙离子进入末端。钙离子使充满神经递质分子的突触小泡与膜融合，将其内容释放到突触间隙中。神经递质在突触间隙中扩散，激活突触后神经元上的受体。轴突末端的高细胞钙引发线粒体钙吸收，这反过来又激活了线粒体的能量代谢，产生ATP以支持持续的神经传递。

An [[autapse]] is a synapse in which a neuron's axon connects to its own dendrites.

自突触是指神经元的轴突与自己的树突相连的突触。

The [[human brain]] has some 8.6 x 1010 (eighty six billion) neurons.<ref>{{ cite journal | vauthors = Herculano-Houzel S | title = The human brain in numbers: a linearly scaled-up primate brain | journal = Frontiers in Human Neuroscience | volume = 3 | pages = 31 | date = November 2009 | pmid = 19915731 | doi = 10.3389/neuro.09.031.2009 | pmc = 2776484 | doi-access = free }}</ref> Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 1015 synapses (1 quadrillion). [[Synaptic pruning|This number declines with age]], stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5 x 1014 synapses (100 to 500 trillion).<ref>{{cite journal | vauthors = Drachman DA | title = Do we have brain to spare? | journal = Neurology | volume = 64 | issue = 12 | pages = 2004–5 | date = June 2005 | pmid = 15985565 | doi = 10.1212/01.WNL.0000166914.38327.BB | s2cid = 38482114 }}</ref>

[[File:Axon Propagation.svg|thumb|563x563px|An annotated diagram of the stages of an action potential propagating down an axon including the role of ion concentration and pump and channel proteins.一个动作电位沿轴突传播的阶段的注释图，包括离子浓度和泵及通道蛋白的作用。]]

人脑有大约8.6 x 1010（86亿）个神经元。每个神经元平均有7000个与其他神经元的突触连接。据估计，一个三岁孩子的大脑大约有1015个突触（1万亿）。这个数字随着年龄的增长而下降，到成年后趋于稳定。对成年人的估计有所不同，从1014到5 x 1014个突触（100到500万亿）不等。

=== Nonelectrochemical signaling非电化学信号传递 ===

Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through:
* force generated by the enlargement of dendritic spines<ref>{{cite journal |last1=Ucar |first1=Hasan |last2=Watanabe |first2=Satoshi |last3=Noguchi |first3=Jun |last4=Morimoto |first4=Yuichi |last5=Iino |first5=Yusuke |last6=Yagishita |first6=Sho |last7=Takahashi |first7=Noriko |last8=Kasai |first8=Haruo |title=Mechanical actions of dendritic-spine enlargement on presynaptic exocytosis |journal=Nature |date=December 2021 |volume=600 |issue=7890 |pages=686–689 |doi=10.1038/s41586-021-04125-7 |language=en |issn=1476-4687}} Lay summary: {{cite news |title=Forceful synapses reveal mechanical interactions in the brain |url=https://www.nature.com/articles/d41586-021-03516-0 |access-date=21 February 2022 |work=Nature |date=24 November 2021 |language=en |doi=10.1038/d41586-021-03516-0}}</ref>
* the transfer of [[protein]]s – transneuronally transported proteins (TNTPs)<ref>{{cite news |title=Researchers discover new type of cellular communication in the brain |url=https://medicalxpress.com/news/2022-01-cellular-brain.html |access-date=12 February 2022 |work=The Scripps Research Institute |language=en}}</ref><ref>{{cite journal |last1=Schiapparelli |first1=Lucio M. |last2=Sharma |first2=Pranav |last3=He |first3=Hai-Yan |last4=Li |first4=Jianli |last5=Shah |first5=Sahil H. |last6=McClatchy |first6=Daniel B. |last7=Ma |first7=Yuanhui |last8=Liu |first8=Han-Hsuan |last9=Goldberg |first9=Jeffrey L. |last10=Yates |first10=John R. |last11=Cline |first11=Hollis T. |title=Proteomic screen reveals diverse protein transport between connected neurons in the visual system |journal=Cell Reports |date=25 January 2022 |volume=38 |issue=4 |doi=10.1016/j.celrep.2021.110287 |language=English |issn=2211-1247}}</ref>

除了电和化学信号，研究表明健康人脑中的神经元还可以通过以下方式交流：
*树突棘扩大产生的力
*蛋白质的转移--经神经元转运蛋白（TNTPs）。

They can also get modulated by input from the environment and [[hormone]]s released from other parts of the organism,<ref>{{cite journal |last1=Levitan |first1=Irwin B. |last2=Kaczmarek |first2=Leonard K. |title=Electrical Signaling in Neurons |doi=10.1093/med/9780199773893.001.0001/med-9780199773893-chapter-3 |publisher=Oxford University Press}}</ref> which could be influenced more or less directly by neurons. This also applies to [[neurotrophin]]s such as [[BDNF]]. The [[gut microbiome]] is also connected with the brain.<ref>{{cite journal |last1=O’Leary |first1=Olivia F. |last2=Ogbonnaya |first2=Ebere S. |last3=Felice |first3=Daniela |last4=Levone |first4=Brunno R. |last5=C. Conroy |first5=Lorraine |last6=Fitzgerald |first6=Patrick |last7=Bravo |first7=Javier A. |last8=Forsythe |first8=Paul |last9=Bienenstock |first9=John |last10=Dinan |first10=Timothy G. |last11=Cryan |first11=John F. |title=The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus |journal=European Neuropsychopharmacology |date=1 February 2018 |volume=28 |issue=2 |pages=307–316 |doi=10.1016/j.euroneuro.2017.12.004 |language=en |issn=0924-977X}}</ref>

它们也可以被来自环境的输入和机体其他部分释放的激素所调控，这些都可以或多或少地被神经元直接影响。这也适用于神经营养素，如BDNF。肠道微生物组也与大脑有关。

==Mechanisms for propagating action potentials动作电位的传播机制==
In 1937 [[John Zachary Young]] suggested that the [[squid giant axon]] could be used to study neuronal electrical properties.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Milestones in Neuroscience Research |url = http://faculty.washington.edu/chudler/hist.html |work = Neuroscience for Kids |access-date = 2009-06-20}}</ref> It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the [[membrane potential]].

1937年，约翰-扎卡里-杨提出，乌贼巨大轴突可用于研究神经元的电特性。它比人类神经元大，但与人类神经元相似，因此更容易研究。通过将电极插入乌贼巨轴突，对膜电位进行了精确测量。

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate [[subthreshold membrane potential oscillations]]. These signals are generated and propagated by charge-carrying [[ions]] including sodium (Na+), potassium (K+), chloride (Cl−), and [[Calcium signaling|calcium (Ca2+)]].

轴突和胞体的细胞膜含有电压门控离子通道，使神经元能够产生和传播电信号（动作电位）。一些神经元还产生阈下膜电位振荡。这些信号是由携带电荷的离子产生和传播的，包括钠（Na+）、钾（K+）、氯（Cl-）和钙（Ca2+）。

Several stimuli can activate a neuron leading to electrical activity, including [[Mechanoreceptor|pressure]], stretch, chemical transmitters, and changes of the electric potential across the cell membrane.<ref>{{cite web|first1=Joe |last1=Patlak |first2=Ray |last2=Gibbons | name-list-style = vanc |title=Electrical Activity of Nerves |url=http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |work=Action Potentials in Nerve Cells |date=2000-11-01 |access-date=2009-06-20 |url-status=dead |archive-url=https://web.archive.org/web/20090827220335/http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |archive-date=August 27, 2009 }}</ref> Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.<ref name="Harris-Warrick">{{cite journal |last1=Harris-Warrick |first1=RM |title=Neuromodulation and flexibility in Central Pattern Generator networks. |journal=Current Opinion in Neurobiology |date=October 2011 |volume=21 |issue=5 |pages=685–92 |doi=10.1016/j.conb.2011.05.011 |pmid=21646013|pmc=3171584 }}</ref>

有几种刺激可以激活神经元，导致电活动，包括压力、拉伸、化学传导物和细胞膜上的电势变化。刺激导致细胞膜内特定的离子通道打开，使得离子流经细胞膜，改变膜电位。神经元必须保持界定其神经元类型的特定电特性。

Thin neurons and axons require less [[metabolism|metabolic]] expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of [[myelin]] around their axons. The sheaths are formed by [[glia]]l cells: [[oligodendrocyte]]s in the central nervous system and [[Schwann cell]]s in the peripheral nervous system. The sheath enables action potentials to travel [[saltatory conduction|faster]] than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed [[node of Ranvier|nodes of Ranvier]], which contain a high density of voltage-gated ion channels. [[Multiple sclerosis]] is a neurological disorder that results from demyelination of axons in the central nervous system.

薄的神经元和轴突需要较少的代谢支出来产生和传导动作电位，但较粗的轴突能更快地传递冲动。为了在保持快速传导的同时尽量减少代谢支出，许多神经元的轴突周围有绝缘的髓鞘。这些髓鞘是由胶质细胞形成的：中枢神经系统的少突胶质细胞和周围神经系统的许旺细胞。髓鞘使得动作电位比相同直径的无髓轴突走得更快，同时消耗更少的能量。周围神经中的髓鞘通常沿着轴突生长，长度约为1毫米，并且点缀着无髓鞘的郎飞氏结，其中包含高密度的电压门控离子通道。多发性硬化症是一种神经系统疾病，由中枢神经系统中轴突的脱髓鞘导致。

Some neurons do not generate action potentials, but instead generate a [[graded potential|graded electrical signal]], which in turn causes graded neurotransmitter release. Such [[non-spiking neurons]] tend to be sensory neurons or interneurons, because they cannot carry signals long distances.

有些神经元不产生动作电位，而是产生一个分级的电信号，反过来引起分级的神经递质释放。这样的非脉冲神经元往往是感觉神经元或中间神经元，因为它们不能长距离携带信号。

==Neural coding神经编码==
[[Neural coding]] is concerned with how sensory and other information is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the [[Stimulus (physiology)|stimulus]] and the individual or [[Neural ensemble|ensemble]] neuronal responses, and the relationships among the electrical activities of the neurons within the ensemble.<ref name="Brown">{{cite journal | vauthors = Brown EN, Kass RE, Mitra PP | title = Multiple neural spike train data analysis: state-of-the-art and future challenges | journal = Nature Neuroscience | volume = 7 | issue = 5 | pages = 456–61 | date = May 2004 | pmid = 15114358 | doi = 10.1038/nn1228 | s2cid = 562815 }}</ref> It is thought that neurons can encode both [[Digital data|digital]] and [[analog signal|analog]] information.<ref>{{cite book | vauthors = Thorpe SJ |chapter=Spike arrival times: A highly efficient coding scheme for neural networks |chapter-url= http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf |pages= 91–94 |title=Parallel processing in neural systems and computers| veditors = Eckmiller R, Hartmann G, Hauske G |date=1990|publisher=North-Holland|isbn=9780444883902 |url={{google books |plainurl=y |id=boBqAAAAMAAJ}}|language=en|archive-url=https://web.archive.org/web/20120215151304/http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf|archive-date=2012-02-15}}</ref>

神经编码关注的是感觉和其他信息如何在大脑中被神经元所表达。研究神经编码的主要目的是描述刺激与单个或集合神经元反应之间的关系，以及集合内神经元电活动之间的关系。人们认为，神经元既可以编码数字信息，也可以编码模拟信息。

==All-or-none principle全有或全无原则==

[[File:All-or-none_law_en.svg|thumb|318x318px|As long as the stimulus reaches the threshold, the full response would be given. Larger stimulus does not result in a larger response, vice versa.只要刺激达到阈值，就会有充分的反应。较大的刺激不会导致较大的反应，反之亦然。<ref name=":0">{{Cite book|title=Biological psychology|last=Kalat, James W|year=2016|isbn=9781305105409|edition=12|location=Australia|oclc=898154491}}</ref>{{Rp|31}}]]
{{Main|All-or-none law}}

The conduction of nerve impulses is an example of an [[All-or-none law|all-or-none]] response. In other words, if a neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal, but can increase firing frequency.<ref name=":0" />{{Rp|31}} Receptors respond in different ways to stimuli. Slowly adapting or [[tonic (physiology)|tonic receptors]] respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can't become "stronger" for a specific frequency.

神经冲动的传导是一个全有或全无反应的例子。换句话说，如果一个神经元有任何反应，那么它必须完全响应。更大的刺激强度，如更亮的图像/更响的声音，不会产生更强的信号，但可以增加放电频率。[34]：31受体以不同方式回应刺激。缓慢适应的或紧张性的受体对稳定的刺激作出响应，并产生稳定的放电率。紧张性受体最常通过增加其放电频率对刺激强度的增加作出反应，通常是一个与每秒钟的脉冲相关的刺激的幂函数。这可以比喻为光的内在属性，即一个特定频率（颜色）的更大强度需要更多的光子，因为光子不能对一个特定频率变得 "更强"。

Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with steady stimulus; examples include [[Human skin|skin]] which, when touched causes neurons to fire, but if the object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function.

其他受体类型包括时相性或瞬变性受体，其放电随着稳定的刺激而减少或停止；比如包括皮肤，当被触摸时引起神经元放电，但如果物体保持均匀的压力，神经元就停止放电。对压力和振动有反应的皮肤和肌肉的神经元有过滤的附属结构来帮助它们发挥作用。

The [[pacinian corpuscle]] is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus is transferred to the axon, which fires. If the pressure is steady, stimulus ends; thus, typically these neurons respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of a number of other neurons.<ref>{{cite book | last1 = Eckert | first1 = Roger | last2 = Randall | first2 = David | name-list-style = vanc | title = Animal physiology: mechanisms and adaptations | year = 1983 | publisher = W.H. Freeman | location = San Francisco | isbn = 978-0-7167-1423-1 | page = [https://archive.org/details/animalphysiology0000ecke/page/239 239] | url = https://archive.org/details/animalphysiology0000ecke/page/239 }}</ref>

帕西尼氏小体就是这样一个结构。它有像洋葱一样的同心层，围绕着轴突终端形成。当施加压力使小体变形时，机械刺激被转移到轴突上，轴突就会放电。如果压力是稳定的，刺激就会结束；因此，通常这些神经元在最初的变形过程中会有短暂的去极化反应，而当压力被移除时又会有短暂的去极化反应，从而使小体再次改变形状。其他类型的适应对扩展其他一些神经元的功能很重要。[35]

==Etymology and spelling词源和拼写==

The German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] introduced the term ''neuron'' in 1891,<ref name="finger"/> based on the [[Greek language|ancient Greek]] νεῦρον ''neuron'' 'sinew, cord, nerve'.<ref name="oed">''[[Oxford English Dictionary]]'', 3rd edition, 2003, ''s.v.''</ref>

德国解剖学家Heinrich Wilhelm Waldeyer于1891年提出了神经元一词，[36]其依据是古希腊语νεῦρον neuron's sinew, cord, nerve'。[37]

The word was adopted in French with the spelling ''neurone''. That spelling was also used by many writers in English,<ref name="mehta">{{cite journal | vauthors = Mehta AR, Mehta PR, Anderson SP, MacKinnon BL, Compston A | title = Grey Matter Etymology and the neuron(e) | journal = Brain | volume = 143 | issue = 1 | pages = 374–379 | date = January 2020 | pmid = 31844876 | pmc = 6935745 | doi = 10.1093/brain/awz367 | url = }}</ref> but has now become rare in American usage and uncommon in British usage.<ref name="ngram">{{cite web |title=Google Books Ngram Viewer |url=https://books.google.com/ngrams/graph?content=neuron%2Cneurone&year_start=1900&year_end=2008&case_insensitive=on&corpus=15&smoothing=3&direct_url=t4%3B%2Cneuron%3B%2Cc0%3B%2Cs0%3B%3Bneuron%3B%2Cc0%3B%3BNeuron%3B%2Cc0%3B%3BNEURON%3B%2Cc0%3B.t4%3B%2Cneurone%3B%2Cc0%3B%2Cs0%3B%3Bneurone%3B%2Cc0%3B%3BNeurone%3B%2Cc0%3B%3BNEURONE%3B%2Cc0 |website=books.google.com |access-date=19 December 2020 |language=en}}</ref><ref name="oed"/>

这个词以前在法语中被采用，拼写为neurone。这种拼法也曾被许多英语作家使用，[38]但现在在美国的用法中已经很少见，在英国的用法中也不常见。[39] [37]

==History历史==
{{Further|History of neuroscience}}
[[File:Golgi Hippocampus.jpg|left|thumb|Drawing by Camillo Golgi of a [[hippocampus]] stained using the [[silver nitrate]] method卡米洛-高尔基绘制的使用硝酸银法染色的海马体。]]
[[File:Purkinje cell by Cajal.png|thumb|Drawing of a Purkinje cell in the [[cerebellar cortex]] done by Santiago Ramón y Cajal, demonstrating the ability of Golgi's staining method to reveal fine detail圣地亚哥-拉蒙-卡亚尔（Santiago Ramón y Cajal）绘制的小脑皮层中的浦肯野细胞图，展示了高尔基染色法揭示精细细节的能力。]]

The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist [[Santiago Ramón y Cajal]].<ref name="López-Muñoz">{{cite journal | vauthors = López-Muñoz F, Boya J, Alamo C | title = Neuron theory, the cornerstone of neuroscience, on the centenary of the Nobel Prize award to Santiago Ramón y Cajal | journal = Brain Research Bulletin | volume = 70 | issue = 4–6 | pages = 391–405 | date = October 2006 | pmid = 17027775 | doi = 10.1016/j.brainresbull.2006.07.010 | s2cid = 11273256 }}</ref>

神经元作为神经系统主要功能单位的地位，在19世纪末通过西班牙解剖学家圣地亚哥-拉蒙-卡亚尔的作品首次得到承认。[40]

To make the structure of individual neurons visible, [[Santiago Ramón y Cajal|Ramón y Cajal]] improved a [[Golgi's method|silver staining process]] that had been developed by [[Camillo Golgi]].<ref name="López-Muñoz" /> The improved process involves a technique called "double impregnation" and is still in use.

为了使单个神经元的结构清晰可见，Ramón y Cajal改进了Camillo Golgi开发的银染工艺。[40]改进后的工艺涉及一种称为 "双浸渍 "的技术，现在仍在使用。

In 1888 Ramón y Cajal published a paper about the bird cerebellum. In this paper, he stated that he could not find evidence for [[anastomosis]] between axons and dendrites and called each nervous element "an absolutely autonomous canton."<ref name="López-Muñoz" /><ref name="finger">{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=Ramon y Cajal's first paper on the Golgi stain was on the bird cerebellum, and it appeared in the ''Revista''<nowiki> in 1888. He acknowledged that he found the nerve fibers to be very intricate, but stated that he could find no evidence for either axons or dendrites undergoing anastomosis and forming nets. He called each nervous element 'an absolutely autonomous canton.'</nowiki>}}</ref> This became known as the [[neuron doctrine]], one of the central tenets of modern [[neuroscience]].<ref name="López-Muñoz" />

1888年，Ramón y Cajal发表了一篇关于鸟类小脑的论文。在这篇论文中，他说他找不到轴突和树突之间结合的证据，并称每个神经元素为 "一个绝对自主的州县"[40] [36]，这被称为神经元学说，是现代神经科学的核心原则之一。[40]

In 1891, the German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] wrote a highly influential review of the neuron doctrine in which he introduced the term ''neuron'' to describe the anatomical and physiological unit of the nervous system.<ref>{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=... a man who would write a highly influential review of the evidence in favor of the neuron doctrine two years later. In his paper, Waldeyer (1891), ... , wrote that nerve cells terminate freely with end arborizations and that the 'neuron' is the anatomical and physiological unit of the nervous system. The word 'neuron' was born this way.}}</ref><ref>{{cite web|url=http://www.whonamedit.com/doctor.cfm/1846.html|title=Whonamedit - dictionary of medical eponyms|website=www.whonamedit.com|quote=Today, Wilhelm von Waldeyer-Hartz is remembered as the founder of the neurone theory, coining the term "neurone" to describe the cellular function unit of the nervous system and enunciating and clarifying that concept in 1891.}}</ref>

1891年，德国解剖学家Heinrich Wilhelm Waldeyer写了一篇对神经元学说有很大影响的综述，他在其中提出了神经元这一术语来描述神经系统的解剖学和生理学单位。[41] [42]

The silver impregnation stains are a useful method for [[Neuroanatomy|neuroanatomical]] investigations because, for reasons unknown, it stains only a small percentage of cells in a tissue, exposing the complete micro structure of individual neurons without much overlap from other cells.<ref name="Grant">{{cite journal | vauthors = Grant G | title = How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal | journal = Brain Research Reviews | volume = 55 | issue = 2 | pages = 490–8 | date = October 2007 | pmid = 17306375 | doi = 10.1016/j.brainresrev.2006.11.004 | s2cid = 24331507 }}</ref>

银浸渍染色法是神经解剖学研究的有效方法，因为——由于未知的原因——它只会对组织中的一小部分细胞进行染色，暴露出单个神经元的完整微观结构，而不会与其他细胞有太多的重叠。[43]

===Neuron doctrine神经元学说===
[[File:PurkinjeCell.jpg|thumb|Drawing of neurons in the pigeon [[cerebellum]], by Spanish neuroscientist [[Santiago Ramón y Cajal]] in 1899. (A) denotes [[Purkinje cell]]s and (B) denotes [[granule cells]], both of which are multipolar.鸽子小脑中的神经元图，由西班牙神经科学家圣地亚哥-拉蒙-卡亚尔于1899年绘制。(A）表示浦肯野细胞，（B）表示颗粒细胞，两者都是多极的。]]

The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramón y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in a meshwork), acting as metabolically distinct units.

神经元学说是现在的一个基本观点，即神经元是神经系统的基本结构和功能单位。该理论是由圣地亚哥-拉蒙-卡亚尔在19世纪末提出的。它认为，神经元是离散的细胞（不以网状结构连接），作为新陈代谢的不同单位发挥作用。

Later discoveries yielded refinements to the doctrine. For example, [[Neuroglia|glial cells]], which are non-neuronal, play an essential role in information processing.<ref>{{cite journal | vauthors = Witcher MR, Kirov SA, Harris KM | title = Plasticity of perisynaptic astroglia during synaptogenesis in the mature rat hippocampus | journal = Glia | volume = 55 | issue = 1 | pages = 13–23 | date = January 2007 | pmid = 17001633 | doi = 10.1002/glia.20415 | citeseerx = 10.1.1.598.7002 | s2cid = 10664003 }}</ref> Also, electrical synapses are more common than previously thought,<ref>{{cite journal | vauthors = Connors BW, Long MA | title = Electrical synapses in the mammalian brain | journal = Annual Review of Neuroscience | volume = 27 | issue = 1 | pages = 393–418 | year = 2004 | pmid = 15217338 | doi = 10.1146/annurev.neuro.26.041002.131128 | url = https://zenodo.org/record/894386 }}</ref> comprising direct, cytoplasmic connections between neurons. In fact, neurons can form even tighter couplings: the squid giant axon arises from the fusion of multiple axons.<ref>{{cite journal | vauthors = Guillery RW | title = Observations of synaptic structures: origins of the neuron doctrine and its current status | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 360 | issue = 1458 | pages = 1281–307 | date = June 2005 | pmid = 16147523 | pmc = 1569502 | doi = 10.1098/rstb.2003.1459 }}</ref>

后来的发现使这一学说得到了完善。例如，非神经元的胶质细胞在信息处理中起着至关重要的作用。[44] 另外，电突触比以前认为得更常见，[45] 包括神经元之间的直接胞质连接。事实上，神经元可以形成更紧密的耦合：乌贼的巨型轴突来自于多个轴突的融合。[46]

Ramón y Cajal also postulated the Law of Dynamic Polarization, which states that a neuron receives signals at its dendrites and cell body and transmits them, as action potentials, along the axon in one direction: away from the cell body.<ref name="sabb">{{cite journal | vauthors = Sabbatini RM | date = April–July 2003 | url = http://www.cerebromente.org.br/n17/history/neurons3_i.htm | title = Neurons and Synapses: The History of Its Discovery | journal = Brain & Mind Magazine | pages = 17 }}</ref> The Law of Dynamic Polarization has important exceptions; dendrites can serve as synaptic output sites of neurons<ref>{{cite journal | vauthors = Djurisic M, Antic S, Chen WR, Zecevic D | title = Voltage imaging from dendrites of mitral cells: EPSP attenuation and spike trigger zones | journal = The Journal of Neuroscience | volume = 24 | issue = 30 | pages = 6703–14 | date = July 2004 | pmid = 15282273 | pmc = 6729725 | doi = 10.1523/JNEUROSCI.0307-04.2004 | hdl = 1912/2958 }}
</ref> and axons can receive synaptic inputs.<ref>{{cite journal | vauthors = Cochilla AJ, Alford S | title = Glutamate receptor-mediated synaptic excitation in axons of the lamprey | journal = The Journal of Physiology | volume = 499 | issue = Pt 2 | pages = 443–57 | date = March 1997 | pmid = 9080373 | pmc = 1159318 | doi = 10.1113/jphysiol.1997.sp021940 }}</ref>

拉蒙-卡哈尔还提出了动态极化定律，即神经元在其树突和细胞体上接收信号，并作为动作电位沿轴突向一个方向传输：离开细胞体。[47] 动态极化定律有重要的例外；树突可以作为神经元的突触输出点[48] ，轴突可以接受突触输入。[49]

===Compartmental modelling of neurons 神经元的间室模型===

Although neurons are often described of as "fundamental units" of the brain, they perform internal computations. Neurons integrate input within dendrites, and this complexity is lost in models that assume neurons to be a fundamental unit. Dendritic branches can be modeled as spatial compartments, whose activity is related due to passive membrane properties, but may also be different depending on input from synapses. [[Compartmental modelling of dendrites]] is especially helpful for understanding the behavior of neurons that are too small to record with electrodes, as is the case for ''Drosophila melanogaster''.<ref>{{cite journal | vauthors = Gouwens NW, Wilson RI | title = Signal propagation in Drosophila central neurons | journal = Journal of Neuroscience | volume = 29 | issue = 19 | pages = 6239–6249 | year = 2009 | pmid = 19439602 | pmc = 2709801 | doi = 10.1523/jneurosci.0764-09.2009 | doi-access = free }}</ref>

尽管神经元经常被描述为大脑的 "基本单位"，但它们执行内部计算。神经元在树突内整合输入，这种复杂性在假定神经元是一个基本单位的模型中丢失。树突分支可以被建模为空间隔间，其活性与被动膜特性相关，但也可能因来自突触的输入的差异而有所不同。树突的间室模型对于理解那些太小而无法用电极记录的神经元的行为特别有帮助，黑腹果蝇就是这种情况。[50]

==Neurons in the brain大脑中的神经元==

The number of neurons in the brain varies dramatically from species to species.<ref name="nervenet">{{cite journal | vauthors = Williams RW, Herrup K | title = The control of neuron number | journal = Annual Review of Neuroscience | volume = 11 | issue = 1 | pages = 423–53 | year = 1988 | pmid = 3284447 | doi = 10.1146/annurev.ne.11.030188.002231 }}</ref> In a human, there are an estimated 10–20 billion neurons in the [[cerebral cortex]] and 55–70 billion neurons in the [[cerebellum]].<ref name="pmid27187682">{{cite journal | vauthors = von Bartheld CS, Bahney J, Herculano-Houzel S | title = The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting | journal = The Journal of Comparative Neurology | volume = 524 | issue = 18 | pages = 3865–3895 | date = December 2016 | pmid = 27187682 | pmc = 5063692 | doi = 10.1002/cne.24040 }}</ref> By contrast, the [[nematode]] worm ''[[Caenorhabditis elegans]]'' has just 302 neurons, making it an ideal [[model organism]] as scientists have been able to map all of its neurons. The fruit fly ''[[Drosophila melanogaster]]'', a common subject in biological experiments, has around 100,000 neurons and exhibits many complex behaviors. Many properties of neurons, from the type of neurotransmitters used to ion channel composition, are maintained across species, allowing scientists to study processes occurring in more complex organisms in much simpler experimental systems.

大脑中的神经元数量因物种不同而有很大差异。[51] 在人类中，大脑皮层中估计有100-200亿个神经元，小脑中有550-700亿个神经元。[52] 相比之下，秀丽隐杆线虫只有302个神经元，使其成为理想的模型生物，因为科学家已经能够绘制其所有的神经元。黑腹果蝇是生物实验中常见的对象，它有大约10万个神经元，表现出许多复杂的行为。神经元的许多特性，从使用的神经递质类型到离子通道组成，在不同的物种中都保持不变，使科学家能够在更简单的实验系统中研究发生在更复杂生物体中的过程。

==Neurological disorders神经系统疾病==
{{Main主要文章|Neurology神经病学}}
{{More citations needed|date=May 2018}}

'''[[Charcot–Marie–Tooth disease]]''' (CMT) is a heterogeneous inherited disorder of nerves ([[neuropathy]]) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs extending to the hands and arms in advanced stages. Presently incurable, this disease is one of the most common inherited neurological disorders, with 36 in 100,000 affected.<ref name=Krajewski>{{cite journal | vauthors = Krajewski KM, Lewis RA, Fuerst DR, Turansky C, Hinderer SR, Garbern J, Kamholz J, Shy ME | title = Neurological dysfunction and axonal degeneration in Charcot-Marie-Tooth disease type 1A | journal = Brain | volume = 123 | issue = 7 | pages = 1516–27 | date = July 2000 | pmid = 10869062 | doi = 10.1093/brain/123.7.1516 | doi-access = free }}</ref>

腓骨肌萎缩症（CMT）是一种异质性的遗传性神经疾病（神经病变），其特点是肌肉组织和触觉的丧失，主要是在脚和腿上，在晚期会延伸到手和胳膊。该病目前无法治愈，是最常见的遗传性神经系统疾病之一，每10万人中会有36人罹患此病。[53]

'''[[Alzheimer's disease]]''' (AD), also known simply as ''Alzheimer's'', is a [[neurodegenerative disease]] characterized by progressive [[cognitive]] deterioration, together with declining activities of daily living and [[neuropsychiatric]] symptoms or behavioral changes.<ref name="nihstages">{{cite web|title=About Alzheimer's Disease: Symptoms|url=http://www.nia.nih.gov/alzheimers/topics/symptoms|publisher=National Institute on Aging|access-date=28 December 2011|url-status=live|archive-url=https://web.archive.org/web/20120115201854/http://www.nia.nih.gov/alzheimers/topics/symptoms|archive-date=15 January 2012|df=dmy-all}}</ref> The most striking early symptom is loss of short-term memory ([[amnesia]]), which usually manifests as minor forgetfulness that becomes steadily more pronounced with illness progression, with relative preservation of older memories. As the disorder progresses, cognitive (intellectual) impairment extends to the domains of language ([[aphasia]]), skilled movements ([[apraxia]]), and recognition ([[agnosia]]), and functions such as decision-making and planning become impaired.<ref name="BMJ2009">{{cite journal | vauthors = Burns A, Iliffe S | title = Alzheimer's disease | journal = BMJ | volume = 338 | pages = b158 | date = February 2009 | pmid = 19196745 | doi = 10.1136/bmj.b158 | s2cid = 8570146 | url = https://semanticscholar.org/paper/0fccf0616b35e3bb427c3783a44777e4dc228713 }}</ref><ref name=NEJM2010>{{cite journal | vauthors = Querfurth HW, LaFerla FM | title = Alzheimer's disease | journal = The New England Journal of Medicine | volume = 362 | issue = 4 | pages = 329–44 | date = January 2010 | pmid = 20107219 | doi = 10.1056/NEJMra0909142 | s2cid = 205115756 | url = https://semanticscholar.org/paper/7bc445c5ddf7869b9f71a5390ff9e9e992533ee3 }}</ref>

阿尔茨海默病（AD），也被简单地称为阿尔茨海默病，是一种神经退行性疾病，其特点是认知能力逐渐退化，伴随着日常生活活动能力下降和神经精神症状或行为变化。[54] 最突出的早期症状是短期记忆的丧失（失忆），通常表现为轻微的遗忘，随着病情的发展，遗忘的程度会逐渐加重，但老的记忆却记忆得相对清楚。随着病情的发展，认知（智力）损害扩展到语言（失语）、熟练动作（失用）和识别（失认）等领域，决策和计划等功能也会受到损害[55][56] 。

'''[[Parkinson's disease]]''' (PD), also known as ''Parkinson disease'', is a degenerative disorder of the central nervous system that often impairs motor skills and speech.<ref name=NIH2016>{{cite web|title=Parkinson's Disease Information Page|url=https://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|website=NINDS|access-date=18 July 2016|date=30 June 2016|url-status=live|archive-url=https://web.archive.org/web/20170104201403/http://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|archive-date=4 January 2017|df=dmy-all}}</ref> Parkinson's disease belongs to a group of conditions called [[movement disorders]].<ref>{{cite web | title = Movement Disorders| url = http://www.neuromodulation.com/movement-disorders | work = The International Neuromodulation Society }}</ref> It is characterized by muscle rigidity, [[tremor]], a slowing of physical movement ([[bradykinesia]]), and in extreme cases, a loss of physical movement ([[akinesia]]). The primary symptoms are the results of decreased stimulation of the [[motor cortex]] by the [[basal ganglia]], normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level [[cognitive dysfunction]] and subtle language problems. PD is both chronic and progressive.

帕金森病（PD），又称帕金森病，是一种中枢神经系统的退行性疾病，通常会损害运动技能和语言能力。[57] 帕金森病属于一组被称为运动障碍的疾病。[58] 它的特点是肌肉僵硬、震颤、身体运动变慢（运动迟缓），在极端情况下，身体运动丧失（运动不能）。主要症状是基底神经节对运动皮层刺激减少的结果，通常是由于大脑多巴胺能神经元中产生的多巴胺形成和作用不足造成的。次要症状可能包括高水平的认知功能障碍和微妙的语言问题。帕金森病既是慢性的，也是渐进的。

'''[[Myasthenia gravis]]''' is a neuromuscular disease leading to fluctuating [[muscle weakness]] and fatigability during simple activities. Weakness is typically caused by circulating [[antibodies]] that block [[acetylcholine receptors]] at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with [[immunosuppressants]], [[cholinesterase]] inhibitors and, in selected cases, [[thymectomy]].

重症肌无力是一种神经肌肉疾病，导致简单活动时出现波动性的肌肉无力和疲劳。肌无力通常是由阻断突触后神经肌肉接头处的乙酰胆碱受体的循环抗体引起的，它抑制了神经递质乙酰胆碱的刺激作用。肌无力症用免疫抑制剂、胆碱酯酶抑制剂来治疗，在某些情况下还可以进行胸腺切除术。

===Demyelination脱髓鞘症===
{{Further|Demyelinating disease}}
[[File:Guillain-barré syndrome - Nerve Damage.gif|thumb|Guillain–Barré syndrome – demyelination格林-巴利综合征——脱髓鞘症]]

[[Demyelination]] is the act of demyelinating, or the loss of the myelin sheath insulating the nerves. When myelin degrades, conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. This leads to certain neurodegenerative disorders like [[multiple sclerosis]] and [[chronic inflammatory demyelinating polyneuropathy]].

脱髓鞘是指脱髓鞘的行为，或绝缘于神经的髓鞘的丧失。当髓鞘退化时，信号沿神经的传导会受到影响或丧失，神经最终会萎缩。这导致了某些神经退行性疾病，如多发性硬化症和慢性炎症性脱髓鞘多发性神经病。

===Axonal degeneration轴突变性===
Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration, which is the rapid separation of the proximal and distal ends, occurring within 30 minutes of injury. Degeneration follows with swelling of the [[axolemma]], and eventually leads to bead-like formation. Granular disintegration of the axonal [[cytoskeleton]] and inner [[organelle]]s occurs after axolemma degradation. Early changes include accumulation of [[mitochondria]] in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The disintegration is dependent on [[ubiquitin]] and [[calpain]] [[proteases]] (caused by the influx of calcium ion), suggesting that axonal degeneration is an active process that produces complete fragmentation. The process takes about roughly 24 hours in the PNS and longer in the CNS. The signaling pathways leading to axolemma degeneration are unknown.

尽管大多数损伤反应包括钙离子流入信号，以促进断裂部分的重新愈合，但轴突损伤最初会导致急性轴突变性，即在损伤后30分钟内近端和远端迅速分离。退化后，轴突肿胀，最终形成串珠状肿胀。轴索细胞骨架和内部细胞器的颗粒状解体发生在轴索退化之后。早期的变化包括线粒体在损伤部位的结旁区堆积。内质网降解、线粒体膨胀并最终解体。解体依赖于泛素和钙蛋白酶（由钙离子的涌入引起），表明轴突变性是一个完全破碎的活跃过程。这一过程在PNS（周围神经系统）中大约需要24小时，在CNS（中枢神经系统）中则需要更长时间。导致轴突变性的信号传导途径尚不清楚。

==Neurogenesis神经发生==
{{Main|Neurogenesis}}

Neurons are born through the process of [[neurogenesis]], in which [[neural stem cell]]s divide to produce differentiated neurons. Once fully differentiated neurons are formed, they are no longer capable of undergoing [[mitosis]]. Neurogenesis primarily occurs in the embryo of most organisms.

神经元是通过神经发生的过程诞生的，其中神经干细胞分裂产生分化的神经元。一旦完全分化的神经元形成，它们就不再能够进行有丝分裂。神经发生主要发生在大多数生物体的胚胎中。

[[Adult neurogenesis]] can occur and studies of the age of human neurons suggest that this process occurs only for a minority of cells, and that the vast majority of neurons in the [[neocortex]] forms before birth and persists without replacement. The extent to which adult neurogenesis exists in humans, and its contribution to cognition are controversial, with conflicting reports published in 2018.<ref>{{cite journal | vauthors = Kempermann G, Gage FH, Aigner L, Song H, Curtis MA, Thuret S, Kuhn HG, Jessberger S, Frankland PW, Cameron HA, Gould E, Hen R, Abrous DN, Toni N, Schinder AF, Zhao X, Lucassen PJ, Frisén J | title = Human Adult Neurogenesis: Evidence and Remaining Questions | journal = Cell Stem Cell | volume = 23 | issue = 1 | pages = 25–30 | date = July 2018 | pmid = 29681514 | pmc = 6035081 | doi = 10.1016/j.stem.2018.04.004 }}</ref>

成年神经发生能够发生，对人类神经元年龄的研究表明，这一过程只发生在少数细胞中，新皮层中的绝大多数神经元在出生前就已形成，并持续存在而不被替换。人类中成年神经发生存在的程度，以及它对认知的贡献是有争议的，2018年发表的报告相互矛盾。[59]

The body contains a variety of stem cell types that have the capacity to differentiate into neurons. Researchers found a way to transform human skin cells into nerve cells using [[transdifferentiation]], in which "cells are forced to adopt new identities".<ref name=twsX33>{{Cite journal |doi=10.1038/news.2011.328 | last = Callaway | first = Ewen |title= How to make a human neuron | journal = Nature |quote= By transforming cells from human skin into working nerve cells, researchers may have come up with a model for nervous-system diseases and perhaps even regenerative therapies based on cell transplants. The achievement, reported online today in ''Nature'', is the latest in a fast-moving field called transdifferentiation, in which cells are forced to adopt new identities. In the past year, researchers have converted connective tissue cells found in skin into heart cells, blood cells, and liver cells.
|date= 26 May 2011 }}</ref>

人体含有各种干细胞类型，它们有能力分化为神经元。研究人员发现了一种利用横向分化将人类皮肤细胞转化为神经细胞的方法，其中 "细胞被迫采用新的身份"。[60]

During [[neurogenesis]] in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that populate cortical layers. [[Epigenetics|Epigenetic]] modifications play a key role in regulating [[gene expression]] in differentiating [[neural stem cells]], and are critical for cell fate determination in the developing and adult mammalian brain. Epigenetic modifications include [[DNA methylation|DNA cytosine methylation]] to form [[5-methylcytosine]] and [[DNA demethylation|5-methylcytosine demethylation]].<ref name=Wang2016>{{cite journal | vauthors = Wang Z, Tang B, He Y, Jin P | title = DNA methylation dynamics in neurogenesis | journal = Epigenomics | volume = 8 | issue = 3 | pages = 401–14 | date = March 2016 | pmid = 26950681 | pmc = 4864063 | doi = 10.2217/epi.15.119 }}</ref> These modifications are critical for cell fate determination in the developing and adult mammalian brain. [[DNA methylation|DNA cytosine methylation]] is catalyzed by [[DNA methyltransferase|DNA methyltransferases (DNMTs)]]. Methylcytosine demethylation is catalyzed in several stages by [[TET enzymes]] that carry out oxidative reactions (e.g. [[5-methylcytosine]] to [[5-hydroxymethylcytosine]]) and enzymes of the DNA [[base excision repair]] (BER) pathway.<ref name=Wang2016/>

在哺乳动物大脑的神经发生过程中，祖细胞和干细胞从增殖性分裂发展到分化性分裂。这一进展导致了皮层中的神经元和胶质细胞的出现。表观遗传学修饰在调节分化中的神经干细胞的基因表达方面起着关键作用，对发育中和成年哺乳动物大脑中的细胞命运决定至关重要。表观遗传修饰包括DNA胞嘧啶甲基化形成5-甲基胞嘧啶和5-甲基胞嘧啶去甲基化。[61] 这些修饰对于发育中和成年哺乳动物大脑的细胞命运决定至关重要。DNA胞嘧啶甲基化是由DNA甲基转移酶（DNMTs）催化的。甲基胞嘧啶去甲基化是由进行氧化反应（如5-甲基胞嘧啶到5-羟甲基胞嘧啶）的TET酶和DNA碱基切除修复（BER）途径的酶分几个阶段催化的[61] 。

At different stages of mammalian nervous system development two DNA repair processes are employed in the repair of DNA double-strand breaks. These pathways are [[homologous recombination]]al repair used in proliferating neural precursor cells, and [[non-homologous end joining]] used mainly at later developmental stages<ref>{{cite journal | vauthors = Orii KE, Lee Y, Kondo N, McKinnon PJ | title = Selective utilization of nonhomologous end-joining and homologous recombination DNA repair pathways during nervous system development | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 26 | pages = 10017–22 | date = June 2006 | pmid = 16777961 | pmc = 1502498 | doi = 10.1073/pnas.0602436103 | bibcode = 2006PNAS..10310017O | doi-access = free }}</ref>

在哺乳动物神经系统发育的不同阶段，有两种DNA修复过程被用于修复DNA双链断裂。这些途径是用于增殖期神经前体细胞的同源重组修复，以及主要用于后期发育阶段的非同源末端连接[62] 。

==Nerve regeneration神经再生==
{{Main|Neuroregeneration}}
Peripheral axons can regrow if they are severed,<ref name="Yiu_2006">{{cite journal | vauthors = Yiu G, He Z | title = Glial inhibition of CNS axon regeneration | journal = Nature Reviews. Neuroscience | volume = 7 | issue = 8 | pages = 617–27 | date = August 2006 | pmid = 16858390 | pmc = 2693386 | doi = 10.1038/nrn1956 }}</ref> but one neuron cannot be functionally replaced by one of another type ([[Llinás' law]]).<ref name="llinas2014"/>

外围轴突如果被切断，可以重新生长，[63]但一个神经元在功能上不能被另一种类型的神经元取代（Llinás法则）[15]。

== See also ==
{{Div col|colwidth=20em}}
* [[Artificial neuron]]
* [[Bidirectional cell]]
* [[Biological neuron model]]
* [[Compartmental neuron models]]
* [[Connectome]]
* [[Dogiel cell]]
* [[List of animals by number of neurons]]
* [[List of neuroscience databases]]
* [[Neuronal galvanotropism]]
* [[Neuroplasticity]]
* [[Growth cone]]
* [[Sholl analysis]]
{{Div col end}}

*人工神经元
*双向细胞
*生物神经元模型
*间室神经元模型
*连接组
*锥体细胞
*按神经元数量排列的动物名单
*神经科学数据库列表
*神经元向电性
*神经可塑性
*生长锥
*肖尔分析

== References参考文献 ==

{{Reflist}}

== Further reading进一步阅读 ==
{{refbegin}}
* {{cite journal | vauthors = Bullock TH, Bennett MV, Johnston D, Josephson R, Marder E, Fields RD | title = Neuroscience. The neuron doctrine, redux | journal = Science | volume = 310 | issue = 5749 | pages = 791–3 | date = November 2005 | pmid = 16272104 | doi = 10.1126/science.1114394 | s2cid = 170670241 }}
* {{Cite book | vauthors = Kandel ER, Schwartz JH, Jessell TM |year=2000 |title=Principles of Neural Science |edition=4th |publisher=McGraw-Hill |location=New York |isbn=0-8385-7701-6 }}
* {{Cite book | vauthors = Peters A, Palay SL, Webster HS |year=1991 |title=The Fine Structure of the Nervous System |edition=3rd |location=New York |publisher=Oxford University Press |isbn=0-19-506571-9 }}
* {{Cite book | vauthors = Ramón y Cajal S |year=1933 |title=Histology |edition=10th |publisher=Wood |location=Baltimore }}
* {{Cite book | vauthors = Roberts A, Bush BM |year=1981 |title=Neurones without Impulses |publisher=Cambridge University Press |location=Cambridge |isbn=0-521-29935-7 }}
* {{Cite book |title=Clinical Neuroanatomy | vauthors = Snell RS |date=2010 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-9427-5 |language=en |url=https://www.google.com/books/edition/_/ABPmvroyrD0C }}
{{refend}}

== External links外部链接 ==
{{sisterlinks|d=Q43054|n=no|b=Human_Anatomy/The_Neuron|v=no|voy=no|wikt=neuron|m=no|mw=no|s=no|species=no}}
*{{Curlie|Science/Biology/Neurobiology/|Neurobiology}}
* [https://web.archive.org/web/20130425202653/http://ibro.info/ IBRO (International Brain Research Organization)]. Fostering neuroscience research especially in less well-funded countries.
* [http://NeuronBank.org NeuronBank] an online neuromics tool for cataloging neuronal types and synaptic connectivity.
* [https://web.archive.org/web/20190621124504/http://brainmaps.org/ High Resolution Neuroanatomical Images of Primate and Non-Primate Brains].
* The [[v:Topic:Neuroscience|Department of Neuroscience]] at [[v:|Wikiversity]], which presently offers two courses: [[v:Fundamentals of Neuroscience|Fundamentals of Neuroscience]] and [[v:Comparative Neuroscience|Comparative Neuroscience]].
* [https://www.neuinfo.org/mynif/search.php?q=Neuron&t=data&s=cover&b=0&r=20 NIF Search – Neuron] via the [[Neuroscience Information Framework]]
* [https://web.archive.org/web/20110813070057/http://ccdb.ucsd.edu/sand/main?event=showMPByType&typeid=0&start=1&pl=y Cell Centered Database – Neuron]
* [http://neurolex.org/wiki/Category:Neuron Complete list of neuron types] according to the Petilla convention, at [[NeuroLex]].
* [http://NeuroMorpho.org NeuroMorpho.Org] an online database of digital reconstructions of neuronal morphology.
* [https://web.archive.org/web/20111008142032/http://www.immunoportal.com/modules.php?name=gallery2&g2_view=keyalbum.KeywordAlbum&g2_keyword=Neuron Immunohistochemistry Image Gallery: Neuron]
* [https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/v/anatomy-of-a-neuron Khan Academy: Anatomy of a neuron]
* [http://www.histology-world.com/photoalbum/thumbnails.php?album=96 Neuron images]

* IBRO (国际大脑研究组织)。促进神经科学研究，尤其是在资金不足的国家。
* NeuronBank 是一个在线神经病学工具，用于编目神经元类型和突触连接。
* 灵长类动物和非灵长类动物大脑的高分辨率神经解剖图像。
* 维基大学神经科学系，目前提供两门课程: 神经科学基础和比较神经科学。
* NIF 搜索-神经元通过神经科学信息框架
* 细胞中心数据库-神经元
* 完整的神经元类型清单根据 Petilla 公约，在 NeuroLex。
* NeuroMorpho. Org，一个神经形态学数字重建的在线数据库。
* Immunohistochemistry Image Gallery: Neuron
* Khan Academy: Anatomy of a neuron
* Neuron images

{{Nervous system tumors}}
{{Nervous tissue}}
{{Portal bar|Biology|Medicine}}
{{Authority control}}

[[Category:Neurons| ]]
[[Category:Medical terminology]]

Category:Medical terminology

类别: 医学术语

<noinclude>

This page was moved from [[wikipedia:en:Neuron]]. Its edit history can be viewed at [[神经元/edithistory]]</noinclude>

[[Category:待整理页面]]

神经元

2022-04-30T05:57:11Z

耿淅耀：

此词条由神经动力学读书会词条梳理志愿者[[用户:Autumnwolfberry|Autumnwolfberry]]翻译审校，未经专家审核，带来阅读不便，请见谅。

{{short description|Electrically excitable cell that communicates via synapses}}
{{About|the type of cell}}
{{Distinguish|Neutron}}
{{Infobox neuron
|name = Neuron
|image = Blausen 0657 MultipolarNeuron.png
|caption =Anatomy of a [[multipolar neuron]]
|function =
|neurotransmitter =
|morphology =
|afferents =
|efferents =
}}

A '''neuron''' or '''nerve cell''' is an [[membrane potential#Cell excitability|electrically excitable]] [[cell (biology)|cell]] that communicates with other cells via specialized connections called [[synapse]]s. The neuron is the main component of [[nervous tissue]] in all [[Animalia|animals]] except [[sponge]]s and [[placozoa]]. [[Plant]]s and [[fungi]] do not have nerve cells.

神经元或神经细胞是一种可电兴奋的细胞，通过称为突触的专门连接与其他细胞进行交流。神经元是所有动物神经组织的主要组成部分，除了海绵动物门和扁盘动物门。植物和真菌没有神经细胞。

Neurons are typically classified into three types based on their function. [[Sensory neuron]]s respond to [[Stimulus (physiology)|stimuli]] such as touch, sound, or light that affect the cells of the [[Sense|sensory organs]], and they send signals to the spinal cord or brain. [[Motor neuron]]s receive signals from the brain and spinal cord to control everything from [[muscle contraction]]s to [[gland|glandular output]]. [[Interneuron]]s connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together they form what is called a [[neural circuit]].

神经元通常根据其功能被分为三种类型。感觉神经元对影响感觉器官细胞的刺激，如触摸、声音或光线作出反应，并向脊髓或大脑发送信号。运动神经元接收来自大脑和脊髓的信号，控制从肌肉收缩到腺体输出的一切。中间神经元将神经元与大脑或脊髓同一区域内的其他神经元连接起来。当多个神经元连接在一起时，它们形成所谓的神经回路。

A typical neuron consists of a cell body ([[Soma (biology)|soma]]), [[dendrite]]s, and a single [[axon]]. The soma is a compact structure and the axon and dendrites are filaments extruding from the soma. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The axon leaves the soma at a swelling called the [[axon hillock]] and travels for as far as 1 meter in humans or more in other species. It branches but usually maintains a constant diameter. At the farthest tip of the axon's branches are [[axon terminals]], where the neuron can transmit a signal across the [[synapse]] to another cell. Neurons may lack dendrites or have no axon. The term [[neurite]] is used to describe either a dendrite or an axon, particularly when the cell is [[Cellular differentiation|undifferentiated]].

一个典型的神经元由一个细胞体（soma：胞体）、树突和一个轴突组成。胞体是一个紧凑的结构，轴突和树突是从胞体中挤出的丝状物。树突通常有大量的分支，并从胞体中延伸出几百微米。轴突在一个称为轴突丘的肿胀处离开胞体，在人类中最远可达1米，在其他物种中则更远。它有分支，但通常保持一个恒定的直径。在轴突分支的最远端是轴突终端，在那里神经元可以通过突触向另一个细胞传递信号。神经元可能缺乏树突或没有轴突。术语神经突被用来描述树突或轴突，特别是当细胞未分化时。

Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to a dendrite of another. However, synapses can connect an axon to another axon or a dendrite to another dendrite.

大多数神经元通过树突和胞体接收信号，并沿轴突发出信号。在大多数突触中，信号从一个神经元的轴突交叉到另一个神经元的树突。然而，突触可以将一个轴突连接到另一个轴突，或者将一个树突连接到另一个树突。

The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to maintenance of [[voltage]] gradients across their [[Cell membrane|membranes]]. If the voltage changes by a large enough amount over a short interval, the neuron generates an [[All-or-none law|all-or-nothing]] [[electrochemical]] pulse called an [[action potential]]. This potential travels rapidly along the axon and activates synaptic connections as it reaches them. Synaptic signals may be [[Excitatory postsynaptic potential|excitatory]] or [[Inhibitory postsynaptic potential|inhibitory]], increasing or reducing the net voltage that reaches the soma.

信号传递过程部分是电子的，部分是化学的。神经元具有电兴奋性，这是由于其膜上的电压梯度得到了维持。如果电压在短时间内发生足够大的变化，神经元就会产生一个全有或全无的电化学脉冲，称为动作电位。这个电位沿轴突迅速传播，到达突触连接时激活它们。突触信号可能是兴奋性的或抑制性的，增加或减少到达胞体的净电压。

In most cases, neurons are generated by [[neural stem cell]]s during brain development and childhood. [[Neurogenesis]] largely ceases during adulthood in most areas of the brain.

在大多数情况下，神经元是在大脑发育和儿童时期由神经干细胞生成的。在大脑的大多数区域，神经元的生成在成年后基本停止。

{{toclimit|3}}

== Nervous system ==
== 神经系统 ==

[[File:Anatomy of a Neuron with Synapse.png|thumb|upright=1.15|Schematic of an anatomically accurate single pyramidal neuron, the primary excitatory neuron of cerebral cortex, with a synaptic connection from an incoming axon onto a dendritic spine.]]
{{unreferenced section|date=December 2020}}

解剖学上准确的单个锥体神经元的示意图，大脑皮层的主要兴奋性神经元，具有从传入轴突到树突棘的突触连接。

Neurons are the primary components of the nervous system, along with the [[glial cells]] that give them structural and metabolic support. The nervous system is made up of the [[central nervous system]], which includes the [[brain]] and [[spinal cord]], and the [[peripheral nervous system]], which includes the [[autonomic nervous system|autonomic]] and [[somatic nervous system]]s. In vertebrates, the majority of neurons belong to the [[central nervous system]], but some reside in peripheral [[ganglion|ganglia]], and many sensory neurons are situated in sensory organs such as the [[retina]] and [[cochlea]].

神经元是神经系统的主要组成部分，同时还有给予其结构和代谢支持的胶质细胞。神经系统由中枢神经系统和周围神经系统组成，前者包括大脑和脊髓，后者包括自主神经和躯体神经系统。在脊椎动物中，大多数神经元属于中枢神经系统，但也有一些居住在周围神经节中，许多感觉神经元位于感觉器官中，如视网膜和耳蜗。

Axons may bundle into [[nerve fascicle|fascicle]]s that make up the [[nerve]]s in the [[peripheral nervous system]] (like strands of wire make up cables). Bundles of axons in the central nervous system are called [[nerve tract|tracts]].

轴突可以捆绑成束，组成周围神经系统的神经（就像电线股组成的电缆）。中枢神经系统中的轴突束被称为束。

== Anatomy and histology ==
==解剖学和组织学==

[[File:Components of neuron.jpg|thumb|upright=1.8|Diagram of the components of a neuron]]
Neurons are highly specialized for the processing and transmission of cellular signals. Given their diversity of functions performed in different parts of the nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 [[Micrometre|micrometers]] in diameter.<ref>{{cite web |first = Melissa |last = Davies |title = The Neuron: size comparison |url = https://www.ualberta.ca/~neuro/OnlineIntro/NeuronExample.htm |work = Neuroscience: A journey through the brain |date = 2002-04-09 |access-date = 2009-06-20}}</ref>

神经元对细胞信号的处理和传送是高度专业化。鉴于它们在神经系统的不同部分所执行的功能的多样性，它们的形状、大小和电化学特性也有很大差异。例如，一个神经元的胞体的直径可以从4到100微米不等。

*The '''[[Soma (biology)|soma]]''' is the body of the neuron. As it contains the [[cell nucleus|nucleus]], most [[protein biosynthesis|protein synthesis]] occurs here. The nucleus can range from 3 to 18 micrometers in diameter.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Brain Facts and Figures |url = http://faculty.washington.edu/chudler/facts.html |work = Neuroscience for Kids |access-date = 2009-06-20 }}</ref>
*细胞体是神经元的主体。由于它含有细胞核，大多数蛋白质合成发生在这里。细胞核的直径可以从3到18微米不等。

*The '''[[dendrites]]''' of a neuron are cellular extensions with many branches. This overall shape and structure is referred to metaphorically as a dendritic tree. This is where the majority of input to the neuron occurs via the [[dendritic spine]].
*神经元的树突是有许多分支的细胞延伸。这种整体形状和结构被比喻为树突树。神经元的大部分输入是通过树突棘发生的。

*The '''[[axon]]''' is a finer, cable-like projection that can extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length. The axon primarily carries [[nerve signal]]s away from the soma, and carries some types of information back to it. Many neurons have only one axon, but this axon may—and usually will—undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the '''[[axon hillock]]'''. Besides being an anatomical structure, the axon hillock also has the greatest density of [[voltage-dependent sodium channels]]. This makes it the most easily excited part of the neuron and the spike initiation zone for the axon. In electrophysiological terms, it has the most negative [[threshold potential]].
*轴突是一种较细的、像电缆一样的突起，其长度可以是胞体直径的几十倍、几百倍、甚至几万倍。轴突主要携带神经信号离开胞体，并将某些类型的信息带回胞体。许多神经元只有一个轴突，但这个轴突可能--通常也会--发生广泛的分支，从而能够与许多靶细胞进行交流。轴突从胞体中出现的部分被称为轴突丘。除了是一种解剖结构外，轴突丘还具有最大密度的电压依赖性钠离子通道。这使得它成为神经元最容易兴奋的部分和轴突的锋电位触发区。在电生理学方面，它具有最负的阈值电位。

**While the axon and axon hillock are generally involved in information outflow, this region can also receive input from other neurons.
**虽然轴突和轴突丘通常会参与信息外流，但这一区域也能接受来自其他神经元的输入。

*The '''[[axon terminal]]''' is found at the end of the axon farthest from the soma and contains [[synapses]]. Synaptic boutons are specialized structures where [[neurotransmitter]] chemicals are released to communicate with target neurons. In addition to synaptic boutons at the axon terminal, a neuron may have ''en passant'' boutons, which are located along the length of the axon.
*轴突终端位于轴突离胞体最远的一端，包含突触。突触结是专门的结构，神经递质化学物质在此释放，与目标神经元进行交流。除了轴突末端的突触结外，神经元还可能有沿轴突长度方向分布的 "中途结"。

[[File:Neuron Cell Body.png|thumb|Neuron cell body]]
神经元细胞体

The accepted view of the neuron attributes dedicated functions to its various anatomical components; however, dendrites and axons often act in ways contrary to their so-called main function.<ref>{{Cite web |date=2021-01-14 |title=16.7: Nervous System |url=https://bio.libretexts.org/Courses/Lumen_Learning/Book%3A_Fundamentals_of_Biology_I_(Lumen)/16%3A_Module_13%3A_Overview_of_Body_Systems/16.7%3A_Nervous_System |access-date=2022-02-28 |website=Biology LibreTexts |language=en}}</ref>

公认的神经元观点将专门的功能归于其各种解剖成分；然而，树突和轴突的作用方式往往与它们所谓的主要功能相反。

[[File:Complete neuron cell diagram en.svg|thumb|right|Diagram of a typical myelinated vertebrate motor neuron]]
[[File:BN1 Neurology.webm|thumb|Neurology Video]]

thumb|right|Diagram of a typical myelinated vertebrate motor neuron
thumb|Neurology Video

典型的有髓的脊椎动物运动神经元示意图
神经病学视频

Axons and dendrites in the central nervous system are typically only about one micrometer thick, while some in the peripheral nervous system are much thicker. The soma is usually about 10–25 micrometers in diameter and often is not much larger than the cell nucleus it contains. The longest axon of a human [[motor neuron]] can be over a meter long, reaching from the base of the spine to the toes.

中枢神经系统中的轴突和树突通常只有约1微米厚，而周围神经系统中的一些轴突和树突则要厚得多。胞体的直径通常约为10-25微米，通常不比其包含的细胞核大多少。人类运动神经元最长的轴突可以超过一米长，从脊柱底部一直延伸到脚趾。

Sensory neurons can have axons that run from the toes to the [[posterior column]] of the spinal cord, over 1.5 meters in adults. [[Giraffe]]s have single axons several meters in length running along the entire length of their necks. Much of what is known about axonal function comes from studying the [[squid giant axon]], an ideal experimental preparation because of its relatively immense size (0.5–1 millimeters thick, several centimeters long).

感觉神经元的轴突可以从脚趾一直延伸到脊髓的后柱，成年人的轴突长度超过1.5米。长颈鹿有几米长的单根轴突，沿其脖子的整个长度运行。人们对轴突功能的了解大多来自于对鱿鱼巨型轴突的研究，由于其相对巨大的尺寸（0.5-1毫米厚，数厘米长），这是一种理想的实验准备。

Fully differentiated neurons are permanently [[G0 phase|postmitotic]]<ref>{{cite journal | vauthors = Herrup K, Yang Y | title = Cell cycle regulation in the postmitotic neuron: oxymoron or new biology? | journal = Nature Reviews. Neuroscience | volume = 8 | issue = 5 | pages = 368–78 | date = May 2007 | pmid = 17453017 | doi = 10.1038/nrn2124 | s2cid = 12908713 }}</ref> however, stem cells present in the adult brain may regenerate functional neurons throughout the life of an organism (see [[neurogenesis]]). [[Astrocyte]]s are star-shaped [[glial cell]]s. They have been observed to turn into neurons by virtue of their stem cell-like characteristic of [[pluripotency]].

完全分化的神经元是永久性的有丝分裂后的细胞，然而，存在于成人大脑中的干细胞可以在有机体的整个生命过程中再生出功能性神经元（见神经元的生成）。星形胶质细胞是星形的胶质细胞。它们已经被观察到可以凭借其类干细胞的多能性特征而变成神经元。

===Membrane===
===膜结构===

{{unreferenced section|date=December 2020}}
Like all animal cells, the cell body of every neuron is enclosed by a [[plasma membrane]], a bilayer of [[lipid]] molecules with many types of protein structures embedded in it. A lipid bilayer is a powerful electrical [[Insulator (electricity)|insulator]], but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are [[voltage-gated ion channel|voltage gated]], meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The [[ion]] materials include [[sodium]], [[potassium]], [[chloride]], and [[calcium]]. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane.

Like all animal cells, the cell body of every neuron is enclosed by a plasma membrane, a bilayer of lipid molecules with many types of protein structures embedded in it. A lipid bilayer is a powerful electrical insulator, but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are voltage gated, meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The ion materials include sodium, potassium, chloride, and calcium. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane.

像所有的动物细胞一样，每个神经元的细胞体都被一个质膜所包围，质膜是由脂质分子组成的双层膜，其中嵌入了许多类型的蛋白质结构。脂质双层是一个强大的电绝缘体，但在神经元中，嵌入膜中的许多蛋白质结构是电活性的。这些结构包括允许带电离子流过膜的离子通道和以化学方式将离子从膜的一侧输送到另一侧的离子泵。大多数离子通道只对特定类型的离子有渗透性。一些离子通道是电压门控的，这意味着它们可以通过改变膜上的电压差在开放和关闭状态之间进行切换。其他的是化学门控，意味着它们可以通过与扩散在细胞外液中的化学物质的相互作用在开放和关闭状态之间切换。离子材料包括钠、钾、氯和钙。离子通道和离子泵之间的相互作用在膜上产生一个电压差，通常在基线上小于1/10伏。这个电压有两个功能：首先，它为嵌入膜中的各种电压依赖性蛋白机械提供了动力源；其次，它为膜的不同部分之间的电信号传输提供了一个基础。

===Histology and internal structure===
===组织学和内部结构===

[[File:Gyrus Dentatus 40x.jpg|thumb|250px|Golgi-stained neurons in human hippocampal tissue]]
高尔基染色神经元在人海马组织

[[Image:SUM 110913 Cort Neurons 2.5d in vitro 488 Phalloidin no perm 4 cmle-2.png|thumb|300px|Actin filaments in a mouse cortical neuron in culture]]
培养中的小鼠皮质神经元中的肌动蛋白丝

Numerous microscopic clumps called [[Nissl body|Nissl bodies]] (or Nissl substance) are seen when nerve cell bodies are stained with a basophilic ("base-loving") dye. These structures consist of [[Endoplasmic reticulum#Rough endoplasmic reticulum|rough endoplasmic reticulum]] and associated [[ribosomal RNA]]. Named after German psychiatrist and neuropathologist [[Franz Nissl]] (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as [[aniline]] or (weakly) [[haematoxylin]]<ref>{{cite book|title=State Hospitals Bulletin|url={{google books |plainurl=y |id=Wp8CAAAAYAAJ|page=378}}|year=1897|publisher=State Commission in Lunacy.|page=378}}</ref> highlight negatively charged components, and so bind to the phosphate backbone of the ribosomal RNA.

当用嗜碱性（"嗜碱"）染料对神经细胞体进行染色时，可以看到许多称为尼氏体（或尼氏物质）的微观团块。这些结构由粗糙的内质网和相关的核糖体RNA组成。它们以德国精神病学家和神经病理学家弗朗茨-尼斯尔（1860-1919）的名字命名，参与蛋白质的合成，其突出性可以用神经细胞代谢非常活跃的事实来解释。嗜碱性染料如苯胺或（弱）血红蛋白会突出带负电的成分，因此与核糖体RNA的磷酸盐骨架结合。

The cell body of a neuron is supported by a complex mesh of structural proteins called [[neurofilament]]s, which together with neurotubules (neuronal microtubules) are assembled into larger neurofibrils.<ref name="Webster">{{cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |website=www.merriam-webster.com}}</ref> Some neurons also contain pigment granules, such as [[neuromelanin]] (a brownish-black pigment that is byproduct of synthesis of [[catecholamine]]s), and [[lipofuscin]] (a yellowish-brown pigment), both of which accumulate with age.<ref>{{cite journal | vauthors = Zecca L, Gallorini M, Schünemann V, Trautwein AX, Gerlach M, Riederer P, Vezzoni P, Tampellini D | title = Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes | journal = Journal of Neurochemistry | volume = 76 | issue = 6 | pages = 1766–73 | date = March 2001 | pmid = 11259494 | doi = 10.1046/j.1471-4159.2001.00186.x | s2cid = 31301135 }}</ref><ref>{{cite journal | vauthors = Herrero MT, Hirsch EC, Kastner A, Luquin MR, Javoy-Agid F, Gonzalo LM, Obeso JA, Agid Y | title = Neuromelanin accumulation with age in catecholaminergic neurons from Macaca fascicularis brainstem | journal = Developmental Neuroscience | volume = 15 | issue = 1 | pages = 37–48 | date = 1993 | pmid = 7505739 | doi = 10.1159/000111315 }}</ref><ref>{{cite journal | vauthors = Brunk UT, Terman A | title = Lipofuscin: mechanisms of age-related accumulation and influence on cell function | journal = Free Radical Biology & Medicine | volume = 33 | issue = 5 | pages = 611–9 | date = September 2002 | pmid = 12208347 | doi = 10.1016/s0891-5849(02)00959-0 }}</ref> Other structural proteins that are important for neuronal function are [[actin]] and the [[tubulin]] of [[microtubule]]s. [[Class III β-tubulin]] is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule.<ref>{{cite journal | vauthors = Zhao B, Meka DP, Scharrenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F | title = Microtubules Modulate F-actin Dynamics during Neuronal Polarization | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 9583 | date = August 2017 | pmid = 28851982 | pmc = 5575062 | doi = 10.1038/s41598-017-09832-8 | bibcode = 2017NatSR...7.9583Z }}</ref>

神经元的细胞体由称为神经丝的结构蛋白的复杂网状结构支撑，它与神经管（神经元微管）一起被组装成较大的神经纤维。一些神经元还含有色素颗粒，如神经黑色素（一种棕黑色的色素，是儿茶酚胺合成的副产品）和脂褐素（一种黄褐色的色素），这两种物质都会随着年龄的增长而积累。对神经元功能很重要的其他结构蛋白是肌动蛋白和微管的管蛋白。第三类β-管蛋白几乎只在神经元中发现。在神经元发育过程中，肌动蛋白主要存在于轴突和树突的顶端。在那里，肌动蛋白的动态可以通过与微管的相互作用而被调节。

There are different internal structural characteristics between axons and dendrites. Typical axons almost never contain [[ribosomes]], except some in the initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases.

轴突和树突之间存在着不同的内部结构特征。典型的轴突几乎不含核糖体，除了在初始段有一些。树突含有颗粒状的内质网或核糖体，随着与细胞体距离的增加，其数量逐渐减少。

==Classification==
==分类==
[[File:GFPneuron.png|thumb|250px|right|Image of pyramidal neurons in mouse [[cerebral cortex]] expressing [[green fluorescent protein]]. The red staining indicates [[GABA]]ergic interneurons.<ref>{{cite journal | vauthors = Lee WC, Huang H, Feng G, Sanes JR, Brown EN, So PT, Nedivi E | title = Dynamic remodeling of dendritic arbors in GABAergic interneurons of adult visual cortex | journal = PLOS Biology | volume = 4 | issue = 2 | pages = e29 | date = February 2006 | pmid = 16366735 | pmc = 1318477 | doi = 10.1371/journal.pbio.0040029 |doi-access=free }}</ref>]]

[[File:smi32neuron.jpg|thumb|250px|right|SMI32-stained pyramidal neurons in [[cerebral cortex]]]]

{{See also|List of distinct cell types in the adult human body#Nervous system}}
另见：成人体内不同的细胞类型列表 § 神经系统

Neurons vary in shape and size and can be classified by their [[Morphology (biology)|morphology]] and function.<ref name="Al">{{cite book|last=Al|first=Martini, Frederic Et|title=Anatomy and Physiology' 2007 Ed.2007 Edition|url={{google books |plainurl=y |id=joJb82gVsLoC|page=288}}|publisher=Rex Bookstore, Inc.|isbn=978-971-23-4807-5|pages=288}}</ref> The anatomist [[Camillo Golgi]] grouped neurons into two types; type I with long axons used to move signals over long distances and type II with short axons, which can often be confused with dendrites. Type I cells can be further classified by the location of the soma. The basic morphology of type I neurons, represented by spinal [[motor neurons]], consists of a cell body called the soma and a long thin axon covered by a [[myelin sheath]]. The dendritic tree wraps around the cell body and receives signals from other neurons. The end of the axon has branching [[axon terminal]]s that release neurotransmitters into a gap called the [[synaptic cleft]] between the terminals and the dendrites of the next neuron.

神经元的形状和大小各不相同，可按其形态和功能进行分类。解剖学家卡米洛-高尔基将神经元分为两类；I型有长轴，用于长距离移动信号；II型有短轴，常与树突相混淆。I型细胞可按胞体的位置进一步分类。以脊髓运动神经元为代表的I型神经元的基本形态包括一个称为胞体的细胞体和一个由髓鞘覆盖的细长轴突。树突树环绕着细胞体，接收来自其他神经元的信号。轴突的末端有分支的轴突终端，将神经递质释放到终端和下一个神经元树突之间的间隙中，称为突触间隙。

===Structural classification===
=== 结构分类===

====Polarity====
====极性=====

[[File:Neurons uni bi multi pseudouni.svg|thumb|Different kinds of neurons: 1 [[Unipolar neuron]] 2 [[Bipolar neuron]] 3 [[Multipolar neuron]] 4 [[Pseudounipolar neuron]] ]]

不同种类的神经元：
1 Unipolar neuron单极神经元
2 Bipolar neuron双极神经元
3 Multipolar neuron多极神经元
4 Pseudounipolar neuron伪单极神经元

Most neurons can be anatomically characterized as:
大多数神经元在解剖学上可以被描述为：

*[[Unipolar neuron|Unipolar]]: single process
*[[Bipolar cell|Bipolar]]: 1 axon and 1 dendrite
*[[Multipolar neuron|Multipolar]]: 1 axon and 2 or more dendrites
**[[Golgi I]]: neurons with long-projecting axonal processes; examples are pyramidal cells, Purkinje cells, and anterior horn cells
**[[Golgi II]]: neurons whose axonal process projects locally; the best example is the granule cell
*[[Anaxonic neuron|Anaxonic]]: where the axon cannot be distinguished from the dendrite(s)
*[[Pseudounipolar cells|Pseudounipolar]]: 1 process which then serves as both an axon and a dendrite

* 单极性：单一原生质过程
* 双极性：1个轴突和1个树突
* 多极性：1个轴突和2个或更多的树突
** 高尔基I型：具有长轴突的神经元；比如锥体细胞、浦肯野细胞和前角细胞。
** 高尔基II型：其轴突过程在局部投射的神经元；最好的例子是颗粒细胞
* 无轴性：轴突与树突无法区分的神经元类型。
* 假单极神经元：1个原生质过程，然后既是轴突又是树突。

====Other====
====其他====

Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are:

一些独特的神经元类型可以根据其在神经系统中的位置和独特的形状来识别。一些例子是：

*[[Basket cell]]s, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and [[cerebellum]]
*[[Betz cell]]s, large motor neurons
*[[Lugaro cell]]s, interneurons of the cerebellum
*[[Medium spiny neuron]]s, most neurons in the [[corpus striatum]]
*[[Purkinje cell]]s, huge neurons in the cerebellum, a type of Golgi I multipolar neuron
*[[Pyramidal cell]]s, neurons with triangular soma, a type of Golgi I
*[[Renshaw cell]]s, neurons with both ends linked to [[alpha motor neuron]]s
*[[Unipolar brush cell]]s, interneurons with unique dendrite ending in a brush-like tuft
*[[Granule cell]]s, a type of Golgi II neuron
*[[Anterior horn (spinal cord)|Anterior horn]] cells, [[motoneurons]] located in the spinal cord
*[[Spindle cell]]s, interneurons that connect widely separated areas of the brain

*Basket cells, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and cerebellum
*Betz cells, large motor neurons
*Lugaro cells, interneurons of the cerebellum
*Medium spiny neurons, most neurons in the corpus striatum
*Purkinje cells, huge neurons in the cerebellum, a type of Golgi I multipolar neuron
*Pyramidal cells, neurons with triangular soma, a type of Golgi I
*Renshaw cells, neurons with both ends linked to alpha motor neurons
*Unipolar brush cells, interneurons with unique dendrite ending in a brush-like tuft
*Granule cells, a type of Golgi II neuron
*Anterior horn cells, motoneurons located in the spinal cord
*Spindle cells, interneurons that connect widely separated areas of the brain

*篮状细胞，在目标细胞的胞体周围形成密集的终端丛，发现于大脑皮层和小脑的中间神经元。
*贝兹细胞，大运动神经元
*卢加洛细胞，小脑的中间神经元
*中型多棘神经元，纹状体中的大多数神经元
*浦肯野细胞，小脑中的巨大神经元，一种高尔基I型多极神经元
*锥体细胞，具有三角形胞体的神经元，是高尔基I型的一种。
*伦肖细胞，两端与α运动神经元相连的神经元
*单极刷细胞，具有独特的树突末端为刷状簇的中间神经元
*颗粒细胞，高尔基II型神经元的一种类型
*前角细胞，位于脊髓中的运动神经元
*纺锤体细胞，连接大脑广泛分布的中间神经元
*纺锤体细胞的运动神经元、连接大脑广泛分离区域的中间神经元

===Functional classification===
===功能分类===

====Direction====
===方向===

*[[Afferent neuron]]s convey information from tissues and organs into the central nervous system and are also called [[sensory neurons]].
*[[Efferent neuron]]s (motor neurons) transmit signals from the central nervous system to the effector cells.
*[[Interneuron]]s connect neurons within specific regions of the central nervous system.

* 传入神经元将信息从组织和器官传入中枢神经系统，也被称为感觉神经元。
* 传出神经元(运动神经元) 将信号从中枢神经系统传递给效应细胞。
* 中间神经元连接中枢神经系统特定区域内的神经元。

Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain.

传入和传出也泛指分别为大脑带来信息或从大脑发出信息的神经元。

====Action on other neurons====
==== 对其他神经元的影响====
A neuron affects other neurons by releasing a neurotransmitter that binds to [[receptor (biochemistry)|chemical receptor]]s. The effect upon the postsynaptic neuron is determined by the type of receptor that is activated, not by the presynaptic neuron or by the neurotransmitter. A neurotransmitter can be thought of as a key, and a receptor as a lock: the same neurotransmitter can activate multiple types of receptors. Receptors can be classified broadly as ''excitatory'' (causing an increase in firing rate), ''inhibitory'' (causing a decrease in firing rate), or ''modulatory'' (causing long-lasting effects not directly related to firing rate).

一个神经元通过释放一种与化学受体结合的神经递质来影响其他神经元。对突触后神经元的影响是由被激活的受体类型决定的，而不是由突触前神经元或神经递质决定的。可以认为神经递质是一把钥匙，而受体是一把锁：同一神经递质可以激活多种类型的受体。受体可大致分为兴奋性（导致放电率增加）、抑制性（导致放电率下降）或调节性（导致与放电率无直接关系的长期影响）。

The two most common (90%+) neurotransmitters in the brain, [[glutamate]] and [[GABA]], have largely consistent actions. Glutamate acts on several types of receptors, and has effects that are excitatory at [[ionotropic receptor]]s and a modulatory effect at [[metabotropic receptor]]s. Similarly, GABA acts on several types of receptors, but all of them have inhibitory effects (in adult animals, at least). Because of this consistency, it is common for neuroscientists to refer to cells that release glutamate as "excitatory neurons", and cells that release GABA as "inhibitory neurons". Some other types of neurons have consistent effects, for example, "excitatory" motor neurons in the spinal cord that release [[acetylcholine]], and "inhibitory" [[spinal neuron]]s that release [[glycine]].

大脑中最常见的两种（90%以上）神经递质，即谷氨酸和GABA，其作用基本一致。谷氨酸作用于几种类型的受体，在离子型受体上有兴奋作用，在代谢型受体上有调节作用。同样，GABA作用于几种类型的受体，但它们都有抑制作用（至少在成年动物中）。由于这种一致性，神经科学家通常把释放谷氨酸的细胞称为 "兴奋性神经元"，而把释放GABA的细胞称为 "抑制性神经元"。其他一些类型的神经元也有一致的影响，例如，脊髓中释放乙酰胆碱的 "兴奋性 "运动神经元，以及释放甘氨酸的 "抑制性 "脊髓神经元。

The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neuron. In principle, a single neuron, releasing a single neurotransmitter, can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still. For example, [[photoreceptor cell]]s in the retina constantly release the neurotransmitter glutamate in the absence of light. So-called OFF [[retinal bipolar cells|bipolar cells]] are, like most neurons, excited by the released glutamate. However, neighboring target neurons called ON bipolar cells are instead inhibited by glutamate, because they lack typical [[ionotropic receptor|ionotropic]] [[glutamate receptors]] and instead express a class of inhibitory [[metabotropic receptor|metabotropic]] glutamate receptors.<ref>{{cite journal | vauthors = Gerber U | title = Metabotropic glutamate receptors in vertebrate retina | journal = Documenta Ophthalmologica. Advances in Ophthalmology | volume = 106 | issue = 1 | pages = 83–7 | date = January 2003 | pmid = 12675489 | doi = 10.1023/A:1022477203420 | s2cid = 22296630 }}</ref> When light is present, the photoreceptors cease releasing glutamate, which relieves the ON bipolar cells from inhibition, activating them; this simultaneously removes the excitation from the OFF bipolar cells, silencing them.

兴奋性和抑制性神经递质之间的区别不是绝对的。相反，它取决于突触后神经元上存在的化学受体的类别。原则上，一个神经元，释放一种神经递质，可以对某些目标产生兴奋作用，对其他目标产生抑制作用，对其他目标仍有调节作用。例如，视网膜上的感光细胞在没有光的情况下不断释放神经递质谷氨酸。像大多数神经元一样，所谓的关闭双极细胞被释放的谷氨酸所激发。然而，被称为ON双极细胞的邻近目标神经元反而受到谷氨酸的抑制，因为它们缺乏典型的离子型谷氨酸受体，而是表达一类抑制性的代谢型谷氨酸受体。当有光时，光感受器停止释放谷氨酸，这解除了ON双极细胞的抑制，激活了它们；这同时消除了OFF双极细胞的兴奋，使它们沉默。

It is possible to identify the type of inhibitory effect a presynaptic neuron will have on a postsynaptic neuron, based on the proteins the presynaptic neuron expresses. [[Parvalbumin]]-expressing neurons typically dampen the output signal of the postsynaptic neuron in the [[visual cortex]], whereas [[somatostatin]]-expressing neurons typically block dendritic inputs to the postsynaptic neuron.<ref name="pmid22878717">{{cite journal | vauthors = Wilson NR, Runyan CA, Wang FL, Sur M | title = Division and subtraction by distinct cortical inhibitory networks in vivo | journal = Nature | volume = 488 | issue = 7411 | pages = 343–8 | date = August 2012 | pmid = 22878717 | pmc = 3653570 | doi = 10.1038/nature11347 | bibcode = 2012Natur.488..343W | hdl = 1721.1/92709 }}</ref>

根据突触前神经元表达的蛋白质，可以确定突触前神经元对突触后神经元的抑制作用的类型。表达副白蛋白的神经元通常会抑制视觉皮层中突触后神经元的输出信号，而表达躯干素的神经元通常会阻断突触后神经元的树突输入。

====Discharge patterns====
====放电模式====

Neurons have intrinsic electroresponsive properties like intrinsic transmembrane voltage [[Neural oscillation|oscillatory]] patterns.<ref name="llinas2014">{{cite journal | vauthors = Llinás RR | title = Intrinsic electrical properties of mammalian neurons and CNS function: a historical perspective | journal = Frontiers in Cellular Neuroscience | volume = 8 | pages = 320 | date = 2014-01-01 | pmid = 25408634 | pmc = 4219458 | doi = 10.3389/fncel.2014.00320 | doi-access = free }}</ref> So neurons can be classified according to their [[electrophysiology|electrophysiological]] characteristics:

神经元具有内在的电反应特性，如内在的跨膜电压振荡模式。因此，可以根据神经元的电生理特性对其进行分类：

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.
*Phasic or bursting. Neurons that fire in bursts are called phasic.
*Fast spiking. Some neurons are notable for their high firing rates, for example some types of cortical inhibitory interneurons, cells in [[globus pallidus]], [[retinal ganglion cells]].<ref>{{cite conference | title = Ion conductances related to shaping the repetitive firing in rat retinal ganglion cells | vauthors = Kolodin YO, Veselovskaia NN, Veselovsky NS, Fedulova SA | conference = Acta Physiologica Congress | url = http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | access-date = 2009-06-20 | archive-url = https://web.archive.org/web/20121007164451/http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | archive-date = 2012-10-07 | url-status = dead }}</ref><ref>{{cite web|url=http://ykolodin.50webs.com/ |title=Ionic conductances underlying excitability in tonically firing retinal ganglion cells of adult rat |publisher=Ykolodin.50webs.com |date=2008-04-27 |access-date=2013-02-16}}</ref>

*紧张性或规律性棘波。一些神经元通常持续（紧张地）活跃，通常以恒定的频率放电。例如：神经干细胞中的interneurons。
*瞬变性或爆发性。爆发性放电的神经元被称为瞬变性的。
*快闪性。一些神经元因其高放电率而引人注目，例如某些类型的皮质抑制性中间神经元、苍白球、视网膜神经节细胞。

====Neurotransmitter ====
====神经递质====

[[File:Neurotransmitters.jpg|thumb|Synaptic vesicles containing neurotransmitters]]
{{Main|Neurotransmitter}}
[[Neurotransmitter]]s are chemical messengers passed from one neuron to another neuron or to a [[muscle cell]] or [[Gland|gland cell]].

含有神经递质的突触小泡。
神经递质是由一个神经元传递给另一个神经元或肌肉细胞或腺体细胞的化学信使。

*Cholinergic neurons – acetylcholine. [[Acetylcholine]] is released from presynaptic neurons into the synaptic cleft. It acts as a [[ligand]] for both ligand-gated ion channels and [[Metabotropic receptor|metabotropic]] (GPCRs) [[Muscarinic acetylcholine receptor|muscarinic receptors]]. [[Nicotinic receptors]] are pentameric ligand-gated ion channels composed of alpha and beta subunits that bind [[nicotine]]. Ligand binding opens the channel causing influx of [[Sodium|Na+]] depolarization and increases the probability of presynaptic neurotransmitter release. Acetylcholine is synthesized from [[choline]] and [[acetyl coenzyme A]].
*Adrenergic neurons – noradrenaline. [[Noradrenaline]] (norepinephrine) is released from most [[postganglionic]] neurons in the [[sympathetic nervous system]] onto two sets of GPCRs: [[Adrenergic receptor|alpha adrenoceptor]]s and [[beta adrenoceptor]]s. Noradrenaline is one of the three common [[catecholamine]] neurotransmitter, and the most prevalent of them in the [[peripheral nervous system]]; as with other catecholamines, it is synthesised from [[tyrosine]].
*GABAergic neurons – [[gamma aminobutyric acid]]. GABA is one of two neuroinhibitors in the [[central nervous system]] (CNS), along with glycine. GABA has a homologous function to [[Acetylcholine|ACh]], gating anion channels that allow [[Chlorine|Cl−]] ions to enter the post synaptic neuron. Cl− causes hyperpolarization within the neuron, decreasing the probability of an action potential firing as the voltage becomes more negative (for an action potential to fire, a positive voltage threshold must be reached). GABA is synthesized from glutamate neurotransmitters by the enzyme [[glutamate decarboxylase]].
*Glutamatergic neurons – glutamate. [[Glutamate]] is one of two primary excitatory amino acid neurotransmitters, along with [[Aspartic acid|aspartate]]. Glutamate receptors are one of four categories, three of which are ligand-gated ion channels and one of which is a [[G protein|G-protein]] coupled receptor (often referred to as GPCR).

*胆碱能神经元--乙酰胆碱。乙酰胆碱从突触前神经元释放到突触间隙中。它是配体门控离子通道和代谢型（GPCRs：G蛋白耦联受体）毒蕈碱受体的配体。烟碱受体是由结合了尼古丁的α和β亚基组成的五聚体配体门控离子通道。配体结合后打开通道，造成Na+的流入，使其去极化，并增加突触前神经递质释放的概率。乙酰胆碱是由胆碱和乙酰辅酶A合成的。
*肾上腺素能神经元--去甲肾上腺素。去甲肾上腺素（norepinephrine去甲肾上腺素）从交感神经系统的大多数神经节后神经元释放到两组GPCRs上：α肾上腺素受体和β肾上腺素受体。去甲肾上腺素是三种常见的儿茶酚胺神经递质之一，也是周围神经系统中最普遍的一种；与其他儿茶酚胺一样，它是由酪氨酸合成的。
*GABA能神经元--γ氨基丁酸。GABA与甘氨酸一起是中枢神经系统（CNS）中的两种神经抑制剂之一。GABA具有与ACh相同的功能，对允许Cl-离子进入突触后神经元的阴离子通道进行门控。Cl-导致神经元内的超极化，随着电压变得更负，降低了动作电位放电的概率（要引发动作电位，必须达到一个正电压阈值）。GABA是由谷氨酸神经递质通过谷氨酸脱羧酶合成的。
*谷氨酸能神经元--谷氨酸。谷氨酸与天门冬氨酸一起是两种主要的兴奋性氨基酸神经递质之一。谷氨酸受体是四类之一，其中三类是配体门控离子通道，一类是G-蛋白耦联受体（通常称为GPCR）。

:#[[AMPA]] and [[Kainic acid|Kainate]] receptors function as [[Ion|cation]] channels permeable to Na+ cation channels mediating fast excitatory synaptic transmission.
:#[[N-Methyl-D-aspartic acid|NMDA]] receptors are another cation channel that is more permeable to [[Calcium in biology|Ca2+]]. The function of NMDA receptors depend on glycine receptor binding as a co-[[agonist]] within the channel pore. NMDA receptors do not function without both ligands present.
:#Metabotropic receptors, GPCRs modulate synaptic transmission and postsynaptic excitability.
::Glutamate can cause excitotoxicity when blood flow to the brain is interrupted, resulting in [[brain damage]]. When blood flow is suppressed, glutamate is released from presynaptic neurons, causing greater NMDA and AMPA receptor activation than normal outside of stress conditions, leading to elevated Ca2+ and Na+ entering the post synaptic neuron and cell damage. Glutamate is synthesized from the amino acid glutamine by the enzyme [[Glutamine oxoglutarate aminotransferase|glutamate synthase]].

:#AMPA和红藻氨酸受体作为阳离子通道可渗透到Na+阳离子通道，介导快速兴奋性突触传递。
:#NMDA受体是另一个对Ca2+更易渗透的阳离子通道。NMDA受体的功能取决于甘氨酸受体的结合，作为通道孔内的共轭物。如果没有这两种配体存在，NMDA受体就不能发挥作用。
:#促代谢受体，GPCRs调节突触传递和突触后兴奋性。
::当流向大脑的血流被中断时，谷氨酸可引起兴奋性毒性，导致大脑损伤。当血流被抑制时，谷氨酸从突触前的神经元中释放出来，导致NMDA和AMPA受体的激活比压力条件以外的正常情况下更大，导致升高的Ca2+和Na+进入突触后的神经元和细胞损伤。谷氨酸是由谷氨酸合成酶从氨基酸谷氨酰胺中合成的。

*Dopaminergic neurons—[[dopamine]]. [[Dopamine]] is a neurotransmitter that acts on D1 type (D1 and D5) Gs-coupled receptors, which increase cAMP and PKA, and D2 type (D2, D3, and D4) receptors, which activate Gi-coupled receptors that decrease cAMP and PKA. Dopamine is connected to mood and behavior and modulates both pre- and post-synaptic neurotransmission. Loss of dopamine neurons in the [[substantia nigra]] has been linked to [[Parkinson's disease]]. Dopamine is synthesized from the amino acid [[tyrosine]]. Tyrosine is catalyzed into levodopa (or [[L-DOPA]]) by [[Tyrosine hydroxylase|tyrosine hydroxlase]], and levodopa is then converted into dopamine by the aromatic amino acid [[Carboxy-lyases|decarboxylase]].
*Serotonergic neurons—[[serotonin]]. [[Serotonin]] (5-Hydroxytryptamine, 5-HT) can act as excitatory or inhibitory. Of its four 5-HT receptor classes, 3 are GPCR and 1 is a ligand-gated cation channel. Serotonin is synthesized from [[tryptophan]] by [[tryptophan hydroxylase]], and then further by decarboxylase. A lack of 5-HT at postsynaptic neurons has been linked to depression. Drugs that block the presynaptic [[serotonin transporter]] are used for treatment, such as [[Prozac]] and [[Zoloft]].
*Purinergic neurons—ATP. [[Adenosine triphosphate|ATP]] is a neurotransmitter acting at both ligand-gated ion channels ([[P2X]] receptors) and GPCRs ([[P2Y receptor|P2Y]]) receptors. ATP is, however, best known as a [[cotransmitter]]. Such [[purinergic signalling]] can also be mediated by other [[purine]]s like [[adenosine]], which particularly acts at P2Y receptors.
*Histaminergic neurons—[[histamine]]. [[Histamine]] is a [[monoamine neurotransmitter]] and [[neuromodulator]]. Histamine-producing neurons are found in the [[tuberomammillary nucleus]] of the [[hypothalamus]].<ref>{{cite journal | vauthors = Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y | title = Histamine: neural circuits and new medications | journal = Sleep | volume = 42 | issue = 1 | date = January 2019 | pmid = 30239935 | pmc = 6335869 | doi = 10.1093/sleep/zsy183 }}</ref> Histamine is involved in [[arousal]] and regulating sleep/wake behaviors.

*多巴胺能神经元——多巴胺。多巴胺是一种神经递质，作用于D1型（D1和D5）Gs耦联受体，增加cAMP和PKA，以及D2型（D2、D3和D4）受体，激活Gi耦联受体，减少cAMP和PKA。多巴胺与情绪和行为有关，调节突触前和突触后的神经传递。黑质中的多巴胺神经元的丧失与帕金森病有关。多巴胺是由氨基酸酪氨酸合成的。酪氨酸被酪氨酸羟化酶催化为左旋多巴（或L-DOPA），然后左旋多巴被芳香族氨基酸脱羧酶转化为多巴胺。
*羟色胺能神经元——羟色胺。羟色胺（5-Hydroxytryptamine，5-HT）可以起到兴奋性或抑制性作用。在其四个5-HT受体类别中，3个是GPCR，1个是配体门控的阳离子通道。羟色胺由色氨酸经色氨酸羟化酶合成，然后再经脱羧酶进一步合成。突触后神经元缺乏5-HT与抑郁症有关。阻断突触前5-羟色胺转运体的药物被用于治疗，如百忧解和左洛复。
*嘌呤神经元——ATP。ATP是一种同时作用于配体门控离子通道（P2X受体）和GPCRs（P2Y）受体的神经递质。然而，ATP最有名的是作为一种共传导剂。这种嘌呤信号也可以由其他嘌呤介导，如腺苷，它特别作用于P2Y受体。
*组胺能神经元——组胺。组胺是一种单胺类神经递质和神经调节剂。产生组胺的神经元存在于下丘脑的管状乳头核。组胺参与唤醒和调节睡眠/觉醒行为。

====Multimodel classification====
====多模式分类====

Since 2012 there has been a push from the cellular and computational neuroscience community to come up with a universal classification of neurons that will apply to all neurons in the brain as well as across species. This is done by considering the three essential qualities of all neurons: electrophysiology, morphology, and the individual transcriptome of the cells. Besides being universal this classification has the advantage of being able to classify astrocytes as well. A method called Patch-Seq in which all three qualities can be measured at once is used extensively by the Allen Institute for Brain Science.<ref>{{cite web |url=https://www.news-medical.net/news/20201203/Patch-seq-technique-helps-depict-the-variation-of-neural-cells-in-the-brain.aspx |title=Patch-seq technique helps depict the variation of neural cells in the brain |work=News-medical.net |date=3 December 2020 |access-date=26 August 2021 |url-status=live}}</ref>

自2012年以来，细胞和计算神经科学界一直在推动提出一个通用的神经元分类，该分类将适用于大脑中的所有神经元以及跨物种。这是通过考虑所有神经元的三个基本属性来实现的：电生理学、形态学和细胞的个体转录组。除了具有普遍性之外，这种分类法还有一个优点，就是能够对星形胶质细胞进行分类。艾伦脑科学研究所广泛使用一种叫做Patch-Seq的方法，可以同时测量所有三种属性。

==Connectivity==
==连接性==

{{Main|Synapse|Chemical synapse}}
[[File:Chemical synapse schema cropped.jpg|thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell]]
[[File:Neuro Muscular Junction.png|thumb|Chemical synapse|left]]
Neurons communicate with each other via [[synapses]], where either the [[axon terminal]] of one cell contacts another neuron's dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in the cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the [[supraoptic nucleus]], have only one or two dendrites, each of which receives thousands of synapses.

thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell
thumb|Chemical synapse|left
Neurons communicate with each other via synapses, where either the axon terminal of one cell contacts another neuron's dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in the cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the supraoptic nucleus, have only one or two dendrites, each of which receives thousands of synapses.

神经元通过突触相互沟通，一个细胞的轴突终端接触到另一个神经元的树突、胞体，或者更少见的轴突。像小脑中的浦肯野细胞这样的神经元可以有超过1000个树突分支，与成千上万的其他细胞建立连接; 其他的神经元，如视上核的大细胞神经元，只有一个或两个树突，每个树突接收数千个突触。

Synapses can be [[EPSP|excitatory]] or [[IPSP|inhibitory]], either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive [[gap junction|junctions]] between cells.<ref>{{cite book |last1=Macpherson |first1=Gordon |title=Black's Medical Dictionary |date=2002 |publisher=Scarecrow Press |location=Lanham, MD |isbn=0810849844 |pages=431–434 |edition=40 }}</ref>

Synapses can be excitatory or inhibitory, either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive junctions between cells.

突触可以是兴奋性的，也可以是抑制性的，分别增加或减少目标神经元的活动。有些神经元还通过电突触进行交流，这些突触是细胞之间直接的电传导连接。

When an action potential reaches the axon terminal, it opens [[Voltage-dependent calcium channel|voltage-gated calcium channels]], allowing [[Calcium in biology|calcium ions]] to enter the terminal. Calcium causes [[synaptic vesicles]] filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the [[axon terminal]] triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial [[energy metabolism]] to produce [[Adenosine triphosphate|ATP]] to support continuous neurotransmission.<ref name="pmid23746507">{{cite journal | vauthors = Ivannikov MV, Macleod GT | title = Mitochondrial free Ca²⁺ levels and their effects on energy metabolism in Drosophila motor nerve terminals | journal = Biophysical Journal | volume = 104 | issue = 11 | pages = 2353–61 | date = June 2013 | pmid = 23746507 | pmc = 3672877 | doi = 10.1016/j.bpj.2013.03.064 | bibcode = 2013BpJ...104.2353I }}</ref>

When an action potential reaches the axon terminal, it opens voltage-gated calcium channels, allowing calcium ions to enter the terminal. Calcium causes synaptic vesicles filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the axon terminal triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial energy metabolism to produce ATP to support continuous neurotransmission.

当一个动作电位到达轴突末端时，它打开电压门控钙通道，允许钙离子进入末端。钙导致充满神经递质分子的突触小泡与膜融合，释放其内容物进入突触间隙。神经递质扩散到突触间隙，激活突触后神经元上的受体。轴突末端的高浓度胞浆钙触发了线粒体的钙摄取，进而激活线粒体的能量代谢，产生 ATP 来支持持续的神经传导。

An [[autapse]] is a synapse in which a neuron's axon connects to its own dendrites.

An autapse is a synapse in which a neuron's axon connects to its own dendrites.

自体突触是神经元的轴突与其自身的树突连接的突触。

The [[human brain]] has some 8.6 x 1010 (eighty six billion) neurons.<ref>{{ cite journal | vauthors = Herculano-Houzel S | title = The human brain in numbers: a linearly scaled-up primate brain | journal = Frontiers in Human Neuroscience | volume = 3 | pages = 31 | date = November 2009 | pmid = 19915731 | doi = 10.3389/neuro.09.031.2009 | pmc = 2776484 | doi-access = free }}</ref> Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 1015 synapses (1 quadrillion). [[Synaptic pruning|This number declines with age]], stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5 x 1014 synapses (100 to 500 trillion).<ref>{{cite journal | vauthors = Drachman DA | title = Do we have brain to spare? | journal = Neurology | volume = 64 | issue = 12 | pages = 2004–5 | date = June 2005 | pmid = 15985565 | doi = 10.1212/01.WNL.0000166914.38327.BB | s2cid = 38482114 }}</ref>
[[File:Axon Propagation.svg|thumb|563x563px|An annotated diagram of the stages of an action potential propagating down an axon including the role of ion concentration and pump and channel proteins.]]

The human brain has some 8.6 x 1010 (eighty six billion) neurons. Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 1015 synapses (1 quadrillion). This number declines with age, stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5 x 1014 synapses (100 to 500 trillion).
thumb|563x563px|An annotated diagram of the stages of an action potential propagating down an axon including the role of ion concentration and pump and channel proteins.

人类大脑有大约8.6 x 1010(860亿)神经元。每个神经元平均有7000个与其他神经元的突触连接。据估计，一个三岁儿童的大脑约有1015个突触(1千万亿次)。这个数字随着年龄的增长而下降，成年后趋于稳定。对于一个成年人来说，估计范围从1014到5x1014个突触(100到500万亿)不等。563x563px | 动作电位沿轴突传递的各个阶段的注释图表，包括离子浓度、泵浦和通道蛋白的作用。

=== Nonelectrochemical signaling ===
Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through:
* force generated by the enlargement of dendritic spines<ref>{{cite journal |last1=Ucar |first1=Hasan |last2=Watanabe |first2=Satoshi |last3=Noguchi |first3=Jun |last4=Morimoto |first4=Yuichi |last5=Iino |first5=Yusuke |last6=Yagishita |first6=Sho |last7=Takahashi |first7=Noriko |last8=Kasai |first8=Haruo |title=Mechanical actions of dendritic-spine enlargement on presynaptic exocytosis |journal=Nature |date=December 2021 |volume=600 |issue=7890 |pages=686–689 |doi=10.1038/s41586-021-04125-7 |language=en |issn=1476-4687}} Lay summary: {{cite news |title=Forceful synapses reveal mechanical interactions in the brain |url=https://www.nature.com/articles/d41586-021-03516-0 |access-date=21 February 2022 |work=Nature |date=24 November 2021 |language=en |doi=10.1038/d41586-021-03516-0}}</ref>
* the transfer of [[protein]]s – transneuronally transported proteins (TNTPs)<ref>{{cite news |title=Researchers discover new type of cellular communication in the brain |url=https://medicalxpress.com/news/2022-01-cellular-brain.html |access-date=12 February 2022 |work=The Scripps Research Institute |language=en}}</ref><ref>{{cite journal |last1=Schiapparelli |first1=Lucio M. |last2=Sharma |first2=Pranav |last3=He |first3=Hai-Yan |last4=Li |first4=Jianli |last5=Shah |first5=Sahil H. |last6=McClatchy |first6=Daniel B. |last7=Ma |first7=Yuanhui |last8=Liu |first8=Han-Hsuan |last9=Goldberg |first9=Jeffrey L. |last10=Yates |first10=John R. |last11=Cline |first11=Hollis T. |title=Proteomic screen reveals diverse protein transport between connected neurons in the visual system |journal=Cell Reports |date=25 January 2022 |volume=38 |issue=4 |doi=10.1016/j.celrep.2021.110287 |language=English |issn=2211-1247}}</ref>

Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through:
* force generated by the enlargement of dendritic spines Lay summary: 
* the transfer of proteins – transneuronally transported proteins (TNTPs)

除了电信号和化学信号之外，研究表明，健康人脑中的神经元还可以通过树突棘增大产生的力进行交流

They can also get modulated by input from the environment and [[hormone]]s released from other parts of the organism,<ref>{{cite journal |last1=Levitan |first1=Irwin B. |last2=Kaczmarek |first2=Leonard K. |title=Electrical Signaling in Neurons |doi=10.1093/med/9780199773893.001.0001/med-9780199773893-chapter-3 |publisher=Oxford University Press}}</ref> which could be influenced more or less directly by neurons. This also applies to [[neurotrophin]]s such as [[BDNF]]. The [[gut microbiome]] is also connected with the brain.<ref>{{cite journal |last1=O’Leary |first1=Olivia F. |last2=Ogbonnaya |first2=Ebere S. |last3=Felice |first3=Daniela |last4=Levone |first4=Brunno R. |last5=C. Conroy |first5=Lorraine |last6=Fitzgerald |first6=Patrick |last7=Bravo |first7=Javier A. |last8=Forsythe |first8=Paul |last9=Bienenstock |first9=John |last10=Dinan |first10=Timothy G. |last11=Cryan |first11=John F. |title=The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus |journal=European Neuropsychopharmacology |date=1 February 2018 |volume=28 |issue=2 |pages=307–316 |doi=10.1016/j.euroneuro.2017.12.004 |language=en |issn=0924-977X}}</ref>

They can also get modulated by input from the environment and hormones released from other parts of the organism, which could be influenced more or less directly by neurons. This also applies to neurotrophins such as BDNF. The gut microbiome is also connected with the brain.

它们也可以通过环境的输入和生物体其他部分释放的激素进行调节，这些激素或多或少会受到神经元的直接影响。这也适用于神经营养因子，如 BDNF。肠道微生物组也与大脑相连。

==Mechanisms for propagating action potentials==
In 1937 [[John Zachary Young]] suggested that the [[squid giant axon]] could be used to study neuronal electrical properties.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Milestones in Neuroscience Research |url = http://faculty.washington.edu/chudler/hist.html |work = Neuroscience for Kids |access-date = 2009-06-20}}</ref> It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the [[membrane potential]].

In 1937 John Zachary Young suggested that the squid giant axon could be used to study neuronal electrical properties. It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the membrane potential.

在1937年 John Zachary Young 提出，乌贼巨大神经轴可以用来研究神经元的电学特性。它比人类神经元大，但类似于人类神经元，使它更容易研究。通过在乌贼巨大的轴突上插入电极，我们可以精确地测量膜电位。

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate [[subthreshold membrane potential oscillations]]. These signals are generated and propagated by charge-carrying [[ions]] including sodium (Na+), potassium (K+), chloride (Cl−), and [[Calcium signaling|calcium (Ca2+)]].

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate subthreshold membrane potential oscillations. These signals are generated and propagated by charge-carrying ions including sodium (Na+), potassium (K+), chloride (Cl−), and calcium (Ca2+).

轴突和胞体的细胞膜包含电压门控离子通道，使神经元能够产生和传播电信号(动作电位)。一些神经元也会产生阈下膜电位振荡。这些信号是由钠离子(Na +)、钾离子(k +)、氯离子(Cl -)和钙离子(Ca 2 + )产生和传播的。

Several stimuli can activate a neuron leading to electrical activity, including [[Mechanoreceptor|pressure]], stretch, chemical transmitters, and changes of the electric potential across the cell membrane.<ref>{{cite web|first1=Joe |last1=Patlak |first2=Ray |last2=Gibbons | name-list-style = vanc |title=Electrical Activity of Nerves |url=http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |work=Action Potentials in Nerve Cells |date=2000-11-01 |access-date=2009-06-20 |url-status=dead |archive-url=https://web.archive.org/web/20090827220335/http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |archive-date=August 27, 2009 }}</ref> Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.<ref name="Harris-Warrick">{{cite journal |last1=Harris-Warrick |first1=RM |title=Neuromodulation and flexibility in Central Pattern Generator networks. |journal=Current Opinion in Neurobiology |date=October 2011 |volume=21 |issue=5 |pages=685–92 |doi=10.1016/j.conb.2011.05.011 |pmid=21646013|pmc=3171584 }}</ref>

Several stimuli can activate a neuron leading to electrical activity, including pressure, stretch, chemical transmitters, and changes of the electric potential across the cell membrane. Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.

几个刺激可以激活一个神经元，导致电活动，包括压力，伸展，化学传递物，和电势的变化跨越细胞膜。刺激引起细胞膜上特定的离子通道打开，导致离子流通过细胞膜，改变膜电位。神经元必须保持特定的电特性，这些特性决定了它们的神经元类型。

Thin neurons and axons require less [[metabolism|metabolic]] expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of [[myelin]] around their axons. The sheaths are formed by [[glia]]l cells: [[oligodendrocyte]]s in the central nervous system and [[Schwann cell]]s in the peripheral nervous system. The sheath enables action potentials to travel [[saltatory conduction|faster]] than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed [[node of Ranvier|nodes of Ranvier]], which contain a high density of voltage-gated ion channels. [[Multiple sclerosis]] is a neurological disorder that results from demyelination of axons in the central nervous system.

Thin neurons and axons require less metabolic expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of myelin around their axons. The sheaths are formed by glial cells: oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. The sheath enables action potentials to travel faster than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed nodes of Ranvier, which contain a high density of voltage-gated ion channels. Multiple sclerosis is a neurological disorder that results from demyelination of axons in the central nervous system.

较薄的神经元和轴突产生和携带动作电位所需的代谢费用较少，但较厚的轴突传递冲动的速度更快。为了在保持快速传导的同时尽量减少代谢费用，许多神经元的轴突周围有绝缘的髓鞘。这些鞘由胶质细胞组成: 中枢神经系统的少突胶质细胞和周围神经系统的雪旺细胞。鞘使动作电位的传递速度快于相同直径的无髓鞘轴突，同时使用更少的能量。周围神经中的髓鞘通常沿轴突分为约1毫米长的部分，其间穿插着未鞘的郎飞结，其中含有高密度的电压门控离子通道。多发性硬化症是由中枢神经系统轴突脱髓鞘而引起的神经系统疾病。

Some neurons do not generate action potentials, but instead generate a [[graded potential|graded electrical signal]], which in turn causes graded neurotransmitter release. Such [[non-spiking neurons]] tend to be sensory neurons or interneurons, because they cannot carry signals long distances.

Some neurons do not generate action potentials, but instead generate a graded electrical signal, which in turn causes graded neurotransmitter release. Such non-spiking neurons tend to be sensory neurons or interneurons, because they cannot carry signals long distances.

有些神经元不产生动作电位，而是产生一个分级的电信号，这反过来又导致分级的神经递质释放。这种非脉冲神经元往往是感觉神经元或中间神经元，因为他们不能携带信号长距离。

==Neural coding==
[[Neural coding]] is concerned with how sensory and other information is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the [[Stimulus (physiology)|stimulus]] and the individual or [[Neural ensemble|ensemble]] neuronal responses, and the relationships among the electrical activities of the neurons within the ensemble.<ref name="Brown">{{cite journal | vauthors = Brown EN, Kass RE, Mitra PP | title = Multiple neural spike train data analysis: state-of-the-art and future challenges | journal = Nature Neuroscience | volume = 7 | issue = 5 | pages = 456–61 | date = May 2004 | pmid = 15114358 | doi = 10.1038/nn1228 | s2cid = 562815 }}</ref> It is thought that neurons can encode both [[Digital data|digital]] and [[analog signal|analog]] information.<ref>{{cite book | vauthors = Thorpe SJ |chapter=Spike arrival times: A highly efficient coding scheme for neural networks |chapter-url= http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf |pages= 91–94 |title=Parallel processing in neural systems and computers| veditors = Eckmiller R, Hartmann G, Hauske G |date=1990|publisher=North-Holland|isbn=9780444883902 |url={{google books |plainurl=y |id=boBqAAAAMAAJ}}|language=en|archive-url=https://web.archive.org/web/20120215151304/http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf|archive-date=2012-02-15}}</ref>

Neural coding is concerned with how sensory and other information is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the stimulus and the individual or ensemble neuronal responses, and the relationships among the electrical activities of the neurons within the ensemble. It is thought that neurons can encode both digital and analog information.

神经编码研究的是感觉和其他信息在大脑中如何通过神经元来表达。研究神经编码的主要目的是描述刺激与个体或整体神经元反应之间的关系，以及整体神经元电活动之间的关系。人们认为神经元可以同时编码数字和模拟信息。

==All-or-none principle==
[[File:All-or-none_law_en.svg|thumb|318x318px|As long as the stimulus reaches the threshold, the full response would be given. Larger stimulus does not result in a larger response, vice versa.<ref name=":0">{{Cite book|title=Biological psychology|last=Kalat, James W|year=2016|isbn=9781305105409|edition=12|location=Australia|oclc=898154491}}</ref>{{Rp|31}}]]
{{Main|All-or-none law}}
The conduction of nerve impulses is an example of an [[All-or-none law|all-or-none]] response. In other words, if a neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal, but can increase firing frequency.<ref name=":0" />{{Rp|31}} Receptors respond in different ways to stimuli. Slowly adapting or [[tonic (physiology)|tonic receptors]] respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can't become "stronger" for a specific frequency.

thumb|318x318px|As long as the stimulus reaches the threshold, the full response would be given. Larger stimulus does not result in a larger response, vice versa.

The conduction of nerve impulses is an example of an all-or-none response. In other words, if a neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal, but can increase firing frequency. Receptors respond in different ways to stimuli. Slowly adapting or tonic receptors respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can't become "stronger" for a specific frequency.

= = All-or-none 原理 = 拇指 | 318x318px | 只要刺激达到阈值，就会给出完整的反应。更大的刺激不会导致更大的反应，反之亦然。神经冲动的传导就是“全有或全无”反应的一个例子。换句话说，如果一个神经元有任何反应，那么它必须完全有反应。更强烈的刺激，比如更清晰的图像/更响亮的声音，不会产生更强烈的信号，但会增加射频。受体对刺激有不同的反应。缓慢适应或紧张受体对稳定的刺激作出反应，产生稳定的放电频率。紧张性受体对刺激强度增加的反应通常是通过增加发射频率来实现的，通常是作为刺激每秒对冲动的幂函数。这可以比作光的固有属性，即特定频率(颜色)的强度越大，需要的光子就越多，因为光子在特定频率下不能变得“更强”。

Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with steady stimulus; examples include [[Human skin|skin]] which, when touched causes neurons to fire, but if the object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function.

Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with steady stimulus; examples include skin which, when touched causes neurons to fire, but if the object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function.

其他受体类型包括快速适应或相位受体，在稳定的刺激下，神经活动减少或停止; 例如皮肤，当接触时会导致神经元活动，但如果物体保持平衡的压力，神经元停止活动。对压力和振动有反应的皮肤和肌肉的神经元有过滤的辅助结构来帮助它们的功能。

The [[pacinian corpuscle]] is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus is transferred to the axon, which fires. If the pressure is steady, stimulus ends; thus, typically these neurons respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of a number of other neurons.<ref>{{cite book | last1 = Eckert | first1 = Roger | last2 = Randall | first2 = David | name-list-style = vanc | title = Animal physiology: mechanisms and adaptations | year = 1983 | publisher = W.H. Freeman | location = San Francisco | isbn = 978-0-7167-1423-1 | page = [https://archive.org/details/animalphysiology0000ecke/page/239 239] | url = https://archive.org/details/animalphysiology0000ecke/page/239 }}</ref>

The pacinian corpuscle is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus is transferred to the axon, which fires. If the pressure is steady, stimulus ends; thus, typically these neurons respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of a number of other neurons.

太平洋小体就是这样一种构造。它有像洋葱一样的同心层，在轴突末端周围形成。当施加压力使小体发生变形时，机械刺激转移到轴突上，轴突就会发射信号。如果压力是稳定的，刺激结束; 因此，典型的这些神经元在初始变形期间和压力消除时会作出短暂的去极化反应，这导致小体再次改变形状。其他类型的适应在扩展其他神经元的功能方面也很重要。

==Etymology and spelling==

==Etymology and spelling==

= = 词源和拼写 = =

The German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] introduced the term ''neuron'' in 1891,<ref name="finger"/> based on the [[Greek language|ancient Greek]] νεῦρον ''neuron'' 'sinew, cord, nerve'.<ref name="oed">''[[Oxford English Dictionary]]'', 3rd edition, 2003, ''s.v.''</ref>

The German anatomist Heinrich Wilhelm Waldeyer introduced the term neuron in 1891, based on the ancient Greek νεῦρον neuron 'sinew, cord, nerve'.Oxford English Dictionary, 3rd edition, 2003, s.v.

1891年，德国解剖学家海因里希 · 威廉 · 沃德耶根据古希腊人的神经元肌腱、脊髓和神经，提出了神经元一词。牛津英语词典，第三版，2003，s.v。

The word was adopted in French with the spelling ''neurone''. That spelling was also used by many writers in English,<ref name="mehta">{{cite journal | vauthors = Mehta AR, Mehta PR, Anderson SP, MacKinnon BL, Compston A | title = Grey Matter Etymology and the neuron(e) | journal = Brain | volume = 143 | issue = 1 | pages = 374–379 | date = January 2020 | pmid = 31844876 | pmc = 6935745 | doi = 10.1093/brain/awz367 | url = }}</ref> but has now become rare in American usage and uncommon in British usage.<ref name="ngram">{{cite web |title=Google Books Ngram Viewer |url=https://books.google.com/ngrams/graph?content=neuron%2Cneurone&year_start=1900&year_end=2008&case_insensitive=on&corpus=15&smoothing=3&direct_url=t4%3B%2Cneuron%3B%2Cc0%3B%2Cs0%3B%3Bneuron%3B%2Cc0%3B%3BNeuron%3B%2Cc0%3B%3BNEURON%3B%2Cc0%3B.t4%3B%2Cneurone%3B%2Cc0%3B%2Cs0%3B%3Bneurone%3B%2Cc0%3B%3BNeurone%3B%2Cc0%3B%3BNEURONE%3B%2Cc0 |website=books.google.com |access-date=19 December 2020 |language=en}}</ref><ref name="oed"/>

The word was adopted in French with the spelling neurone. That spelling was also used by many writers in English, but has now become rare in American usage and uncommon in British usage.

这个词在法语中采用了 neurone 的拼法。这种拼写也被许多英语作家使用，但是现在在美国已经很少见了，在英国也很少见。

==History==
{{Further|History of neuroscience}}
[[File:Golgi Hippocampus.jpg|left|thumb|Drawing by Camillo Golgi of a [[hippocampus]] stained using the [[silver nitrate]] method]]
[[File:Purkinje cell by Cajal.png|thumb|Drawing of a Purkinje cell in the [[cerebellar cortex]] done by Santiago Ramón y Cajal, demonstrating the ability of Golgi's staining method to reveal fine detail]]
The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist [[Santiago Ramón y Cajal]].<ref name="López-Muñoz">{{cite journal | vauthors = López-Muñoz F, Boya J, Alamo C | title = Neuron theory, the cornerstone of neuroscience, on the centenary of the Nobel Prize award to Santiago Ramón y Cajal | journal = Brain Research Bulletin | volume = 70 | issue = 4–6 | pages = 391–405 | date = October 2006 | pmid = 17027775 | doi = 10.1016/j.brainresbull.2006.07.010 | s2cid = 11273256 }}</ref>

The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist Santiago Ramón y Cajal.

神经元作为神经系统主要功能单位的地位在19世纪晚期通过西班牙解剖学家圣地亚哥·拉蒙-卡哈尔的工作首次得到确认。

To make the structure of individual neurons visible, [[Santiago Ramón y Cajal|Ramón y Cajal]] improved a [[Golgi's method|silver staining process]] that had been developed by [[Camillo Golgi]].<ref name="López-Muñoz" /> The improved process involves a technique called "double impregnation" and is still in use.

To make the structure of individual neurons visible, Ramón y Cajal improved a silver staining process that had been developed by Camillo Golgi. The improved process involves a technique called "double impregnation" and is still in use.

为了使单个神经元的结构可见，拉蒙 · 卡哈尔改进了卡米洛 · 高尔基发明的银染方法。改进后的工艺采用了一种称为“双浸渍”的技术，目前仍在使用。

In 1888 Ramón y Cajal published a paper about the bird cerebellum. In this paper, he stated that he could not find evidence for [[anastomosis]] between axons and dendrites and called each nervous element "an absolutely autonomous canton."<ref name="López-Muñoz" /><ref name="finger">{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=Ramon y Cajal's first paper on the Golgi stain was on the bird cerebellum, and it appeared in the ''Revista''<nowiki> in 1888. He acknowledged that he found the nerve fibers to be very intricate, but stated that he could find no evidence for either axons or dendrites undergoing anastomosis and forming nets. He called each nervous element 'an absolutely autonomous canton.'</nowiki>}}</ref> This became known as the [[neuron doctrine]], one of the central tenets of modern [[neuroscience]].<ref name="López-Muñoz" />

In 1888 Ramón y Cajal published a paper about the bird cerebellum. In this paper, he stated that he could not find evidence for anastomosis between axons and dendrites and called each nervous element "an absolutely autonomous canton." This became known as the neuron doctrine, one of the central tenets of modern neuroscience.

1888年，拉蒙和卡哈尔发表了一篇关于鸟类小脑的论文。在这篇论文中，他说他找不到轴突和树突之间吻合的证据，并称每一个神经元为“一个绝对独立的广州”这就是众所周知的神经元学说，现代神经科学的核心原则之一。

In 1891, the German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] wrote a highly influential review of the neuron doctrine in which he introduced the term ''neuron'' to describe the anatomical and physiological unit of the nervous system.<ref>{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=... a man who would write a highly influential review of the evidence in favor of the neuron doctrine two years later. In his paper, Waldeyer (1891), ... , wrote that nerve cells terminate freely with end arborizations and that the 'neuron' is the anatomical and physiological unit of the nervous system. The word 'neuron' was born this way.}}</ref><ref>{{cite web|url=http://www.whonamedit.com/doctor.cfm/1846.html|title=Whonamedit - dictionary of medical eponyms|website=www.whonamedit.com|quote=Today, Wilhelm von Waldeyer-Hartz is remembered as the founder of the neurone theory, coining the term "neurone" to describe the cellular function unit of the nervous system and enunciating and clarifying that concept in 1891.}}</ref>

In 1891, the German anatomist Heinrich Wilhelm Waldeyer wrote a highly influential review of the neuron doctrine in which he introduced the term neuron to describe the anatomical and physiological unit of the nervous system.

1891年，德国解剖学家海因里希 · 威廉 · 沃德耶对神经元学说写了一篇极具影响力的评论，其中他引入了神经元这一术语来描述神经系统的解剖学和生理学单位。

The silver impregnation stains are a useful method for [[Neuroanatomy|neuroanatomical]] investigations because, for reasons unknown, it stains only a small percentage of cells in a tissue, exposing the complete micro structure of individual neurons without much overlap from other cells.<ref name="Grant">{{cite journal | vauthors = Grant G | title = How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal | journal = Brain Research Reviews | volume = 55 | issue = 2 | pages = 490–8 | date = October 2007 | pmid = 17306375 | doi = 10.1016/j.brainresrev.2006.11.004 | s2cid = 24331507 }}</ref>

The silver impregnation stains are a useful method for neuroanatomical investigations because, for reasons unknown, it stains only a small percentage of cells in a tissue, exposing the complete micro structure of individual neurons without much overlap from other cells.

银染色法是神经解剖学研究的有效方法，因为不知道什么原因，它只染色组织中的一小部分细胞，暴露出单个神经元的完整微观结构，与其他细胞没有太多重叠。

===Neuron doctrine===
[[File:PurkinjeCell.jpg|thumb|Drawing of neurons in the pigeon [[cerebellum]], by Spanish neuroscientist [[Santiago Ramón y Cajal]] in 1899. (A) denotes [[Purkinje cell]]s and (B) denotes [[granule cells]], both of which are multipolar.]]
The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramón y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in a meshwork), acting as metabolically distinct units.

The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramón y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in a meshwork), acting as metabolically distinct units.

神经元学说认为神经元是神经系统的基本结构和功能单位。这个理论是圣地亚哥·拉蒙-卡哈尔在19世纪末提出的。它认为，神经元是离散的细胞(不连接在网) ，作为代谢不同的单位。

Later discoveries yielded refinements to the doctrine. For example, [[Neuroglia|glial cells]], which are non-neuronal, play an essential role in information processing.<ref>{{cite journal | vauthors = Witcher MR, Kirov SA, Harris KM | title = Plasticity of perisynaptic astroglia during synaptogenesis in the mature rat hippocampus | journal = Glia | volume = 55 | issue = 1 | pages = 13–23 | date = January 2007 | pmid = 17001633 | doi = 10.1002/glia.20415 | citeseerx = 10.1.1.598.7002 | s2cid = 10664003 }}</ref> Also, electrical synapses are more common than previously thought,<ref>{{cite journal | vauthors = Connors BW, Long MA | title = Electrical synapses in the mammalian brain | journal = Annual Review of Neuroscience | volume = 27 | issue = 1 | pages = 393–418 | year = 2004 | pmid = 15217338 | doi = 10.1146/annurev.neuro.26.041002.131128 | url = https://zenodo.org/record/894386 }}</ref> comprising direct, cytoplasmic connections between neurons. In fact, neurons can form even tighter couplings: the squid giant axon arises from the fusion of multiple axons.<ref>{{cite journal | vauthors = Guillery RW | title = Observations of synaptic structures: origins of the neuron doctrine and its current status | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 360 | issue = 1458 | pages = 1281–307 | date = June 2005 | pmid = 16147523 | pmc = 1569502 | doi = 10.1098/rstb.2003.1459 }}</ref>

Later discoveries yielded refinements to the doctrine. For example, glial cells, which are non-neuronal, play an essential role in information processing. Also, electrical synapses are more common than previously thought, comprising direct, cytoplasmic connections between neurons. In fact, neurons can form even tighter couplings: the squid giant axon arises from the fusion of multiple axons.

后来的发现对这一学说进行了改进。例如，神经胶质细胞是非神经元细胞，在信息处理中起着重要作用。此外，电突触比以前认为的更常见，包括神经元之间的直接细胞质连接。事实上，神经元之间可以形成更紧密的联结: 乌贼巨大神经轴神经元来自于多个轴突的融合。

Ramón y Cajal also postulated the Law of Dynamic Polarization, which states that a neuron receives signals at its dendrites and cell body and transmits them, as action potentials, along the axon in one direction: away from the cell body.<ref name="sabb">{{cite journal | vauthors = Sabbatini RM | date = April–July 2003 | url = http://www.cerebromente.org.br/n17/history/neurons3_i.htm | title = Neurons and Synapses: The History of Its Discovery | journal = Brain & Mind Magazine | pages = 17 }}</ref> The Law of Dynamic Polarization has important exceptions; dendrites can serve as synaptic output sites of neurons<ref>{{cite journal | vauthors = Djurisic M, Antic S, Chen WR, Zecevic D | title = Voltage imaging from dendrites of mitral cells: EPSP attenuation and spike trigger zones | journal = The Journal of Neuroscience | volume = 24 | issue = 30 | pages = 6703–14 | date = July 2004 | pmid = 15282273 | pmc = 6729725 | doi = 10.1523/JNEUROSCI.0307-04.2004 | hdl = 1912/2958 }}
</ref> and axons can receive synaptic inputs.<ref>{{cite journal | vauthors = Cochilla AJ, Alford S | title = Glutamate receptor-mediated synaptic excitation in axons of the lamprey | journal = The Journal of Physiology | volume = 499 | issue = Pt 2 | pages = 443–57 | date = March 1997 | pmid = 9080373 | pmc = 1159318 | doi = 10.1113/jphysiol.1997.sp021940 }}</ref>

Ramón y Cajal also postulated the Law of Dynamic Polarization, which states that a neuron receives signals at its dendrites and cell body and transmits them, as action potentials, along the axon in one direction: away from the cell body. The Law of Dynamic Polarization has important exceptions; dendrites can serve as synaptic output sites of neurons
and axons can receive synaptic inputs.

拉蒙 · 卡哈尔还提出了动态极化定律，该定律指出，神经元在树突和细胞体处接收信号，并作为动作电位沿轴突向一个方向传递: 远离细胞体。动态极化定律有一些重要的例外，树突可以作为神经元的突触输出位点，轴突可以接收突触输入。

===Compartmental modelling of neurons===
Although neurons are often described of as "fundamental units" of the brain, they perform internal computations. Neurons integrate input within dendrites, and this complexity is lost in models that assume neurons to be a fundamental unit. Dendritic branches can be modeled as spatial compartments, whose activity is related due to passive membrane properties, but may also be different depending on input from synapses. [[Compartmental modelling of dendrites]] is especially helpful for understanding the behavior of neurons that are too small to record with electrodes, as is the case for ''Drosophila melanogaster''.<ref>{{cite journal | vauthors = Gouwens NW, Wilson RI | title = Signal propagation in Drosophila central neurons | journal = Journal of Neuroscience | volume = 29 | issue = 19 | pages = 6239–6249 | year = 2009 | pmid = 19439602 | pmc = 2709801 | doi = 10.1523/jneurosci.0764-09.2009 | doi-access = free }}</ref>

Although neurons are often described of as "fundamental units" of the brain, they perform internal computations. Neurons integrate input within dendrites, and this complexity is lost in models that assume neurons to be a fundamental unit. Dendritic branches can be modeled as spatial compartments, whose activity is related due to passive membrane properties, but may also be different depending on input from synapses. Compartmental modelling of dendrites is especially helpful for understanding the behavior of neurons that are too small to record with electrodes, as is the case for Drosophila melanogaster.

= = = = 神经元的分室模型虽然神经元常常被描述为大脑的“基本单位”，但它们执行内部计算。神经元整合树突内的输入，这种复杂性在假定神经元是基本单位的模型中丢失了。树突状分支可以被模拟为空间隔室，其活动与被动膜特性有关，但也可能因突触输入的不同而有所不同。树突的分室模型特别有助于理解神经元的行为，因为神经元太小，不能用电极记录，就像黑腹果蝇的情况一样。

==Neurons in the brain==
The number of neurons in the brain varies dramatically from species to species.<ref name="nervenet">{{cite journal | vauthors = Williams RW, Herrup K | title = The control of neuron number | journal = Annual Review of Neuroscience | volume = 11 | issue = 1 | pages = 423–53 | year = 1988 | pmid = 3284447 | doi = 10.1146/annurev.ne.11.030188.002231 }}</ref> In a human, there are an estimated 10–20 billion neurons in the [[cerebral cortex]] and 55–70 billion neurons in the [[cerebellum]].<ref name="pmid27187682">{{cite journal | vauthors = von Bartheld CS, Bahney J, Herculano-Houzel S | title = The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting | journal = The Journal of Comparative Neurology | volume = 524 | issue = 18 | pages = 3865–3895 | date = December 2016 | pmid = 27187682 | pmc = 5063692 | doi = 10.1002/cne.24040 }}</ref> By contrast, the [[nematode]] worm ''[[Caenorhabditis elegans]]'' has just 302 neurons, making it an ideal [[model organism]] as scientists have been able to map all of its neurons. The fruit fly ''[[Drosophila melanogaster]]'', a common subject in biological experiments, has around 100,000 neurons and exhibits many complex behaviors. Many properties of neurons, from the type of neurotransmitters used to ion channel composition, are maintained across species, allowing scientists to study processes occurring in more complex organisms in much simpler experimental systems.

The number of neurons in the brain varies dramatically from species to species. In a human, there are an estimated 10–20 billion neurons in the cerebral cortex and 55–70 billion neurons in the cerebellum. By contrast, the nematode worm Caenorhabditis elegans has just 302 neurons, making it an ideal model organism as scientists have been able to map all of its neurons. The fruit fly Drosophila melanogaster, a common subject in biological experiments, has around 100,000 neurons and exhibits many complex behaviors. Many properties of neurons, from the type of neurotransmitters used to ion channel composition, are maintained across species, allowing scientists to study processes occurring in more complex organisms in much simpler experimental systems.

= = 大脑中的神经元 = = 大脑中神经元的数量因物种而异。据估计，人类大脑皮层中有100-200亿个神经元，小脑中有550-700亿个神经元。相比之下，线虫秀丽隐桿线虫只有302个神经元，这使它成为一个理想的模式生物，因为科学家已经能够绘制它所有的神经元。果蝇黑腹果蝇是生物学实验中的常见实验对象，它有大约10万个神经元，表现出许多复杂的行为。神经元的许多特性，从神经递质的类型到离子通道的组成，跨物种保持，使科学家能够在更简单的实验系统中研究更复杂的生物体中发生的过程。

==Neurological disorders==
{{Main|Neurology}}
{{More citations needed|date=May 2018}}
'''[[Charcot–Marie–Tooth disease]]''' (CMT) is a heterogeneous inherited disorder of nerves ([[neuropathy]]) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs extending to the hands and arms in advanced stages. Presently incurable, this disease is one of the most common inherited neurological disorders, with 36 in 100,000 affected.<ref name=Krajewski>{{cite journal | vauthors = Krajewski KM, Lewis RA, Fuerst DR, Turansky C, Hinderer SR, Garbern J, Kamholz J, Shy ME | title = Neurological dysfunction and axonal degeneration in Charcot-Marie-Tooth disease type 1A | journal = Brain | volume = 123 | issue = 7 | pages = 1516–27 | date = July 2000 | pmid = 10869062 | doi = 10.1093/brain/123.7.1516 | doi-access = free }}</ref>

Charcot–Marie–Tooth disease (CMT) is a heterogeneous inherited disorder of nerves (neuropathy) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs extending to the hands and arms in advanced stages. Presently incurable, this disease is one of the most common inherited neurological disorders, with 36 in 100,000 affected.

神经系统疾病腓骨肌萎缩症(腓骨肌萎缩症)是一种异质性遗传性神经系统疾病(神经病) ，即肌肉组织和触觉的拥有属性丧失，主要发生在晚期延伸到手和手臂的脚和腿部。目前无法治愈，这种疾病是最常见的遗传性神经系统疾病之一，每10万人中就有36人患病。

'''[[Alzheimer's disease]]''' (AD), also known simply as ''Alzheimer's'', is a [[neurodegenerative disease]] characterized by progressive [[cognitive]] deterioration, together with declining activities of daily living and [[neuropsychiatric]] symptoms or behavioral changes.<ref name="nihstages">{{cite web|title=About Alzheimer's Disease: Symptoms|url=http://www.nia.nih.gov/alzheimers/topics/symptoms|publisher=National Institute on Aging|access-date=28 December 2011|url-status=live|archive-url=https://web.archive.org/web/20120115201854/http://www.nia.nih.gov/alzheimers/topics/symptoms|archive-date=15 January 2012|df=dmy-all}}</ref> The most striking early symptom is loss of short-term memory ([[amnesia]]), which usually manifests as minor forgetfulness that becomes steadily more pronounced with illness progression, with relative preservation of older memories. As the disorder progresses, cognitive (intellectual) impairment extends to the domains of language ([[aphasia]]), skilled movements ([[apraxia]]), and recognition ([[agnosia]]), and functions such as decision-making and planning become impaired.<ref name="BMJ2009">{{cite journal | vauthors = Burns A, Iliffe S | title = Alzheimer's disease | journal = BMJ | volume = 338 | pages = b158 | date = February 2009 | pmid = 19196745 | doi = 10.1136/bmj.b158 | s2cid = 8570146 | url = https://semanticscholar.org/paper/0fccf0616b35e3bb427c3783a44777e4dc228713 }}</ref><ref name=NEJM2010>{{cite journal | vauthors = Querfurth HW, LaFerla FM | title = Alzheimer's disease | journal = The New England Journal of Medicine | volume = 362 | issue = 4 | pages = 329–44 | date = January 2010 | pmid = 20107219 | doi = 10.1056/NEJMra0909142 | s2cid = 205115756 | url = https://semanticscholar.org/paper/7bc445c5ddf7869b9f71a5390ff9e9e992533ee3 }}</ref>

Alzheimer's disease (AD), also known simply as Alzheimer's, is a neurodegenerative disease characterized by progressive cognitive deterioration, together with declining activities of daily living and neuropsychiatric symptoms or behavioral changes. The most striking early symptom is loss of short-term memory (amnesia), which usually manifests as minor forgetfulness that becomes steadily more pronounced with illness progression, with relative preservation of older memories. As the disorder progresses, cognitive (intellectual) impairment extends to the domains of language (aphasia), skilled movements (apraxia), and recognition (agnosia), and functions such as decision-making and planning become impaired.

阿尔茨海默氏症，也简称为阿尔茨海默氏症，是一种神经退行性疾病/拥有属性的认知退化，伴随着日常生活能力下降和神经精神症状或行为改变。最显著的早期症状是短期记忆的丧失(遗忘症) ，通常表现为轻微的健忘，随着疾病的进展，这种健忘逐渐变得更加明显，而较老的记忆相对保留。随着病情的发展，认知(智力)障碍会扩展到语言(失语症)、技能动作(失认症)和认知(失认症)等领域，决策和计划等功能也会受到损害。

'''[[Parkinson's disease]]''' (PD), also known as ''Parkinson disease'', is a degenerative disorder of the central nervous system that often impairs motor skills and speech.<ref name=NIH2016>{{cite web|title=Parkinson's Disease Information Page|url=https://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|website=NINDS|access-date=18 July 2016|date=30 June 2016|url-status=live|archive-url=https://web.archive.org/web/20170104201403/http://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|archive-date=4 January 2017|df=dmy-all}}</ref> Parkinson's disease belongs to a group of conditions called [[movement disorders]].<ref>{{cite web | title = Movement Disorders| url = http://www.neuromodulation.com/movement-disorders | work = The International Neuromodulation Society }}</ref> It is characterized by muscle rigidity, [[tremor]], a slowing of physical movement ([[bradykinesia]]), and in extreme cases, a loss of physical movement ([[akinesia]]). The primary symptoms are the results of decreased stimulation of the [[motor cortex]] by the [[basal ganglia]], normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level [[cognitive dysfunction]] and subtle language problems. PD is both chronic and progressive.

Parkinson's disease (PD), also known as Parkinson disease, is a degenerative disorder of the central nervous system that often impairs motor skills and speech. Parkinson's disease belongs to a group of conditions called movement disorders. It is characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia), and in extreme cases, a loss of physical movement (akinesia). The primary symptoms are the results of decreased stimulation of the motor cortex by the basal ganglia, normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level cognitive dysfunction and subtle language problems. PD is both chronic and progressive.

帕金森氏病，又称帕金森氏症，是一种中枢神经系统退行性疾病，通常会损害运动技能和语言能力。帕金森氏病属于一组被称为运动障碍的疾病。这是拥有属性肌肉僵硬，震颤，身体运动减缓(运动迟缓) ，在极端情况下，身体运动丧失(运动不能)。主要症状是基底神经节对运动皮层刺激减少的结果，通常是由大脑多巴胺能神经元产生的多巴胺的形成和作用不足引起的。次要症状可能包括高度认知功能障碍和微妙的语言问题。帕金森病既是慢性的，也是进行性的。

'''[[Myasthenia gravis]]''' is a neuromuscular disease leading to fluctuating [[muscle weakness]] and fatigability during simple activities. Weakness is typically caused by circulating [[antibodies]] that block [[acetylcholine receptors]] at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with [[immunosuppressants]], [[cholinesterase]] inhibitors and, in selected cases, [[thymectomy]].

Myasthenia gravis is a neuromuscular disease leading to fluctuating muscle weakness and fatigability during simple activities. Weakness is typically caused by circulating antibodies that block acetylcholine receptors at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with immunosuppressants, cholinesterase inhibitors and, in selected cases, thymectomy.

重症肌无力是一种导致简单活动时肌肉无力和疲劳波动的神经肌肉疾病。弱点通常是由于循环抗体阻断突触后神经肌肉接点的乙酰胆碱受体，抑制神经递质乙酰胆碱的刺激作用。用免疫抑制剂、胆碱酯酶抑制剂治疗重症肌无力，并在选定的病例中行胸腺切除术。

===Demyelination===
{{Further|Demyelinating disease}}
[[File:Guillain-barré syndrome - Nerve Damage.gif|thumb|Guillain–Barré syndrome – demyelination]]
[[Demyelination]] is the act of demyelinating, or the loss of the myelin sheath insulating the nerves. When myelin degrades, conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. This leads to certain neurodegenerative disorders like [[multiple sclerosis]] and [[chronic inflammatory demyelinating polyneuropathy]].

thumb|Guillain–Barré syndrome – demyelination
Demyelination is the act of demyelinating, or the loss of the myelin sheath insulating the nerves. When myelin degrades, conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. This leads to certain neurodegenerative disorders like multiple sclerosis and chronic inflammatory demyelinating polyneuropathy.

脱髓鞘病变脱髓鞘病变脱髓鞘病变脱髓鞘病变是一种脱髓鞘的行为，即髓鞘的丧失使神经绝缘。当髓磷脂退化时，沿着神经传导的信号可能受损或丢失，最终导致神经萎缩。这会导致某些神经退行性疾病，如多发性硬化症和慢性炎症性脱髓鞘性多发性神经病。

===Axonal degeneration===
Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration, which is the rapid separation of the proximal and distal ends, occurring within 30 minutes of injury. Degeneration follows with swelling of the [[axolemma]], and eventually leads to bead-like formation. Granular disintegration of the axonal [[cytoskeleton]] and inner [[organelle]]s occurs after axolemma degradation. Early changes include accumulation of [[mitochondria]] in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The disintegration is dependent on [[ubiquitin]] and [[calpain]] [[proteases]] (caused by the influx of calcium ion), suggesting that axonal degeneration is an active process that produces complete fragmentation. The process takes about roughly 24 hours in the PNS and longer in the CNS. The signaling pathways leading to axolemma degeneration are unknown.

Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration, which is the rapid separation of the proximal and distal ends, occurring within 30 minutes of injury. Degeneration follows with swelling of the axolemma, and eventually leads to bead-like formation. Granular disintegration of the axonal cytoskeleton and inner organelles occurs after axolemma degradation. Early changes include accumulation of mitochondria in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The disintegration is dependent on ubiquitin and calpain proteases (caused by the influx of calcium ion), suggesting that axonal degeneration is an active process that produces complete fragmentation. The process takes about roughly 24 hours in the PNS and longer in the CNS. The signaling pathways leading to axolemma degeneration are unknown.

虽然大多数损伤反应包括钙离子内流信号促进断裂部分的再封闭，轴突损伤最初导致急性轴突变性，即损伤后30分钟内发生的近端和远端的快速分离。退行性变伴随腋窝肿胀，最终导致珠状形成。轴突降解后，轴突细胞骨架和内部细胞器发生颗粒解体。早期变化包括损伤部位的副结节区域线粒体积累。内质网降解，线粒体肿胀，最终解体。分化依赖于泛素和钙蛋白酶(由钙离子内流引起) ，提示轴突变性是一个活跃的过程，产生完全的分裂。这个过程在 PNS 大约需要24小时，在 CNS 则需要更长的时间。导致腋窝变性的信号通路尚不清楚。

==Neurogenesis==
{{Main|Neurogenesis}}
Neurons are born through the process of [[neurogenesis]], in which [[neural stem cell]]s divide to produce differentiated neurons. Once fully differentiated neurons are formed, they are no longer capable of undergoing [[mitosis]]. Neurogenesis primarily occurs in the embryo of most organisms.

Neurons are born through the process of neurogenesis, in which neural stem cells divide to produce differentiated neurons. Once fully differentiated neurons are formed, they are no longer capable of undergoing mitosis. Neurogenesis primarily occurs in the embryo of most organisms.

神经发生神经元是通过神经发生的过程产生的，神经干细胞在这个过程中分裂产生分化的神经元。一旦完全分化的神经元形成，它们就不能进行有丝分裂。神经发生主要发生在大多数生物体的胚胎中。

[[Adult neurogenesis]] can occur and studies of the age of human neurons suggest that this process occurs only for a minority of cells, and that the vast majority of neurons in the [[neocortex]] forms before birth and persists without replacement. The extent to which adult neurogenesis exists in humans, and its contribution to cognition are controversial, with conflicting reports published in 2018.<ref>{{cite journal | vauthors = Kempermann G, Gage FH, Aigner L, Song H, Curtis MA, Thuret S, Kuhn HG, Jessberger S, Frankland PW, Cameron HA, Gould E, Hen R, Abrous DN, Toni N, Schinder AF, Zhao X, Lucassen PJ, Frisén J | title = Human Adult Neurogenesis: Evidence and Remaining Questions | journal = Cell Stem Cell | volume = 23 | issue = 1 | pages = 25–30 | date = July 2018 | pmid = 29681514 | pmc = 6035081 | doi = 10.1016/j.stem.2018.04.004 }}</ref>

Adult neurogenesis can occur and studies of the age of human neurons suggest that this process occurs only for a minority of cells, and that the vast majority of neurons in the neocortex forms before birth and persists without replacement. The extent to which adult neurogenesis exists in humans, and its contribution to cognition are controversial, with conflicting reports published in 2018.

成年神经发生可以发生，对人类神经元年龄的研究表明，这一过程只发生在少数细胞中，而且大多数新皮层神经元在出生前形成，并且不需要替换就能持续存在。成人神经发生在人类中的存在程度及其对认知的贡献是有争议的，2018年发表的报告相互矛盾。

The body contains a variety of stem cell types that have the capacity to differentiate into neurons. Researchers found a way to transform human skin cells into nerve cells using [[transdifferentiation]], in which "cells are forced to adopt new identities".<ref name=twsX33>{{Cite journal |doi=10.1038/news.2011.328 | last = Callaway | first = Ewen |title= How to make a human neuron | journal = Nature |quote= By transforming cells from human skin into working nerve cells, researchers may have come up with a model for nervous-system diseases and perhaps even regenerative therapies based on cell transplants. The achievement, reported online today in ''Nature'', is the latest in a fast-moving field called transdifferentiation, in which cells are forced to adopt new identities. In the past year, researchers have converted connective tissue cells found in skin into heart cells, blood cells, and liver cells.
|date= 26 May 2011 }}</ref>

The body contains a variety of stem cell types that have the capacity to differentiate into neurons. Researchers found a way to transform human skin cells into nerve cells using transdifferentiation, in which "cells are forced to adopt new identities".

身体包含各种干细胞类型，有能力分化成神经元。研究人员发现了一种利用分化转移将人类皮肤细胞转化为神经细胞的方法，在这种方法中，“细胞被迫采用新的身份”。

During [[neurogenesis]] in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that populate cortical layers. [[Epigenetics|Epigenetic]] modifications play a key role in regulating [[gene expression]] in differentiating [[neural stem cells]], and are critical for cell fate determination in the developing and adult mammalian brain. Epigenetic modifications include [[DNA methylation|DNA cytosine methylation]] to form [[5-methylcytosine]] and [[DNA demethylation|5-methylcytosine demethylation]].<ref name=Wang2016>{{cite journal | vauthors = Wang Z, Tang B, He Y, Jin P | title = DNA methylation dynamics in neurogenesis | journal = Epigenomics | volume = 8 | issue = 3 | pages = 401–14 | date = March 2016 | pmid = 26950681 | pmc = 4864063 | doi = 10.2217/epi.15.119 }}</ref> These modifications are critical for cell fate determination in the developing and adult mammalian brain. [[DNA methylation|DNA cytosine methylation]] is catalyzed by [[DNA methyltransferase|DNA methyltransferases (DNMTs)]]. Methylcytosine demethylation is catalyzed in several stages by [[TET enzymes]] that carry out oxidative reactions (e.g. [[5-methylcytosine]] to [[5-hydroxymethylcytosine]]) and enzymes of the DNA [[base excision repair]] (BER) pathway.<ref name=Wang2016/>

During neurogenesis in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that populate cortical layers. Epigenetic modifications play a key role in regulating gene expression in differentiating neural stem cells, and are critical for cell fate determination in the developing and adult mammalian brain. Epigenetic modifications include DNA cytosine methylation to form 5-methylcytosine and 5-methylcytosine demethylation. These modifications are critical for cell fate determination in the developing and adult mammalian brain. DNA cytosine methylation is catalyzed by DNA methyltransferases (DNMTs). Methylcytosine demethylation is catalyzed in several stages by TET enzymes that carry out oxidative reactions (e.g. 5-methylcytosine to 5-hydroxymethylcytosine) and enzymes of the DNA base excision repair (BER) pathway.

在哺乳动物大脑的神经发生过程中，祖细胞和干细胞从增殖分裂进入分化分裂。这种进展导致了构成皮层的神经元和神经胶质。表观遗传修饰是神经干细胞分化过程中调控基因表达的重要环节，对发育中和成年哺乳动物脑细胞命运的决定具有重要意义。表观遗传修饰包括 DNA 胞嘧啶甲基化形成5-甲基胞嘧啶和5-甲基胞嘧啶去甲基化。这些修饰对于发育中和成年哺乳动物大脑中细胞命运的决定至关重要。DNA 甲基转移酶(DNA methyltransferases，DNMTs)催化 DNA 胞嘧啶甲基化。甲基胞嘧啶去甲基化在几个阶段被 TET 酶催化进行氧化反应(例如:。5-甲基胞嘧啶5-羟甲基胞嘧啶)和 DNA 碱基切除修复途径中的酶。

At different stages of mammalian nervous system development two DNA repair processes are employed in the repair of DNA double-strand breaks. These pathways are [[homologous recombination]]al repair used in proliferating neural precursor cells, and [[non-homologous end joining]] used mainly at later developmental stages<ref>{{cite journal | vauthors = Orii KE, Lee Y, Kondo N, McKinnon PJ | title = Selective utilization of nonhomologous end-joining and homologous recombination DNA repair pathways during nervous system development | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 26 | pages = 10017–22 | date = June 2006 | pmid = 16777961 | pmc = 1502498 | doi = 10.1073/pnas.0602436103 | bibcode = 2006PNAS..10310017O | doi-access = free }}</ref>

At different stages of mammalian nervous system development two DNA repair processes are employed in the repair of DNA double-strand breaks. These pathways are homologous recombinational repair used in proliferating neural precursor cells, and non-homologous end joining used mainly at later developmental stages

在哺乳动物神经系统发育的不同阶段，两种 DNA 修复过程被用于修复 DNA 双链断裂。这些途径是用于增殖的神经前体细胞的同源重组修复，而非同源性末端接合主要用于发育后期

== Nerve regeneration ==
{{Main|Neuroregeneration}}
Peripheral axons can regrow if they are severed,<ref name="Yiu_2006">{{cite journal | vauthors = Yiu G, He Z | title = Glial inhibition of CNS axon regeneration | journal = Nature Reviews. Neuroscience | volume = 7 | issue = 8 | pages = 617–27 | date = August 2006 | pmid = 16858390 | pmc = 2693386 | doi = 10.1038/nrn1956 }}</ref> but one neuron cannot be functionally replaced by one of another type ([[Llinás' law]]).<ref name="llinas2014"/>

Peripheral axons can regrow if they are severed, but one neuron cannot be functionally replaced by one of another type (Llinás' law).

= = 神经再生 = = 周围神经轴突被切断后可以再生，但是一个神经元在功能上不能被另一种神经元所取代(利纳斯定律)。

== See also ==
{{Div col|colwidth=20em}}
* [[Artificial neuron]]
* [[Bidirectional cell]]
* [[Biological neuron model]]
* [[Compartmental neuron models]]
* [[Connectome]]
* [[Dogiel cell]]
* [[List of animals by number of neurons]]
* [[List of neuroscience databases]]
* [[Neuronal galvanotropism]]
* [[Neuroplasticity]]
* [[Growth cone]]
* [[Sholl analysis]]
{{Div col end}}

* Artificial neuron
* Bidirectional cell
* Biological neuron model
* Compartmental neuron models
* Connectome
* Dogiel cell
* List of animals by number of neurons
* List of neuroscience databases
* Neuronal galvanotropism
* Neuroplasticity
* Growth cone
* Sholl analysis

生物神经元模型神经连接体 Dogiel 细胞动物名单神经元向电流性神经元可塑性神经生长锥 Sholl 分析人工神经元神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神

== References ==

== References ==

= = 参考文献 = =

{{Reflist}}

== Further reading ==
{{refbegin}}
* {{cite journal | vauthors = Bullock TH, Bennett MV, Johnston D, Josephson R, Marder E, Fields RD | title = Neuroscience. The neuron doctrine, redux | journal = Science | volume = 310 | issue = 5749 | pages = 791–3 | date = November 2005 | pmid = 16272104 | doi = 10.1126/science.1114394 | s2cid = 170670241 }}
* {{Cite book | vauthors = Kandel ER, Schwartz JH, Jessell TM |year=2000 |title=Principles of Neural Science |edition=4th |publisher=McGraw-Hill |location=New York |isbn=0-8385-7701-6 }}
* {{Cite book | vauthors = Peters A, Palay SL, Webster HS |year=1991 |title=The Fine Structure of the Nervous System |edition=3rd |location=New York |publisher=Oxford University Press |isbn=0-19-506571-9 }}
* {{Cite book | vauthors = Ramón y Cajal S |year=1933 |title=Histology |edition=10th |publisher=Wood |location=Baltimore }}
* {{Cite book | vauthors = Roberts A, Bush BM |year=1981 |title=Neurones without Impulses |publisher=Cambridge University Press |location=Cambridge |isbn=0-521-29935-7 }}
* {{Cite book |title=Clinical Neuroanatomy | vauthors = Snell RS |date=2010 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-9427-5 |language=en |url=https://www.google.com/books/edition/_/ABPmvroyrD0C }}
{{refend}}

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= = 进一步阅读 = =
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== External links ==
{{sisterlinks|d=Q43054|n=no|b=Human_Anatomy/The_Neuron|v=no|voy=no|wikt=neuron|m=no|mw=no|s=no|species=no}}
*{{Curlie|Science/Biology/Neurobiology/|Neurobiology}}
* [https://web.archive.org/web/20130425202653/http://ibro.info/ IBRO (International Brain Research Organization)]. Fostering neuroscience research especially in less well-funded countries.
* [http://NeuronBank.org NeuronBank] an online neuromics tool for cataloging neuronal types and synaptic connectivity.
* [https://web.archive.org/web/20190621124504/http://brainmaps.org/ High Resolution Neuroanatomical Images of Primate and Non-Primate Brains].
* The [[v:Topic:Neuroscience|Department of Neuroscience]] at [[v:|Wikiversity]], which presently offers two courses: [[v:Fundamentals of Neuroscience|Fundamentals of Neuroscience]] and [[v:Comparative Neuroscience|Comparative Neuroscience]].
* [https://www.neuinfo.org/mynif/search.php?q=Neuron&t=data&s=cover&b=0&r=20 NIF Search – Neuron] via the [[Neuroscience Information Framework]]
* [https://web.archive.org/web/20110813070057/http://ccdb.ucsd.edu/sand/main?event=showMPByType&typeid=0&start=1&pl=y Cell Centered Database – Neuron]
* [http://neurolex.org/wiki/Category:Neuron Complete list of neuron types] according to the Petilla convention, at [[NeuroLex]].
* [http://NeuroMorpho.org NeuroMorpho.Org] an online database of digital reconstructions of neuronal morphology.
* [https://web.archive.org/web/20111008142032/http://www.immunoportal.com/modules.php?name=gallery2&g2_view=keyalbum.KeywordAlbum&g2_keyword=Neuron Immunohistochemistry Image Gallery: Neuron]
* [https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/v/anatomy-of-a-neuron Khan Academy: Anatomy of a neuron]
* [http://www.histology-world.com/photoalbum/thumbnails.php?album=96 Neuron images]

*
* IBRO (International Brain Research Organization). Fostering neuroscience research especially in less well-funded countries.
* NeuronBank an online neuromics tool for cataloging neuronal types and synaptic connectivity.
* High Resolution Neuroanatomical Images of Primate and Non-Primate Brains.
* The Department of Neuroscience at Wikiversity, which presently offers two courses: Fundamentals of Neuroscience and Comparative Neuroscience.
* NIF Search – Neuron via the Neuroscience Information Framework
* Cell Centered Database – Neuron
* Complete list of neuron types according to the Petilla convention, at NeuroLex.
* NeuroMorpho.Org an online database of digital reconstructions of neuronal morphology.
* Immunohistochemistry Image Gallery: Neuron
* Khan Academy: Anatomy of a neuron
* Neuron images

= = = 外部链接 = =
*
* IBRO (国际大脑研究组织)。促进神经科学研究，尤其是在资金不足的国家。
* NeuronBank 是一个在线神经病学工具，用于编目神经元类型和突触连接。
* 灵长类动物和非灵长类动物大脑的高分辨率神经解剖图像。
* 维基大学神经科学系，目前提供两门课程: 神经科学基础和比较神经科学。
* NIF 搜索-神经元通过神经科学信息框架
* 细胞中心数据库-神经元
* 完整的神经元类型清单根据 Petilla 公约，在 NeuroLex。
* NeuroMorpho. Org，一个神经形态学数字重建的在线数据库。
* Immunohistochemistry Image Gallery: Neuron

* Khan Academy: Anatomy of a neuron

* Neuron images

{{Nervous system tumors}}
{{Nervous tissue}}
{{Portal bar|Biology|Medicine}}
{{Authority control}}

[[Category:Neurons| ]]
[[Category:Medical terminology]]

Category:Medical terminology

类别: 医学术语

<noinclude>

This page was moved from [[wikipedia:en:Neuron]]. Its edit history can be viewed at [[神经元/edithistory]]</noinclude>

[[Category:待整理页面]]

神经元

2022-04-30T05:13:19Z

耿淅耀：

此词条由神经动力学读书会词条梳理志愿者[[用户:Autumnwolfberry|Autumnwolfberry]]翻译审校，未经专家审核，带来阅读不便，请见谅。

{{short description|Electrically excitable cell that communicates via synapses}}
{{About|the type of cell}}
{{Distinguish|Neutron}}
{{Infobox neuron
|name = Neuron
|image = Blausen 0657 MultipolarNeuron.png
|caption =Anatomy of a [[multipolar neuron]]
|function =
|neurotransmitter =
|morphology =
|afferents =
|efferents =
}}
A '''neuron''' or '''nerve cell''' is an [[membrane potential#Cell excitability|electrically excitable]] [[cell (biology)|cell]] that communicates with other cells via specialized connections called [[synapse]]s. The neuron is the main component of [[nervous tissue]] in all [[Animalia|animals]] except [[sponge]]s and [[placozoa]]. [[Plant]]s and [[fungi]] do not have nerve cells.

神经元或神经细胞是一种可电兴奋的细胞，通过称为突触的专门连接与其他细胞进行交流。神经元是所有动物神经组织的主要组成部分，除了海绵动物门和扁盘动物门。植物和真菌没有神经细胞。

Neurons are typically classified into three types based on their function. [[Sensory neuron]]s respond to [[Stimulus (physiology)|stimuli]] such as touch, sound, or light that affect the cells of the [[Sense|sensory organs]], and they send signals to the spinal cord or brain. [[Motor neuron]]s receive signals from the brain and spinal cord to control everything from [[muscle contraction]]s to [[gland|glandular output]]. [[Interneuron]]s connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together they form what is called a [[neural circuit]].

神经元通常根据其功能被分为三种类型。感觉神经元对影响感觉器官细胞的刺激，如触摸、声音或光线作出反应，并向脊髓或大脑发送信号。运动神经元接收来自大脑和脊髓的信号，控制从肌肉收缩到腺体输出的一切。中间神经元将神经元与大脑或脊髓同一区域内的其他神经元连接起来。当多个神经元连接在一起时，它们形成所谓的神经回路。

A typical neuron consists of a cell body ([[Soma (biology)|soma]]), [[dendrite]]s, and a single [[axon]]. The soma is a compact structure and the axon and dendrites are filaments extruding from the soma. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The axon leaves the soma at a swelling called the [[axon hillock]] and travels for as far as 1 meter in humans or more in other species. It branches but usually maintains a constant diameter. At the farthest tip of the axon's branches are [[axon terminals]], where the neuron can transmit a signal across the [[synapse]] to another cell. Neurons may lack dendrites or have no axon. The term [[neurite]] is used to describe either a dendrite or an axon, particularly when the cell is [[Cellular differentiation|undifferentiated]].

一个典型的神经元由一个细胞体（soma：胞体）、树突和一个轴突组成。胞体是一个紧凑的结构，轴突和树突是从胞体中挤出的丝状物。树突通常有大量的分支，并从胞体中延伸出几百微米。轴突在一个称为轴突丘的肿胀处离开胞体，在人类中最远可达1米，在其他物种中则更远。它有分支，但通常保持一个恒定的直径。在轴突分支的最远端是轴突终端，在那里神经元可以通过突触向另一个细胞传递信号。神经元可能缺乏树突或没有轴突。术语神经突被用来描述树突或轴突，特别是当细胞未分化时。

Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to a dendrite of another. However, synapses can connect an axon to another axon or a dendrite to another dendrite.

大多数神经元通过树突和胞体接收信号，并沿轴突发出信号。在大多数突触中，信号从一个神经元的轴突交叉到另一个神经元的树突。然而，突触可以将一个轴突连接到另一个轴突，或者将一个树突连接到另一个树突。

The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to maintenance of [[voltage]] gradients across their [[Cell membrane|membranes]]. If the voltage changes by a large enough amount over a short interval, the neuron generates an [[All-or-none law|all-or-nothing]] [[electrochemical]] pulse called an [[action potential]]. This potential travels rapidly along the axon and activates synaptic connections as it reaches them. Synaptic signals may be [[Excitatory postsynaptic potential|excitatory]] or [[Inhibitory postsynaptic potential|inhibitory]], increasing or reducing the net voltage that reaches the soma.

信号传递过程部分是电子的，部分是化学的。神经元具有电兴奋性，这是由于其膜上的电压梯度得到了维持。如果电压在短时间内发生足够大的变化，神经元就会产生一个全有或全无的电化学脉冲，称为动作电位。这个电位沿轴突迅速传播，到达突触连接时激活它们。突触信号可能是兴奋性的或抑制性的，增加或减少到达胞体的净电压。

In most cases, neurons are generated by [[neural stem cell]]s during brain development and childhood. [[Neurogenesis]] largely ceases during adulthood in most areas of the brain.

在大多数情况下，神经元是在大脑发育和儿童时期由神经干细胞生成的。在大脑的大多数区域，神经元的生成在成年后基本停止。

{{toclimit|3}}

== Nervous system ==
[[File:Anatomy of a Neuron with Synapse.png|thumb|upright=1.15|Schematic of an anatomically accurate single pyramidal neuron, the primary excitatory neuron of cerebral cortex, with a synaptic connection from an incoming axon onto a dendritic spine.]]
{{unreferenced section|date=December 2020}}
Neurons are the primary components of the nervous system, along with the [[glial cells]] that give them structural and metabolic support. The nervous system is made up of the [[central nervous system]], which includes the [[brain]] and [[spinal cord]], and the [[peripheral nervous system]], which includes the [[autonomic nervous system|autonomic]] and [[somatic nervous system]]s. In vertebrates, the majority of neurons belong to the [[central nervous system]], but some reside in peripheral [[ganglion|ganglia]], and many sensory neurons are situated in sensory organs such as the [[retina]] and [[cochlea]].

thumb|upright=1.15|Schematic of an anatomically accurate single pyramidal neuron, the primary excitatory neuron of cerebral cortex, with a synaptic connection from an incoming axon onto a dendritic spine.

Neurons are the primary components of the nervous system, along with the glial cells that give them structural and metabolic support. The nervous system is made up of the central nervous system, which includes the brain and spinal cord, and the peripheral nervous system, which includes the autonomic and somatic nervous systems. In vertebrates, the majority of neurons belong to the central nervous system, but some reside in peripheral ganglia, and many sensory neurons are situated in sensory organs such as the retina and cochlea.

这是一个解剖学上精确的单锥体神经元原理图，它是大脑皮层的初级兴奋性神经元，与来自轴突的突触连接在树突棘上。神经元是神经系统的主要组成部分，还有神经胶质细胞，它们为神经元提供结构和代谢支持。神经系统由中枢神经系统组成，中枢神经系统包括大脑和脊髓，周围神经系统神经系统包括自主神经系统和躯体神经系统。在脊椎动物中，大多数神经元属于中枢神经系统，但也有一些位于外周神经节，许多感觉神经元位于视网膜和耳蜗等感觉器官中。

Axons may bundle into [[nerve fascicle|fascicle]]s that make up the [[nerve]]s in the [[peripheral nervous system]] (like strands of wire make up cables). Bundles of axons in the central nervous system are called [[nerve tract|tracts]].

Axons may bundle into fascicles that make up the nerves in the peripheral nervous system (like strands of wire make up cables). Bundles of axons in the central nervous system are called tracts.

轴突可以束成束簇，组成周围神经系统中的神经(就像线束组成电缆一样)。中枢神经系统中的轴突束称为束。

== Anatomy and histology ==
[[File:Components of neuron.jpg|thumb|upright=1.8|Diagram of the components of a neuron]]
Neurons are highly specialized for the processing and transmission of cellular signals. Given their diversity of functions performed in different parts of the nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 [[Micrometre|micrometers]] in diameter.<ref>{{cite web |first = Melissa |last = Davies |title = The Neuron: size comparison |url = https://www.ualberta.ca/~neuro/OnlineIntro/NeuronExample.htm |work = Neuroscience: A journey through the brain |date = 2002-04-09 |access-date = 2009-06-20}}</ref>

thumb|upright=1.8|Diagram of the components of a neuron
Neurons are highly specialized for the processing and transmission of cellular signals. Given their diversity of functions performed in different parts of the nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 micrometers in diameter.

神经元的组成成分图神经元是一种高度专门化的细胞信号处理和传输系统。由于它们在神经系统的不同部分执行不同的功能，它们的形状、大小和电化学性质有很大的不同。例如，一个神经元的胞体直径可以从4微米到100微米不等。

*The '''[[Soma (biology)|soma]]''' is the body of the neuron. As it contains the [[cell nucleus|nucleus]], most [[protein biosynthesis|protein synthesis]] occurs here. The nucleus can range from 3 to 18 micrometers in diameter.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Brain Facts and Figures |url = http://faculty.washington.edu/chudler/facts.html |work = Neuroscience for Kids |access-date = 2009-06-20 }}</ref>
*The '''[[dendrites]]''' of a neuron are cellular extensions with many branches. This overall shape and structure is referred to metaphorically as a dendritic tree. This is where the majority of input to the neuron occurs via the [[dendritic spine]].
*The '''[[axon]]''' is a finer, cable-like projection that can extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length. The axon primarily carries [[nerve signal]]s away from the soma, and carries some types of information back to it. Many neurons have only one axon, but this axon may—and usually will—undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the '''[[axon hillock]]'''. Besides being an anatomical structure, the axon hillock also has the greatest density of [[voltage-dependent sodium channels]]. This makes it the most easily excited part of the neuron and the spike initiation zone for the axon. In electrophysiological terms, it has the most negative [[threshold potential]].
**While the axon and axon hillock are generally involved in information outflow, this region can also receive input from other neurons.
*The '''[[axon terminal]]''' is found at the end of the axon farthest from the soma and contains [[synapses]]. Synaptic boutons are specialized structures where [[neurotransmitter]] chemicals are released to communicate with target neurons. In addition to synaptic boutons at the axon terminal, a neuron may have ''en passant'' boutons, which are located along the length of the axon.

*The soma is the body of the neuron. As it contains the nucleus, most protein synthesis occurs here. The nucleus can range from 3 to 18 micrometers in diameter.
*The dendrites of a neuron are cellular extensions with many branches. This overall shape and structure is referred to metaphorically as a dendritic tree. This is where the majority of input to the neuron occurs via the dendritic spine.
*The axon is a finer, cable-like projection that can extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length. The axon primarily carries nerve signals away from the soma, and carries some types of information back to it. Many neurons have only one axon, but this axon may—and usually will—undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the axon hillock. Besides being an anatomical structure, the axon hillock also has the greatest density of voltage-dependent sodium channels. This makes it the most easily excited part of the neuron and the spike initiation zone for the axon. In electrophysiological terms, it has the most negative threshold potential.
**While the axon and axon hillock are generally involved in information outflow, this region can also receive input from other neurons.
*The axon terminal is found at the end of the axon farthest from the soma and contains synapses. Synaptic boutons are specialized structures where neurotransmitter chemicals are released to communicate with target neurons. In addition to synaptic boutons at the axon terminal, a neuron may have en passant boutons, which are located along the length of the axon.

* 躯体是神经元的主体。由于它包含细胞核，大多数蛋白质的合成都发生在这里。原子核的直径从3微米到18微米不等。
* 神经元的树突是由许多分支组成的细胞延伸。这种整体的形状和结构被隐喻地称为树枝状树。这是神经元的大部分输入通过树突棘发生的地方。
* 轴突是一种更细的类似电缆的突出物，可以延伸数十倍、数百倍、甚至数万倍于胞体直径的长度。轴突主要将神经信号从躯体上带走，并将某些类型的信息带回躯体。许多神经元只有一个轴突，但是这个轴突可能ー而且通常会ー经历广泛的分支，从而能够与许多靶细胞交流。轴突从胞体中伸出的部分称为轴突岗。轴突丘除了具有解剖学结构外，还具有最大的电压依赖性钠通道密度。这使得它成为神经元最容易兴奋的部分和轴突的尖峰起始区。用电生理学的术语来说，它具有最大的负阈电位。
*
* 虽然轴突和轴突柄通常参与信息流出，这一区域也可以接收来自其他神经元的输入。
* 轴突终末位于距离胞体最远的轴突末端，含有突触。突触扣是神经递质化学物质释放与目标神经元通讯的特殊结构。除了轴突末端的突触结，神经元还可能有沿轴突长度方向的通道结。

[[File:Neuron Cell Body.png|thumb|Neuron cell body]]

thumb|Neuron cell body

拇指 | 神经元细胞体

The accepted view of the neuron attributes dedicated functions to its various anatomical components; however, dendrites and axons often act in ways contrary to their so-called main function.<ref>{{Cite web |date=2021-01-14 |title=16.7: Nervous System |url=https://bio.libretexts.org/Courses/Lumen_Learning/Book%3A_Fundamentals_of_Biology_I_(Lumen)/16%3A_Module_13%3A_Overview_of_Body_Systems/16.7%3A_Nervous_System |access-date=2022-02-28 |website=Biology LibreTexts |language=en}}</ref>

The accepted view of the neuron attributes dedicated functions to its various anatomical components; however, dendrites and axons often act in ways contrary to their so-called main function.

人们普遍认为，神经元的各种解剖学组成部分具有专门的功能; 然而，树突和轴突的作用方式往往与它们所谓的主要功能相反。

[[File:Complete neuron cell diagram en.svg|thumb|right|Diagram of a typical myelinated vertebrate motor neuron]]
[[File:BN1 Neurology.webm|thumb|Neurology Video]]

thumb|right|Diagram of a typical myelinated vertebrate motor neuron
thumb|Neurology Video

拇指 | 右手 | 典型脊椎动物运动神经元拇指有髓鞘图解 | 神经病学视频

Axons and dendrites in the central nervous system are typically only about one micrometer thick, while some in the peripheral nervous system are much thicker. The soma is usually about 10–25 micrometers in diameter and often is not much larger than the cell nucleus it contains. The longest axon of a human [[motor neuron]] can be over a meter long, reaching from the base of the spine to the toes.

Axons and dendrites in the central nervous system are typically only about one micrometer thick, while some in the peripheral nervous system are much thicker. The soma is usually about 10–25 micrometers in diameter and often is not much larger than the cell nucleus it contains. The longest axon of a human motor neuron can be over a meter long, reaching from the base of the spine to the toes.

中枢神经系统中的轴突和树突通常只有一微米厚，而周围神经系统中的某些轴突要厚得多。躯体的直径通常在10-25微米左右，通常并不比它所包含的细胞核大多少。人类运动神经元最长的轴突可以超过一米长，从脊柱底部延伸到脚趾。

Sensory neurons can have axons that run from the toes to the [[posterior column]] of the spinal cord, over 1.5 meters in adults. [[Giraffe]]s have single axons several meters in length running along the entire length of their necks. Much of what is known about axonal function comes from studying the [[squid giant axon]], an ideal experimental preparation because of its relatively immense size (0.5–1 millimeters thick, several centimeters long).

Sensory neurons can have axons that run from the toes to the posterior column of the spinal cord, over 1.5 meters in adults. Giraffes have single axons several meters in length running along the entire length of their necks. Much of what is known about axonal function comes from studying the squid giant axon, an ideal experimental preparation because of its relatively immense size (0.5–1 millimeters thick, several centimeters long).

感觉神经元的轴突从脚趾延伸到脊髓的后柱，成年人的轴突长度超过1.5米。长颈鹿的整个脖子上都有几米长的单轴。关于轴突功能的大部分已知信息来自于对乌贼巨大神经轴的研究，这是一种理想的实验准备，因为它相对巨大(0.5-1毫米厚，几厘米长)。

Fully differentiated neurons are permanently [[G0 phase|postmitotic]]<ref>{{cite journal | vauthors = Herrup K, Yang Y | title = Cell cycle regulation in the postmitotic neuron: oxymoron or new biology? | journal = Nature Reviews. Neuroscience | volume = 8 | issue = 5 | pages = 368–78 | date = May 2007 | pmid = 17453017 | doi = 10.1038/nrn2124 | s2cid = 12908713 }}</ref> however, stem cells present in the adult brain may regenerate functional neurons throughout the life of an organism (see [[neurogenesis]]). [[Astrocyte]]s are star-shaped [[glial cell]]s. They have been observed to turn into neurons by virtue of their stem cell-like characteristic of [[pluripotency]].

Fully differentiated neurons are permanently postmitotic however, stem cells present in the adult brain may regenerate functional neurons throughout the life of an organism (see neurogenesis). Astrocytes are star-shaped glial cells. They have been observed to turn into neurons by virtue of their stem cell-like characteristic of pluripotency.

然而，完全分化的神经元是永久性的有丝分裂后细胞，存在于成人大脑中的干细胞可以在有机体的一生中再生出功能性神经元(见神经发生)。星形胶质细胞是星形的胶质细胞。他们已经被观察到由于他们的干细胞样特征的多能性转变成神经元。

===Membrane===
{{unreferenced section|date=December 2020}}
Like all animal cells, the cell body of every neuron is enclosed by a [[plasma membrane]], a bilayer of [[lipid]] molecules with many types of protein structures embedded in it. A lipid bilayer is a powerful electrical [[Insulator (electricity)|insulator]], but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are [[voltage-gated ion channel|voltage gated]], meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The [[ion]] materials include [[sodium]], [[potassium]], [[chloride]], and [[calcium]]. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane.

Like all animal cells, the cell body of every neuron is enclosed by a plasma membrane, a bilayer of lipid molecules with many types of protein structures embedded in it. A lipid bilayer is a powerful electrical insulator, but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are voltage gated, meaning that they can be switched between open and closed states by altering the voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The ion materials include sodium, potassium, chloride, and calcium. The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically a bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane.

像所有的动物细胞一样，每个神经元的细胞体都被一层质膜包裹着，质膜是一层脂质分子双层膜，其中包含许多种类型的蛋白质结构。类脂双分子层是一种强大的电绝缘体，但是在神经元中，嵌入在膜中的许多蛋白质结构是电活性的。这些包括允许带电离子通过膜流动的离子通道和从膜的一边到另一边以化学方式传输离子的离子泵。大多数离子通道只能透过特定类型的离子。有些离子通道是电压门控的，这意味着它们可以通过改变膜上的电压差在开态和闭态之间进行切换。其他的化学门控，这意味着他们可以转换开放和关闭状态与化学物质的相互作用，扩散通过细胞外液。离子物质包括钠、钾、氯和钙。离子通道和离子泵之间的相互作用产生跨膜的电压差，通常比基线的1/10伏特小一点。这个电压有两个作用: 第一，它为嵌入在膜中的各种依赖电压的蛋白质机械提供电源; 第二，它为膜的不同部分之间的电信号传输提供了基础。

===Histology and internal structure===
[[File:Gyrus Dentatus 40x.jpg|thumb|250px|Golgi-stained neurons in human hippocampal tissue]]

thumb|250px|Golgi-stained neurons in human hippocampal tissue

= = 组织学和内部结构 = = = 拇指 | 250px | 高尔基染色神经元在人海马组织

[[Image:SUM 110913 Cort Neurons 2.5d in vitro 488 Phalloidin no perm 4 cmle-2.png|thumb|300px|Actin filaments in a mouse cortical neuron in culture]]

thumb|300px|Actin filaments in a mouse cortical neuron in culture

大拇指 | 300px | 微丝在培养的小鼠皮层神经元中

Numerous microscopic clumps called [[Nissl body|Nissl bodies]] (or Nissl substance) are seen when nerve cell bodies are stained with a basophilic ("base-loving") dye. These structures consist of [[Endoplasmic reticulum#Rough endoplasmic reticulum|rough endoplasmic reticulum]] and associated [[ribosomal RNA]]. Named after German psychiatrist and neuropathologist [[Franz Nissl]] (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as [[aniline]] or (weakly) [[haematoxylin]]<ref>{{cite book|title=State Hospitals Bulletin|url={{google books |plainurl=y |id=Wp8CAAAAYAAJ|page=378}}|year=1897|publisher=State Commission in Lunacy.|page=378}}</ref> highlight negatively charged components, and so bind to the phosphate backbone of the ribosomal RNA.

Numerous microscopic clumps called Nissl bodies (or Nissl substance) are seen when nerve cell bodies are stained with a basophilic ("base-loving") dye. These structures consist of rough endoplasmic reticulum and associated ribosomal RNA. Named after German psychiatrist and neuropathologist Franz Nissl (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as aniline or (weakly) haematoxylin highlight negatively charged components, and so bind to the phosphate backbone of the ribosomal RNA.

当神经细胞体被嗜碱性染料染色时，可以看到大量被称为尼氏小体(或尼氏物质)的显微团块。这些结构包括粗糙的内质网和相关的核糖体 RNA。以德国精神病学家和神经病理学家弗朗茨 · 尼斯(1860-1919)命名，它们参与蛋白质合成，其突出性可以用神经细胞代谢非常活跃这一事实来解释。嗜碱性染料，如苯胺或(弱)苏木精突出带负电荷的成分，因此结合到磷酸盐骨架的核糖体 RNA。

The cell body of a neuron is supported by a complex mesh of structural proteins called [[neurofilament]]s, which together with neurotubules (neuronal microtubules) are assembled into larger neurofibrils.<ref name="Webster">{{cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |website=www.merriam-webster.com}}</ref> Some neurons also contain pigment granules, such as [[neuromelanin]] (a brownish-black pigment that is byproduct of synthesis of [[catecholamine]]s), and [[lipofuscin]] (a yellowish-brown pigment), both of which accumulate with age.<ref>{{cite journal | vauthors = Zecca L, Gallorini M, Schünemann V, Trautwein AX, Gerlach M, Riederer P, Vezzoni P, Tampellini D | title = Iron, neuromelanin and ferritin content in the substantia nigra of normal subjects at different ages: consequences for iron storage and neurodegenerative processes | journal = Journal of Neurochemistry | volume = 76 | issue = 6 | pages = 1766–73 | date = March 2001 | pmid = 11259494 | doi = 10.1046/j.1471-4159.2001.00186.x | s2cid = 31301135 }}</ref><ref>{{cite journal | vauthors = Herrero MT, Hirsch EC, Kastner A, Luquin MR, Javoy-Agid F, Gonzalo LM, Obeso JA, Agid Y | title = Neuromelanin accumulation with age in catecholaminergic neurons from Macaca fascicularis brainstem | journal = Developmental Neuroscience | volume = 15 | issue = 1 | pages = 37–48 | date = 1993 | pmid = 7505739 | doi = 10.1159/000111315 }}</ref><ref>{{cite journal | vauthors = Brunk UT, Terman A | title = Lipofuscin: mechanisms of age-related accumulation and influence on cell function | journal = Free Radical Biology & Medicine | volume = 33 | issue = 5 | pages = 611–9 | date = September 2002 | pmid = 12208347 | doi = 10.1016/s0891-5849(02)00959-0 }}</ref> Other structural proteins that are important for neuronal function are [[actin]] and the [[tubulin]] of [[microtubule]]s. [[Class III β-tubulin]] is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule.<ref>{{cite journal | vauthors = Zhao B, Meka DP, Scharrenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F | title = Microtubules Modulate F-actin Dynamics during Neuronal Polarization | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 9583 | date = August 2017 | pmid = 28851982 | pmc = 5575062 | doi = 10.1038/s41598-017-09832-8 | bibcode = 2017NatSR...7.9583Z }}</ref>

The cell body of a neuron is supported by a complex mesh of structural proteins called neurofilaments, which together with neurotubules (neuronal microtubules) are assembled into larger neurofibrils. Some neurons also contain pigment granules, such as neuromelanin (a brownish-black pigment that is byproduct of synthesis of catecholamines), and lipofuscin (a yellowish-brown pigment), both of which accumulate with age. Other structural proteins that are important for neuronal function are actin and the tubulin of microtubules. Class III β-tubulin is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule.

神经元的细胞体由称为神经丝的复杂结构蛋白网支撑，神经丝连同神经小管(神经元微管)组装成较大的神经原纤维。有些神经元还含有色素颗粒，如神经黑色素(儿茶酚胺合成的副产物)和脂褐素(黄褐色色素) ，这两种物质都会随着年龄的增长而累积。其他对神经元功能有重要作用的结构蛋白是肌动蛋白和微管的微管蛋白。III 类 β- 微管蛋白几乎只存在于神经元中。在神经元发育过程中，肌动蛋白主要存在于轴突和树突的顶端。在那里，肌动蛋白的动力学可以通过微管的相互作用来调节。

There are different internal structural characteristics between axons and dendrites. Typical axons almost never contain [[ribosomes]], except some in the initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases.

There are different internal structural characteristics between axons and dendrites. Typical axons almost never contain ribosomes, except some in the initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases.

轴突与树突之间存在不同的内部结构特征。典型的轴突几乎从不包含核糖体，除了在最初的部分。树突含有颗粒状的内质网或核糖体，随着与细胞体距离的增加，其数量逐渐减少。

==Classification==
[[File:GFPneuron.png|thumb|250px|right|Image of pyramidal neurons in mouse [[cerebral cortex]] expressing [[green fluorescent protein]]. The red staining indicates [[GABA]]ergic interneurons.<ref>{{cite journal | vauthors = Lee WC, Huang H, Feng G, Sanes JR, Brown EN, So PT, Nedivi E | title = Dynamic remodeling of dendritic arbors in GABAergic interneurons of adult visual cortex | journal = PLOS Biology | volume = 4 | issue = 2 | pages = e29 | date = February 2006 | pmid = 16366735 | pmc = 1318477 | doi = 10.1371/journal.pbio.0040029 |doi-access=free }}</ref>]]

[[File:smi32neuron.jpg|thumb|250px|right|SMI32-stained pyramidal neurons in [[cerebral cortex]]]]
{{See also|List of distinct cell types in the adult human body#Nervous system}}
Neurons vary in shape and size and can be classified by their [[Morphology (biology)|morphology]] and function.<ref name="Al">{{cite book|last=Al|first=Martini, Frederic Et|title=Anatomy and Physiology' 2007 Ed.2007 Edition|url={{google books |plainurl=y |id=joJb82gVsLoC|page=288}}|publisher=Rex Bookstore, Inc.|isbn=978-971-23-4807-5|pages=288}}</ref> The anatomist [[Camillo Golgi]] grouped neurons into two types; type I with long axons used to move signals over long distances and type II with short axons, which can often be confused with dendrites. Type I cells can be further classified by the location of the soma. The basic morphology of type I neurons, represented by spinal [[motor neurons]], consists of a cell body called the soma and a long thin axon covered by a [[myelin sheath]]. The dendritic tree wraps around the cell body and receives signals from other neurons. The end of the axon has branching [[axon terminal]]s that release neurotransmitters into a gap called the [[synaptic cleft]] between the terminals and the dendrites of the next neuron.

Neurons vary in shape and size and can be classified by their morphology and function. The anatomist Camillo Golgi grouped neurons into two types; type I with long axons used to move signals over long distances and type II with short axons, which can often be confused with dendrites. Type I cells can be further classified by the location of the soma. The basic morphology of type I neurons, represented by spinal motor neurons, consists of a cell body called the soma and a long thin axon covered by a myelin sheath. The dendritic tree wraps around the cell body and receives signals from other neurons. The end of the axon has branching axon terminals that release neurotransmitters into a gap called the synaptic cleft between the terminals and the dendrites of the next neuron.

神经元的形状和大小各不相同，可以根据形态和功能进行分类。解剖学家卡米洛 · 高尔基将神经元分为两种类型: i 型神经元具有长轴突，用于远距离传递信号; II 型神经元具有短轴突，这通常与树突相混淆。I 型细胞可以根据胞体的位置进一步分类。以脊髓运动神经元为代表的 i 型神经元的基本形态包括一个被称为胞体的细胞体和一个被髓鞘覆盖的长而薄的轴突。树突状树包裹着细胞体，接收来自其他神经元的信号。轴突的末端有分支的轴突终末，它将神经递质释放到末梢和下一个神经元的树突之间的突触间隙中。

===Structural classification===

===Structural classification===

= = = 结构分类 = = =

====Polarity====
[[File:Neurons uni bi multi pseudouni.svg|thumb|Different kinds of neurons: 1 [[Unipolar neuron]] 2 [[Bipolar neuron]] 3 [[Multipolar neuron]] 4 [[Pseudounipolar neuron]] ]]
Most neurons can be anatomically characterized as:

Most neurons can be anatomically characterized as:

= = = = 极性 = = = 大多数神经元在解剖学上可以分为:

*[[Unipolar neuron|Unipolar]]: single process
*[[Bipolar cell|Bipolar]]: 1 axon and 1 dendrite
*[[Multipolar neuron|Multipolar]]: 1 axon and 2 or more dendrites
**[[Golgi I]]: neurons with long-projecting axonal processes; examples are pyramidal cells, Purkinje cells, and anterior horn cells
**[[Golgi II]]: neurons whose axonal process projects locally; the best example is the granule cell
*[[Anaxonic neuron|Anaxonic]]: where the axon cannot be distinguished from the dendrite(s)
*[[Pseudounipolar cells|Pseudounipolar]]: 1 process which then serves as both an axon and a dendrite

*Unipolar: single process
*Bipolar: 1 axon and 1 dendrite
*Multipolar: 1 axon and 2 or more dendrites
**Golgi I: neurons with long-projecting axonal processes; examples are pyramidal cells, Purkinje cells, and anterior horn cells
**Golgi II: neurons whose axonal process projects locally; the best example is the granule cell
*Anaxonic: where the axon cannot be distinguished from the dendrite(s)
*Pseudounipolar: 1 process which then serves as both an axon and a dendrite

* 单极性: 单突
* 双极性: 1个轴突和1个树突
* 多极性: 1个轴突和2个或更多树突
*
* Golgi i: 具有长轴突突起的神经元; 例如锥体细胞、浦肯野细胞和前角细胞
*
* Golgi II: 轴突突起局部突起的神经元; 最好的例子是细胞
* 非轴突颗粒: 轴突与树突无法区分
* 伪伏极性: 1突起既是轴突又是树突

====Other====
Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are:

Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are:

一些独特的神经元类型可以根据它们在神经系统中的位置和不同的形状来确定。一些例子如下:

*[[Basket cell]]s, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and [[cerebellum]]
*[[Betz cell]]s, large motor neurons
*[[Lugaro cell]]s, interneurons of the cerebellum
*[[Medium spiny neuron]]s, most neurons in the [[corpus striatum]]
*[[Purkinje cell]]s, huge neurons in the cerebellum, a type of Golgi I multipolar neuron
*[[Pyramidal cell]]s, neurons with triangular soma, a type of Golgi I
*[[Renshaw cell]]s, neurons with both ends linked to [[alpha motor neuron]]s
*[[Unipolar brush cell]]s, interneurons with unique dendrite ending in a brush-like tuft
*[[Granule cell]]s, a type of Golgi II neuron
*[[Anterior horn (spinal cord)|Anterior horn]] cells, [[motoneurons]] located in the spinal cord
*[[Spindle cell]]s, interneurons that connect widely separated areas of the brain

*Basket cells, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and cerebellum
*Betz cells, large motor neurons
*Lugaro cells, interneurons of the cerebellum
*Medium spiny neurons, most neurons in the corpus striatum
*Purkinje cells, huge neurons in the cerebellum, a type of Golgi I multipolar neuron
*Pyramidal cells, neurons with triangular soma, a type of Golgi I
*Renshaw cells, neurons with both ends linked to alpha motor neurons
*Unipolar brush cells, interneurons with unique dendrite ending in a brush-like tuft
*Granule cells, a type of Golgi II neuron
*Anterior horn cells, motoneurons located in the spinal cord
*Spindle cells, interneurons that connect widely separated areas of the brain

篮状细胞---- 中间神经元，围绕靶细胞胞体形成密集的神经丛，见于皮质和小脑
* Betz 细胞，大型运动神经元
* Lugaro 细胞，小脑中间神经元
* 中棘神经元，纹状体大多数神经元
* Purkinje 细胞，小脑中的巨型神经元，一种高尔基 i 多极神经元
* 锥体细胞，具有三角形胞体的神经元，一种高尔基 i Renshaw 细胞,神经元的两端与 α 运动神经元相连
* 单极刷细胞、具有独特树突末端的刷状丛
* 颗粒细胞、一种高尔基 II 神经元
* 前角细胞、位于脊髓
* 纺锤体细胞的运动神经元、连接大脑广泛分离区域的中间神经元

===Functional classification===

===Functional classification===

= = = 功能分类 = = =

====Direction====

====Direction====

= = = 方向 = = =

*[[Afferent neuron]]s convey information from tissues and organs into the central nervous system and are also called [[sensory neurons]].
*[[Efferent neuron]]s (motor neurons) transmit signals from the central nervous system to the effector cells.
*[[Interneuron]]s connect neurons within specific regions of the central nervous system.

*Afferent neurons convey information from tissues and organs into the central nervous system and are also called sensory neurons.
*Efferent neurons (motor neurons) transmit signals from the central nervous system to the effector cells.
*Interneurons connect neurons within specific regions of the central nervous system.

* 传入神经元从组织和器官向中枢神经系统传递信息，也称为感觉神经元。
* 传出神经元(运动神经元)从中枢神经系统向效应细胞传递信号。
* 中间神经元连接中枢神经系统特定区域的神经元。

Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain.

Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain.

传入和传出也泛指神经元，它们分别把信息带到大脑或从大脑发送信息。

====Action on other neurons====
A neuron affects other neurons by releasing a neurotransmitter that binds to [[receptor (biochemistry)|chemical receptor]]s. The effect upon the postsynaptic neuron is determined by the type of receptor that is activated, not by the presynaptic neuron or by the neurotransmitter. A neurotransmitter can be thought of as a key, and a receptor as a lock: the same neurotransmitter can activate multiple types of receptors. Receptors can be classified broadly as ''excitatory'' (causing an increase in firing rate), ''inhibitory'' (causing a decrease in firing rate), or ''modulatory'' (causing long-lasting effects not directly related to firing rate).

A neuron affects other neurons by releasing a neurotransmitter that binds to chemical receptors. The effect upon the postsynaptic neuron is determined by the type of receptor that is activated, not by the presynaptic neuron or by the neurotransmitter. A neurotransmitter can be thought of as a key, and a receptor as a lock: the same neurotransmitter can activate multiple types of receptors. Receptors can be classified broadly as excitatory (causing an increase in firing rate), inhibitory (causing a decrease in firing rate), or modulatory (causing long-lasting effects not directly related to firing rate).

= = = 对其他神经元的作用 = = = = 一个神经元通过释放一种结合在化学受体上的神经递质来影响其他神经元。对突触后神经元的影响取决于被激活的受体类型，而不是突触前神经元或神经递质。神经递质可以被认为是一把钥匙，受体是一把锁: 同一种神经递质可以激活多种类型的受体。受体可以大致分为兴奋性(引起放电频率的增加)、抑制性(引起放电频率的降低)或调节性(引起与放电频率无直接关系的长期效应)。

The two most common (90%+) neurotransmitters in the brain, [[glutamate]] and [[GABA]], have largely consistent actions. Glutamate acts on several types of receptors, and has effects that are excitatory at [[ionotropic receptor]]s and a modulatory effect at [[metabotropic receptor]]s. Similarly, GABA acts on several types of receptors, but all of them have inhibitory effects (in adult animals, at least). Because of this consistency, it is common for neuroscientists to refer to cells that release glutamate as "excitatory neurons", and cells that release GABA as "inhibitory neurons". Some other types of neurons have consistent effects, for example, "excitatory" motor neurons in the spinal cord that release [[acetylcholine]], and "inhibitory" [[spinal neuron]]s that release [[glycine]].

The two most common (90%+) neurotransmitters in the brain, glutamate and GABA, have largely consistent actions. Glutamate acts on several types of receptors, and has effects that are excitatory at ionotropic receptors and a modulatory effect at metabotropic receptors. Similarly, GABA acts on several types of receptors, but all of them have inhibitory effects (in adult animals, at least). Because of this consistency, it is common for neuroscientists to refer to cells that release glutamate as "excitatory neurons", and cells that release GABA as "inhibitory neurons". Some other types of neurons have consistent effects, for example, "excitatory" motor neurons in the spinal cord that release acetylcholine, and "inhibitory" spinal neurons that release glycine.

大脑中最常见的两种(90% 以上)神经递质——谷氨酸和 γ- 氨基丁酸(GABA)具有基本一致的作用。谷氨酸作用于多种受体，对离子型受体具有兴奋作用，对亲代谢型受体具有调节作用。类似地，GABA 作用于几种类型的受体，但是它们都有抑制作用(至少在成年动物中是这样)。由于这种一致性，神经科学家通常将释放谷氨酸的细胞称为“兴奋性神经元”，将释放 GABA 的细胞称为“抑制性神经元”。其他一些类型的神经元具有一致的效果，例如，脊髓中释放乙酰胆碱的“兴奋性”运动神经元，以及释放甘氨酸的“抑制性”脊髓神经元。

The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neuron. In principle, a single neuron, releasing a single neurotransmitter, can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still. For example, [[photoreceptor cell]]s in the retina constantly release the neurotransmitter glutamate in the absence of light. So-called OFF [[retinal bipolar cells|bipolar cells]] are, like most neurons, excited by the released glutamate. However, neighboring target neurons called ON bipolar cells are instead inhibited by glutamate, because they lack typical [[ionotropic receptor|ionotropic]] [[glutamate receptors]] and instead express a class of inhibitory [[metabotropic receptor|metabotropic]] glutamate receptors.<ref>{{cite journal | vauthors = Gerber U | title = Metabotropic glutamate receptors in vertebrate retina | journal = Documenta Ophthalmologica. Advances in Ophthalmology | volume = 106 | issue = 1 | pages = 83–7 | date = January 2003 | pmid = 12675489 | doi = 10.1023/A:1022477203420 | s2cid = 22296630 }}</ref> When light is present, the photoreceptors cease releasing glutamate, which relieves the ON bipolar cells from inhibition, activating them; this simultaneously removes the excitation from the OFF bipolar cells, silencing them.

The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neuron. In principle, a single neuron, releasing a single neurotransmitter, can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still. For example, photoreceptor cells in the retina constantly release the neurotransmitter glutamate in the absence of light. So-called OFF bipolar cells are, like most neurons, excited by the released glutamate. However, neighboring target neurons called ON bipolar cells are instead inhibited by glutamate, because they lack typical ionotropic glutamate receptors and instead express a class of inhibitory metabotropic glutamate receptors. When light is present, the photoreceptors cease releasing glutamate, which relieves the ON bipolar cells from inhibition, activating them; this simultaneously removes the excitation from the OFF bipolar cells, silencing them.

兴奋性神经递质和抑制性神经递质之间的区别不是绝对的。相反，它取决于突触后神经元上的化学受体类别。原则上，一个单一的神经元，释放一个单一的神经递质，可以对某些目标产生兴奋作用，抑制作用对其他目标产生抑制作用，对其他目标产生调节作用。例如，视网膜上的感光细胞在没有光的情况下不断地释放神经递质谷氨酸。所谓的 OFF 双极细胞，像大多数神经元一样，被释放的谷氨酸激活。然而，由于缺乏典型的促离子型谷氨酸受体而表达一类抑制性代谢型谷氨酸受体，相邻的目标神经元 ON 双极细胞被谷氨酸所抑制。当有光时，光感受器停止释放谷氨酸，从而减轻 ON 双极细胞的抑制，激活它们; 这同时消除 OFF 双极细胞的兴奋，使它们沉默。

It is possible to identify the type of inhibitory effect a presynaptic neuron will have on a postsynaptic neuron, based on the proteins the presynaptic neuron expresses. [[Parvalbumin]]-expressing neurons typically dampen the output signal of the postsynaptic neuron in the [[visual cortex]], whereas [[somatostatin]]-expressing neurons typically block dendritic inputs to the postsynaptic neuron.<ref name="pmid22878717">{{cite journal | vauthors = Wilson NR, Runyan CA, Wang FL, Sur M | title = Division and subtraction by distinct cortical inhibitory networks in vivo | journal = Nature | volume = 488 | issue = 7411 | pages = 343–8 | date = August 2012 | pmid = 22878717 | pmc = 3653570 | doi = 10.1038/nature11347 | bibcode = 2012Natur.488..343W | hdl = 1721.1/92709 }}</ref>

It is possible to identify the type of inhibitory effect a presynaptic neuron will have on a postsynaptic neuron, based on the proteins the presynaptic neuron expresses. Parvalbumin-expressing neurons typically dampen the output signal of the postsynaptic neuron in the visual cortex, whereas somatostatin-expressing neurons typically block dendritic inputs to the postsynaptic neuron.

基于突触前神经元表达的蛋白质，可以确定突触前神经元对突触后神经元的抑制作用类型。小白蛋白表达的神经元通常会抑制视皮层突触后神经元的输出信号，而生长抑素表达的神经元通常会阻断突触后神经元的树突输入。

====Discharge patterns====
Neurons have intrinsic electroresponsive properties like intrinsic transmembrane voltage [[Neural oscillation|oscillatory]] patterns.<ref name="llinas2014">{{cite journal | vauthors = Llinás RR | title = Intrinsic electrical properties of mammalian neurons and CNS function: a historical perspective | journal = Frontiers in Cellular Neuroscience | volume = 8 | pages = 320 | date = 2014-01-01 | pmid = 25408634 | pmc = 4219458 | doi = 10.3389/fncel.2014.00320 | doi-access = free }}</ref> So neurons can be classified according to their [[electrophysiology|electrophysiological]] characteristics:

Neurons have intrinsic electroresponsive properties like intrinsic transmembrane voltage oscillatory patterns. So neurons can be classified according to their electrophysiological characteristics:

= = = = = = = 放电模式神经元具有内在的电响应特性，如内在的跨膜电压振荡模式。因此，神经元可以根据它们的电生理特性进行分类:

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.
*Phasic or bursting. Neurons that fire in bursts are called phasic.
*Fast spiking. Some neurons are notable for their high firing rates, for example some types of cortical inhibitory interneurons, cells in [[globus pallidus]], [[retinal ganglion cells]].<ref>{{cite conference | title = Ion conductances related to shaping the repetitive firing in rat retinal ganglion cells | vauthors = Kolodin YO, Veselovskaia NN, Veselovsky NS, Fedulova SA | conference = Acta Physiologica Congress | url = http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | access-date = 2009-06-20 | archive-url = https://web.archive.org/web/20121007164451/http://www.blackwellpublishing.com/aphmeeting/abstract.asp?MeetingID=&id=61198 | archive-date = 2012-10-07 | url-status = dead }}</ref><ref>{{cite web|url=http://ykolodin.50webs.com/ |title=Ionic conductances underlying excitability in tonically firing retinal ganglion cells of adult rat |publisher=Ykolodin.50webs.com |date=2008-04-27 |access-date=2013-02-16}}</ref>

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.
*Phasic or bursting. Neurons that fire in bursts are called phasic.
*Fast spiking. Some neurons are notable for their high firing rates, for example some types of cortical inhibitory interneurons, cells in globus pallidus, retinal ganglion cells.

* 补品或有规律的峰值。一些神经元典型地持续(音调上)活跃，典型地以一个恒定的频率放电。例如: 神经纹状体的中间神经元。
* 相位或爆裂。神经元在爆发中发出的信号称为相位信号。
* 快速尖峰。一些神经元因其高放电率而显著，例如某些类型的皮层抑制性中间神经元、苍白球细胞、视网膜神经节细胞。

====Neurotransmitter ====
[[File:Neurotransmitters.jpg|thumb|Synaptic vesicles containing neurotransmitters]]
{{Main|Neurotransmitter}}
[[Neurotransmitter]]s are chemical messengers passed from one neuron to another neuron or to a [[muscle cell]] or [[Gland|gland cell]].

thumb|Synaptic vesicles containing neurotransmitters

Neurotransmitters are chemical messengers passed from one neuron to another neuron or to a muscle cell or gland cell.

神经递质含有神经递质的突触小泡神经递质是化学信使，从一个神经元传递到另一个神经元，或传递到肌肉细胞或腺细胞。

*Cholinergic neurons – acetylcholine. [[Acetylcholine]] is released from presynaptic neurons into the synaptic cleft. It acts as a [[ligand]] for both ligand-gated ion channels and [[Metabotropic receptor|metabotropic]] (GPCRs) [[Muscarinic acetylcholine receptor|muscarinic receptors]]. [[Nicotinic receptors]] are pentameric ligand-gated ion channels composed of alpha and beta subunits that bind [[nicotine]]. Ligand binding opens the channel causing influx of [[Sodium|Na+]] depolarization and increases the probability of presynaptic neurotransmitter release. Acetylcholine is synthesized from [[choline]] and [[acetyl coenzyme A]].
*Adrenergic neurons – noradrenaline. [[Noradrenaline]] (norepinephrine) is released from most [[postganglionic]] neurons in the [[sympathetic nervous system]] onto two sets of GPCRs: [[Adrenergic receptor|alpha adrenoceptor]]s and [[beta adrenoceptor]]s. Noradrenaline is one of the three common [[catecholamine]] neurotransmitter, and the most prevalent of them in the [[peripheral nervous system]]; as with other catecholamines, it is synthesised from [[tyrosine]].
*GABAergic neurons – [[gamma aminobutyric acid]]. GABA is one of two neuroinhibitors in the [[central nervous system]] (CNS), along with glycine. GABA has a homologous function to [[Acetylcholine|ACh]], gating anion channels that allow [[Chlorine|Cl−]] ions to enter the post synaptic neuron. Cl− causes hyperpolarization within the neuron, decreasing the probability of an action potential firing as the voltage becomes more negative (for an action potential to fire, a positive voltage threshold must be reached). GABA is synthesized from glutamate neurotransmitters by the enzyme [[glutamate decarboxylase]].
*Glutamatergic neurons – glutamate. [[Glutamate]] is one of two primary excitatory amino acid neurotransmitters, along with [[Aspartic acid|aspartate]]. Glutamate receptors are one of four categories, three of which are ligand-gated ion channels and one of which is a [[G protein|G-protein]] coupled receptor (often referred to as GPCR).

*Cholinergic neurons – acetylcholine. Acetylcholine is released from presynaptic neurons into the synaptic cleft. It acts as a ligand for both ligand-gated ion channels and metabotropic (GPCRs) muscarinic receptors. Nicotinic receptors are pentameric ligand-gated ion channels composed of alpha and beta subunits that bind nicotine. Ligand binding opens the channel causing influx of Na+ depolarization and increases the probability of presynaptic neurotransmitter release. Acetylcholine is synthesized from choline and acetyl coenzyme A.
*Adrenergic neurons – noradrenaline. Noradrenaline (norepinephrine) is released from most postganglionic neurons in the sympathetic nervous system onto two sets of GPCRs: alpha adrenoceptors and beta adrenoceptors. Noradrenaline is one of the three common catecholamine neurotransmitter, and the most prevalent of them in the peripheral nervous system; as with other catecholamines, it is synthesised from tyrosine.
*GABAergic neurons – gamma aminobutyric acid. GABA is one of two neuroinhibitors in the central nervous system (CNS), along with glycine. GABA has a homologous function to ACh, gating anion channels that allow Cl− ions to enter the post synaptic neuron. Cl− causes hyperpolarization within the neuron, decreasing the probability of an action potential firing as the voltage becomes more negative (for an action potential to fire, a positive voltage threshold must be reached). GABA is synthesized from glutamate neurotransmitters by the enzyme glutamate decarboxylase.
*Glutamatergic neurons – glutamate. Glutamate is one of two primary excitatory amino acid neurotransmitters, along with aspartate. Glutamate receptors are one of four categories, three of which are ligand-gated ion channels and one of which is a G-protein coupled receptor (often referred to as GPCR).

* 胆碱能神经元-乙酰胆碱。乙酰胆碱从突触前神经元释放到突触间隙。它既是配体门控离子通道的配体，也是代谢型毒蕈碱受体的配体。烟碱受体是一种配体门控的五聚体离子通道，由与尼古丁结合的 α 和 β 亚基组成。配体结合通道打开引起钠离子内流的通道，增加突触前神经递质释放的可能性。乙酰胆碱是由胆碱和乙酰辅酶 a 合成的。
* 肾上腺素能神经元-去甲肾上腺素。去甲肾上腺素(去甲肾上腺素)从交感神经的大多数节后神经元释放到两组 GPCRs 上: 阿尔法肾上腺素受体和 β 肾上腺素受体。去甲肾上腺素是3种常见的儿茶酚胺类神经递质之一，在周围神经系统中最为普遍; 和其他儿茶酚胺一样，去甲肾上腺素也是由酪氨酸合成的。
* gaba 能神经元-γ- 氨基丁酸。GABA 是中枢神经系统(CNS)和甘氨酸的两种神经抑制剂之一。GABA 对乙酰胆碱具有同源功能，门控阴离子通道允许 Cl - 离子进入突触后神经元。Cl-会引起神经元内的超极化，当电压变得更负时，降低了动作电位激活的概率(对于动作电位激活，必须达到一个正电压阈值)。GABA 是由谷氨酸脱羧酶合成的谷氨酸神经递质合成的。
* 谷氨酸能神经元ー谷氨酸。谷氨酸和天冬氨酸是两种主要的兴奋性氨基酸类神经递质之一。谷氨酸受体是四类受体之一，其中三类是配体门控离子通道，其中一类是 g 蛋白偶联受体(通常称为 GPCR)。

:#[[AMPA]] and [[Kainic acid|Kainate]] receptors function as [[Ion|cation]] channels permeable to Na+ cation channels mediating fast excitatory synaptic transmission.
:#[[N-Methyl-D-aspartic acid|NMDA]] receptors are another cation channel that is more permeable to [[Calcium in biology|Ca2+]]. The function of NMDA receptors depend on glycine receptor binding as a co-[[agonist]] within the channel pore. NMDA receptors do not function without both ligands present.
:#Metabotropic receptors, GPCRs modulate synaptic transmission and postsynaptic excitability.
::Glutamate can cause excitotoxicity when blood flow to the brain is interrupted, resulting in [[brain damage]]. When blood flow is suppressed, glutamate is released from presynaptic neurons, causing greater NMDA and AMPA receptor activation than normal outside of stress conditions, leading to elevated Ca2+ and Na+ entering the post synaptic neuron and cell damage. Glutamate is synthesized from the amino acid glutamine by the enzyme [[Glutamine oxoglutarate aminotransferase|glutamate synthase]].

:#AMPA and Kainate receptors function as cation channels permeable to Na+ cation channels mediating fast excitatory synaptic transmission.
:#NMDA receptors are another cation channel that is more permeable to Ca2+. The function of NMDA receptors depend on glycine receptor binding as a co-agonist within the channel pore. NMDA receptors do not function without both ligands present.
:#Metabotropic receptors, GPCRs modulate synaptic transmission and postsynaptic excitability.
::Glutamate can cause excitotoxicity when blood flow to the brain is interrupted, resulting in brain damage. When blood flow is suppressed, glutamate is released from presynaptic neurons, causing greater NMDA and AMPA receptor activation than normal outside of stress conditions, leading to elevated Ca2+ and Na+ entering the post synaptic neuron and cell damage. Glutamate is synthesized from the amino acid glutamine by the enzyme glutamate synthase.

# ampa 和 Kainate 受体作为钠离子通道的阳离子通道介导快速兴奋性突触传递。: # nmda 受体是另一种阳离子通道，对钙离子通透性更强。NMDA 受体的功能依赖于通道孔中的甘氨酸受体结合作为一种共同激动剂。如果没有这两种配体的存在，NMDA 受体就不能发挥作用。
* # 亲代谢型受体，GPCRs 调节突触传递和突触后兴奋性。
* 当流向大脑的血液中断时，谷氨酸会引起兴奋毒性，造成脑损伤。当血流受到抑制时，突触前神经元释放谷氨酸，导致 NMDA 和 AMPA 受体激活超过正常应激条件下，导致 Ca2 + 和 Na + 升高进入突触后神经元和细胞损伤。谷氨酸是由谷氨酰胺氨基酸合成酶谷氨酸。

*Dopaminergic neurons—[[dopamine]]. [[Dopamine]] is a neurotransmitter that acts on D1 type (D1 and D5) Gs-coupled receptors, which increase cAMP and PKA, and D2 type (D2, D3, and D4) receptors, which activate Gi-coupled receptors that decrease cAMP and PKA. Dopamine is connected to mood and behavior and modulates both pre- and post-synaptic neurotransmission. Loss of dopamine neurons in the [[substantia nigra]] has been linked to [[Parkinson's disease]]. Dopamine is synthesized from the amino acid [[tyrosine]]. Tyrosine is catalyzed into levodopa (or [[L-DOPA]]) by [[Tyrosine hydroxylase|tyrosine hydroxlase]], and levodopa is then converted into dopamine by the aromatic amino acid [[Carboxy-lyases|decarboxylase]].
*Serotonergic neurons—[[serotonin]]. [[Serotonin]] (5-Hydroxytryptamine, 5-HT) can act as excitatory or inhibitory. Of its four 5-HT receptor classes, 3 are GPCR and 1 is a ligand-gated cation channel. Serotonin is synthesized from [[tryptophan]] by [[tryptophan hydroxylase]], and then further by decarboxylase. A lack of 5-HT at postsynaptic neurons has been linked to depression. Drugs that block the presynaptic [[serotonin transporter]] are used for treatment, such as [[Prozac]] and [[Zoloft]].
*Purinergic neurons—ATP. [[Adenosine triphosphate|ATP]] is a neurotransmitter acting at both ligand-gated ion channels ([[P2X]] receptors) and GPCRs ([[P2Y receptor|P2Y]]) receptors. ATP is, however, best known as a [[cotransmitter]]. Such [[purinergic signalling]] can also be mediated by other [[purine]]s like [[adenosine]], which particularly acts at P2Y receptors.
*Histaminergic neurons—[[histamine]]. [[Histamine]] is a [[monoamine neurotransmitter]] and [[neuromodulator]]. Histamine-producing neurons are found in the [[tuberomammillary nucleus]] of the [[hypothalamus]].<ref>{{cite journal | vauthors = Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y | title = Histamine: neural circuits and new medications | journal = Sleep | volume = 42 | issue = 1 | date = January 2019 | pmid = 30239935 | pmc = 6335869 | doi = 10.1093/sleep/zsy183 }}</ref> Histamine is involved in [[arousal]] and regulating sleep/wake behaviors.

*Dopaminergic neurons—dopamine. Dopamine is a neurotransmitter that acts on D1 type (D1 and D5) Gs-coupled receptors, which increase cAMP and PKA, and D2 type (D2, D3, and D4) receptors, which activate Gi-coupled receptors that decrease cAMP and PKA. Dopamine is connected to mood and behavior and modulates both pre- and post-synaptic neurotransmission. Loss of dopamine neurons in the substantia nigra has been linked to Parkinson's disease. Dopamine is synthesized from the amino acid tyrosine. Tyrosine is catalyzed into levodopa (or L-DOPA) by tyrosine hydroxlase, and levodopa is then converted into dopamine by the aromatic amino acid decarboxylase.
*Serotonergic neurons—serotonin. Serotonin (5-Hydroxytryptamine, 5-HT) can act as excitatory or inhibitory. Of its four 5-HT receptor classes, 3 are GPCR and 1 is a ligand-gated cation channel. Serotonin is synthesized from tryptophan by tryptophan hydroxylase, and then further by decarboxylase. A lack of 5-HT at postsynaptic neurons has been linked to depression. Drugs that block the presynaptic serotonin transporter are used for treatment, such as Prozac and Zoloft.
*Purinergic neurons—ATP. ATP is a neurotransmitter acting at both ligand-gated ion channels (P2X receptors) and GPCRs (P2Y) receptors. ATP is, however, best known as a cotransmitter. Such purinergic signalling can also be mediated by other purines like adenosine, which particularly acts at P2Y receptors.
*Histaminergic neurons—histamine. Histamine is a monoamine neurotransmitter and neuromodulator. Histamine-producing neurons are found in the tuberomammillary nucleus of the hypothalamus. Histamine is involved in arousal and regulating sleep/wake behaviors.

* 多巴胺能神经元ーー多巴胺。多巴胺是一种神经递质，作用于 d1型(d1和 D5) gs 偶联受体，增加 cAMP 和 PKA，以及 d2型(D2，d3和 D4)受体，激活 gi 偶联受体，减少 cAMP 和 PKA。多巴胺与情绪和行为有关，同时调节突触前和突触后的神经传导。黑质多巴胺神经元的缺失与帕金森氏症有关。多巴胺由氨基酸酪氨酸合成。酪氨酸被酪氨酸羟化酶催化转化为左旋多巴，然后左旋多巴被芳香族氨基酸脱羧酶转化为多巴。
* 5- 羟色胺能神经元ーー5- 羟色胺。血清素(血清素，5-HT)可以起兴奋性或抑制性作用。其4个5-ht 受体类别中，3个为 GPCR，1个为配体门控阳离子通道。5- 羟色胺由色氨酸合成，然后再由色氨酸羟化酶脱羧酶合成。突触后神经元缺乏5-ht 与抑郁症有关。阻断突触前血清素转运体的药物用于治疗，如百忧解和左洛复。
* 嘌呤能神经元ー atp。ATP 是作用于配体门控离子通道(P2X 受体)和 gpcr (P2Y)受体的神经递质。然而，ATP 最为人所知的是作为一种辅助传递器。这种嘌呤能信号也可以通过其他嘌呤如腺苷介导，特别是作用于 P2Y 受体。
* 组胺能神经元ー组胺。组胺是一种单胺类神经递质和神经调质。产生组胺的神经元存在于下丘脑的结节微核。组胺参与觉醒和调节睡眠/觉醒行为。

====Multimodel classification====
Since 2012 there has been a push from the cellular and computational neuroscience community to come up with a universal classification of neurons that will apply to all neurons in the brain as well as across species. This is done by considering the three essential qualities of all neurons: electrophysiology, morphology, and the individual transcriptome of the cells. Besides being universal this classification has the advantage of being able to classify astrocytes as well. A method called Patch-Seq in which all three qualities can be measured at once is used extensively by the Allen Institute for Brain Science.<ref>{{cite web |url=https://www.news-medical.net/news/20201203/Patch-seq-technique-helps-depict-the-variation-of-neural-cells-in-the-brain.aspx |title=Patch-seq technique helps depict the variation of neural cells in the brain |work=News-medical.net |date=3 December 2020 |access-date=26 August 2021 |url-status=live}}</ref>

Since 2012 there has been a push from the cellular and computational neuroscience community to come up with a universal classification of neurons that will apply to all neurons in the brain as well as across species. This is done by considering the three essential qualities of all neurons: electrophysiology, morphology, and the individual transcriptome of the cells. Besides being universal this classification has the advantage of being able to classify astrocytes as well. A method called Patch-Seq in which all three qualities can be measured at once is used extensively by the Allen Institute for Brain Science.

自2012年以来，细胞和计算神经科学团体一直在推动对神经元进行通用分类，这种分类将适用于大脑中的所有神经元以及跨物种的神经元。这是通过考虑所有神经元的3个基本特性来完成的: 电生理学、形态学和单个细胞的转录组。这种分类方法除了具有普遍性外，还具有能够对星形胶质细胞进行分类的优点。艾伦脑科学研究所(Allen Institute for Brain Science)广泛使用了一种称为 Patch-Seq 的方法，这种方法可以同时测量这三种特性。

==Connectivity==
{{Main|Synapse|Chemical synapse}}
[[File:Chemical synapse schema cropped.jpg|thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell]]
[[File:Neuro Muscular Junction.png|thumb|Chemical synapse|left]]
Neurons communicate with each other via [[synapses]], where either the [[axon terminal]] of one cell contacts another neuron's dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in the cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the [[supraoptic nucleus]], have only one or two dendrites, each of which receives thousands of synapses.

thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell
thumb|Chemical synapse|left
Neurons communicate with each other via synapses, where either the axon terminal of one cell contacts another neuron's dendrite, soma or, less commonly, axon. Neurons such as Purkinje cells in the cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the supraoptic nucleus, have only one or two dendrites, each of which receives thousands of synapses.

神经元通过突触相互沟通，一个细胞的轴突终端接触到另一个神经元的树突、胞体，或者更少见的轴突。像小脑中的浦肯野细胞这样的神经元可以有超过1000个树突分支，与成千上万的其他细胞建立连接; 其他的神经元，如视上核的大细胞神经元，只有一个或两个树突，每个树突接收数千个突触。

Synapses can be [[EPSP|excitatory]] or [[IPSP|inhibitory]], either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive [[gap junction|junctions]] between cells.<ref>{{cite book |last1=Macpherson |first1=Gordon |title=Black's Medical Dictionary |date=2002 |publisher=Scarecrow Press |location=Lanham, MD |isbn=0810849844 |pages=431–434 |edition=40 }}</ref>

Synapses can be excitatory or inhibitory, either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive junctions between cells.

突触可以是兴奋性的，也可以是抑制性的，分别增加或减少目标神经元的活动。有些神经元还通过电突触进行交流，这些突触是细胞之间直接的电传导连接。

When an action potential reaches the axon terminal, it opens [[Voltage-dependent calcium channel|voltage-gated calcium channels]], allowing [[Calcium in biology|calcium ions]] to enter the terminal. Calcium causes [[synaptic vesicles]] filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the [[axon terminal]] triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial [[energy metabolism]] to produce [[Adenosine triphosphate|ATP]] to support continuous neurotransmission.<ref name="pmid23746507">{{cite journal | vauthors = Ivannikov MV, Macleod GT | title = Mitochondrial free Ca²⁺ levels and their effects on energy metabolism in Drosophila motor nerve terminals | journal = Biophysical Journal | volume = 104 | issue = 11 | pages = 2353–61 | date = June 2013 | pmid = 23746507 | pmc = 3672877 | doi = 10.1016/j.bpj.2013.03.064 | bibcode = 2013BpJ...104.2353I }}</ref>

When an action potential reaches the axon terminal, it opens voltage-gated calcium channels, allowing calcium ions to enter the terminal. Calcium causes synaptic vesicles filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the axon terminal triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial energy metabolism to produce ATP to support continuous neurotransmission.

当一个动作电位到达轴突末端时，它打开电压门控钙通道，允许钙离子进入末端。钙导致充满神经递质分子的突触小泡与膜融合，释放其内容物进入突触间隙。神经递质扩散到突触间隙，激活突触后神经元上的受体。轴突末端的高浓度胞浆钙触发了线粒体的钙摄取，进而激活线粒体的能量代谢，产生 ATP 来支持持续的神经传导。

An [[autapse]] is a synapse in which a neuron's axon connects to its own dendrites.

An autapse is a synapse in which a neuron's axon connects to its own dendrites.

自体突触是神经元的轴突与其自身的树突连接的突触。

The [[human brain]] has some 8.6 x 1010 (eighty six billion) neurons.<ref>{{ cite journal | vauthors = Herculano-Houzel S | title = The human brain in numbers: a linearly scaled-up primate brain | journal = Frontiers in Human Neuroscience | volume = 3 | pages = 31 | date = November 2009 | pmid = 19915731 | doi = 10.3389/neuro.09.031.2009 | pmc = 2776484 | doi-access = free }}</ref> Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 1015 synapses (1 quadrillion). [[Synaptic pruning|This number declines with age]], stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5 x 1014 synapses (100 to 500 trillion).<ref>{{cite journal | vauthors = Drachman DA | title = Do we have brain to spare? | journal = Neurology | volume = 64 | issue = 12 | pages = 2004–5 | date = June 2005 | pmid = 15985565 | doi = 10.1212/01.WNL.0000166914.38327.BB | s2cid = 38482114 }}</ref>
[[File:Axon Propagation.svg|thumb|563x563px|An annotated diagram of the stages of an action potential propagating down an axon including the role of ion concentration and pump and channel proteins.]]

The human brain has some 8.6 x 1010 (eighty six billion) neurons. Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 1015 synapses (1 quadrillion). This number declines with age, stabilizing by adulthood. Estimates vary for an adult, ranging from 1014 to 5 x 1014 synapses (100 to 500 trillion).
thumb|563x563px|An annotated diagram of the stages of an action potential propagating down an axon including the role of ion concentration and pump and channel proteins.

人类大脑有大约8.6 x 1010(860亿)神经元。每个神经元平均有7000个与其他神经元的突触连接。据估计，一个三岁儿童的大脑约有1015个突触(1千万亿次)。这个数字随着年龄的增长而下降，成年后趋于稳定。对于一个成年人来说，估计范围从1014到5x1014个突触(100到500万亿)不等。563x563px | 动作电位沿轴突传递的各个阶段的注释图表，包括离子浓度、泵浦和通道蛋白的作用。

=== Nonelectrochemical signaling ===
Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through:
* force generated by the enlargement of dendritic spines<ref>{{cite journal |last1=Ucar |first1=Hasan |last2=Watanabe |first2=Satoshi |last3=Noguchi |first3=Jun |last4=Morimoto |first4=Yuichi |last5=Iino |first5=Yusuke |last6=Yagishita |first6=Sho |last7=Takahashi |first7=Noriko |last8=Kasai |first8=Haruo |title=Mechanical actions of dendritic-spine enlargement on presynaptic exocytosis |journal=Nature |date=December 2021 |volume=600 |issue=7890 |pages=686–689 |doi=10.1038/s41586-021-04125-7 |language=en |issn=1476-4687}} Lay summary: {{cite news |title=Forceful synapses reveal mechanical interactions in the brain |url=https://www.nature.com/articles/d41586-021-03516-0 |access-date=21 February 2022 |work=Nature |date=24 November 2021 |language=en |doi=10.1038/d41586-021-03516-0}}</ref>
* the transfer of [[protein]]s – transneuronally transported proteins (TNTPs)<ref>{{cite news |title=Researchers discover new type of cellular communication in the brain |url=https://medicalxpress.com/news/2022-01-cellular-brain.html |access-date=12 February 2022 |work=The Scripps Research Institute |language=en}}</ref><ref>{{cite journal |last1=Schiapparelli |first1=Lucio M. |last2=Sharma |first2=Pranav |last3=He |first3=Hai-Yan |last4=Li |first4=Jianli |last5=Shah |first5=Sahil H. |last6=McClatchy |first6=Daniel B. |last7=Ma |first7=Yuanhui |last8=Liu |first8=Han-Hsuan |last9=Goldberg |first9=Jeffrey L. |last10=Yates |first10=John R. |last11=Cline |first11=Hollis T. |title=Proteomic screen reveals diverse protein transport between connected neurons in the visual system |journal=Cell Reports |date=25 January 2022 |volume=38 |issue=4 |doi=10.1016/j.celrep.2021.110287 |language=English |issn=2211-1247}}</ref>

Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through:
* force generated by the enlargement of dendritic spines Lay summary: 
* the transfer of proteins – transneuronally transported proteins (TNTPs)

除了电信号和化学信号之外，研究表明，健康人脑中的神经元还可以通过树突棘增大产生的力进行交流

They can also get modulated by input from the environment and [[hormone]]s released from other parts of the organism,<ref>{{cite journal |last1=Levitan |first1=Irwin B. |last2=Kaczmarek |first2=Leonard K. |title=Electrical Signaling in Neurons |doi=10.1093/med/9780199773893.001.0001/med-9780199773893-chapter-3 |publisher=Oxford University Press}}</ref> which could be influenced more or less directly by neurons. This also applies to [[neurotrophin]]s such as [[BDNF]]. The [[gut microbiome]] is also connected with the brain.<ref>{{cite journal |last1=O’Leary |first1=Olivia F. |last2=Ogbonnaya |first2=Ebere S. |last3=Felice |first3=Daniela |last4=Levone |first4=Brunno R. |last5=C. Conroy |first5=Lorraine |last6=Fitzgerald |first6=Patrick |last7=Bravo |first7=Javier A. |last8=Forsythe |first8=Paul |last9=Bienenstock |first9=John |last10=Dinan |first10=Timothy G. |last11=Cryan |first11=John F. |title=The vagus nerve modulates BDNF expression and neurogenesis in the hippocampus |journal=European Neuropsychopharmacology |date=1 February 2018 |volume=28 |issue=2 |pages=307–316 |doi=10.1016/j.euroneuro.2017.12.004 |language=en |issn=0924-977X}}</ref>

They can also get modulated by input from the environment and hormones released from other parts of the organism, which could be influenced more or less directly by neurons. This also applies to neurotrophins such as BDNF. The gut microbiome is also connected with the brain.

它们也可以通过环境的输入和生物体其他部分释放的激素进行调节，这些激素或多或少会受到神经元的直接影响。这也适用于神经营养因子，如 BDNF。肠道微生物组也与大脑相连。

==Mechanisms for propagating action potentials==
In 1937 [[John Zachary Young]] suggested that the [[squid giant axon]] could be used to study neuronal electrical properties.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Milestones in Neuroscience Research |url = http://faculty.washington.edu/chudler/hist.html |work = Neuroscience for Kids |access-date = 2009-06-20}}</ref> It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the [[membrane potential]].

In 1937 John Zachary Young suggested that the squid giant axon could be used to study neuronal electrical properties. It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the membrane potential.

在1937年 John Zachary Young 提出，乌贼巨大神经轴可以用来研究神经元的电学特性。它比人类神经元大，但类似于人类神经元，使它更容易研究。通过在乌贼巨大的轴突上插入电极，我们可以精确地测量膜电位。

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate [[subthreshold membrane potential oscillations]]. These signals are generated and propagated by charge-carrying [[ions]] including sodium (Na+), potassium (K+), chloride (Cl−), and [[Calcium signaling|calcium (Ca2+)]].

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate subthreshold membrane potential oscillations. These signals are generated and propagated by charge-carrying ions including sodium (Na+), potassium (K+), chloride (Cl−), and calcium (Ca2+).

轴突和胞体的细胞膜包含电压门控离子通道，使神经元能够产生和传播电信号(动作电位)。一些神经元也会产生阈下膜电位振荡。这些信号是由钠离子(Na +)、钾离子(k +)、氯离子(Cl -)和钙离子(Ca 2 + )产生和传播的。

Several stimuli can activate a neuron leading to electrical activity, including [[Mechanoreceptor|pressure]], stretch, chemical transmitters, and changes of the electric potential across the cell membrane.<ref>{{cite web|first1=Joe |last1=Patlak |first2=Ray |last2=Gibbons | name-list-style = vanc |title=Electrical Activity of Nerves |url=http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |work=Action Potentials in Nerve Cells |date=2000-11-01 |access-date=2009-06-20 |url-status=dead |archive-url=https://web.archive.org/web/20090827220335/http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |archive-date=August 27, 2009 }}</ref> Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.<ref name="Harris-Warrick">{{cite journal |last1=Harris-Warrick |first1=RM |title=Neuromodulation and flexibility in Central Pattern Generator networks. |journal=Current Opinion in Neurobiology |date=October 2011 |volume=21 |issue=5 |pages=685–92 |doi=10.1016/j.conb.2011.05.011 |pmid=21646013|pmc=3171584 }}</ref>

Several stimuli can activate a neuron leading to electrical activity, including pressure, stretch, chemical transmitters, and changes of the electric potential across the cell membrane. Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.

几个刺激可以激活一个神经元，导致电活动，包括压力，伸展，化学传递物，和电势的变化跨越细胞膜。刺激引起细胞膜上特定的离子通道打开，导致离子流通过细胞膜，改变膜电位。神经元必须保持特定的电特性，这些特性决定了它们的神经元类型。

Thin neurons and axons require less [[metabolism|metabolic]] expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of [[myelin]] around their axons. The sheaths are formed by [[glia]]l cells: [[oligodendrocyte]]s in the central nervous system and [[Schwann cell]]s in the peripheral nervous system. The sheath enables action potentials to travel [[saltatory conduction|faster]] than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed [[node of Ranvier|nodes of Ranvier]], which contain a high density of voltage-gated ion channels. [[Multiple sclerosis]] is a neurological disorder that results from demyelination of axons in the central nervous system.

Thin neurons and axons require less metabolic expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of myelin around their axons. The sheaths are formed by glial cells: oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. The sheath enables action potentials to travel faster than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed nodes of Ranvier, which contain a high density of voltage-gated ion channels. Multiple sclerosis is a neurological disorder that results from demyelination of axons in the central nervous system.

较薄的神经元和轴突产生和携带动作电位所需的代谢费用较少，但较厚的轴突传递冲动的速度更快。为了在保持快速传导的同时尽量减少代谢费用，许多神经元的轴突周围有绝缘的髓鞘。这些鞘由胶质细胞组成: 中枢神经系统的少突胶质细胞和周围神经系统的雪旺细胞。鞘使动作电位的传递速度快于相同直径的无髓鞘轴突，同时使用更少的能量。周围神经中的髓鞘通常沿轴突分为约1毫米长的部分，其间穿插着未鞘的郎飞结，其中含有高密度的电压门控离子通道。多发性硬化症是由中枢神经系统轴突脱髓鞘而引起的神经系统疾病。

Some neurons do not generate action potentials, but instead generate a [[graded potential|graded electrical signal]], which in turn causes graded neurotransmitter release. Such [[non-spiking neurons]] tend to be sensory neurons or interneurons, because they cannot carry signals long distances.

Some neurons do not generate action potentials, but instead generate a graded electrical signal, which in turn causes graded neurotransmitter release. Such non-spiking neurons tend to be sensory neurons or interneurons, because they cannot carry signals long distances.

有些神经元不产生动作电位，而是产生一个分级的电信号，这反过来又导致分级的神经递质释放。这种非脉冲神经元往往是感觉神经元或中间神经元，因为他们不能携带信号长距离。

==Neural coding==
[[Neural coding]] is concerned with how sensory and other information is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the [[Stimulus (physiology)|stimulus]] and the individual or [[Neural ensemble|ensemble]] neuronal responses, and the relationships among the electrical activities of the neurons within the ensemble.<ref name="Brown">{{cite journal | vauthors = Brown EN, Kass RE, Mitra PP | title = Multiple neural spike train data analysis: state-of-the-art and future challenges | journal = Nature Neuroscience | volume = 7 | issue = 5 | pages = 456–61 | date = May 2004 | pmid = 15114358 | doi = 10.1038/nn1228 | s2cid = 562815 }}</ref> It is thought that neurons can encode both [[Digital data|digital]] and [[analog signal|analog]] information.<ref>{{cite book | vauthors = Thorpe SJ |chapter=Spike arrival times: A highly efficient coding scheme for neural networks |chapter-url= http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf |pages= 91–94 |title=Parallel processing in neural systems and computers| veditors = Eckmiller R, Hartmann G, Hauske G |date=1990|publisher=North-Holland|isbn=9780444883902 |url={{google books |plainurl=y |id=boBqAAAAMAAJ}}|language=en|archive-url=https://web.archive.org/web/20120215151304/http://pop.cerco.ups-tlse.fr/fr_vers/documents/thorpe_sj_90_91.pdf|archive-date=2012-02-15}}</ref>

Neural coding is concerned with how sensory and other information is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the stimulus and the individual or ensemble neuronal responses, and the relationships among the electrical activities of the neurons within the ensemble. It is thought that neurons can encode both digital and analog information.

神经编码研究的是感觉和其他信息在大脑中如何通过神经元来表达。研究神经编码的主要目的是描述刺激与个体或整体神经元反应之间的关系，以及整体神经元电活动之间的关系。人们认为神经元可以同时编码数字和模拟信息。

==All-or-none principle==
[[File:All-or-none_law_en.svg|thumb|318x318px|As long as the stimulus reaches the threshold, the full response would be given. Larger stimulus does not result in a larger response, vice versa.<ref name=":0">{{Cite book|title=Biological psychology|last=Kalat, James W|year=2016|isbn=9781305105409|edition=12|location=Australia|oclc=898154491}}</ref>{{Rp|31}}]]
{{Main|All-or-none law}}
The conduction of nerve impulses is an example of an [[All-or-none law|all-or-none]] response. In other words, if a neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal, but can increase firing frequency.<ref name=":0" />{{Rp|31}} Receptors respond in different ways to stimuli. Slowly adapting or [[tonic (physiology)|tonic receptors]] respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can't become "stronger" for a specific frequency.

thumb|318x318px|As long as the stimulus reaches the threshold, the full response would be given. Larger stimulus does not result in a larger response, vice versa.

The conduction of nerve impulses is an example of an all-or-none response. In other words, if a neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal, but can increase firing frequency. Receptors respond in different ways to stimuli. Slowly adapting or tonic receptors respond to steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can't become "stronger" for a specific frequency.

= = All-or-none 原理 = 拇指 | 318x318px | 只要刺激达到阈值，就会给出完整的反应。更大的刺激不会导致更大的反应，反之亦然。神经冲动的传导就是“全有或全无”反应的一个例子。换句话说，如果一个神经元有任何反应，那么它必须完全有反应。更强烈的刺激，比如更清晰的图像/更响亮的声音，不会产生更强烈的信号，但会增加射频。受体对刺激有不同的反应。缓慢适应或紧张受体对稳定的刺激作出反应，产生稳定的放电频率。紧张性受体对刺激强度增加的反应通常是通过增加发射频率来实现的，通常是作为刺激每秒对冲动的幂函数。这可以比作光的固有属性，即特定频率(颜色)的强度越大，需要的光子就越多，因为光子在特定频率下不能变得“更强”。

Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with steady stimulus; examples include [[Human skin|skin]] which, when touched causes neurons to fire, but if the object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function.

Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with steady stimulus; examples include skin which, when touched causes neurons to fire, but if the object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function.

其他受体类型包括快速适应或相位受体，在稳定的刺激下，神经活动减少或停止; 例如皮肤，当接触时会导致神经元活动，但如果物体保持平衡的压力，神经元停止活动。对压力和振动有反应的皮肤和肌肉的神经元有过滤的辅助结构来帮助它们的功能。

The [[pacinian corpuscle]] is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus is transferred to the axon, which fires. If the pressure is steady, stimulus ends; thus, typically these neurons respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of a number of other neurons.<ref>{{cite book | last1 = Eckert | first1 = Roger | last2 = Randall | first2 = David | name-list-style = vanc | title = Animal physiology: mechanisms and adaptations | year = 1983 | publisher = W.H. Freeman | location = San Francisco | isbn = 978-0-7167-1423-1 | page = [https://archive.org/details/animalphysiology0000ecke/page/239 239] | url = https://archive.org/details/animalphysiology0000ecke/page/239 }}</ref>

The pacinian corpuscle is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus is transferred to the axon, which fires. If the pressure is steady, stimulus ends; thus, typically these neurons respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of a number of other neurons.

太平洋小体就是这样一种构造。它有像洋葱一样的同心层，在轴突末端周围形成。当施加压力使小体发生变形时，机械刺激转移到轴突上，轴突就会发射信号。如果压力是稳定的，刺激结束; 因此，典型的这些神经元在初始变形期间和压力消除时会作出短暂的去极化反应，这导致小体再次改变形状。其他类型的适应在扩展其他神经元的功能方面也很重要。

==Etymology and spelling==

==Etymology and spelling==

= = 词源和拼写 = =

The German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] introduced the term ''neuron'' in 1891,<ref name="finger"/> based on the [[Greek language|ancient Greek]] νεῦρον ''neuron'' 'sinew, cord, nerve'.<ref name="oed">''[[Oxford English Dictionary]]'', 3rd edition, 2003, ''s.v.''</ref>

The German anatomist Heinrich Wilhelm Waldeyer introduced the term neuron in 1891, based on the ancient Greek νεῦρον neuron 'sinew, cord, nerve'.Oxford English Dictionary, 3rd edition, 2003, s.v.

1891年，德国解剖学家海因里希 · 威廉 · 沃德耶根据古希腊人的神经元肌腱、脊髓和神经，提出了神经元一词。牛津英语词典，第三版，2003，s.v。

The word was adopted in French with the spelling ''neurone''. That spelling was also used by many writers in English,<ref name="mehta">{{cite journal | vauthors = Mehta AR, Mehta PR, Anderson SP, MacKinnon BL, Compston A | title = Grey Matter Etymology and the neuron(e) | journal = Brain | volume = 143 | issue = 1 | pages = 374–379 | date = January 2020 | pmid = 31844876 | pmc = 6935745 | doi = 10.1093/brain/awz367 | url = }}</ref> but has now become rare in American usage and uncommon in British usage.<ref name="ngram">{{cite web |title=Google Books Ngram Viewer |url=https://books.google.com/ngrams/graph?content=neuron%2Cneurone&year_start=1900&year_end=2008&case_insensitive=on&corpus=15&smoothing=3&direct_url=t4%3B%2Cneuron%3B%2Cc0%3B%2Cs0%3B%3Bneuron%3B%2Cc0%3B%3BNeuron%3B%2Cc0%3B%3BNEURON%3B%2Cc0%3B.t4%3B%2Cneurone%3B%2Cc0%3B%2Cs0%3B%3Bneurone%3B%2Cc0%3B%3BNeurone%3B%2Cc0%3B%3BNEURONE%3B%2Cc0 |website=books.google.com |access-date=19 December 2020 |language=en}}</ref><ref name="oed"/>

The word was adopted in French with the spelling neurone. That spelling was also used by many writers in English, but has now become rare in American usage and uncommon in British usage.

这个词在法语中采用了 neurone 的拼法。这种拼写也被许多英语作家使用，但是现在在美国已经很少见了，在英国也很少见。

==History==
{{Further|History of neuroscience}}
[[File:Golgi Hippocampus.jpg|left|thumb|Drawing by Camillo Golgi of a [[hippocampus]] stained using the [[silver nitrate]] method]]
[[File:Purkinje cell by Cajal.png|thumb|Drawing of a Purkinje cell in the [[cerebellar cortex]] done by Santiago Ramón y Cajal, demonstrating the ability of Golgi's staining method to reveal fine detail]]
The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist [[Santiago Ramón y Cajal]].<ref name="López-Muñoz">{{cite journal | vauthors = López-Muñoz F, Boya J, Alamo C | title = Neuron theory, the cornerstone of neuroscience, on the centenary of the Nobel Prize award to Santiago Ramón y Cajal | journal = Brain Research Bulletin | volume = 70 | issue = 4–6 | pages = 391–405 | date = October 2006 | pmid = 17027775 | doi = 10.1016/j.brainresbull.2006.07.010 | s2cid = 11273256 }}</ref>

The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist Santiago Ramón y Cajal.

神经元作为神经系统主要功能单位的地位在19世纪晚期通过西班牙解剖学家圣地亚哥·拉蒙-卡哈尔的工作首次得到确认。

To make the structure of individual neurons visible, [[Santiago Ramón y Cajal|Ramón y Cajal]] improved a [[Golgi's method|silver staining process]] that had been developed by [[Camillo Golgi]].<ref name="López-Muñoz" /> The improved process involves a technique called "double impregnation" and is still in use.

To make the structure of individual neurons visible, Ramón y Cajal improved a silver staining process that had been developed by Camillo Golgi. The improved process involves a technique called "double impregnation" and is still in use.

为了使单个神经元的结构可见，拉蒙 · 卡哈尔改进了卡米洛 · 高尔基发明的银染方法。改进后的工艺采用了一种称为“双浸渍”的技术，目前仍在使用。

In 1888 Ramón y Cajal published a paper about the bird cerebellum. In this paper, he stated that he could not find evidence for [[anastomosis]] between axons and dendrites and called each nervous element "an absolutely autonomous canton."<ref name="López-Muñoz" /><ref name="finger">{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=Ramon y Cajal's first paper on the Golgi stain was on the bird cerebellum, and it appeared in the ''Revista''<nowiki> in 1888. He acknowledged that he found the nerve fibers to be very intricate, but stated that he could find no evidence for either axons or dendrites undergoing anastomosis and forming nets. He called each nervous element 'an absolutely autonomous canton.'</nowiki>}}</ref> This became known as the [[neuron doctrine]], one of the central tenets of modern [[neuroscience]].<ref name="López-Muñoz" />

In 1888 Ramón y Cajal published a paper about the bird cerebellum. In this paper, he stated that he could not find evidence for anastomosis between axons and dendrites and called each nervous element "an absolutely autonomous canton." This became known as the neuron doctrine, one of the central tenets of modern neuroscience.

1888年，拉蒙和卡哈尔发表了一篇关于鸟类小脑的论文。在这篇论文中，他说他找不到轴突和树突之间吻合的证据，并称每一个神经元为“一个绝对独立的广州”这就是众所周知的神经元学说，现代神经科学的核心原则之一。

In 1891, the German anatomist [[Heinrich Wilhelm Gottfried von Waldeyer-Hartz|Heinrich Wilhelm Waldeyer]] wrote a highly influential review of the neuron doctrine in which he introduced the term ''neuron'' to describe the anatomical and physiological unit of the nervous system.<ref>{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|url=https://www.google.com/books/edition/_/BdRqAAAAMAAJ?hl=en&gbpv=1&pg=PA47|isbn=9780195146943|oclc=27151391|page=47 |quote=... a man who would write a highly influential review of the evidence in favor of the neuron doctrine two years later. In his paper, Waldeyer (1891), ... , wrote that nerve cells terminate freely with end arborizations and that the 'neuron' is the anatomical and physiological unit of the nervous system. The word 'neuron' was born this way.}}</ref><ref>{{cite web|url=http://www.whonamedit.com/doctor.cfm/1846.html|title=Whonamedit - dictionary of medical eponyms|website=www.whonamedit.com|quote=Today, Wilhelm von Waldeyer-Hartz is remembered as the founder of the neurone theory, coining the term "neurone" to describe the cellular function unit of the nervous system and enunciating and clarifying that concept in 1891.}}</ref>

In 1891, the German anatomist Heinrich Wilhelm Waldeyer wrote a highly influential review of the neuron doctrine in which he introduced the term neuron to describe the anatomical and physiological unit of the nervous system.

1891年，德国解剖学家海因里希 · 威廉 · 沃德耶对神经元学说写了一篇极具影响力的评论，其中他引入了神经元这一术语来描述神经系统的解剖学和生理学单位。

The silver impregnation stains are a useful method for [[Neuroanatomy|neuroanatomical]] investigations because, for reasons unknown, it stains only a small percentage of cells in a tissue, exposing the complete micro structure of individual neurons without much overlap from other cells.<ref name="Grant">{{cite journal | vauthors = Grant G | title = How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal | journal = Brain Research Reviews | volume = 55 | issue = 2 | pages = 490–8 | date = October 2007 | pmid = 17306375 | doi = 10.1016/j.brainresrev.2006.11.004 | s2cid = 24331507 }}</ref>

The silver impregnation stains are a useful method for neuroanatomical investigations because, for reasons unknown, it stains only a small percentage of cells in a tissue, exposing the complete micro structure of individual neurons without much overlap from other cells.

银染色法是神经解剖学研究的有效方法，因为不知道什么原因，它只染色组织中的一小部分细胞，暴露出单个神经元的完整微观结构，与其他细胞没有太多重叠。

===Neuron doctrine===
[[File:PurkinjeCell.jpg|thumb|Drawing of neurons in the pigeon [[cerebellum]], by Spanish neuroscientist [[Santiago Ramón y Cajal]] in 1899. (A) denotes [[Purkinje cell]]s and (B) denotes [[granule cells]], both of which are multipolar.]]
The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramón y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in a meshwork), acting as metabolically distinct units.

The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system. The theory was put forward by Santiago Ramón y Cajal in the late 19th century. It held that neurons are discrete cells (not connected in a meshwork), acting as metabolically distinct units.

神经元学说认为神经元是神经系统的基本结构和功能单位。这个理论是圣地亚哥·拉蒙-卡哈尔在19世纪末提出的。它认为，神经元是离散的细胞(不连接在网) ，作为代谢不同的单位。

Later discoveries yielded refinements to the doctrine. For example, [[Neuroglia|glial cells]], which are non-neuronal, play an essential role in information processing.<ref>{{cite journal | vauthors = Witcher MR, Kirov SA, Harris KM | title = Plasticity of perisynaptic astroglia during synaptogenesis in the mature rat hippocampus | journal = Glia | volume = 55 | issue = 1 | pages = 13–23 | date = January 2007 | pmid = 17001633 | doi = 10.1002/glia.20415 | citeseerx = 10.1.1.598.7002 | s2cid = 10664003 }}</ref> Also, electrical synapses are more common than previously thought,<ref>{{cite journal | vauthors = Connors BW, Long MA | title = Electrical synapses in the mammalian brain | journal = Annual Review of Neuroscience | volume = 27 | issue = 1 | pages = 393–418 | year = 2004 | pmid = 15217338 | doi = 10.1146/annurev.neuro.26.041002.131128 | url = https://zenodo.org/record/894386 }}</ref> comprising direct, cytoplasmic connections between neurons. In fact, neurons can form even tighter couplings: the squid giant axon arises from the fusion of multiple axons.<ref>{{cite journal | vauthors = Guillery RW | title = Observations of synaptic structures: origins of the neuron doctrine and its current status | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 360 | issue = 1458 | pages = 1281–307 | date = June 2005 | pmid = 16147523 | pmc = 1569502 | doi = 10.1098/rstb.2003.1459 }}</ref>

Later discoveries yielded refinements to the doctrine. For example, glial cells, which are non-neuronal, play an essential role in information processing. Also, electrical synapses are more common than previously thought, comprising direct, cytoplasmic connections between neurons. In fact, neurons can form even tighter couplings: the squid giant axon arises from the fusion of multiple axons.

后来的发现对这一学说进行了改进。例如，神经胶质细胞是非神经元细胞，在信息处理中起着重要作用。此外，电突触比以前认为的更常见，包括神经元之间的直接细胞质连接。事实上，神经元之间可以形成更紧密的联结: 乌贼巨大神经轴神经元来自于多个轴突的融合。

Ramón y Cajal also postulated the Law of Dynamic Polarization, which states that a neuron receives signals at its dendrites and cell body and transmits them, as action potentials, along the axon in one direction: away from the cell body.<ref name="sabb">{{cite journal | vauthors = Sabbatini RM | date = April–July 2003 | url = http://www.cerebromente.org.br/n17/history/neurons3_i.htm | title = Neurons and Synapses: The History of Its Discovery | journal = Brain & Mind Magazine | pages = 17 }}</ref> The Law of Dynamic Polarization has important exceptions; dendrites can serve as synaptic output sites of neurons<ref>{{cite journal | vauthors = Djurisic M, Antic S, Chen WR, Zecevic D | title = Voltage imaging from dendrites of mitral cells: EPSP attenuation and spike trigger zones | journal = The Journal of Neuroscience | volume = 24 | issue = 30 | pages = 6703–14 | date = July 2004 | pmid = 15282273 | pmc = 6729725 | doi = 10.1523/JNEUROSCI.0307-04.2004 | hdl = 1912/2958 }}
</ref> and axons can receive synaptic inputs.<ref>{{cite journal | vauthors = Cochilla AJ, Alford S | title = Glutamate receptor-mediated synaptic excitation in axons of the lamprey | journal = The Journal of Physiology | volume = 499 | issue = Pt 2 | pages = 443–57 | date = March 1997 | pmid = 9080373 | pmc = 1159318 | doi = 10.1113/jphysiol.1997.sp021940 }}</ref>

Ramón y Cajal also postulated the Law of Dynamic Polarization, which states that a neuron receives signals at its dendrites and cell body and transmits them, as action potentials, along the axon in one direction: away from the cell body. The Law of Dynamic Polarization has important exceptions; dendrites can serve as synaptic output sites of neurons
and axons can receive synaptic inputs.

拉蒙 · 卡哈尔还提出了动态极化定律，该定律指出，神经元在树突和细胞体处接收信号，并作为动作电位沿轴突向一个方向传递: 远离细胞体。动态极化定律有一些重要的例外，树突可以作为神经元的突触输出位点，轴突可以接收突触输入。

===Compartmental modelling of neurons===
Although neurons are often described of as "fundamental units" of the brain, they perform internal computations. Neurons integrate input within dendrites, and this complexity is lost in models that assume neurons to be a fundamental unit. Dendritic branches can be modeled as spatial compartments, whose activity is related due to passive membrane properties, but may also be different depending on input from synapses. [[Compartmental modelling of dendrites]] is especially helpful for understanding the behavior of neurons that are too small to record with electrodes, as is the case for ''Drosophila melanogaster''.<ref>{{cite journal | vauthors = Gouwens NW, Wilson RI | title = Signal propagation in Drosophila central neurons | journal = Journal of Neuroscience | volume = 29 | issue = 19 | pages = 6239–6249 | year = 2009 | pmid = 19439602 | pmc = 2709801 | doi = 10.1523/jneurosci.0764-09.2009 | doi-access = free }}</ref>

Although neurons are often described of as "fundamental units" of the brain, they perform internal computations. Neurons integrate input within dendrites, and this complexity is lost in models that assume neurons to be a fundamental unit. Dendritic branches can be modeled as spatial compartments, whose activity is related due to passive membrane properties, but may also be different depending on input from synapses. Compartmental modelling of dendrites is especially helpful for understanding the behavior of neurons that are too small to record with electrodes, as is the case for Drosophila melanogaster.

= = = = 神经元的分室模型虽然神经元常常被描述为大脑的“基本单位”，但它们执行内部计算。神经元整合树突内的输入，这种复杂性在假定神经元是基本单位的模型中丢失了。树突状分支可以被模拟为空间隔室，其活动与被动膜特性有关，但也可能因突触输入的不同而有所不同。树突的分室模型特别有助于理解神经元的行为，因为神经元太小，不能用电极记录，就像黑腹果蝇的情况一样。

==Neurons in the brain==
The number of neurons in the brain varies dramatically from species to species.<ref name="nervenet">{{cite journal | vauthors = Williams RW, Herrup K | title = The control of neuron number | journal = Annual Review of Neuroscience | volume = 11 | issue = 1 | pages = 423–53 | year = 1988 | pmid = 3284447 | doi = 10.1146/annurev.ne.11.030188.002231 }}</ref> In a human, there are an estimated 10–20 billion neurons in the [[cerebral cortex]] and 55–70 billion neurons in the [[cerebellum]].<ref name="pmid27187682">{{cite journal | vauthors = von Bartheld CS, Bahney J, Herculano-Houzel S | title = The search for true numbers of neurons and glial cells in the human brain: A review of 150 years of cell counting | journal = The Journal of Comparative Neurology | volume = 524 | issue = 18 | pages = 3865–3895 | date = December 2016 | pmid = 27187682 | pmc = 5063692 | doi = 10.1002/cne.24040 }}</ref> By contrast, the [[nematode]] worm ''[[Caenorhabditis elegans]]'' has just 302 neurons, making it an ideal [[model organism]] as scientists have been able to map all of its neurons. The fruit fly ''[[Drosophila melanogaster]]'', a common subject in biological experiments, has around 100,000 neurons and exhibits many complex behaviors. Many properties of neurons, from the type of neurotransmitters used to ion channel composition, are maintained across species, allowing scientists to study processes occurring in more complex organisms in much simpler experimental systems.

The number of neurons in the brain varies dramatically from species to species. In a human, there are an estimated 10–20 billion neurons in the cerebral cortex and 55–70 billion neurons in the cerebellum. By contrast, the nematode worm Caenorhabditis elegans has just 302 neurons, making it an ideal model organism as scientists have been able to map all of its neurons. The fruit fly Drosophila melanogaster, a common subject in biological experiments, has around 100,000 neurons and exhibits many complex behaviors. Many properties of neurons, from the type of neurotransmitters used to ion channel composition, are maintained across species, allowing scientists to study processes occurring in more complex organisms in much simpler experimental systems.

= = 大脑中的神经元 = = 大脑中神经元的数量因物种而异。据估计，人类大脑皮层中有100-200亿个神经元，小脑中有550-700亿个神经元。相比之下，线虫秀丽隐桿线虫只有302个神经元，这使它成为一个理想的模式生物，因为科学家已经能够绘制它所有的神经元。果蝇黑腹果蝇是生物学实验中的常见实验对象，它有大约10万个神经元，表现出许多复杂的行为。神经元的许多特性，从神经递质的类型到离子通道的组成，跨物种保持，使科学家能够在更简单的实验系统中研究更复杂的生物体中发生的过程。

==Neurological disorders==
{{Main|Neurology}}
{{More citations needed|date=May 2018}}
'''[[Charcot–Marie–Tooth disease]]''' (CMT) is a heterogeneous inherited disorder of nerves ([[neuropathy]]) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs extending to the hands and arms in advanced stages. Presently incurable, this disease is one of the most common inherited neurological disorders, with 36 in 100,000 affected.<ref name=Krajewski>{{cite journal | vauthors = Krajewski KM, Lewis RA, Fuerst DR, Turansky C, Hinderer SR, Garbern J, Kamholz J, Shy ME | title = Neurological dysfunction and axonal degeneration in Charcot-Marie-Tooth disease type 1A | journal = Brain | volume = 123 | issue = 7 | pages = 1516–27 | date = July 2000 | pmid = 10869062 | doi = 10.1093/brain/123.7.1516 | doi-access = free }}</ref>

Charcot–Marie–Tooth disease (CMT) is a heterogeneous inherited disorder of nerves (neuropathy) that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs extending to the hands and arms in advanced stages. Presently incurable, this disease is one of the most common inherited neurological disorders, with 36 in 100,000 affected.

神经系统疾病腓骨肌萎缩症(腓骨肌萎缩症)是一种异质性遗传性神经系统疾病(神经病) ，即肌肉组织和触觉的拥有属性丧失，主要发生在晚期延伸到手和手臂的脚和腿部。目前无法治愈，这种疾病是最常见的遗传性神经系统疾病之一，每10万人中就有36人患病。

'''[[Alzheimer's disease]]''' (AD), also known simply as ''Alzheimer's'', is a [[neurodegenerative disease]] characterized by progressive [[cognitive]] deterioration, together with declining activities of daily living and [[neuropsychiatric]] symptoms or behavioral changes.<ref name="nihstages">{{cite web|title=About Alzheimer's Disease: Symptoms|url=http://www.nia.nih.gov/alzheimers/topics/symptoms|publisher=National Institute on Aging|access-date=28 December 2011|url-status=live|archive-url=https://web.archive.org/web/20120115201854/http://www.nia.nih.gov/alzheimers/topics/symptoms|archive-date=15 January 2012|df=dmy-all}}</ref> The most striking early symptom is loss of short-term memory ([[amnesia]]), which usually manifests as minor forgetfulness that becomes steadily more pronounced with illness progression, with relative preservation of older memories. As the disorder progresses, cognitive (intellectual) impairment extends to the domains of language ([[aphasia]]), skilled movements ([[apraxia]]), and recognition ([[agnosia]]), and functions such as decision-making and planning become impaired.<ref name="BMJ2009">{{cite journal | vauthors = Burns A, Iliffe S | title = Alzheimer's disease | journal = BMJ | volume = 338 | pages = b158 | date = February 2009 | pmid = 19196745 | doi = 10.1136/bmj.b158 | s2cid = 8570146 | url = https://semanticscholar.org/paper/0fccf0616b35e3bb427c3783a44777e4dc228713 }}</ref><ref name=NEJM2010>{{cite journal | vauthors = Querfurth HW, LaFerla FM | title = Alzheimer's disease | journal = The New England Journal of Medicine | volume = 362 | issue = 4 | pages = 329–44 | date = January 2010 | pmid = 20107219 | doi = 10.1056/NEJMra0909142 | s2cid = 205115756 | url = https://semanticscholar.org/paper/7bc445c5ddf7869b9f71a5390ff9e9e992533ee3 }}</ref>

Alzheimer's disease (AD), also known simply as Alzheimer's, is a neurodegenerative disease characterized by progressive cognitive deterioration, together with declining activities of daily living and neuropsychiatric symptoms or behavioral changes. The most striking early symptom is loss of short-term memory (amnesia), which usually manifests as minor forgetfulness that becomes steadily more pronounced with illness progression, with relative preservation of older memories. As the disorder progresses, cognitive (intellectual) impairment extends to the domains of language (aphasia), skilled movements (apraxia), and recognition (agnosia), and functions such as decision-making and planning become impaired.

阿尔茨海默氏症，也简称为阿尔茨海默氏症，是一种神经退行性疾病/拥有属性的认知退化，伴随着日常生活能力下降和神经精神症状或行为改变。最显著的早期症状是短期记忆的丧失(遗忘症) ，通常表现为轻微的健忘，随着疾病的进展，这种健忘逐渐变得更加明显，而较老的记忆相对保留。随着病情的发展，认知(智力)障碍会扩展到语言(失语症)、技能动作(失认症)和认知(失认症)等领域，决策和计划等功能也会受到损害。

'''[[Parkinson's disease]]''' (PD), also known as ''Parkinson disease'', is a degenerative disorder of the central nervous system that often impairs motor skills and speech.<ref name=NIH2016>{{cite web|title=Parkinson's Disease Information Page|url=https://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|website=NINDS|access-date=18 July 2016|date=30 June 2016|url-status=live|archive-url=https://web.archive.org/web/20170104201403/http://www.ninds.nih.gov/Disorders/All-Disorders/Parkinsons-Disease-Information-Page|archive-date=4 January 2017|df=dmy-all}}</ref> Parkinson's disease belongs to a group of conditions called [[movement disorders]].<ref>{{cite web | title = Movement Disorders| url = http://www.neuromodulation.com/movement-disorders | work = The International Neuromodulation Society }}</ref> It is characterized by muscle rigidity, [[tremor]], a slowing of physical movement ([[bradykinesia]]), and in extreme cases, a loss of physical movement ([[akinesia]]). The primary symptoms are the results of decreased stimulation of the [[motor cortex]] by the [[basal ganglia]], normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level [[cognitive dysfunction]] and subtle language problems. PD is both chronic and progressive.

Parkinson's disease (PD), also known as Parkinson disease, is a degenerative disorder of the central nervous system that often impairs motor skills and speech. Parkinson's disease belongs to a group of conditions called movement disorders. It is characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia), and in extreme cases, a loss of physical movement (akinesia). The primary symptoms are the results of decreased stimulation of the motor cortex by the basal ganglia, normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level cognitive dysfunction and subtle language problems. PD is both chronic and progressive.

帕金森氏病，又称帕金森氏症，是一种中枢神经系统退行性疾病，通常会损害运动技能和语言能力。帕金森氏病属于一组被称为运动障碍的疾病。这是拥有属性肌肉僵硬，震颤，身体运动减缓(运动迟缓) ，在极端情况下，身体运动丧失(运动不能)。主要症状是基底神经节对运动皮层刺激减少的结果，通常是由大脑多巴胺能神经元产生的多巴胺的形成和作用不足引起的。次要症状可能包括高度认知功能障碍和微妙的语言问题。帕金森病既是慢性的，也是进行性的。

'''[[Myasthenia gravis]]''' is a neuromuscular disease leading to fluctuating [[muscle weakness]] and fatigability during simple activities. Weakness is typically caused by circulating [[antibodies]] that block [[acetylcholine receptors]] at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with [[immunosuppressants]], [[cholinesterase]] inhibitors and, in selected cases, [[thymectomy]].

Myasthenia gravis is a neuromuscular disease leading to fluctuating muscle weakness and fatigability during simple activities. Weakness is typically caused by circulating antibodies that block acetylcholine receptors at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with immunosuppressants, cholinesterase inhibitors and, in selected cases, thymectomy.

重症肌无力是一种导致简单活动时肌肉无力和疲劳波动的神经肌肉疾病。弱点通常是由于循环抗体阻断突触后神经肌肉接点的乙酰胆碱受体，抑制神经递质乙酰胆碱的刺激作用。用免疫抑制剂、胆碱酯酶抑制剂治疗重症肌无力，并在选定的病例中行胸腺切除术。

===Demyelination===
{{Further|Demyelinating disease}}
[[File:Guillain-barré syndrome - Nerve Damage.gif|thumb|Guillain–Barré syndrome – demyelination]]
[[Demyelination]] is the act of demyelinating, or the loss of the myelin sheath insulating the nerves. When myelin degrades, conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. This leads to certain neurodegenerative disorders like [[multiple sclerosis]] and [[chronic inflammatory demyelinating polyneuropathy]].

thumb|Guillain–Barré syndrome – demyelination
Demyelination is the act of demyelinating, or the loss of the myelin sheath insulating the nerves. When myelin degrades, conduction of signals along the nerve can be impaired or lost, and the nerve eventually withers. This leads to certain neurodegenerative disorders like multiple sclerosis and chronic inflammatory demyelinating polyneuropathy.

脱髓鞘病变脱髓鞘病变脱髓鞘病变脱髓鞘病变是一种脱髓鞘的行为，即髓鞘的丧失使神经绝缘。当髓磷脂退化时，沿着神经传导的信号可能受损或丢失，最终导致神经萎缩。这会导致某些神经退行性疾病，如多发性硬化症和慢性炎症性脱髓鞘性多发性神经病。

===Axonal degeneration===
Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration, which is the rapid separation of the proximal and distal ends, occurring within 30 minutes of injury. Degeneration follows with swelling of the [[axolemma]], and eventually leads to bead-like formation. Granular disintegration of the axonal [[cytoskeleton]] and inner [[organelle]]s occurs after axolemma degradation. Early changes include accumulation of [[mitochondria]] in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The disintegration is dependent on [[ubiquitin]] and [[calpain]] [[proteases]] (caused by the influx of calcium ion), suggesting that axonal degeneration is an active process that produces complete fragmentation. The process takes about roughly 24 hours in the PNS and longer in the CNS. The signaling pathways leading to axolemma degeneration are unknown.

Although most injury responses include a calcium influx signaling to promote resealing of severed parts, axonal injuries initially lead to acute axonal degeneration, which is the rapid separation of the proximal and distal ends, occurring within 30 minutes of injury. Degeneration follows with swelling of the axolemma, and eventually leads to bead-like formation. Granular disintegration of the axonal cytoskeleton and inner organelles occurs after axolemma degradation. Early changes include accumulation of mitochondria in the paranodal regions at the site of injury. Endoplasmic reticulum degrades and mitochondria swell up and eventually disintegrate. The disintegration is dependent on ubiquitin and calpain proteases (caused by the influx of calcium ion), suggesting that axonal degeneration is an active process that produces complete fragmentation. The process takes about roughly 24 hours in the PNS and longer in the CNS. The signaling pathways leading to axolemma degeneration are unknown.

虽然大多数损伤反应包括钙离子内流信号促进断裂部分的再封闭，轴突损伤最初导致急性轴突变性，即损伤后30分钟内发生的近端和远端的快速分离。退行性变伴随腋窝肿胀，最终导致珠状形成。轴突降解后，轴突细胞骨架和内部细胞器发生颗粒解体。早期变化包括损伤部位的副结节区域线粒体积累。内质网降解，线粒体肿胀，最终解体。分化依赖于泛素和钙蛋白酶(由钙离子内流引起) ，提示轴突变性是一个活跃的过程，产生完全的分裂。这个过程在 PNS 大约需要24小时，在 CNS 则需要更长的时间。导致腋窝变性的信号通路尚不清楚。

==Neurogenesis==
{{Main|Neurogenesis}}
Neurons are born through the process of [[neurogenesis]], in which [[neural stem cell]]s divide to produce differentiated neurons. Once fully differentiated neurons are formed, they are no longer capable of undergoing [[mitosis]]. Neurogenesis primarily occurs in the embryo of most organisms.

Neurons are born through the process of neurogenesis, in which neural stem cells divide to produce differentiated neurons. Once fully differentiated neurons are formed, they are no longer capable of undergoing mitosis. Neurogenesis primarily occurs in the embryo of most organisms.

神经发生神经元是通过神经发生的过程产生的，神经干细胞在这个过程中分裂产生分化的神经元。一旦完全分化的神经元形成，它们就不能进行有丝分裂。神经发生主要发生在大多数生物体的胚胎中。

[[Adult neurogenesis]] can occur and studies of the age of human neurons suggest that this process occurs only for a minority of cells, and that the vast majority of neurons in the [[neocortex]] forms before birth and persists without replacement. The extent to which adult neurogenesis exists in humans, and its contribution to cognition are controversial, with conflicting reports published in 2018.<ref>{{cite journal | vauthors = Kempermann G, Gage FH, Aigner L, Song H, Curtis MA, Thuret S, Kuhn HG, Jessberger S, Frankland PW, Cameron HA, Gould E, Hen R, Abrous DN, Toni N, Schinder AF, Zhao X, Lucassen PJ, Frisén J | title = Human Adult Neurogenesis: Evidence and Remaining Questions | journal = Cell Stem Cell | volume = 23 | issue = 1 | pages = 25–30 | date = July 2018 | pmid = 29681514 | pmc = 6035081 | doi = 10.1016/j.stem.2018.04.004 }}</ref>

Adult neurogenesis can occur and studies of the age of human neurons suggest that this process occurs only for a minority of cells, and that the vast majority of neurons in the neocortex forms before birth and persists without replacement. The extent to which adult neurogenesis exists in humans, and its contribution to cognition are controversial, with conflicting reports published in 2018.

成年神经发生可以发生，对人类神经元年龄的研究表明，这一过程只发生在少数细胞中，而且大多数新皮层神经元在出生前形成，并且不需要替换就能持续存在。成人神经发生在人类中的存在程度及其对认知的贡献是有争议的，2018年发表的报告相互矛盾。

The body contains a variety of stem cell types that have the capacity to differentiate into neurons. Researchers found a way to transform human skin cells into nerve cells using [[transdifferentiation]], in which "cells are forced to adopt new identities".<ref name=twsX33>{{Cite journal |doi=10.1038/news.2011.328 | last = Callaway | first = Ewen |title= How to make a human neuron | journal = Nature |quote= By transforming cells from human skin into working nerve cells, researchers may have come up with a model for nervous-system diseases and perhaps even regenerative therapies based on cell transplants. The achievement, reported online today in ''Nature'', is the latest in a fast-moving field called transdifferentiation, in which cells are forced to adopt new identities. In the past year, researchers have converted connective tissue cells found in skin into heart cells, blood cells, and liver cells.
|date= 26 May 2011 }}</ref>

The body contains a variety of stem cell types that have the capacity to differentiate into neurons. Researchers found a way to transform human skin cells into nerve cells using transdifferentiation, in which "cells are forced to adopt new identities".

身体包含各种干细胞类型，有能力分化成神经元。研究人员发现了一种利用分化转移将人类皮肤细胞转化为神经细胞的方法，在这种方法中，“细胞被迫采用新的身份”。

During [[neurogenesis]] in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that populate cortical layers. [[Epigenetics|Epigenetic]] modifications play a key role in regulating [[gene expression]] in differentiating [[neural stem cells]], and are critical for cell fate determination in the developing and adult mammalian brain. Epigenetic modifications include [[DNA methylation|DNA cytosine methylation]] to form [[5-methylcytosine]] and [[DNA demethylation|5-methylcytosine demethylation]].<ref name=Wang2016>{{cite journal | vauthors = Wang Z, Tang B, He Y, Jin P | title = DNA methylation dynamics in neurogenesis | journal = Epigenomics | volume = 8 | issue = 3 | pages = 401–14 | date = March 2016 | pmid = 26950681 | pmc = 4864063 | doi = 10.2217/epi.15.119 }}</ref> These modifications are critical for cell fate determination in the developing and adult mammalian brain. [[DNA methylation|DNA cytosine methylation]] is catalyzed by [[DNA methyltransferase|DNA methyltransferases (DNMTs)]]. Methylcytosine demethylation is catalyzed in several stages by [[TET enzymes]] that carry out oxidative reactions (e.g. [[5-methylcytosine]] to [[5-hydroxymethylcytosine]]) and enzymes of the DNA [[base excision repair]] (BER) pathway.<ref name=Wang2016/>

During neurogenesis in the mammalian brain, progenitor and stem cells progress from proliferative divisions to differentiative divisions. This progression leads to the neurons and glia that populate cortical layers. Epigenetic modifications play a key role in regulating gene expression in differentiating neural stem cells, and are critical for cell fate determination in the developing and adult mammalian brain. Epigenetic modifications include DNA cytosine methylation to form 5-methylcytosine and 5-methylcytosine demethylation. These modifications are critical for cell fate determination in the developing and adult mammalian brain. DNA cytosine methylation is catalyzed by DNA methyltransferases (DNMTs). Methylcytosine demethylation is catalyzed in several stages by TET enzymes that carry out oxidative reactions (e.g. 5-methylcytosine to 5-hydroxymethylcytosine) and enzymes of the DNA base excision repair (BER) pathway.

在哺乳动物大脑的神经发生过程中，祖细胞和干细胞从增殖分裂进入分化分裂。这种进展导致了构成皮层的神经元和神经胶质。表观遗传修饰是神经干细胞分化过程中调控基因表达的重要环节，对发育中和成年哺乳动物脑细胞命运的决定具有重要意义。表观遗传修饰包括 DNA 胞嘧啶甲基化形成5-甲基胞嘧啶和5-甲基胞嘧啶去甲基化。这些修饰对于发育中和成年哺乳动物大脑中细胞命运的决定至关重要。DNA 甲基转移酶(DNA methyltransferases，DNMTs)催化 DNA 胞嘧啶甲基化。甲基胞嘧啶去甲基化在几个阶段被 TET 酶催化进行氧化反应(例如:。5-甲基胞嘧啶5-羟甲基胞嘧啶)和 DNA 碱基切除修复途径中的酶。

At different stages of mammalian nervous system development two DNA repair processes are employed in the repair of DNA double-strand breaks. These pathways are [[homologous recombination]]al repair used in proliferating neural precursor cells, and [[non-homologous end joining]] used mainly at later developmental stages<ref>{{cite journal | vauthors = Orii KE, Lee Y, Kondo N, McKinnon PJ | title = Selective utilization of nonhomologous end-joining and homologous recombination DNA repair pathways during nervous system development | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 26 | pages = 10017–22 | date = June 2006 | pmid = 16777961 | pmc = 1502498 | doi = 10.1073/pnas.0602436103 | bibcode = 2006PNAS..10310017O | doi-access = free }}</ref>

At different stages of mammalian nervous system development two DNA repair processes are employed in the repair of DNA double-strand breaks. These pathways are homologous recombinational repair used in proliferating neural precursor cells, and non-homologous end joining used mainly at later developmental stages

在哺乳动物神经系统发育的不同阶段，两种 DNA 修复过程被用于修复 DNA 双链断裂。这些途径是用于增殖的神经前体细胞的同源重组修复，而非同源性末端接合主要用于发育后期

== Nerve regeneration ==
{{Main|Neuroregeneration}}
Peripheral axons can regrow if they are severed,<ref name="Yiu_2006">{{cite journal | vauthors = Yiu G, He Z | title = Glial inhibition of CNS axon regeneration | journal = Nature Reviews. Neuroscience | volume = 7 | issue = 8 | pages = 617–27 | date = August 2006 | pmid = 16858390 | pmc = 2693386 | doi = 10.1038/nrn1956 }}</ref> but one neuron cannot be functionally replaced by one of another type ([[Llinás' law]]).<ref name="llinas2014"/>

Peripheral axons can regrow if they are severed, but one neuron cannot be functionally replaced by one of another type (Llinás' law).

= = 神经再生 = = 周围神经轴突被切断后可以再生，但是一个神经元在功能上不能被另一种神经元所取代(利纳斯定律)。

== See also ==
{{Div col|colwidth=20em}}
* [[Artificial neuron]]
* [[Bidirectional cell]]
* [[Biological neuron model]]
* [[Compartmental neuron models]]
* [[Connectome]]
* [[Dogiel cell]]
* [[List of animals by number of neurons]]
* [[List of neuroscience databases]]
* [[Neuronal galvanotropism]]
* [[Neuroplasticity]]
* [[Growth cone]]
* [[Sholl analysis]]
{{Div col end}}

* Artificial neuron
* Bidirectional cell
* Biological neuron model
* Compartmental neuron models
* Connectome
* Dogiel cell
* List of animals by number of neurons
* List of neuroscience databases
* Neuronal galvanotropism
* Neuroplasticity
* Growth cone
* Sholl analysis

生物神经元模型神经连接体 Dogiel 细胞动物名单神经元向电流性神经元可塑性神经生长锥 Sholl 分析人工神经元神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神经元向电流性神

== References ==

== References ==

= = 参考文献 = =

{{Reflist}}

== Further reading ==
{{refbegin}}
* {{cite journal | vauthors = Bullock TH, Bennett MV, Johnston D, Josephson R, Marder E, Fields RD | title = Neuroscience. The neuron doctrine, redux | journal = Science | volume = 310 | issue = 5749 | pages = 791–3 | date = November 2005 | pmid = 16272104 | doi = 10.1126/science.1114394 | s2cid = 170670241 }}
* {{Cite book | vauthors = Kandel ER, Schwartz JH, Jessell TM |year=2000 |title=Principles of Neural Science |edition=4th |publisher=McGraw-Hill |location=New York |isbn=0-8385-7701-6 }}
* {{Cite book | vauthors = Peters A, Palay SL, Webster HS |year=1991 |title=The Fine Structure of the Nervous System |edition=3rd |location=New York |publisher=Oxford University Press |isbn=0-19-506571-9 }}
* {{Cite book | vauthors = Ramón y Cajal S |year=1933 |title=Histology |edition=10th |publisher=Wood |location=Baltimore }}
* {{Cite book | vauthors = Roberts A, Bush BM |year=1981 |title=Neurones without Impulses |publisher=Cambridge University Press |location=Cambridge |isbn=0-521-29935-7 }}
* {{Cite book |title=Clinical Neuroanatomy | vauthors = Snell RS |date=2010 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-9427-5 |language=en |url=https://www.google.com/books/edition/_/ABPmvroyrD0C }}
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= = 进一步阅读 = =
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== External links ==
{{sisterlinks|d=Q43054|n=no|b=Human_Anatomy/The_Neuron|v=no|voy=no|wikt=neuron|m=no|mw=no|s=no|species=no}}
*{{Curlie|Science/Biology/Neurobiology/|Neurobiology}}
* [https://web.archive.org/web/20130425202653/http://ibro.info/ IBRO (International Brain Research Organization)]. Fostering neuroscience research especially in less well-funded countries.
* [http://NeuronBank.org NeuronBank] an online neuromics tool for cataloging neuronal types and synaptic connectivity.
* [https://web.archive.org/web/20190621124504/http://brainmaps.org/ High Resolution Neuroanatomical Images of Primate and Non-Primate Brains].
* The [[v:Topic:Neuroscience|Department of Neuroscience]] at [[v:|Wikiversity]], which presently offers two courses: [[v:Fundamentals of Neuroscience|Fundamentals of Neuroscience]] and [[v:Comparative Neuroscience|Comparative Neuroscience]].
* [https://www.neuinfo.org/mynif/search.php?q=Neuron&t=data&s=cover&b=0&r=20 NIF Search – Neuron] via the [[Neuroscience Information Framework]]
* [https://web.archive.org/web/20110813070057/http://ccdb.ucsd.edu/sand/main?event=showMPByType&typeid=0&start=1&pl=y Cell Centered Database – Neuron]
* [http://neurolex.org/wiki/Category:Neuron Complete list of neuron types] according to the Petilla convention, at [[NeuroLex]].
* [http://NeuroMorpho.org NeuroMorpho.Org] an online database of digital reconstructions of neuronal morphology.
* [https://web.archive.org/web/20111008142032/http://www.immunoportal.com/modules.php?name=gallery2&g2_view=keyalbum.KeywordAlbum&g2_keyword=Neuron Immunohistochemistry Image Gallery: Neuron]
* [https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/v/anatomy-of-a-neuron Khan Academy: Anatomy of a neuron]
* [http://www.histology-world.com/photoalbum/thumbnails.php?album=96 Neuron images]

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* IBRO (International Brain Research Organization). Fostering neuroscience research especially in less well-funded countries.
* NeuronBank an online neuromics tool for cataloging neuronal types and synaptic connectivity.
* High Resolution Neuroanatomical Images of Primate and Non-Primate Brains.
* The Department of Neuroscience at Wikiversity, which presently offers two courses: Fundamentals of Neuroscience and Comparative Neuroscience.
* NIF Search – Neuron via the Neuroscience Information Framework
* Cell Centered Database – Neuron
* Complete list of neuron types according to the Petilla convention, at NeuroLex.
* NeuroMorpho.Org an online database of digital reconstructions of neuronal morphology.
* Immunohistochemistry Image Gallery: Neuron
* Khan Academy: Anatomy of a neuron
* Neuron images

= = = 外部链接 = =
*
* IBRO (国际大脑研究组织)。促进神经科学研究，尤其是在资金不足的国家。
* NeuronBank 是一个在线神经病学工具，用于编目神经元类型和突触连接。
* 灵长类动物和非灵长类动物大脑的高分辨率神经解剖图像。
* 维基大学神经科学系，目前提供两门课程: 神经科学基础和比较神经科学。
* NIF 搜索-神经元通过神经科学信息框架
* 细胞中心数据库-神经元
* 完整的神经元类型清单根据 Petilla 公约，在 NeuroLex。
* NeuroMorpho. Org，一个神经形态学数字重建的在线数据库。
* Immunohistochemistry Image Gallery: Neuron

* Khan Academy: Anatomy of a neuron

* Neuron images

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[[Category:Neurons| ]]
[[Category:Medical terminology]]

Category:Medical terminology

类别: 医学术语

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This page was moved from [[wikipedia:en:Neuron]]. Its edit history can be viewed at [[神经元/edithistory]]</noinclude>

[[Category:待整理页面]]

用户:耿淅耀

2022-03-23T07:27:56Z

耿淅耀：创建个人主页

大家好！我叫耿淅耀，一个爱好广泛的普通人。

目前就读于华中科技大学材料学院，但有时或许更偏爱生物和能源。

第一次参加集智的读书会主题是“因果涌现”，目前则是“神经动力学模型”。

不时沉思，时常活泼，偶尔清醒，遇到真正喜欢的就不愿意撒手~

在集智的日子里，请多多指教！

若联系可加微信：gengxiyao-seven