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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.

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.

== Nervous system ==

== 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.]]

[[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}}

{{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 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.

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]].

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 [[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]].

[[File:Components of neuron.jpg|thumb|upright=1.8|Diagram of the components of a neuron]]

[[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>

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>

*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 '''[[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]].

*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.

*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.

**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.

**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"。

* 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]]

[[File:Neuron Cell Body.png|thumb|Neuron cell body]]

 

神经元细胞体

 

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.<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]]

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

thumb|Neurology Video

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

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。

 

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. [[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。

 

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 [[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]].

{{unreferenced section|date=December 2020}}

{{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 (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.

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。

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===

===Histology and internal structure===

[[File:Gyrus Dentatus 40x.jpg|thumb|250px|Golgi-stained neurons in human hippocampal tissue]]

[[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

 

= = 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]]

[[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]]

 

 

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 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。

 

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 [[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.

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.

 

==Classification==

==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: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]]]]

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

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.

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.

===Structural classification===

===Structural classification===

===Structural classification===

====Polarity====

 

====极性=====

= = = 结构分类 = = =  

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

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

Most neurons can be anatomically characterized as:

Most neurons can be anatomically characterized as:

 

*[[Unipolar neuron|Unipolar]]: single process

*[[Unipolar neuron|Unipolar]]: single process

*[[Pseudounipolar cells|Pseudounipolar]]: 1 process which then serves as both an axon and a dendrite

*[[Pseudounipolar cells|Pseudounipolar]]: 1 process which then serves as both an axon and a dendrite

*Unipolar: single process

* 单极性：单一原生质过程

*Bipolar: 1 axon and 1 dendrite

* 双极性：1个轴突和1个树突

*Multipolar: 1 axon and 2 or more dendrites

* 多极性：1个轴突和2个或更多的树突

**Golgi I: neurons with long-projecting axonal processes; examples are pyramidal cells, Purkinje cells, and anterior horn cells

** 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。

**Golgi II: neurons whose axonal process projects locally; the best example is the granule cell

** 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

*Anaxonic: where the axon cannot be distinguished from the dendrite(s)

* 无轴性：轴突与树突无法区分的神经元类型。

*Pseudounipolar: 1 process which then serves as both an axon and a dendrite

* 假单极神经元：1个原生质过程，然后既是轴突又是树突。

 

 

====Other====

====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:

*[[Basket cell]]s, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and [[cerebellum]]

*[[Basket cell]]s, interneurons that form a dense plexus of terminals around the soma of target cells, found in the cortex and [[cerebellum]]

*Spindle cells, interneurons that connect widely separated areas of the brain

*Spindle cells, interneurons that connect widely separated areas of the brain

* 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

*中型多棘神经元，纹状体中的大多数神经元

* Purkinje 细胞，小脑中的巨型神经元，一种高尔基 i 多极神经元

*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，一种高尔基 i Renshaw 细胞,神经元的两端与 α 运动神经元相连

*锥体细胞，具有三角形胞体的神经元，是高尔基I型的一种。

* 单极刷细胞、具有独特树突末端的刷状丛

*伦肖细胞，两端与α运动神经元相连的神经元

* 颗粒细胞、一种高尔基 II 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

* 前角细胞、位于脊髓

*颗粒细胞，高尔基II型神经元的一种类型

* 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

*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===

===Functional classification===

 

===功能分类===

 

= = = 功能分类 = = =

 

====Direction====

====Direction====

====Direction====

 

===方向===

= = = 方向 = = =  

*[[Afferent neuron]]s convey information from tissues and organs into the central nervous system and are also called [[sensory neurons]].

*[[Afferent neuron]]s convey information from tissues and organs into the central nervous system and are also called [[sensory neurons]].

*[[Interneuron]]s connect neurons within specific regions of the central nervous system.

*[[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.

* 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。

 

 

* 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.

 

====Action on other neurons====

====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 [[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).

 

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 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，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.

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.

 

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.<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>

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 [[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:

 

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.

*Tonic or regular spiking. Some neurons are typically constantly (tonically) active, typically firing at a constant frequency. Example: interneurons in neurostriatum.

*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>

*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.

*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。

*Phasic or bursting. Neurons that fire in bursts are called phasic.

*瞬变性或爆发性。爆发性放电的神经元被称为瞬变性的。

*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.

*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。

[[File:Neurotransmitters.jpg|thumb|Synaptic vesicles containing neurotransmitters]]

[[File:Neurotransmitters.jpg|thumb|Synaptic vesicles containing neurotransmitters]]

{{Main|Neurotransmitter}}

{{Main|Neurotransmitter}}

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

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

 

 

*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]].

*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]].

*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).

*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.

*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。

*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.

*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。

*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.

*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。

*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).

*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）。

 

 

* 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 < sup >-</sup > 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。

:#[[AMPA]] and [[Kainic acid|Kainate]] receptors function as [[Ion|cation]] channels permeable to Na⁺ cation channels mediating fast excitatory synaptic transmission.

:#[[AMPA]] and [[Kainic acid|Kainate]] receptors function as [[Ion|cation]] channels permeable to Na⁺ cation channels mediating fast excitatory synaptic transmission.

::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]].

::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.

:#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 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.

:#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。

:#Metabotropic receptors, GPCRs modulate synaptic transmission and postsynaptic excitability.

:#促代谢受体，GPCRs调节突触传递和突触后兴奋性。

::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.

::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]].

*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]].

*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.

*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.

*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。

*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.

*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。

*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.

*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。

*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.

*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。

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.<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。

{{Main|Synapse|Chemical synapse}}

{{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:Chemical synapse schema cropped.jpg|thumb|right|350px|A signal propagating down an axon to the cell body and dendrites of the next cell]]