树突

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"Dendritic branch" redirects here. For the dendritic cell of the immune system, see Dendritic cell.

25px  此article介紹的是neuronal dendrites in biology。For other uses, see 树突 (disambiguation).

Dendrites (from Greek δένδρον déndron, "tree"), also dendrons, are branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. Electrical stimulation is transmitted onto dendrites by upstream neurons (usually via their axons) via synapses which are located at various points throughout the dendritic tree. Dendrites play a critical role in integrating these synaptic inputs and in determining the extent to which action potentials are produced by the neuron. Dendritic arborization, also known as dendritic branching, is a multi-step biological process by which neurons form new dendritic trees and branches to create new synapses. The morphology of dendrites such as branch density and grouping patterns are highly correlated to the function of the neuron. Malformation of dendrites is also tightly correlated to impaired nervous system function. Some disorders that are associated with the malformation of dendrites are autism, depression, schizophrenia, Down syndrome and anxiety.

Dendrites (from Greek δένδρον déndron, "tree"), also dendrons, are branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. Electrical stimulation is transmitted onto dendrites by upstream neurons (usually via their axons) via synapses which are located at various points throughout the dendritic tree. Dendrites play a critical role in integrating these synaptic inputs and in determining the extent to which action potentials are produced by the neuron. Dendritic arborization, also known as dendritic branching, is a multi-step biological process by which neurons form new dendritic trees and branches to create new synapses. The morphology of dendrites such as branch density and grouping patterns are highly correlated to the function of the neuron. Malformation of dendrites is also tightly correlated to impaired nervous system function. Some disorders that are associated with the malformation of dendrites are autism, depression, schizophrenia, Down syndrome and anxiety.

树突(来源于希腊语 δνδρν d é ndron，“ tree”) ，也是树突，是神经细胞的分支原生质延伸，将其他神经细胞接收到的电化学刺激传递到神经元的细胞体或胞体，树突就是从这个神经元发射出来的。电刺激由上游神经元(通常是通过它们的轴突)通过位于树突树各个点的突触传递到树突上。树突在整合这些突触输入和决定神经元产生动作电位的程度方面起着关键作用。树突树枝化，也称为树突分枝，是一个多步骤的生物过程，神经元形成新的树突和树枝，以创造新的突触。树突的形态如分支密度和分组方式与神经元的功能密切相关。树突畸形也与神经系统功能受损密切相关。与树突畸形有关的一些疾病有自闭症、抑郁症、精神分裂症、唐氏综合症和焦虑症。

Certain classes of dendrites contain small projections referred to as dendritic spines that increase receptive properties of dendrites to isolate signal specificity. Increased neural activity and the establishment of long-term potentiation at dendritic spines change the sizes, shape, and conduction. This ability for dendritic growth is thought to play a role in learning and memory formation. There can be as many as 15,000 spines per cell, each of which serves as a postsynaptic process for individual presynaptic axons. Dendritic branching can be extensive and in some cases is sufficient to receive as many as 100,000 inputs to a single neuron.

The green arrow shows the dendrites emanating from soma

Dendrites are one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being an axon. Axons can be distinguished from dendrites by several features including shape, length, and function. Dendrites often taper off in shape and are shorter, while axons tend to maintain a constant radius and be relatively long. Typically, axons transmit electrochemical signals and dendrites receive the electrochemical signals, although some types of neurons in certain species lack axons and simply transmit signals via their dendrites. Dendrites provide an enlarged surface area to receive signals from the terminal buttons of other axons, and the axon also commonly divides at its far end into many branches (telodendria) each of which ends in a nerve terminal, allowing a chemical signal to pass simultaneously to many target cells. Typically, when an electrochemical signal stimulates a neuron, it occurs at a dendrite and causes changes in the electrical potential across the neuron's plasma membrane. This change in the membrane potential will passively spread across the dendrite but becomes weaker with distance without an action potential. An action potential propagates the electrical activity along the membrane of the neuron's dendrites to the cell body and then afferently down the length of the axon to the axon terminal, where it triggers the release of neurotransmitters into the synaptic cleft. However, synapses involving dendrites can also be axodendritic, involving an axon signaling to a dendrite, or dendrodendritic, involving signaling between dendrites. An autapse is a synapse in which the axon of one neuron transmits signals to its own dendrites.

Certain classes of dendrites contain small projections referred to as dendritic spines that increase receptive properties of dendrites to isolate signal specificity. Increased neural activity and the establishment of long-term potentiation at dendritic spines change the sizes, shape, and conduction. This ability for dendritic growth is thought to play a role in learning and memory formation. There can be as many as 15,000 spines per cell, each of which serves as a postsynaptic process for individual presynaptic axons. Dendritic branching can be extensive and in some cases is sufficient to receive as many as 100,000 inputs to a single neuron. thumb|The green arrow shows the dendrites emanating from soma Dendrites are one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being an axon. Axons can be distinguished from dendrites by several features including shape, length, and function. Dendrites often taper off in shape and are shorter, while axons tend to maintain a constant radius and be relatively long. Typically, axons transmit electrochemical signals and dendrites receive the electrochemical signals, although some types of neurons in certain species lack axons and simply transmit signals via their dendrites. Dendrites provide an enlarged surface area to receive signals from the terminal buttons of other axons, and the axon also commonly divides at its far end into many branches (telodendria) each of which ends in a nerve terminal, allowing a chemical signal to pass simultaneously to many target cells. Typically, when an electrochemical signal stimulates a neuron, it occurs at a dendrite and causes changes in the electrical potential across the neuron's plasma membrane. This change in the membrane potential will passively spread across the dendrite but becomes weaker with distance without an action potential. An action potential propagates the electrical activity along the membrane of the neuron's dendrites to the cell body and then afferently down the length of the axon to the axon terminal, where it triggers the release of neurotransmitters into the synaptic cleft. However, synapses involving dendrites can also be axodendritic, involving an axon signaling to a dendrite, or dendrodendritic, involving signaling between dendrites. An autapse is a synapse in which the axon of one neuron transmits signals to its own dendrites.

某些类型的树突包含被称为树突棘的小投影，增加树突的感受性能隔离信号特异性。增加的神经活动和树突棘上长时程增强作用的建立改变了大小、形状和传导。这种树突生长的能力被认为在学习和记忆形成中起着重要作用。每个细胞可以有多达15,000个棘突，每个棘突作为单个突触前轴突的突触后过程。树突状分支可以是广泛的，在某些情况下足以接收多达100,000输入到一个神经元。绿色箭头显示从树突伸出的树突是从神经元细胞体突出的两种原生质突起之一，另一种是轴突。轴突与树突可以通过几个特征来区分，包括形状、长度和功能。树突的形状往往逐渐变细，变短，而轴突倾向于保持一个恒定的半径，并且相对较长。通常，轴突传递电化学信号，树突接收电化学信号，尽管某些种类的神经元缺乏轴突，仅仅通过树突传递信号。树突提供了一个扩大的表面区域来接收来自其他轴突末端的信号，轴突也通常在其远端分裂成许多分支(端突) ，每个分支都在一个神经末端结束，允许一种化学信号同时传递给许多目标细胞。通常，当一个电化学信号刺激一个神经元时，它发生在一个树突上，并引起神经元质膜上电位的变化。这种膜电位的变化会被动地扩散到整个枝晶，但是随着距离的增加而变弱，没有动作电位。动作电位沿着神经元树突的细胞膜传递电活动到细胞体，然后沿着轴突的长度传递到轴突终端，在那里触发神经递质的释放进入突触间隙。然而，涉及树突的突触也可以是轴突性的，涉及轴突向树突或树突发出信号，涉及树突之间的信号。自体突触是一个神经元的突触，其中一个神经元的轴突将信号传递给自己的树突。

There are three main types of neurons; multipolar, bipolar, and unipolar. Multipolar neurons, such as the one shown in the image, are composed of one axon and many dendritic trees. Pyramidal cells are multipolar cortical neurons with pyramid shaped cell bodies and large dendrites called apical dendrites that extend to the surface of the cortex. Bipolar neurons have one axon and one dendritic tree at opposing ends of the cell body. Unipolar neurons have a stalk that extends from the cell body that separates into two branches with one containing the dendrites and the other with the terminal buttons. Unipolar dendrites are used to detect sensory stimuli such as touch or temperature.

There are three main types of neurons; multipolar, bipolar, and unipolar. Multipolar neurons, such as the one shown in the image, are composed of one axon and many dendritic trees. Pyramidal cells are multipolar cortical neurons with pyramid shaped cell bodies and large dendrites called apical dendrites that extend to the surface of the cortex. Bipolar neurons have one axon and one dendritic tree at opposing ends of the cell body. Unipolar neurons have a stalk that extends from the cell body that separates into two branches with one containing the dendrites and the other with the terminal buttons. Unipolar dendrites are used to detect sensory stimuli such as touch or temperature.

神经元主要有三种类型: 多极、双极和单极。多极神经元，如图所示，由一个轴突和许多树突组成。锥体细胞是多极皮层神经元，具有锥形细胞体和延伸到皮层表面的被称为顶树突的大树突。双极神经元在细胞体的两端各有一个轴突和一个树突树。单极神经元有一根茎从细胞体延伸出来，分成两个分支，一个分支包含树突，另一个分支包含末端的按钮。单极树突被用来检测感官刺激，如触摸或温度。

History

The term dendrites was first used in 1889 by Wilhelm His to describe the number of smaller "protoplasmic processes" that were attached to a nerve cell. German anatomist Otto Friedrich Karl Deiters is generally credited with the discovery of the axon by distinguishing it from the dendrites.

The term dendrites was first used in 1889 by Wilhelm His to describe the number of smaller "protoplasmic processes" that were attached to a nerve cell. German anatomist Otto Friedrich Karl Deiters is generally credited with the discovery of the axon by distinguishing it from the dendrites.

树突这个术语最早是在1889年被威廉用来描述连接到神经细胞上的较小的“原生质突起”的数量。德国解剖学家奥托 · 弗里德里希 · 卡尔 · 戴特通过将轴突与树突区分开来，发现了轴突。

Some of the first intracellular recordings in a nervous system were made in the late 1930s by Kenneth S. Cole and Howard J. Curtis. Swiss Rüdolf Albert von Kölliker and German Robert Remak were the first to identify and characterize the axonal initial segment. Alan Hodgkin and Andrew Huxley also employed the squid giant axon (1939) and by 1952 they had obtained a full quantitative description of the ionic basis of the action potential, leading the formulation of the Hodgkin–Huxley model. Hodgkin and Huxley were awarded jointly the Nobel Prize for this work in 1963. The formulas detailing axonal conductance were extended to vertebrates in the Frankenhaeuser–Huxley equations. Louis-Antoine Ranvier was the first to describe the gaps or nodes found on axons and for this contribution these axonal features are now commonly referred to as the Nodes of Ranvier. Santiago Ramón y Cajal, a Spanish anatomist, proposed that axons were the output components of neurons. He also proposed that neurons were discrete cells that communicated with each other via specialized junctions, or spaces, between cells, now known as a synapse. Ramón y Cajal improved a silver staining process known as Golgi's method, which had been developed by his rival, Camillo Golgi.

Some of the first intracellular recordings in a nervous system were made in the late 1930s by Kenneth S. Cole and Howard J. Curtis. Swiss Rüdolf Albert von Kölliker and German Robert Remak were the first to identify and characterize the axonal initial segment. Alan Hodgkin and Andrew Huxley also employed the squid giant axon (1939) and by 1952 they had obtained a full quantitative description of the ionic basis of the action potential, leading the formulation of the Hodgkin–Huxley model. Hodgkin and Huxley were awarded jointly the Nobel Prize for this work in 1963. The formulas detailing axonal conductance were extended to vertebrates in the Frankenhaeuser–Huxley equations. Louis-Antoine Ranvier was the first to describe the gaps or nodes found on axons and for this contribution these axonal features are now commonly referred to as the Nodes of Ranvier. Santiago Ramón y Cajal, a Spanish anatomist, proposed that axons were the output components of neurons. He also proposed that neurons were discrete cells that communicated with each other via specialized junctions, or spaces, between cells, now known as a synapse. Ramón y Cajal improved a silver staining process known as Golgi's method, which had been developed by his rival, Camillo Golgi.

上世纪30年代末，肯尼斯 · s · 科尔和霍华德 · j · 柯蒂斯首次对神经系统进行了细胞内记录。瑞士的阿尔伯特·冯·科立克和德国的 Robert Remak 是第一个识别和描述轴突初始部分的人。1952年，他们获得了动作电位离子基础的完整定量描述，从而引导了 Hodgkin-Huxley 模型的形成。1963年，霍奇金和赫胥黎因这项工作共同获得了诺贝尔奖。在 Frankenhaeuser-Huxley 方程式中，细化轴突电导的公式被推广到脊椎动物。Louis-Antoine Ranvier 是第一个描述轴突间隙或节点的人，因此这些轴突特征现在通常被称为郎飞结。西班牙解剖学家圣地亚哥·拉蒙-卡哈尔提出轴突是神经元的输出组件。他还提出，神经元是离散的细胞，通过细胞之间的特殊连接或空间彼此沟通，现在称为突触。拉蒙 · 卡哈尔改进了他的竞争对手卡米洛 · 高尔基发明的高尔基染色法。

Dendrite development

During the development of dendrites, several factors can influence differentiation. These include modulation of sensory input, environmental pollutants, body temperature, and drug use. For example, rats raised in dark environments were found to have a reduced number of spines in pyramidal cells located in the primary visual cortex and a marked change in distribution of dendrite branching in layer 4 stellate cells. Experiments done in vitro and in vivo have shown that the presence of afferents and input activity per se can modulate the patterns in which dendrites differentiate.

thumb|right|277px During the development of dendrites, several factors can influence differentiation. These include modulation of sensory input, environmental pollutants, body temperature, and drug use. For example, rats raised in dark environments were found to have a reduced number of spines in pyramidal cells located in the primary visual cortex and a marked change in distribution of dendrite branching in layer 4 stellate cells. Experiments done in vitro and in vivo have shown that the presence of afferents and input activity per se can modulate the patterns in which dendrites differentiate.

= = = 树枝晶发育 = = 拇指 | 右 | 277px 在树枝晶的发育过程中，有几个因素可以影响分化。这些包括调节感觉输入，环境污染物，体温和药物使用。例如，在黑暗环境中长大的老鼠，在初级视皮层锥体细胞中的刺数量减少，在第4层星状细胞中树突分支的分布有明显的变化。体外和体内的实验表明，传入物的存在和输入活性本身可以调节树突分化的模式。

Little is known about the process by which dendrites orient themselves in vivo and are compelled to create the intricate branching pattern unique to each specific neuronal class. One theory on the mechanism of dendritic arbor development is the Synaptotropic Hypothesis. The synaptotropic hypothesis proposes that input from a presynaptic to a postsynaptic cell (and maturation of excitatory synaptic inputs) eventually can change the course of synapse formation at dendritic and axonal arbors. This synapse formation is required for the development of neuronal structure in the functioning brain. A balance between metabolic costs of dendritic elaboration and the need to cover receptive field presumably determine the size and shape of dendrites. A complex array of extracellular and intracellular cues modulates dendrite development including transcription factors, receptor-ligand interactions, various signaling pathways, local translational machinery, cytoskeletal elements, Golgi outposts and endosomes. These contribute to the organization of the dendrites on individual cell bodies and the placement of these dendrites in the neuronal circuitry. For example, it was shown that β-actin zipcode binding protein 1 (ZBP1) contributes to proper dendritic branching. Other important transcription factors involved in the morphology of dendrites include CUT, Abrupt, Collier, Spineless, ACJ6/drifter, CREST, NEUROD1, CREB, NEUROG2 etc. Secreted proteins and cell surface receptors includes neurotrophins and tyrosine kinase receptors, BMP7, Wnt/dishevelled, EPHB 1–3, Semaphorin/plexin-neuropilin, slit-robo, netrin-frazzled, reelin. Rac, CDC42 and RhoA serve as cytoskeletal regulators and the motor protein includes KIF5, dynein, LIS1. Important secretory and endocytic pathways controlling the dendritic development include DAR3 /SAR1, DAR2/Sec23, DAR6/Rab1 etc. All these molecules interplay with each other in controlling dendritic morphogenesis including the acquisition of type specific dendritic arborization, the regulation of dendrite size and the organization of dendrites emanating from different neurons.

Little is known about the process by which dendrites orient themselves in vivo and are compelled to create the intricate branching pattern unique to each specific neuronal class. One theory on the mechanism of dendritic arbor development is the Synaptotropic Hypothesis. The synaptotropic hypothesis proposes that input from a presynaptic to a postsynaptic cell (and maturation of excitatory synaptic inputs) eventually can change the course of synapse formation at dendritic and axonal arbors. This synapse formation is required for the development of neuronal structure in the functioning brain. A balance between metabolic costs of dendritic elaboration and the need to cover receptive field presumably determine the size and shape of dendrites. A complex array of extracellular and intracellular cues modulates dendrite development including transcription factors, receptor-ligand interactions, various signaling pathways, local translational machinery, cytoskeletal elements, Golgi outposts and endosomes. These contribute to the organization of the dendrites on individual cell bodies and the placement of these dendrites in the neuronal circuitry. For example, it was shown that β-actin zipcode binding protein 1 (ZBP1) contributes to proper dendritic branching. Other important transcription factors involved in the morphology of dendrites include CUT, Abrupt, Collier, Spineless, ACJ6/drifter, CREST, NEUROD1, CREB, NEUROG2 etc. Secreted proteins and cell surface receptors includes neurotrophins and tyrosine kinase receptors, BMP7, Wnt/dishevelled, EPHB 1–3, Semaphorin/plexin-neuropilin, slit-robo, netrin-frazzled, reelin. Rac, CDC42 and RhoA serve as cytoskeletal regulators and the motor protein includes KIF5, dynein, LIS1. Important secretory and endocytic pathways controlling the dendritic development include DAR3 /SAR1, DAR2/Sec23, DAR6/Rab1 etc. All these molecules interplay with each other in controlling dendritic morphogenesis including the acquisition of type specific dendritic arborization, the regulation of dendrite size and the organization of dendrites emanating from different neurons.

树突在体内自我定位并被迫创造每个特定神经元类别独有的复杂的分支模式的过程知之甚少。树枝状乔木发展机制的一个理论是突触营养假设。突触营养假设认为，突触前细胞向突触后细胞的输入(以及兴奋性突触输入的成熟)最终可以改变树突状突起和轴突状突起的突触形成过程。这种突触形成是大脑功能中神经元结构发育所必需的。树突细化的代谢成本和覆盖感受野的需要之间的平衡大概决定了树突的大小和形状。一系列复杂的细胞外和细胞内线索调节树突的发展，包括转录因子，受体-配体相互作用，各种信号通路，局部平移机制，细胞骨架元件，高尔基前哨和内涵体。这些促进了单个细胞体上树突的组织和这些树突在神经元电路中的位置。例如，研究表明 β- 肌动蛋白结构蛋白1(β-actin zipcode binding protein 1，ZBP1)有助于树突的分支。其他与树突形态有关的重要转录因子包括 CUT、 stump、 Collier、 Spineless、 ACJ6/drifter、 CREST、 NEUROD1、 CREB、 neurog2等。分泌蛋白和细胞表面受体包括神经营养因子和酪氨酸激酶受体、 BMP7、 Wnt/dishevelled、 EPHB 1-3、 Semaphorin/plexin-neuropilin、 slit-robo、 netrin-frazzled、 reelin。和 RhoA 作为细胞骨架调节剂，运动蛋白包括 KIF5，动力蛋白，LIS1。控制树突发育的重要分泌和内吞途径包括 DAR3/SAR1、 DAR2/Sec23、 DAR6/rab1等。所有这些分子在控制树突形态发生中相互作用，包括获得特定类型的树突树枝化、调节不同神经元产生的树突大小和树突的组织。

Electrical properties

The structure and branching of a neuron's dendrites, as well as the availability and variation of voltage-gated ion conductance, strongly influences how the neuron integrates the input from other neurons. This integration is both temporal, involving the summation of stimuli that arrive in rapid succession, as well as spatial, entailing the aggregation of excitatory and inhibitory inputs from separate branches.

The structure and branching of a neuron's dendrites, as well as the availability and variation of voltage-gated ion conductance, strongly influences how the neuron integrates the input from other neurons. This integration is both temporal, involving the summation of stimuli that arrive in rapid succession, as well as spatial, entailing the aggregation of excitatory and inhibitory inputs from separate branches.

神经元树突的结构和分支，以及电压门控离子电导的有效性和变化，强烈地影响着神经元如何整合来自其他神经元的输入。这种整合既是时间的，包括快速连续到达的刺激的总和，也是空间的，引起来自不同分支的兴奋性和抑制性输入的聚集。

Dendrites were once thought to merely convey electrical stimulation passively. This passive transmission means that voltage changes measured at the cell body are the result of activation of distal synapses propagating the electric signal towards the cell body without the aid of voltage-gated ion channels. Passive cable theory describes how voltage changes at a particular location on a dendrite transmit this electrical signal through a system of converging dendrite segments of different diameters, lengths, and electrical properties. Based on passive cable theory one can track how changes in a neuron's dendritic morphology impacts the membrane voltage at the cell body, and thus how variation in dendrite architectures affects the overall output characteristics of the neuron.

Dendrites were once thought to merely convey electrical stimulation passively. This passive transmission means that voltage changes measured at the cell body are the result of activation of distal synapses propagating the electric signal towards the cell body without the aid of voltage-gated ion channels. Passive cable theory describes how voltage changes at a particular location on a dendrite transmit this electrical signal through a system of converging dendrite segments of different diameters, lengths, and electrical properties. Based on passive cable theory one can track how changes in a neuron's dendritic morphology impacts the membrane voltage at the cell body, and thus how variation in dendrite architectures affects the overall output characteristics of the neuron.

树突曾经被认为只是被动地传递电刺激。这种被动传递意味着，在细胞体上测量到的电压变化是在不借助电压门控离子通道的情况下，将电信号传递到细胞体的远端突触激活的结果。无源电缆理论描述了电压如何在树枝晶的特定位置变化，通过不同直径、长度和电性能的聚合树枝晶片段系统传输这种电信号。基于被动电缆理论，人们可以追踪神经元树突形态的变化如何影响细胞体的膜电位，从而树突结构的变化如何影响神经元的整体输出特性。

Electrochemical signals are propagated by action potentials that utilize intermembrane voltage-gated ion channels to transport sodium ions, calcium ions, and potassium ions. Each ion species has its own corresponding protein channel located in the lipid bilayer of the cell membrane. The cell membrane of neurons covers the axons, cell body, dendrites, etc. The protein channels can differ between chemical species in the amount of required activation voltage and the activation duration.

Electrochemical signals are propagated by action potentials that utilize intermembrane voltage-gated ion channels to transport sodium ions, calcium ions, and potassium ions. Each ion species has its own corresponding protein channel located in the lipid bilayer of the cell membrane. The cell membrane of neurons covers the axons, cell body, dendrites, etc. The protein channels can differ between chemical species in the amount of required activation voltage and the activation duration.

利用膜间电压门控离子通道传输钠离子、钙离子和钾离子的动作电位可以传递电化学信号。每种离子在细胞膜的脂质双分子层中都有自己对应的蛋白通道。神经元的细胞膜包括轴突、胞体、树突等。蛋白质通道在所需的激活电压和激活持续时间方面在化学物种之间可能有所不同。

Action potentials in animal cells are generated by either sodium-gated or calcium-gated ion channels in the plasma membrane. These channels are closed when the membrane potential is near to, or at, the resting potential of the cell. The channels will start to open if the membrane potential increases, allowing sodium or calcium ions to flow into the cell. As more ions enter the cell, the membrane potential continues to rise. The process continues until all of the ion channels are open, causing a rapid increase in the membrane potential that then triggers the decrease in the membrane potential. The depolarizing is caused by the closing of the ion channels that prevent sodium ions from entering the neuron, and they are then actively transported out of the cell. Potassium channels are then activated, and there is an outward flow of potassium ions, returning the electrochemical gradient to the resting potential. After an action potential has occurred, there is a transient negative shift, called the afterhyperpolarization or refractory period, due to additional potassium currents. This is the mechanism that prevents an action potential from traveling back the way it just came.

Action potentials in animal cells are generated by either sodium-gated or calcium-gated ion channels in the plasma membrane. These channels are closed when the membrane potential is near to, or at, the resting potential of the cell. The channels will start to open if the membrane potential increases, allowing sodium or calcium ions to flow into the cell. As more ions enter the cell, the membrane potential continues to rise. The process continues until all of the ion channels are open, causing a rapid increase in the membrane potential that then triggers the decrease in the membrane potential. The depolarizing is caused by the closing of the ion channels that prevent sodium ions from entering the neuron, and they are then actively transported out of the cell. Potassium channels are then activated, and there is an outward flow of potassium ions, returning the electrochemical gradient to the resting potential. After an action potential has occurred, there is a transient negative shift, called the afterhyperpolarization or refractory period, due to additional potassium currents. This is the mechanism that prevents an action potential from traveling back the way it just came.

动物细胞的动作电位是由质膜上的钠门控或钙门控离子通道产生的。这些通道在膜电位接近细胞静息电位时关闭。如果膜电位增加，通道将开始打开，使钠离子或钙离子流入细胞。随着更多的离子进入细胞，膜电位会继续上升。这个过程一直持续到所有的离子通道都打开，导致膜电位的快速增加，然后触发膜电位的减少。去极化是由于阻止钠离子进入神经元的离子通道被关闭，然后钠离子被主动地运出细胞。然后激活钾离子通道，钾离子向外流动，将电化梯度返回到静息电位。在一个动作电位发生后，由于额外的钾电流，会有一个暂时的负移动，称为后超极化或不应期(性)。这种机制可以阻止动作电位回到它刚刚来的方向。

Another important feature of dendrites, endowed by their active voltage gated conductance, is their ability to send action potentials back into the dendritic arbor. Known as back-propagating action potentials, these signals depolarize the dendritic arbor and provide a crucial component toward synapse modulation and long-term potentiation. Furthermore, a train of back-propagating action potentials artificially generated at the soma can induce a calcium action potential (a dendritic spike) at the dendritic initiation zone in certain types of neurons.

Another important feature of dendrites, endowed by their active voltage gated conductance, is their ability to send action potentials back into the dendritic arbor. Known as back-propagating action potentials, these signals depolarize the dendritic arbor and provide a crucial component toward synapse modulation and long-term potentiation. Furthermore, a train of back-propagating action potentials artificially generated at the soma can induce a calcium action potential (a dendritic spike) at the dendritic initiation zone in certain types of neurons.

树突的另一个重要特征是它们的活跃电压门控电导赋予它们将动作电位送回树突乔木的能力。这些被称为反向传播动作电位的信号使树突轴去极化，并为突触调节和长时程增强作用提供了关键成分。此外，在体细胞上人工产生的一系列反向传导的动作电位可以在特定类型的神经元的树突起始区诱导钙动作电位(树突棘)。

Plasticity

Dendrites themselves appear to be capable of plastic changes during the adult life of animals, including invertebrates. Neuronal dendrites have various compartments known as functional units that are able to compute incoming stimuli. These functional units are involved in processing input and are composed of the subdomains of dendrites such as spines, branches, or groupings of branches. Therefore, plasticity that leads to changes in the dendrite structure will affect communication and processing in the cell. During development, dendrite morphology is shaped by intrinsic programs within the cell's genome and extrinsic factors such as signals from other cells. But in adult life, extrinsic signals become more influential and cause more significant changes in dendrite structure compared to intrinsic signals during development. In females, the dendritic structure can change as a result of physiological conditions induced by hormones during periods such as pregnancy, lactation, and following the estrous cycle. This is particularly visible in pyramidal cells of the CA1 region of the hippocampus, where the density of dendrites can vary up to 30%.

Dendrites themselves appear to be capable of plastic changes during the adult life of animals, including invertebrates. Neuronal dendrites have various compartments known as functional units that are able to compute incoming stimuli. These functional units are involved in processing input and are composed of the subdomains of dendrites such as spines, branches, or groupings of branches. Therefore, plasticity that leads to changes in the dendrite structure will affect communication and processing in the cell. During development, dendrite morphology is shaped by intrinsic programs within the cell's genome and extrinsic factors such as signals from other cells. But in adult life, extrinsic signals become more influential and cause more significant changes in dendrite structure compared to intrinsic signals during development. In females, the dendritic structure can change as a result of physiological conditions induced by hormones during periods such as pregnancy, lactation, and following the estrous cycle. This is particularly visible in pyramidal cells of the CA1 region of the hippocampus, where the density of dendrites can vary up to 30%.

在动物包括无脊椎动物的成年生活中，树突本身似乎能够发生可塑性变化。神经元树突有许多被称为功能单元的区域，它们能够计算传入的刺激。这些功能单元参与处理输入，并由树突的子域组成，如棘、分支或分支组。因此，引起枝晶结构变化的可塑性将影响细胞内的通讯和加工。在发育过程中，树突形态是由细胞基因组内的内在程序和外在因素(如来自其他细胞的信号)形成的。但在成人生活中，外源性信号的影响更大，与内源性信号相比，外源性信号对树突结构的影响更为显著。在女性，树枝状结构可以改变的生理条件诱导的时期，如怀孕，哺乳，以及随后的发情周期。这在海马 ca1区的锥体细胞中特别明显，在那里树突的密度可以高达30% 。

References

• Lorenzo, L. E.; Russier, M; Barbe, A; Fritschy, J. M.; Bras, H (2007). "Differential organization of gamma-aminobutyric acid type a and glycine receptors in the somatic and dendritic compartments of rat abducens motoneurons". The Journal of Comparative Neurology. 504 (2): 112–26. doi:10.1002/cne.21442. PMID 17626281. S2CID 26123520.

External links

• 模板:OklahomaHistology - "Slide 3 Spinal cord"
• Dendritic Tree - Cell Centered Database
• Stereo images of dendritic trees in Kryptopterus electroreceptor organs

• - "Slide 3 Spinal cord"
• Dendritic Tree - Cell Centered Database
• Stereo images of dendritic trees in Kryptopterus electroreceptor organs

= = = 外部链接 = = = =-”幻灯片3脊髓”

• 树突树细胞为中心的数据库
• 氪星电感器器官中树突树的立体图像

Category:Neurohistology Category:Neuroplasticity

类别: 神经组织学类别: 神经可塑性

This page was moved from wikipedia:en:Dendrite. Its edit history can be viewed at 树突/edithistory