Ch13 Synaptic Transmission in the nervous system

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=== 神经元突触的分子机制与神经肌肉接头的分子机制相似但不相同 ===
 
=== 神经元突触的分子机制与神经肌肉接头的分子机制相似但不相同 ===
 
<b>The molecular mechanisms of neuronal synapses are similar but not identical to those of the neuromuscular junction</b>
 
<b>The molecular mechanisms of neuronal synapses are similar but not identical to those of the neuromuscular junction</b>
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Chemical synapses use diffusible transmitter molecules to communicate messages between two cells. The first chemical synapse to be understood in detail was the neuromuscular junction (the nerve-muscle synapse) in vertebrate skeletal muscle, which is described in Chapter 8. In this chapter, we are concerned with the properties of the synapses that occur between neurons. We now know that all synapses share certain basic biochemical and physiological mechanisms, and thus many basic insights gained from the neuromuscular junction are also applicable to synapses in the brain. However, neuronal synapses differ from neuromuscular junctions in many important ways; they also differ widely among themselves, and it is the diverse properties of synapses that help make each part of the brain unique.
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化学突触使用可扩散的递质分子在两个细胞之间传递信息。第一个需要详细理解的化学突触是脊椎动物骨骼肌中的神经肌肉接头（神经肌肉突触），这在第 8 章中进行了描述。在本章中，我们关注神经元之间发生的突触的特性。我们现在知道所有突触都有某些基本的生化和生理机制，因此从神经肌肉接头获得的许多基本见解也适用于大脑中的突触。然而，神经元突触在许多重要方面与神经肌肉接头不同;它们之间也有很大差异，正是突触的不同特性有助于使大脑的每个部分都独一无二。
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It is useful to begin by reviewing some of the mechanisms that are common to all chemical synapses (see Figs. 8-2 and 8-3). N13-1 Synaptic transmission at chemical synapses occurs in seven steps:
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首先回顾所有化学突触共有的一些机制是有用的（见图 8-2 和 8-3）。N13-1 化学突触的突触传递分为七个步骤：
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Step 1: Neurotransmitter molecules are packaged into membranous vesicles, and the vesicles are concentrated and docked at the presynaptic terminal.
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第 1 步：神经递质分子被包装成膜囊泡，囊泡浓缩并停靠在突触前末梢。
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Step 2: The presynaptic membrane depolarizes, usually as the result of an action potential, although some synapses respond to graded variations of membrane potential (Vm).
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第 2 步：突触前膜去极化，通常是动作电位的结果，尽管一些突触对膜电位 （Vm） 的分级变化做出反应。
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Step 3: The depolarization causes voltage-gated Ca2+ channels to open and allows Ca2+ ions to flow into the terminal.
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第 3 步：去极化导致电压门控 Ca2+ 通道打开，并允许 Ca2+ 离子流入端子。
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Step 4: The resulting increase in intracellular [Ca2+] triggers fusion of vesicles with the presynaptic membrane (see pp. 219–221), and the rate of transmitter release increases ~100,000-fold above baseline. The Ca2+ dependence of fusion is conferred by neuron-specific protein components of the fusion apparatus called synaptotagmins. The actual fusion events are incredibly fast; each individual exocytosis requires only a fraction of a millisecond to be completed.
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第 4 步：细胞内 [Ca2+] 的增加触发囊泡与突触前膜的融合（参见第 219-221 页），递质释放速率比基线增加 ~100,000 倍。融合的 Ca2+ 依赖性是由融合装置的神经元特异性蛋白质成分（称为突触结合蛋白）赋予的。实际的融合事件非常快;每个单独的胞吐作用只需要几分之一毫秒即可完成。
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Step 5: The transmitter is released into the extracellular space in quantized amounts and diffuses passively across the synaptic cleft.
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第 5 步：递质以量化量释放到细胞外间隙中，并被动地扩散穿过突触间隙。
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Step 6: Some of the transmitter molecules bind to receptors in the postsynaptic membrane, and the activated receptors trigger some postsynaptic event, usually the opening of an ion channel or the activation of a G protein–coupled signal cascade.
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第 6 步：一些递质分子与突触后膜中的受体结合，激活的受体触发一些突触后事件，通常是离子通道的打开或 G 蛋白偶联信号级联的激活。
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Step 7: Transmitter molecules diffuse away from postsynaptic receptors and are eventually cleared away by continued diffusion, enzymatic degradation, or active uptake into cells. In addition, the presynaptic machinery retrieves the membrane of the exocytosed synaptic vesicle, perhaps by endocytosis from the cell surface.
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第 7 步：递质分子从突触后受体扩散出去，最终通过持续扩散、酶降解或主动摄取到细胞中清除。此外，突触前机制可能通过细胞表面的内吞作用取回胞吐作用突触囊泡的膜。
  
 
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2024年12月2日 (一) 16:43的版本

神经系统的突触传递

本页英文内容取自：经典教材医学生理学（第三版） (Medical Physiology, 3rd Edtion, Walter F Boron, published in 2016)

中文内容由 BH1RBH (Jack Tan) 粗糙翻译

蓝色 【注】 后内容为 BH1RBH (Jack Tan) 所加之注释

After meticulous study of spinal reflexes, Charles Sherrington N10-2 deduced that neurons somehow communicate information, one to the next, by a mechanism that is fundamentally different from the way that they conduct signals along their axons. Sherrington had merged his physiological conclusions with the anatomical observations (Fig. 13-1) of his contemporary, the preeminent neuroanatomist Santiago Ramón y Cajal. N10-1 Ramón y Cajal had proposed that neurons are distinct entities, fundamental units of the nervous system that are discontinuous with each other. Discontinuous neurons must nevertheless communicate, and Sherrington in 1897 proposed that the synapse, a specialized apposition between cells, mediates the signals. The word synapse implies “contiguity, not continuity” between neurons, as Ramón y Cajal himself explained it. When the fine structure of synapses was finally revealed with the electron microscope in the 1950s, the vision of Ramón y Cajal and Sherrington was amply sustained. Neurons come very close together at chemical synapses (see p. 206), but their membranes and cytoplasm remain distinct. At electrical synapses (see p. 205), which are less common than chemical synapses, the membranes remain distinct, but ions and other small solutes can diffuse through the gap junctions, a form of continuity.

在对脊髓反射进行细致的研究后，Charles Sherrington [N10-2] 推断出神经元以某种方式将信息从一个传递到另一个，这种机制与它们沿轴突传导信号的方式根本不同。Sherrington 将他的生理学结论与他同时代杰出的神经解剖学家 Santiago Ramón y Cajal 的解剖观察（图 13-1）相结合[N10-1]Ramón y Cajal 提出神经元是不同的实体，是神经系统的基本单位，彼此不连续。然而，不连续的神经元必须进行交流，Sherrington 在 1897 年提出突触，即细胞之间的特殊并置，介导信号。突触这个词意味着神经元之间的“毗连性，而不是连续性”，正如 Ramón y Cajal 本人所解释的那样。当电子显微镜最终在 1950 年代揭示突触的精细结构时，Ramón y Cajal 和 Sherrington 的愿景得到了充分的支持。神经元在化学突触处非常靠近（见第 206 页），但它们的膜和细胞质仍然不同。在电突触（见第 205 页）处，比化学突触更不常见，膜保持清晰，但离子和其他小溶质可以通过间隙连接扩散，这是一种连续性形式。

目录

1 Neuronal Synapses（神经元突触）

1.1 神经元突触的分子机制与神经肌肉接头的分子机制相似但不相同

The molecular mechanisms of neuronal synapses are similar but not identical to those of the neuromuscular junction

Chemical synapses use diffusible transmitter molecules to communicate messages between two cells. The first chemical synapse to be understood in detail was the neuromuscular junction (the nerve-muscle synapse) in vertebrate skeletal muscle, which is described in Chapter 8. In this chapter, we are concerned with the properties of the synapses that occur between neurons. We now know that all synapses share certain basic biochemical and physiological mechanisms, and thus many basic insights gained from the neuromuscular junction are also applicable to synapses in the brain. However, neuronal synapses differ from neuromuscular junctions in many important ways; they also differ widely among themselves, and it is the diverse properties of synapses that help make each part of the brain unique.

化学突触使用可扩散的递质分子在两个细胞之间传递信息。第一个需要详细理解的化学突触是脊椎动物骨骼肌中的神经肌肉接头（神经肌肉突触），这在第 8 章中进行了描述。在本章中，我们关注神经元之间发生的突触的特性。我们现在知道所有突触都有某些基本的生化和生理机制，因此从神经肌肉接头获得的许多基本见解也适用于大脑中的突触。然而，神经元突触在许多重要方面与神经肌肉接头不同;它们之间也有很大差异，正是突触的不同特性有助于使大脑的每个部分都独一无二。


It is useful to begin by reviewing some of the mechanisms that are common to all chemical synapses (see Figs. 8-2 and 8-3). N13-1 Synaptic transmission at chemical synapses occurs in seven steps:

首先回顾所有化学突触共有的一些机制是有用的（见图 8-2 和 8-3）。N13-1 化学突触的突触传递分为七个步骤：


Step 1: Neurotransmitter molecules are packaged into membranous vesicles, and the vesicles are concentrated and docked at the presynaptic terminal.

第 1 步：神经递质分子被包装成膜囊泡，囊泡浓缩并停靠在突触前末梢。

Step 2: The presynaptic membrane depolarizes, usually as the result of an action potential, although some synapses respond to graded variations of membrane potential (Vm).

第 2 步：突触前膜去极化，通常是动作电位的结果，尽管一些突触对膜电位 （Vm） 的分级变化做出反应。

Step 3: The depolarization causes voltage-gated Ca2+ channels to open and allows Ca2+ ions to flow into the terminal.

第 3 步：去极化导致电压门控 Ca2+ 通道打开，并允许 Ca2+ 离子流入端子。

Step 4: The resulting increase in intracellular [Ca2+] triggers fusion of vesicles with the presynaptic membrane (see pp. 219–221), and the rate of transmitter release increases ~100,000-fold above baseline. The Ca2+ dependence of fusion is conferred by neuron-specific protein components of the fusion apparatus called synaptotagmins. The actual fusion events are incredibly fast; each individual exocytosis requires only a fraction of a millisecond to be completed.

第 4 步：细胞内 [Ca2+] 的增加触发囊泡与突触前膜的融合（参见第 219-221 页），递质释放速率比基线增加 ~100,000 倍。融合的 Ca2+ 依赖性是由融合装置的神经元特异性蛋白质成分（称为突触结合蛋白）赋予的。实际的融合事件非常快;每个单独的胞吐作用只需要几分之一毫秒即可完成。


Step 5: The transmitter is released into the extracellular space in quantized amounts and diffuses passively across the synaptic cleft.

第 5 步：递质以量化量释放到细胞外间隙中，并被动地扩散穿过突触间隙。

Step 6: Some of the transmitter molecules bind to receptors in the postsynaptic membrane, and the activated receptors trigger some postsynaptic event, usually the opening of an ion channel or the activation of a G protein–coupled signal cascade.

第 6 步：一些递质分子与突触后膜中的受体结合，激活的受体触发一些突触后事件，通常是离子通道的打开或 G 蛋白偶联信号级联的激活。

Step 7: Transmitter molecules diffuse away from postsynaptic receptors and are eventually cleared away by continued diffusion, enzymatic degradation, or active uptake into cells. In addition, the presynaptic machinery retrieves the membrane of the exocytosed synaptic vesicle, perhaps by endocytosis from the cell surface.

第 7 步：递质分子从突触后受体扩散出去，最终通过持续扩散、酶降解或主动摄取到细胞中清除。此外，突触前机制可能通过细胞表面的内吞作用取回胞吐作用突触囊泡的膜。


1.2 突触前末梢可能接触树突、体细胞或轴突处的神经元，并且可能包含透明囊泡和致密核心颗粒

Presynaptic terminals may contact neurons at the dendrite, soma, or axon and may contain both clear vesicles and dense-core granules


1.3 突触后膜包含递质受体和许多聚集在突触后致密区的蛋白质

The postsynaptic membrane contains transmitter receptors and numerous proteins clustered in the postsynaptic density


1.4 弥散分布的神经元系统使用一些递质来调节大脑的一般兴奋性

Some transmitters are used by diffusely distributed systems of neurons to modulate the general excitability of the brain


1.5 电突触在哺乳动物神经系统中发挥着特殊功能

Electrical synapses serve specialized functions in the mammalian nervous system


2 Reference


来自“http://wiki.jackslab.org/index.php?title=Ch13_Synaptic_Transmission_in_the_nervous_system&oldid=17789”
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