神经生物学 2神经细胞、神经元信息传递和神经反射2
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serial synapse(串联性突触) reciprocal synapse(交互性突触)
经元膜增厚约7nm • 间隙较宽,约20~39nm,其
间有粘多糖(muco polysaccharide)和糖蛋白 ( glycoprotein )。 • 突触小体内有许多的线粒 体和囊泡(vesicles)(囊泡内 含递质),突触后膜上有 相应的受体。
At a chemical synapse, neurons transmit information across a cleft.
Synaptic Transmission(经典的突触传递)
Synapse最初是指细胞与细胞之间 相接处并传递信息的部位。 因此,广义的突触也包括了神经肌接头。 含义: A synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another cell. 组成: In many synapses, the presynaptic axon (synaptic knob) is located on another axon, but some presynaptic sites are located on a dendrite (树突) or soma (胞体) also. 结构:presynaptic membrane, synaptic cleft, postsynaptic membrane
Postsynaptic membrane (突触后膜)
•active zone(激活区) •receptor(受体)
Distinguishing Properties of Electrical and Chemical Synapses
Types of
synapse
Distance
Cytoplasmic continuity
Microstructure of Chemical Synapse
(突触的微细结构)
Presynaptic membrane (突触前膜) 三类突触小泡 (synaptic vesicles), mitochondria, 其他
Synaptic cleft(突触间隙)
宽20~40 nm, 与细胞外 液相通
(非定向突触传递)
The multiple branches are beaded with enlargements (varicosities) that are not covered by Schwann cells and contain synaptic vesicles;
In noradrenergic (去甲肾上腺素能) neurons, the varicosities are about 5m, with up to 20,000 varicosities per neuron;
or longer
Unidirectional
Non-synaptic Chemical Transmission(非突触性化学 传递 )/Non-directed Synaptic Transmission (非定向突触传递)
Varicosity
the way that the postganglionic neurons (节后 神经元) innervate (支配) the smooth muscles;
No recognizable endplates (终板) or other postsynaptic specializations (特化结构);
Non-synaptic Chemical Transmission(非突触性化 学传递 )/Non-directed Synaptic Transmission
Ultrastructural
component
Agent of transmission
Synaptic delay
Direction of transmission
Electrical 3.5 nm
Yes
Gap-junction Ion current
Virtually
Usually
channel
Classificatnal type
• Chemical synapses
release transmitters between two neurons
• Electrical synapses
electrical signals transmit between the preand postsynaptic neurons through gap junctions (缝隙连接)
Transmitter is apparently released at each varicosity, at many locations along each axon;
One neuron innervate many effector cells.
Classification of Synapses - Connection
absent
bidirectional
Chemical 20-40 nm
No
Presynaptic vesicle and active zone; postsynaptic receptors
Chemical transmitters
Significant: at least 0.3 ms; usually 1-5 ms
function
• Excitatory synapses
excites the postsynaptic neurons
• Inhibitory synapses
inhibit the postsynaptic neurons
Chemical Synapse
结构特点: • 突触前、后膜比一般的神