Be出8枪的时Rf chaid desires witha serve ACh aCh pep熟平 Tilhar me 驶故e Nerve ACh/Ca terminal Ca2+ K+ K ACh K Outside Muscle membrane N NaK Inside K K K K K K
K 12 + Outside Inside Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ ACh ACh ACh Ca2+ induces fusion of vesicles with nerve terminal membrane. ACh is released and diffuses across synaptic cleft. ACh ACh binds to its receptor on the postsynaptic membrane Binding of ACh opens channel pore that is permeable to Na+ and K+ . Na+ Na+ K+ Muscle membrane Ca2+ Ca2+
End plate Potential (EPP) The movement of Nat andKt depolarizes muscle membrane potential (EPP) EPP Threshold Presynaptic terminal 90 mV Time(msec) P AP Outside Muscle membrane Inside ACh Receptor Channels Voltage-gated Inward rectifier Na channels K Channels
13 End Plate Potential (EPP) Outside Inside Muscle membrane Presynaptic terminal Muscle Membrane Voltage (mV) Time (msec) -90 mV VK VNa 0 Threshold Presynaptic AP EPP The movement of Na+ and K+ depolarizes muscle membrane potential (EPP) ACh Receptor Channels Voltage-gated Na Channels Inward Rectifier K Channels
ACh Meanwhile ACh ACh CoH邮 erve terminal intinNGr'eipoetgpdcialaged ntoarsialetate Acetate Outside Muscle membrane Inside
14 Meanwhile ... Outside Inside ACh ACh unbinds from its receptor Muscle membrane ACh so the channel closes ACh ACh ACh is hydrolyzed by AChE into Choline and acetate Choline Acetate Choline is taken up into nerve terminal Choline Choline resynthesized into ACh and repackaged into vesicle ACh
Structural reality 0.5um Axon Muscle
15 Structural Reality
Neuromuscular transmission Properties of neuromuscular junction >1: 1 transmission An unidirectional process Time delay. 20nm/0.5-Ims Easily affect by drugs and some factors The nm is a site of considerable clinical Importance
16 Neuromuscular Transmission ➢ Properties of neuromuscular junction ➢ 1:1 transmission ➢ An unidirectional process ➢ Time delay. 20nm/0.5-1ms ➢ Easily affect by drugs and some factors ➢ The NMJ is a site of considerable clinical importance