BIA 已合呼时8FHf ch nei ACh aCh p吧 Nerve ACh/Ca terminalIa+ K K+ ACh Na Nat K Outside Muscle membrane N N Inside K K Kt K Kt 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 andK- depolarizes muscle membrane potential(EPP) EPP ① Threshold Presynaptic 0 terminal -90mV Time(msec) Presynaptic AP Outside Muscle membrane Inside ACh Receptor Channels Voltage-gated Na channels Inward rectifie 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 AChACh Nerve C1o邮Be intioAiipeatqplChiaketdcs terminal into ansiaketate 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 0.5m A Muscle
15 Structural Reality
Neuromuscular transmission Properties of neuromuscular junction 1: 1 transmission a chemical transmission which is designed to assure that every pI desynaptic action potential results in a postsynaptic one An unidirectional process Has a time delay. 20nm/0.5-Ims Is easily affect by drugs and some factors The nmj is a site of considerable clinical Importance
16 Neuromuscular Transmission ➢ Properties of neuromuscular junction ➢ 1:1 transmission: A chemical transmission which is designed to assure that every presynaptic action potential results in a postsynaptic one ➢ An unidirectional process ➢ Has a time delay. 20nm/0.5-1ms ➢ Is easily affect by drugs and some factors ➢ The NMJ is a site of considerable clinical importance