動(dòng)物生理學(xué)2細(xì)胞的基本功能下(編輯修改稿)
2025-05-26 04:06 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 e presynaptic terminal region. This causes: 2) A flow of Ca2+ into the boutons through voltageactivated Ca2+ channels. The elevated Ca2+ triggers: 3) The fusion of synaptic vesicles with presynaptic membrane specializations and the release of packets or quanta of transmitter (Ach) into the cleft. These are the presynaptic events. Postsynaptic Events of Neuromuscular Transmission: 4) ACh diffuses across the cleft. This takes time (up to several hundred ?s). 5) ACh binds to Nicotinic Acetylcholine receptors in the postsynaptic membrane, opening monovalent cation channels. 6) Channel opening depolarizes the postsynaptic membrane, creating an endplate potential (EPP). 7) EPPs spread passively to the excitable muscle membrane. 8) Voltageactivated Na+ channels open giving rise to a muscle AP. 9) Termination of the transmission process occurs via hydrolysis of ACh by acetylcholinesterase present in the junction. Please note: ? Endplate potential is not a “all or none? type ? It can cause action potential of the excitable muscle membrane ? 筒箭毒， ?銀環(huán)蛇毒可以阻斷神經(jīng)肌肉接頭處的傳遞 The structure of striated muscle myofibril and sarere[?sɑ:k?mi?] ? Isotropic (等方性的） band (I band) or light band ? anisotropic band (A band) or dark band ? myosin myofilament （粗肌絲） ? actin myofilament （細(xì)肌絲） sarcotubular system ? transvers tubules (T tubules) ? Sarcoplasmic reticulum, SR( a special type of smooth ER found in smooth and striated muscle ) ? Juctional SR or terminal cisterna ? Triad(the Ttubule and its two terminal cisternae form a triad) The structure of striated muscle Mechanism of muscle contraction Excitationcontraction (EC)coupling ? Ttubules conduct signal APs into the cell ? Depolarization of Ttubule causes calcium release from SR ? Calcium activation of contraction ? Relaxation occurs as a result of the active transport of Ca2+ into the S
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