生理学双语循环课件

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1、1第二节心肌的生物电现象2心肌细胞{工作细胞心室心房自律细胞窦房结房室交界房室束蒲肯野纤维心肌细胞的分类3528.1-529.1Theheartiscomposedofthreemajortypesofcardiacmuscle:atrialmuscle,ventricularmuscle,andspecialized(excitatoryand)conductivemusclefibers.4Theatrialandventriculartypesofmusclecontractinmuchthesamewayasskeletalmu

2、scleexceptthatthedurationofcontractionismuchlonger.5工作细胞678Conversely,thespecializedexcitatoryandconductivefibersexhibitrhythmicityandvaryingratesofconduction,providinganexcitatorysystemthatcontrolstherhythmicalbeatingoftheheart.9一、工作细胞(心室肌)的跨膜电位及形成机制1011（一）静息电位-90mV形成机制

3、钾平衡电位12ventricularmusclefibershavestablerestingmembranepotentialsofabout-90millivolts(mV).ThisvalueapproachestheK+equilibriumpotential.13（1）0期去极化期-90mv+30mv（2）1期快速复极初期+30mv0mv（3）2期平台期0mv（4）3期快速复极末期0mv-90mv（5）4期静息期-90mv（二）动作电位14AP的形成机制O期钠内流钠通道的激活和失活都快，开放时间短，故称快通道。可被河豚毒阻断。

4、151期钾离子快速外流（Ito通道）2期钾离子外流，钙离子内流，两种离子流平衡。16钙通道激活和失活都慢，称为慢通道。可被Mn2+和多种Ca2+阻断剂（如异博定，D-600等）所阻断。173期钾离子快速外流（Ik通道）4期排钠和钙，摄钾。钠钾转运是依靠钠泵，18Phase0istheupstrokeoftheactionpotential.iscausedbyatransientincreaseinNa+conductance.ThisincreaseresultsinaninwardNa+currentthatdepolarizest

5、hemembrane.Atthepeakoftheactionpotential,themembranepotentialapproachestheNa+equilibriumpotential.19Phase1isabriefperiodofinitialrepolarization.Initialrepolarizationiscausedbyanoutwardcurrent,inpartbecauseofthemovementofK+ions(favoredbybothchemicalandelectricalgradients)

6、outofthecellandinpartbecauseofadecreaseinNa+conductance.20Phase2istheplateauoftheactionpotential.,.iscausedbyatransientincreaseinCa2+.conductance,whichresultsinaninwardCa2+current,andbyanincreaseinK+conductance.Duringtheplateau,outwardandinwardcurrentsareapproximatelyequ

7、al,sothemembranepotentialisstableattheplateaulevel.21Phase3isrepolarization.Duringphase3,Ca2+conductancedecreases,andK+conductanceincreasesandthereforeitpredominates.22ThehighK+conductanceresultsinalargeoutwardK+current,whichhyperpolarizesthemembranebacktowardtheK+equili

8、briumpotential.23Phase4istherestingmembranepotential.isaperiodduringwhichinwardandoutwardcurrentsareequ