circulation1-heart as a pump-lw课件

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1、TheHeartasaPumpConductingsystemoftheheart.Excitation-contractioncouplingincardiacmuscleCa2+CharacteristicsoftheheartmusclecontractionDependingonconcentrationofextracelluarCa2+DiffusionofextracellarCa2+intosarcoplasm(mainsource)Sarcoplasmicreticulumreleas

2、eofCa2+ExtracellularCa2+strengthofcontractionSarcoplasmicreticulumislesswelldevelopedanddoesnotstoreenoughCa2+.2.CardiacmuscleasasyncytiumatrialsyncytiumandventricularsyncytiumAPspreadsimmediatelytowholeatriumorventricleentireatriumorventriclecontractsal

3、mostsimultaneouslygapjunction:verypermeabletoionsThestructureofgapjunctions.Gapjunctionsarewater-filledchannelsthroughwhichionscanpassfromonecelltoanother.Thispermitsimpulsestobeconducteddirectlyfromonecelltoanother.CardiacPumpFunctioncardiaccycle:Thecar

4、diaceventsoccurringfromthebeginningoftheoneheartbeattothebeginningofthenextarecalledthecardiaccycle.Heartbeat:60-100/minTimeofCardiaccycle:0.8second(75/min)cardiaccyclesystolediastolesystole:periodofcontractionejectiondiastole:periodofrelaxationfillingS

5、ystolePeriod

6、tionpressurechangesopeningorclosingofvalvesejectionorfillingvolumechangesofventricleMECHANICALEVENTSOFTHECARDIACCYCLEAtrialsystoleVentricularsystole＊Isovolumicventricularcontraction＊VentricularejectionVentriculardiastole＊Isovolumicventricularrelaxation＊V

7、entricularfillingAtrialsystole(a“primer”pump)AtriumcontractsVentriclerelaxedAtriumpressureincreases(Ap>Vp，Aop>Vp)A-VvalveopensSemilunarvalveclosedBloodflowfromatriumtoventricleA-VvalvesemilunarvalveAp:AtriumpressureVp:VentricularpressureAop:Aorticpressur

8、eContractionofatriumincreasesfillingofventricle(25%).Thisphaselastsabout0.1s.semilunarvalveA-VvalveA-VvalvesemilunarvalveVentricularsystole0.3sintraventricularpressuresemilunarvalveopensventricleejectsbloodventriclecontrac