Chapter19_1slideperpg.pdf - Chapter 19 Cardiovascular Physiology(pgs 846-875 I Electrical Events at the Heart A.The Intrinsic Conduction System of the

Chapter19_1slideperpg.pdf - Chapter 19 Cardiovascular...

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Chapter 19: Cardiovascular Physiology (pgs. 846-875) I. Electrical Events at the Heart A.The Intrinsic Conduction System of the Heart B. Action Potentials in Cardiac Cells C.The Electrocardiogram (ECG) & Common ECG Abnormalities II. The Cardiac Cycle: Analyses of the Wiggers diagram III.Cardiac Output = Stroke Volume x Heart Rate A.Factors that Influence Stroke Volume B.Factors that Influence Heart Rate
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CardiacMuscleContraction [ReviewyourAnatomynotesforcardiacmusclecells] Fourmain differences fromskeletalmuscle: Twomusclecellpopulations: cardiac (myocardial) conductivecells (pacemakerorautorhythmic cells)& cardiac (myocardial) contractilecells . ~1%ofcellsareautorhythmic (conductive). Donotneednervoussystemstimulation Candepolarizeentireheart Allcardiomyocytes contractasaunit,ornonedo (gapjunctionssynchronizecardiaccontraction). Longabsoluterefractoryperiod(250ms): Preventstetanic contractions
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SeeFigs.19.18&19.19: Theintrinsicconductionsystemoftheheart Bachmann’sbundle orinteratrialband or AVbundle: onlyelectrical connection betweenatria &ventricles AVnode: impulses pause0.1 seconds
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SeeFig.19.20:Actionpotential initiationbySAnodecells or pacemakercells 1Prepotential (spontaneous) depolarization SlowinfluxofNa + ;slow risefrom‐60mVto‐40mV.Noticethatthe membranepotentialisneveraflatline.
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SeeFig.19.21a: Actionpotentialof cardiaccontractilecells 3 Repolarization isduetoCa 2+ channels inactivating&K + channelsopening.K + effluxbrings membranepotentialbacktorestingstate.
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Fig.19.21b:Actionpotentialofskeletalmusclecells vs.actionpotentialofcardiaccontractilecell Absoluterefractoryperiod Relativerefractoryperiod
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SeeFigs.19.22&19.23:Electrocardiogram (ECGorE K G) ECG compositeofALLelectrical conductances bynodal&contractile cells Recordingelectrodes(leads)areplaced atvarioussitesonthebodysurface Pwave : depolarizationofSAnode Small(lasts~0.08s) ~0.1safterPwavebegins atriacontract
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