18Cardiac Muscle ContractionHeart Physiology: Intrinsic Conduction SystemPacemaker and Action Potentials of the HeartCardiac Membrane PotentialHeart Physiology: Sequence of ExcitationSlide 7Cardiac Intrinsic ConductionSlide 9Heart Excitation Related to ECGSlide 11Slide 12Slide 13Slide 14Slide 15Extrinsic Innervation of the HeartElectrocardiographyECG TracingsHeart SoundsSlide 20Slide 21Cardiac CyclePhases of the Cardiac CycleSlide 24Slide 25Slide 26Cardiac Output (CO) and ReserveCardiac Output: ExampleRegulation of Stroke VolumeFactors Affecting Stroke VolumeFrank-Starling Law of the HeartPreload and AfterloadExtrinsic Factors Influencing Stroke VolumeSlide 34Heart Contractility and NorepinephrineSlide 36Slide 37Slide 38Slide 39Slide 40Slide 41Regulation of Heart RateRegulation of Heart Rate: Autonomic Nervous SystemAtrial (Bainbridge) ReflexChemical Regulation of the HeartSlide 46Congestive Heart Failure (CHF)Developmental Aspects of the HeartSlide 49Slide 50Examples of Congenital Heart DefectsAge-Related Changes Affecting the HeartCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsHuman Anatomy & PhysiologySEVENTH EDITIONElaine N. MariebKatja HoehnPowerPoint® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community CollegeC H A P T E R18The Cardiovascular System: The HeartP A R T BCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsCardiac Muscle ContractionHeart muscle:Is stimulated by nerves and is self-excitable (automaticity)Contracts as a unitHas a long (250 ms) absolute refractory periodCardiac muscle contraction is similar to skeletal muscle contractionCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsHeart Physiology: Intrinsic Conduction SystemAutorhythmic cells:Initiate action potentials Have unstable resting potentials called pacemaker potentialsUse calcium influx (rather than sodium) for rising phase of the action potentialCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsPacemaker and Action Potentials of the HeartFigure 18.13Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsCardiac Membrane PotentialFigure 18.12Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsHeart Physiology: Sequence of ExcitationSinoatrial (SA) node generates impulses about 75 times/minuteAtrioventricular (AV) node delays the impulse approximately 0.1 secondImpulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsHeart Physiology: Sequence of ExcitationAV bundle splits into two pathways in the interventricular septum (bundle branches)Bundle branches carry the impulse toward the apex of the heartPurkinje fibers carry the impulse to the heart apex and ventricular wallsCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsCardiac Intrinsic ConductionFigure 18.14aCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsCardiac Membrane PotentialFigure 18.12Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsSA node generates impulse;atrial excitation beginsImpulse delayedat AV nodeImpulse passes toheart apex; ventricularexcitation beginsVentricular excitationcompleteSA node AV node PurkinjefibersBundlebranchesFigure 18.17Heart Excitation Related to ECGCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsSA node generates impulse;atrial excitation beginsSA nodeFigure 18.17Heart Excitation Related to ECGCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsImpulse delayedat AV nodeAV nodeFigure 18.17Heart Excitation Related to ECGCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsImpulse passes toheart apex; ventricularexcitation beginsBundlebranchesFigure 18.17Heart Excitation Related to ECGCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsVentricular excitationcompletePurkinjefibersFigure 18.17Heart Excitation Related to ECGCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsSA node generates impulse;atrial excitation beginsImpulse delayedat AV nodeImpulse passes toheart apex; ventricularexcitation beginsVentricular excitationcompleteSA node AV node PurkinjefibersBundlebranchesFigure 18.17Heart Excitation Related to ECGCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsExtrinsic Innervation of the HeartHeart is stimulated by the sympathetic cardioacceleratory center Heart is inhibited by the parasympathetic cardioinhibitory centerFigure 18.15Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsElectrocardiographyElectrical activity is recorded by electrocardiogram (ECG)P wave corresponds to depolarization of SA nodeQRS complex corresponds to ventricular depolarizationT wave corresponds to ventricular repolarizationAtrial repolarization record is masked by the larger QRS complexPLAYPLAYInterActive Physiology ®: Intrinsic Conduction System, pages 3–6Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsECG TracingsFigure 18.18Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsHeart SoundsFigure 18.19Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsElectrocardiographyFigure 18.16Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsHeart SoundsHeart sounds (lub-dup) are associated with closing of heart valvesFirst sound occurs as AV valves close and signifies beginning of systoleSecond sound occurs when SL valves close at the beginning of ventricular diastoleCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsCardiac CycleCardiac cycle refers to all events associated with blood flow through the heartSystole – contraction of heart muscleDiastole – relaxation of heart muscleCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsPhases of the Cardiac CycleVentricular filling – mid-to-late diastoleHeart blood pressure is low as blood enters atria and flows into ventriclesAV valves are open, then atrial systole occursCopyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsPhases of the Cardiac CycleVentricular systoleAtria relax Rising ventricular pressure results in closing of AV