CardiovascularPhysiology（心血管生理学）Components of the cardiovascular system:HeartVascular systemBloodSystem Overview The heart is the pumpthat propels theblood through the systemic and pulmonary circuits.Red color indicates blood that isfully oxygenated.Blue color representsblood that is only partially oxygenated.The distribution of blood in a comfortable, restingperson is shown here.Dynamic adjustments inblood delivery allow aperson to respond to widely varying circumstances, including emergencies.FunctionsoftheheartPumping（泵血）Endocrine（内分泌）Atrialnatriureticpeptide(ANP)Brainnatriureticpeptide(BNP)OtherbioactivatorsThe major external andinternal parts of the heart areshown in thisdiagram.The black arrowsindicate the routetaken by theblood as it ispumped along.The Heart Valves of the heartThemajortypesofcardiacmuscle:AtrialmuscleVentricularmuscleSpecializedexcitatoryandconductivemuscleContractilecells（收缩细胞）Autorhythmiccells（自律细胞）Conducting system of the heartCardiac muscleThe sinoatrial node is the hearts pacemaker because it initiates each wave of excitation with atrial contraction. The Bundle of His and other parts of the conducting system deliver the excitation to the apex of the heart so that ventricular contraction occurs in an upward sweep. Sequence of cardiac excitationGeneralprocessofexcitationandcontractionofcardiacmuscleInitiationofactionpotentialsinsinoatrialnodeConductionofactionpotentialsalongspecializedconductivesystemExcitation-contractioncouplingMusclecontractionTransmembranepotentialsrecordedindifferentheartregionsTransmembranepotentialofventricularcellsanditsionicmechanismsRestingPotential:-90mVActionPotentialPhase0:DepolarizationPhase1:EarlyphaseofrapidrepolarizationPhase2:Plateau（平台期）Phase3:LatephaseofrapidrepolarizationPhase4:RestingphaseRestingpotentialK+equilibriumpotentialNa+-inwardbackgroundcurrentElectrogenicNa+-K+pumpIonicmechanismsnPhase0pThresholdpotential(-70mV)pOpeningoffastNa+channelpRegenerativecycle（再生性循环）The action potential of a myocardial pumping cell.nPhase1pTransientoutwardcurrent,ItoK+currentpactivatedat20mVpopeningfor510msnPhase2InwardcurrentOutwardcurrent(Ca2+&Na+)(K+current)TypesofCa2+channelsincardiaccells:(1)L-type(long-lasting)(Nowycky,1985)(2)T-type(transient)(Nowycky,1985)Ca2+ channelsDurationofcurrentlong-lastingtransientActivationkineticsslowerfasterInactivationkineticsslowerfasterThresholdhigh(-35mV)Low(-60mV)cAMP/cGMP-regulatedYesNoPhosphorylation-regulatedYesNoOpenersBay-K-8644-BlockersvarapamilTetramethrinnifedipine,diltiazemNi2+InactivationbyCa2+iYesslightPatch-clamprecordingrun-downrelativelystableL-type T-typeOutwardcurrent(K+current):(1)inwardrectifierK+current(IK1)(2)delayedrectifierK+current(IK)nPhase3InactivationofCa2+channelOutwardK+currentdominatesIK:ProgressivelyincreasedIK1:RegenerativeK+OutwardCurrentnPhase4Na+-Ca2+exchangeSarcolemmalCa2+pumpSRCa2+pumpNa+-K+pumpTransmembranepotentialsrecordedindifferentheartregionsTransmembranepotentialofautorhythmiccellsanditsionicmechanismsPurkinjecells:Fastresponseautorhythmiccells4ContractilecellsAutorhythmiccellsPhase4stablepotentialPhase4spontaneousdepolarization（4期自动去极化）RestingpotentialMaximalrepolarizationpotential（最大复极电位）IonicmechanismPhase03：similartoventricularcellsPhase4：(1)IfFunnycurrent,Pacemakercurrent（起搏电流）(2)IkDecay（钾电流衰减）CharacteristicsofIfchannelNa+,K+Voltage-&time-dependentActivationRepolarizedto-60mVFullactivationHyperpolarizedto-100mVInactivationDepolarizedto-50mVBlockedbyCesium(Cs),notbyTTXSinoatrialcellsMaximalrepolarizationpotential-70mVThresholdpotential-40mVPhase0,3,4Sinoatrialcells:Slowresponseautorhythmiccells403IonicmechanismvPhase0:ICa(ICa,L)403vPhase3:pInactivationofL-typeCa2+channelpOutwardK+current(Ik)403Phase4：pIkdecayInactivatedwhenrepolarizedto-60mVpICa,TActivatedwhendepolarizedto-50mVpIfThe action potential of anautorhythmic cardiac cell.During which phase of the ventricular action potential is the membrane potential closest to the K+ equilibrium potential?(A) Phase 0(B) Phase 1(C) Phase 2(D) Phase 3(E) Phase 4During which phase of the ventricular action potential is the conductance to Ca2+ highest?(A) Phase 0(B) Phase 1(C) Phase 2(D) Phase 3(E) Phase 4Which phase of the ventricular action potential coincides with diastole?(A) Phase 0(B) Phase 1(C) Phase 2(D) Phase 3(E) Phase 4Electrocardiogram (ECG)（心电图）（心电图）Theelectrocardiogram(ECG)measureschangesinskinelectricalvoltage/potentialcausedbyelectricalcurrentsgeneratedbytheheartThe relationship between the electrocardiogram (ECG), recorded as the difference between currents at the left and right wrists, andan action potential typical of ventricular myocardial cells. Electrocardiogram (ECG)Thestandard12leadECGEinthovensTriangleLimbleads(Bipolar)(I,II,III)Augmentedlimbleads(Unipolar)(aVR,aVL,aVF)Chestleads(Unipolar)(V1,V2,V3,V4,V5,V6)IIIIIIaVRaVLaVFV1 V2 V3 V4 V5 V6WillemEinthoven:Dutchphysiologist.Hewona1924NobelPrizeforhiscontributionstoelectrocardiography.Placement of electrodes in electrocardiographyNormalECG0.04 secECGinterpretationMeasurementsRhythmanalysisConductionanalysisWaveformdescriptionComparisonwithpreviousECG(ifany)Pwave:thesequentialdepolarizationoftherightandleftatriaQRScomplex:rightandleftventriculardepolarizationST-Twave:ventricularrepolarizationUwave:originforthiswaveisnotclear-butprobablyrepresentsafterdepolarizationsintheventriclesPRinterval:timeintervalfromonsetofatrialdepolarization(Pwave)toonsetofventriculardepolarization(QRScomplex)QTinterval:durationofventriculardepolarizationandrepolarizationSTsegment:thetimeperiodbetweentheendoftheQRScomplexandthebeginningoftheTwave,duringwhicheachmyocyteisintheplateauphase(phase2)oftheactionpotentialNormalPartial blockComplete blockExcitabilityAutorhythmicityConductivityContractilityElectrophysiologicalproperties（电生理特性）Mechanicalproperty（机械特性）PhysiologicalpropertiesofcardiaccellsFactorsaffectingexcitabilityRestingpotentialThresholdpotentialStatusofNa+orCa2+channelsvExcitability（兴奋性）Hyperkalemia（高钾血症）TheQRScomplexesmaywidensothattheymergewiththeTwaves,resultingina“sinewave”appearance.TheSTsegmentsdisappearwhentheserumpotassiumlevelreaches6mEq/LandtheTwavestypicallybecometallandpeakedatthissamerange.ThePwavesbegintoflattenoutandwidenwhenapatientsserumpotassiumlevelreachesabout6.5mEq/L;thiseffecttendstodisappearwhenlevelsreach7-9mEq/L.Sinusarrestmayoccurwhentheserumpotassiumlevelreachesabout7.5mEq/L,andcardiacstandstillorventricularfibrillationmayoccurwhenserumlevelsreach10to12mEq/L.PeriodicchangesinexcitabilityValuableprotectivemechanismnThelongrefractoryperiodmeansthatcardiacmusclecannotberestimulateduntilcontractionisalmostover&thismakessummation&tetanusofcardiacmuscleimpossiblePrematuresystole&compensatorypause(extrasystole)A 39-year-old lady presenting with frequent palpitations lasting a few monthsA39-year-oldladypresentstoyouwithfrequentpalpitationslastingafewmonths,whicharenotassociatedwithdizziness,syncopeorangina.Shehasenjoyedgoodhealthandisnotonanymedicationorherbalmedicine.Sheisanon-smokerandhasnoknowndiabetes,hypertensionorhypercholesterolaemia.Hermensesisregularandphysicalexaminationisunremarkableotherthanafewprematurebeats.ThisisherECG.Answers:Ventricularprematurebeatsarenoted.PrematureventricularcontractionsunmaskthePwavesvAutorhythmicity（自律性）vAutorhythmicitySAnode100times/minAVnode50times/minBundleofHis40times/minPurkinjefibers 25times/minnNormalpacemaker（正常起搏点）SAnodenLatentpacemaker（潜在起搏点）(Ectopicpacemaker异位起搏点underpathophysiologicalconditions)AVnodeBundleofHisPurkinjefibersThemechanismsofSAnodetocontrollatentpacemakersCapture（夺获）Overdrivesuppression（超速抑制）FactorsAffectingAutorhythmicityMaximalrepolarizationpotentialThresholdpotentialTherateofphase4spontaneousdepolarizationSinusBradycardia（窦性心动过缓）Pacemaker1. Tom, an 80 yr old male, presents to his physician with a resting heart rate of 35 bpm. You classify his heart rate as:A. NormalB. BradycardiaC. Tachycardia2. His pacemaker is most likely located at the:A. Sinoatrial nodeB. Atrial-ventricular nodeC. His Bundle-PurkinjevConductivity（传导性）GapjunctionSAnodeAtriaA-Vnode0.05m/s0.4m/s0.020.05m/sHisbundlePurkinjefiberVentricle1.22.0m/s2.04.0m/s1.0m/sConductingvelocityAtrioventriculardelay（房室延搁）:AsynchronizationofatrialandventriculardepolarizationtoprovideadequatecardiacoutputFactorsAffectingConductivityStructuralfactorsDiameterofcardiaccellsGapjunctionsatIntercalateddiskPhysiologicalfactorsThevelocityandamplitudeofphase0depolarizationExcitabilityofadjacentregionFirstDegreeAVBlockDefinition:1AVBisarhythminwhichtheelectricalimpulsewhichleavestheSAnodeandtravelsthroughtheatria,AVnode,BundleofHistopurkininjiefibersissloweddownandtakeslongerthannormaltoarriveatitsdestination.ThenormalPRintervalis0.12-0.20seconds.A1AVBTisgreaterthan0.20seconds.Thecauserangesfromcoronaryheartdisease,inferiorwallMIs,hyperkalemia,congenitalabnormalities,andmedicationssuchasquinidine,digitalis,betablockers,andcalciumchannelblockers.SeconddegreeAVBlocktype1(Mobitz)Definition:SeconddegreeAVblockisalsoknownasSecondDegreeTypeI,MobitzI,orWenckelbach.ThisarrhythmiaischaracterizedbyaprogressivedelayoftheconductionattheAVnode,untiltheconductioniscompletelyblocked.Thisoccursbecausetheimpulsearrivesduringtheabsoluterefractoryperiod,resultinginanabsenceofconduction,andnoQRS.ThenextPwaveoccursandthecyclebeginsagain.Possiblecausesareacuteinferiorwallmyocardialinfraction,digitalis,betablockers,calciumchannelblockers,rheumaticfever,myocarditis,orexcessivevagaltone.MobitzIIischaracterizedby2-4PwavesbeforeeachQRS.ThePRoftheconductedPwavewillbeconstantforeachQRS.Itisusuallyassociatedwithacuteanteriororanteroseptalmyocardialinfarction.Othercausesarecardiomyopathy,rheumaticheartdisease,coronaryarterydisease,digitalis,betablockers,andcalciumchannelblockers.MobitzIIhasthepotentialofprogressingintoathirddegreeheartblockorventricularstandstill.SeconddegreeAVBlockTypeIIAthirddegreeatrialventricularblockisalsoknowasacompleteheartblockartrioventricularblockof3degreeAVblock.Itisaproblemwithelectricalconduction.AllelectricalconductionfromtheatriaareblockedattheAVjunction,therefore,theatriaandtheventriclesbeatindependentlyfromeachother.Thisarrhythmiaisdangerousbecauseitsignificantlydecreasescardiacoutput,andcouldleadtoasystole.Possiblecauses:acuteinferiorandanteriormyocardicinfraction,coronaryheartdisease,excessivevagaltone,myocarditis,endocarditis,age,edemafromheartsurgery,andmeditationtoxicityfromdigitalis,betablockers,calciumchannelblockers.ThirdDegree-CompleteBlock-+-+-Reentry （折返）（折返）ModelReentrycantakeplacewithinasmalllocalregionwithintheheartoritcanoccur,forexample,betweentheatriaandventricles(globalreentry).Forreentrytooccur,certainconditionsmustbemetthatarerelatedtothefollowing:1.thepresenceofaunidirectionalblockwithinaconductingpathway;2.criticaltiming;3.thelengthoftheeffectiverefractoryperiodofthenormaltissue.Q-T interval recorded on an ECG primarily corresponds to: A Ventricular repolarization B Ventricular depolarization plus ventricular repolarization C Ventricular depolarization and atrial repolarization D Atrial depolarization and conduction through AV node E Purkinje fibers repolarization You see a 55-year-old, white female for a routine check-up. On the ECG you see a prolonged PQ interval suggesting a first-degree atrioventricular block. What is the primary pacemaker of the heart? A Sinoatrial node B Atrioventricular node C Atrioventricular bundle D Right and left bundle branches E Purkinje fibers 1. The portion of the ECG related to the propagation of the cardiac impulse between the AV node through the Purkinje fibers is the:A. QRS complexB. B. Q-R complexC. P-R intervalD. S-T interval2. When running, sympathetic stimulation increases heart rate as well as the rate of contraction and relaxation in the heart. Will running change the ECG in an individual with a normal heart?A. No, only heart rate changesB. Yes, R-R, QT and PR intervals shorten; QRS is minimally shortenedC. Yes, R-R and PR intervals lengthenThe End.