呼吸科呼吸系统课件4

5.4ControlofRespirationBreathingisacriticalrobusthomeostaticprocessthatensuresadequatelevelsofoxygeninbloodandprovidesameanstoremovecarbondioxidefromthebody2022/10/1815.4ControlofRespiration20BasicRequirementsforRespiratoryRegulationItmustbeautomaticMaintenanceofCO2andO2levelsshouldnotdependonlevelsofconsciousnessoralertnessItmustbeadaptabletotheneedsoftheorganismTheremustbemechanismstocompensateforchangesinoxygenuptakeorCO2production.ItmustbesubjecttovoluntarycontrolTheremustbemechanismstovoluntarilyoverridetherespiratorycontrolmechanismsatleastforbriefperiodsoftime2022/10/182BasicRequirementsforRespiraRespiratoryCentersandtheBasicRespiratoryCenterRespiratorycenterBrainregionsorthespinalcordthatinvolveinthegenerationofrhythmicrespiratorypatternandtheregulationofrespiratorymovement;theyarelocatedinthespinalcord,brainstem,cortex,thalamusetc.BasicrespiratorycenterBrainpartsthatareresponsibleforgenerationofbasicrespirationpatternsItislocatedinthebrainstemRespiratoryCentersandtheBaTheExperimentDonebyLumsdenintheCatConclusionsUpperpons-pneumotaxiccenter;lowerpons-apneusticcenter(notaccepted);Spinalcord-Basicrespiratorycenter;spinalcord:CutatBreathingpattern(vagusnerveintact)Breathingpattern(vagusnervecutoff)MidbrainandtheponsNearlynormalDeepandslowMidponsNearlynormalApneusticbreathingPonsandmedullaIrregularCheyne-StokesbreathingMedullaandthespinalcordNobreathingNobreathingTheExperimentDonebyLumsdenRespiratory-RelatedNeuronsintheBasicRespiratoryCenterDorsalrespiratorygroup(DRG)Located

inthedorsalregionofthenucleustractussolitariiMainlycontaininspiratoryneuronsGeneratebasicrhythmVentralrespiratorygroup(VRG)Acolumnofcellsinthegeneralregionofthenucleusambiguus.IthousesbothinspiratoryandexpiratoryneuronsMostneuronsaresilentduringnormalquietrespirationPneumotaticcenterItactstolimitinspiration.Asaresult,itincreasestherateofbreathing2022/10/185Respiratory-RelatedNeuronsinIsthePre-BötzingerComplexEssentialfortheGenerationofBasicRespiratoryPattern?ModifiedfromBrain2011:134;24–35Medullaoblongata=延髓Pons=脑桥Lateralreticularnucleus(LRN)=外侧网状核XII=面神经Obex=栓、门MSA=multiplesystematrophySCA3=spinocerebellarataxiatype3IsthePre-BötzingerComplexEMultipleSystemsAtrophyvs.SpinocerebellarAtaxia3PatientswithmultiplesystemsatrophypresentwithcentralrespiratorydeficitsbutwithoutswallowingproblemsPre-BötzingerComplexneuronsarereducedwhereasambigualmotoneuronsarepreserved.Patientswithspinocerebellarataxia3hasnocentralrespiratorydeficitsbutwithdysphagia,Pre-BötzingerComplexneuronsarepreserved,whereasambigualmotoneuronsarediminished.MultipleSystemsAtrophyvs.SNeuralMechanismsunderlyingtheGenerationofRhythmicRespirationTwoHypothesesOscillatorytheoryorthepacemakerhypothesis(起步细胞学说)Networktheory(神经网络学说)NeuralMechanismsunderlyingtOscillatoryTheoryPacemakerneuronsgeneratetherespiratoryrhythm(Smithetal.,Science,1991).OscillatoryTheoryPacemakerneNeuronsinpre-BötzingercanBurstspontaneouslyRegularfiringinducedbycurrentinjectioninahippocampalgranulecellSpontaneousburstingInaratpre-BötzingerneuronNeuronsinpre-BötzingercanBNeuronsinpre-BötzingercanBurstspontaneouslyRegularfiringinducedbycurrentinjectioninahippocampalgranulecellSpontaneousburstingInaratpre-BötzingerneuronNeuronsinpre-BötzingercanBBasicrespiratorycenter(Medullaandpons)Voluntarycontrol(Cerebrum)SpinalmotorneuronsIntercostals Diaphragm&accessorymusclesMusclesofrespirationCentralChemoreceptorsPeripheralChemoreceptorsChemoreceptorsStretchreceptorsIrritantreceptorsJReceptorsMuscleproprioceptorsMechanoreceptorsPhrenicnervesothernerves2022/10/1812BasicrespiratorycenterVoluntVoluntarycontrolofrespirationisneededinsuckling,swallowing,sniffing,chewing,coughing,vomitingandvocalization.Voluntarycontroloverpulmonaryventilationoriginatesinthemotorcortexofcerebralfrontallobe.Theimpulsesaretransmitteddownthecorticospinaltractstotherespiratoryneuronsinthespinalcord,bypassingthebrainstemrespiratorycenters.VoluntaryControlofBreathingVoluntaryControlofBreathingCHEMICALCONTROLOFRESPIRATIONPeripheralChemoreceptorsystemCentralChemoreceptorsystemCHEMICALCONTROLOFRESPIRATIORespiratoryActivityisSensitivetoOxygen,CarbonDioxide,andHydrogenIonsintheBloodTheoverallgoalofrespirationistomaintainproperconcentrationsofoxygen,carbondioxide,andhydrogenionsinthetissues.Respiratoryactivityishighlysensitivetochangesineachofthese.Excesscarbondioxideorexcesshydrogenionsinthebloodmainlyactonthecentralchemoreceptorsystemwhereashypoxiaactsentirelyontheperipheralchemoreceptorsystem.RespiratoryActivityisSensitPeripheralChemosensoryReceptorSystemAfferentPathwaysCarotidbodies→Carotidsinusnerve→glosopharyngial(IXCN)→medullanearnucleustractussolitarius(NTS)Aorticbodies→Jointhevagus(XCN)→medullanearnucleustractussolitarius(NTS)2022/10/1816PeripheralChemosensoryReceptPeripheralChemoreceptorsshouldbeDistinguishedfromBaroreceptorsCarotidarterybodiesandaorticbodies:chemoreceptorsCarotidbodiesareatthedivisionofthecommoncarotidarteryintotheexternalandinternalcarotid.TheaorticbodyisontheaorticarchCarotidarterysinusandaorticarc:baroreceptors(theyarewithinthewallsofthebloodvessels)BaroreceptorssensethetensionofbloodvesselsPeripheralChemoreceptorsshouFunctionsofPeripheralChemoreceptorsSensePO2,PCO2andH+inthearterialbloodPrimarilysensitiveto↓arterialPO2⇒hyperventilationIntheabsenceofperipheralchemoreceptors,hypoxiaresultsinCNSneuronaldepressionanddepressedventilation↑PaCO2andincreasedH+concentrationstimulatethesereceptorstoalesserextentbutmakethemmoreresponsivetohypoxemiaFunctionsofPeripheralChemorCentralChemoreceptorSystemLocation:VentrallateralsurfaceofthemedullaStimuli:IncreasedH+orhighCO2inCSForextracellularspaceCentralChemoreceptorSystemLo2022/10/18202022/10/1520ArterialPCO2isthemostImportantFactor

inRegulationofRespirationThearterialCO2isheldwithin2-3mmHg.ThearterialCO2isthemostimportantfactorincontrollingrespirationinphysiologicalconditions.WithincreasedarterialPCO2,boththerateandthedepthofrespirationincrease.Peripheralchemoreceptordenervationstudiesshowed20-30%oftheresponsefromcarotidbodies(rapid);theremaining80%fromcentralchemoreceptors(slow).ArterialPCO2isthemostImpoMechanismsUnderlyingHyperventilationfollowingPaCO2IncreaseDirectstimulationStimulationofperipheralchemoreceptprsStimulationofcentralchemoreceptorsIndirectstimulation CO2

ArterialH+

Peripheral chemoreceptorsMechanismsUnderlyingHypervenTheEffectsofLowerPaO2onRespirationNoeffectofventilationwhenPaO2isabove100mmHgVentilationisuponcePaO2isbelow70mmHgandisdoubledwhenPaO2fallsto60mmHgHyperventilationfollowingdecreaseinPaO2issolelymadebystimulatingperipheralchemoreceptorsSeverehypoxiasuppressesrespirationthroughactingonrespiratorycentersofbrainstem2022/10/1823TheEffectsofLowerPaO2onTheEffectsofHydrogenIonsonRespirationAnincreaseinH+concentrationinarterialblood,CSForthelocaltissueofbrainstemstimulatesrespiration.IncreasedH+stimulatesbothperipheralandcentralchemoreceptorswithstimulationoftheperipheralchemoreceptorplayingthemainrole.AsH+cannotpassthroughthebrain-bloodbarrier,increasedH+inarterialbloodstimulatescentralchemoreceptorsthroughCO2.Atbothperipheralandcentralchemoreceptors,H+mediatesincreasedrespirationbyCO2accumulation.CentralchemoreceptorsaremoresensitivetoH+thanperipheralchemoreceptors.2022/10/1824TheEffectsofHydrogenIonsoHowDoesIncreasedArterialH+ActontheCentralChemoreceptorsHowDoesIncreasedArterialH+SignificancesofHydrogenIonsonRespirationCoordinatesmetabolicneedsandrespiration.MaintainspHhomeostasis.2022/10/1826SignificancesofHydrogenIonsOndine’sCurseTheOathbyOndine’shusband:Myeverywakingbreathshallbemypledgeofloveandfaithfulnesstoyou.TheCursemadebyOndine(on-deen):Yousworefaithfulnesstomewitheverywakingbreath,andIacceptedyouroath.Sobeit.Aslongasyouareawake,youshallhaveyourbreath,butshouldyoueverfallasleep,thenthatbreathwillbetakenfromyouandyouwilldie!Theend:Ondine’shusbanddied.2022/10/18Ondine’sCurseTheOathbyOndiCentralAlveolarHypoventilation(Ondine’sCurse)CentralalveolarhypoventilationisararediseaseinindividualswhoarebornwithoutventilatorychemosensitivityBreathingadequatewhenawake,butnotwhenasleeporduringsleepingNoresponsetohypercapniaandhypoxiaCentralAlveolarHypoventilatiEXERCISEANDVENTILATIONEXERCISEANDVENTILATIONExerciseIsAssociatedwithHyperventilationRest MaximalExerciseIntensityMinuteVentilation(L/min)6100ExerciseIsAssociatedwithHyAcuteRespiratoryResponsetoGradedDynamicExerciseExerciseIntensityVentilation(L/min)V/QPAO2(mmHg)PaO2(mmHg)PaCO2(mmHg)ArterialpHRest51103100407.40Walking202103100407.40Jogging453106100367.40Running754110100257.32ConclusionHyperventilationduringexerciseisprimarilycausedbymechanismsbeyondchemicalchangesinthebloodThecortexsendssignalstothebasicrespiratorycenter?Isthereinteractionbetweenthecardiovascularandbasicrespiratorycenters?AcuteRespiratoryResponsetoMECHANICALREFLEXESSeveralmechanicalreflexesthatarisefromthechestwallandlungsaffectventilationandventilatorypatterns.MECHANICALREFLEXESSeveralmecReceptorsAreLocalizedinLungTissueandAirwaysPulmonaryreceptorscanbedividedinto3groups:pulmonarystretch,irritantandJreceptors.Afferentfibersofallthreetypesliepredominantlyinthevagalnerves.ReceptorsAreLocalizedinLunPulmonaryStretchReceptorsThestretchreceptorsaresensoryterminalsofmyelinatedafferentfibersthatliewithinthesmoothmusclelayerofconductingairways.Thestretchreceptorssensechangesinlungvolume.Thestretchreceptorsmediatelunginflationrefelx(Hering-Breuerreflex).PulmonaryStretchReceptorsTheLungStretchReflexesPulmonaryinflationreflex(Hering-Breuerinspiratory-inhibitoryreflex)Inflationoflungsorstretchofairwaysswitchesfrominspirationtoexpiration.Asaresult,inspirationisshortenedwithincreasedbreathingrate.Pulmonarydeflationreflex: