呼吸科呼吸系統(tǒng)4

呼吸科呼吸系統(tǒng)4第1頁/共39頁BasicRequirementsforRespiratoryRegulation2023/3/102ItmustbeautomaticMaintenanceofCO2andO2levelsshouldnotdependonlevelsofconsciousnessoralertnessItmustbeadaptabletotheneedsoftheorganismTheremustbemechanismstocompensateforchangesinoxygenuptakeorCO2production.ItmustbesubjecttovoluntarycontrolTheremustbemechanismstovoluntarilyoverridetherespiratorycontrolmechanismsatleastforbriefperiodsoftime第2頁/共39頁RespiratoryCentersandtheBasicRespiratoryCenterRespiratorycenterBrainregionsorthespinalcordthatinvolveinthegenerationofrhythmicrespiratorypatternandtheregulationofrespiratorymovement;theyarelocatedinthespinalcord,brainstem,cortex,thalamusetc.BasicrespiratorycenterBrainpartsthatareresponsibleforgenerationofbasicrespirationpatternsItislocatedinthebrainstem第3頁/共39頁TheExperimentDonebyLumsdenintheCatConclusionsUpperpons-pneumotaxiccenter;lowerpons-apneusticcenter(notaccepted);Spinalcord-Basicrespiratorycenter;spinalcord:CutatBreathingpattern(vagusnerveintact)Breathingpattern(vagusnervecutoff)MidbrainandtheponsNearlynormalDeepandslowMidponsNearlynormalApneusticbreathingPonsandmedullaIrregularCheyne-StokesbreathingMedullaandthespinalcordNobreathingNobreathing第4頁/共39頁2023/3/105Respiratory-RelatedNeuronsintheBasicRespiratoryCenterDorsalrespiratorygroup(DRG)Located

inthedorsalregionofthenucleustractussolitariiMainlycontaininspiratoryneuronsGeneratebasicrhythmVentralrespiratorygroup(VRG)Acolumnofcellsinthegeneralregionofthenucleusambiguus.IthousesbothinspiratoryandexpiratoryneuronsMostneuronsaresilentduringnormalquietrespirationPneumotaticcenterItactstolimitinspiration.Asaresult,itincreasestherateofbreathing第5頁/共39頁IsthePre-B?tzingerComplexEssentialfortheGenerationofBasicRespiratoryPattern?ModifiedfromBrain2011:134;24–35Medullaoblongata=延髓Pons=腦橋Lateralreticularnucleus(LRN)=外側(cè)網(wǎng)狀核XII=面神經(jīng)Obex=栓、門MSA=multiplesystematrophySCA3=spinocerebellarataxiatype3第6頁/共39頁MultipleSystemsAtrophyvs.SpinocerebellarAtaxia3PatientswithmultiplesystemsatrophypresentwithcentralrespiratorydeficitsbutwithoutswallowingproblemsPre-B?tzingerComplexneuronsarereducedwhereasambigualmotoneuronsarepreserved.Patientswithspinocerebellarataxia3hasnocentralrespiratorydeficitsbutwithdysphagia,Pre-B?tzingerComplexneuronsarepreserved,whereasambigualmotoneuronsarediminished.第7頁/共39頁NeuralMechanismsunderlyingtheGenerationofRhythmicRespirationTwoHypothesesOscillatorytheoryorthepacemakerhypothesis(起步細胞學(xué)說)Networktheory(神經(jīng)網(wǎng)絡(luò)學(xué)說)第8頁/共39頁OscillatoryTheoryPacemakerneuronsgeneratetherespiratoryrhythm(Smithetal.,Science,1991).第9頁/共39頁Neuronsinpre-B?tzingercanBurstspontaneouslyRegularfiringinducedbycurrentinjectioninahippocampalgranulecellSpontaneousburstingInaratpre-B?tzingerneuron第10頁/共39頁Neuronsinpre-B?tzingercanBurstspontaneouslyRegularfiringinducedbycurrentinjectioninahippocampalgranulecellSpontaneousburstingInaratpre-B?tzingerneuron第11頁/共39頁2023/3/1012Basicrespiratorycenter(Medullaandpons)Voluntarycontrol(Cerebrum)SpinalmotorneuronsIntercostals Diaphragm&accessorymusclesMusclesofrespirationCentralChemoreceptorsPeripheralChemoreceptorsChemoreceptorsStretchreceptorsIrritantreceptorsJReceptorsMuscleproprioceptorsMechanoreceptorsPhrenicnervesothernerves第12頁/共39頁Voluntarycontrolofrespirationisneededinsuckling,swallowing,sniffing,chewing,coughing,vomitingandvocalization.Voluntarycontroloverpulmonaryventilationoriginatesinthemotorcortexofcerebralfrontallobe.Theimpulsesaretransmitteddownthecorticospinaltractstotherespiratoryneuronsinthespinalcord,bypassingthebrainstemrespiratorycenters.VoluntaryControlofBreathing第13頁/共39頁ChemicalControlofRespirationPeripheralChemoreceptorsystemCentralChemoreceptorsystem第14頁/共39頁RespiratoryActivityisSensitivetoOxygen,CarbonDioxide,andHydrogenIonsintheBloodTheoverallgoalofrespirationistomaintainproperconcentrationsofoxygen,carbondioxide,andhydrogenionsinthetissues.Respiratoryactivityishighlysensitivetochangesineachofthese.Excesscarbondioxideorexcesshydrogenionsinthebloodmainlyactonthecentralchemoreceptorsystemwhereashypoxiaactsentirelyontheperipheralchemoreceptorsystem.第15頁/共39頁PeripheralChemosensoryReceptorSystem2023/3/1016AfferentPathwaysCarotidbodies→Carotidsinusnerve→glosopharyngial(IXCN)→medullanearnucleustractussolitarius(NTS)Aorticbodies→Jointhevagus(XCN)→medullanearnucleustractussolitarius(NTS)第16頁/共39頁PeripheralChemoreceptorsshouldbeDistinguishedfromBaroreceptorsCarotidarterybodiesandaorticbodies:chemoreceptorsCarotidbodiesareatthedivisionofthecommoncarotidarteryintotheexternalandinternalcarotid.TheaorticbodyisontheaorticarchCarotidarterysinusandaorticarc:baroreceptors(theyarewithinthewallsofthebloodvessels)Baroreceptorssensethetensionofbloodvessels第17頁/共39頁FunctionsofPeripheralChemoreceptorsSensePO2,PCO2andH+inthearterialbloodPrimarilysensitiveto↓arterialPO2?hyperventilationIntheabsenceofperipheralchemoreceptors,hypoxiaresultsinCNSneuronaldepressionanddepressedventilation↑PaCO2andincreasedH+concentrationstimulatethesereceptorstoalesserextentbutmakethemmoreresponsivetohypoxemia第18頁/共39頁CentralChemoreceptorSystemLocation:VentrallateralsurfaceofthemedullaStimuli:IncreasedH+orhighCO2inCSForextracellularspace第19頁/共39頁2023/3/1020第20頁/共39頁ArterialPCO2isthemostImportantFactor

inRegulationofRespirationThearterialCO2isheldwithin2-3mmHg.ThearterialCO2isthemostimportantfactorincontrollingrespirationinphysiologicalconditions.WithincreasedarterialPCO2,boththerateandthedepthofrespirationincrease.Peripheralchemoreceptordenervationstudiesshowed20-30%oftheresponsefromcarotidbodies(rapid);theremaining80%fromcentralchemoreceptors(slow).第21頁/共39頁MechanismsUnderlyingHyperventilationfollowingPaCO2IncreaseDirectstimulationStimulationofperipheralchemoreceptprsStimulationofcentralchemoreceptorsIndirectstimulation CO2

ArterialH+

Peripheral chemoreceptors第22頁/共39頁TheEffectsofLowerPaO2onRespirationNoeffectofventilationwhenPaO2isabove100mmHgVentilationisuponcePaO2isbelow70mmHgandisdoubledwhenPaO2fallsto60mmHgHyperventilationfollowingdecreaseinPaO2issolelymadebystimulatingperipheralchemoreceptorsSeverehypoxiasuppressesrespirationthroughactingonrespiratorycentersofbrainstem2023/3/1023第23頁/共39頁TheEffectsofHydrogenIonsonRespirationAnincreaseinH+concentrationinarterialblood,CSForthelocaltissueofbrainstemstimulatesrespiration.IncreasedH+stimulatesbothperipheralandcentralchemoreceptorswithstimulationoftheperipheralchemoreceptorplayingthemainrole.AsH+cannotpassthroughthebrain-bloodbarrier,increasedH+inarterialbloodstimulatescentralchemoreceptorsthroughCO2.Atbothperipheralandcentralchemoreceptors,H+mediatesincreasedrespirationbyCO2accumulation.CentralchemoreceptorsaremoresensitivetoH+thanperipheralchemoreceptors.2023/3/1024第24頁/共39頁HowDoesIncreasedArterialH+ActontheCentralChemoreceptors第25頁/共39頁SignificancesofHydrogenIonsonRespirationCoordinatesmetabolicneedsandrespiration.MaintainspHhomeostasis.2023/3/1026第26頁/共39頁Ondine’sCurse2023/3/10TheOathbyOndine’shusband:Myeverywakingbreathshallbemypledgeofloveandfaithfulnesstoyou.TheCursemadebyOndine(on-deen):Yousworefaithfulnesstomewitheverywakingbreath,andIacceptedyouroath.Sobeit.Aslongasyouareawake,youshallhaveyourbreath,butshouldyoueverfallasleep,thenthatbreathwillbetakenfromyouandyouwilldie!Theend:Ondine’shusbanddied.第27頁/共39頁CentralAlveolarHypoventilation(Ondine’sCurse)CentralalveolarhypoventilationisararediseaseinindividualswhoarebornwithoutventilatorychemosensitivityBreathingadequatewhenawake,butnotwhenasleeporduringsleepingNoresponsetohypercapniaandhypoxia第28頁/共39頁ExerciseandVentilation第29頁/共39頁ExerciseIsAssociatedwithHyperventilationRest MaximalExerciseIntensityMinuteVentilation(L/min)6100第30頁/共39頁AcuteRespiratoryResponsetoGradedDynamicExerciseExerciseIntensityVentilation(L/min)V/QPAO2(mmHg)PaO2(mmHg)PaCO2(mmHg)ArterialpHRest51103100407.40Walking202103100407.40Jogging453106100367.40Running754110100257.32ConclusionHyperventilationduringexerciseisprimarilycausedbymechanismsbeyondchemicalchangesinthebloodThecortexsendssignalstothebasicrespiratorycenter?Isthereinteractionbetweenthecardiovascularandbasicrespiratorycenters?第31頁/共39頁MechanicalReflexesSeveralmechanicalreflexesthatarisefromthechestwallandlungsaffectventilationandventilatorypatterns.第32頁/共39頁ReceptorsAreLocalizedinLungTissueandAirwaysPulmonaryreceptorscanbedividedinto3groups:pulmonarystretch,irritantandJreceptors.Afferentfibersofallthreetypesliepredominantlyinthevagalnerves.第33頁/共39頁PulmonaryStretchReceptorsThestretchreceptorsaresensoryterminalsofmyelinatedafferentfibersthatliewithinthesmoothmusclelayerofconductingairways.Thestretchreceptorssensechangesinlungvolume.Thestretchreceptorsmediatelunginflationrefelx(Hering-Breuerreflex).第34頁/共39頁LungStretchReflexesPulmonaryinflationreflex(Hering-Breuerinspiratory-inhibitoryreflex)Inflationoflungsorstretchofairwaysswitchesfrominspirationtoexpiration.Asaresult,inspirationisshortenedwithincreasedbreathingrate.Pulmonarydeflationreflex:Deflationoflungspromotesinspir