呼吸科呼吸系统4.ppt

呼吸科呼吸系统呼吸科呼吸系统4 4Basic Requirements for Respiratory Regulation2024/5/24 周五2lItmustbeautomaticlMaintenanceofCO2andO2levelsshouldnotdependonlevelsofconsciousnessoralertnesslItmustbeadaptabletotheneedsoftheorganismlTheremustbemechanismstocompensateforchangesinoxygenuptakeorCO2production.lItmustbesubjecttovoluntarycontrollTheremustbemechanismstovoluntarilyoverridetherespiratorycontrolmechanismsatleastforbriefperiodsoftimeRespiratory Centers and the Basic Respiratory CenterlRespiratory centerlBrainregionsorthespinalcordthatinvolveinthegenerationofrhythmicrespiratorypatternandtheregulationofrespiratorymovement;theyarelocatedinthespinalcord,brainstem,cortex,thalamusetc.lBasic respiratory centerlBrainpartsthatareresponsibleforgenerationofbasicrespirationpatternslItislocatedinthebrainstemThe Experiment Done by Lumsden in the CatConclusionsUpper pons-pneumotaxic center;lower pons-apneustic center(not accepted);Spinal cord-Basic respiratory center;spinal cord:Cut atBreathing pattern(vagus nerve intact)Breathing pattern(vagus nerve cut off)MidbrainandtheponsNearlynormalDeepandslowMidponsNearlynormalApneusticbreathingPonsandmedullaIrregularCheyne-StokesbreathingMedullaandthespinalcordNobreathingNobreathing2024/5/24周五5Respiratory-RelatedNeuronsintheBasicRespiratoryCenterlDorsal respiratory group(DRG)lLocated in the dorsal region of the nucleus tractus solitariilMainly contain inspiratory neuronslGenerate basic rhythmlVentral respiratory group(VRG)lA column of cells in the general region of the nucleus ambiguus.lIt houses both inspiratory and expiratory neuronslMost neurons are silent during normal quiet respirationPneumotatic center It acts to limit inspiration.As a result,it increases the rate of breathingIs the Pre-Btzinger Complex Essential for the Generation of Basic Respiratory Pattern?Modified from Brain 2011:134;2435Medullaoblongata=延髓Pons=脑桥Lateralreticularnucleus(LRN)=外侧网状核XII=面神经Obex=栓、门MSA=multiplesystematrophySCA3=spinocerebellarataxiatype3Multiple Systems Atrophy vs.Spinocerebellar Ataxia 3PatientswithmultiplesystemsatrophypresentwithcentralrespiratorydeficitsbutwithoutswallowingproblemsPre-BtzingerComplexneuronsarereducedwhereasambigualmotoneuronsarepreserved.Patientswithspinocerebellarataxia3hasnocentralrespiratorydeficitsbutwithdysphagia,Pre-BtzingerComplexneuronsarepreserved,whereasambigualmotoneuronsarediminished.Neural Mechanisms underlying the Generation of Rhythmic RespirationTwoHypothesesOscillatorytheoryorthepacemakerhypothesis(起步细胞学说)Networktheory(神经网络学说)Oscillatory TheoryPacemakerneuronsgeneratetherespiratoryrhythm(Smithetal.,Science,1991).Neurons in pre-Btzinger can Burst spontaneously RegularfiringinducedbycurrentinjectioninahippocampalgranulecellSpontaneousburstingInaratpre-BtzingerneuronNeurons in pre-Btzinger can Burst spontaneously RegularfiringinducedbycurrentinjectioninahippocampalgranulecellSpontaneousburstingInaratpre-Btzingerneuron2024/5/24 周五12Basic respiratory center(Medulla and pons)Voluntary control(Cerebrum)SpinalmotorneuronsIntercostalsDiaphragm&accessory musclesMuscles of respirationCentralChemoreceptorsPeripheralChemoreceptorsChemoreceptorsStretch receptorsIrritant receptorsJ ReceptorsMuscle proprioceptorsMechanoreceptors Phrenic nervesother nerveslVoluntary control of respiration is needed in suckling,swallowing,sniffing,chewing,coughing,vomiting and vocalization.lVoluntary control over pulmonary ventilation originates in the motor cortex of cerebral frontal lobe.lThe impulses are transmitted down the corticospinal tracts to the respiratory neurons in the spinal cord,bypassing the brainstem respiratory centers.Voluntary Control of Breathing CHEMICAL CONTROL OF RESPIRATIONPeripheralChemoreceptorsystemCentralChemoreceptorsystemRespiratory Activity is Sensitive to Oxygen,Carbon Dioxide,and Hydrogen Ions in the Blood lTheoverallgoalofrespirationistomaintainproperconcentrationsofoxygen,carbondioxide,andhydrogenionsinthetissues.lRespiratoryactivityishighlysensitivetochangesineachofthese.lExcesscarbondioxideorexcesshydrogenionsinthebloodmainlyactonthecentralchemoreceptorsystemwhereashypoxiaactsentirelyontheperipheralchemoreceptorsystem.PeripheralChemosensoryReceptorSystem2024/5/24周五16Afferent PathwaysCarotid bodies Carotid sinus nerve glosopharyngial(IX CN)medulla near nucleus tractus solitarius(NTS)Aortic bodies Join the vagus(X CN)medulla near nucleus tractus solitarius(NTS)PeripheralChemoreceptorsshouldbeDistinguishedfromBaroreceptorslCarotidarterybodiesandaorticbodies:chemoreceptorslCarotidbodiesareatthedivisionofthecommoncarotidarteryintotheexternalandinternalcarotid.TheaorticbodyisontheaorticarchlCarotidarterysinusandaorticarc:baroreceptors(theyarewithinthewallsofthebloodvessels)lBaroreceptorssensethetensionofbloodvesselsFunctions of Peripheral ChemoreceptorslSensePO2,PCO2andH+inthearterialbloodlPrimarilysensitivetoarterialPO2hyperventilationlIntheabsenceofperipheralchemoreceptors,hypoxiaresultsinCNSneuronaldepressionanddepressedventilationlPaCO2andincreasedH+concentrationstimulatethesereceptorstoalesserextentbutmakethemmoreresponsivetohypoxemiaCentralChemoreceptorSystemLocation:Ventral lateral surface of the medullaStimuli:Increased H+or high CO2 in CSF or extracellular space2024/5/24周五20Arterial PCO2 is the most Important Factor in Regulation of RespirationThe arterial CO2 is held within 2-3 mmHg.The arterial CO2 is the most important factor in controlling respiration in physiological conditions.With increased arterial PCO2,both the rate and the depth of respiration increase.Peripheral chemoreceptor denervation studies showed 20-30%of the response from carotid bodies(rapid);the remaining 80%from central chemoreceptors(slow).Mechanisms Underlying Hyperventilation following PaCO2 IncreaseDirect stimulationlStimulation of peripheral chemoreceptprslStimulation of central chemoreceptorsIndirect stimulation CO2 Arterial H+Peripheral chemoreceptorsTheEffectsofLowerPaO2onRespirationlNoeffectofventilationwhenPaO2isabove100mmHglVentilationisuponcePaO2isbelow70mmHgandisdoubledwhenPaO2fallsto60mmHglHyperventilationfollowingdecreaseinPaO2issolelymadebystimulatingperipheralchemoreceptorslSeverehypoxiasuppressesrespirationthroughactingonrespiratorycentersofbrainstem2024/5/24周五23TheEffectsofHydrogenIonsonRespirationlAnincreaseinH+concentrationinarterialblood,CSForthelocaltissueofbrainstemstimulatesrespiration.lIncreasedH+stimulatesbothperipheralandcentralchemoreceptorswithstimulationoftheperipheralchemoreceptorplayingthemainrole.lAsH+cannotpassthroughthebrain-bloodbarrier,increasedH+inarterialbloodstimulatescentralchemoreceptorsthroughCO2.lAtbothperipheralandcentralchemoreceptors,H+mediatesincreasedrespirationbyCO2accumulation.lCentralchemoreceptorsaremoresensitivetoH+thanperipheralchemoreceptors.2024/5/24周五24HowDoesIncreasedArterialH+ActontheCentralChemoreceptorsSignificancesofHydrogenIonsonRespirationlCoordinatesmetabolicneedsandrespiration.lMaintainspHhomeostasis.2024/5/24周五26OndinesCurse2024/5/24周五The Oath by Ondines husband:Myeverywakingbreathshallbemypledgeofloveandfaithfulnesstoyou.The Curse made by Ondine(on-deen):Yousworefaithfulnesstomewitheverywakingbreath,andIacceptedyouroath.Sobeit.Aslongasyouareawake,youshallhaveyourbreath,butshouldyoueverfallasleep,thenthatbreathwillbetakenfromyouandyouwilldie!Theend:Ondineshusbanddied.CentralAlveolarHypoventilation(OndinesCurse)lCentralalveolarhypoventilationisararediseaseinindividualswhoarebornwithoutventilatorychemosensitivitylBreathingadequatewhenawake,butnotwhenasleeporduringsleepinglNoresponsetohypercapniaandhypoxiaEXERCISE AND VENTILATION Exercise Is Associated with HyperventilationRest Maximal Exercise IntensityMinuteVentilation(L/min)6100Acute Respiratory Response to Graded Dynamic Exercise Exercise IntensityVentilation(L/min)V/QPAO2(mm Hg)PaO2(mm Hg)PaCO2(mm Hg)Arterial pHRest51103100407.40Walking202103100407.40Jogging453106100367.40Running754110100257.32ConclusionHyperventilationduringexerciseisprimarilycausedbymechanismsbeyondchemicalchangesinthebloodThecortexsendssignalstothebasicrespiratorycenter?Isthereinteractionbetweenthecardiovascularandbasicrespiratorycenters?MECHANICALREFLEXESSeveralmechanicalreflexesthatarisefromthechestwallandlungsaffectventilationandventilatorypatterns.Receptors Are Localized in Lung Tissue and AirwayslPulmonaryreceptorscanbedividedinto3groups:pulmonarystretch,irritantandJreceptors.lAfferentfibersofallthreetypesliepredominantlyinthevagalnerves.Pulmonary Stretch ReceptorslThestretchreceptorsaresensoryterminalsofmyelinatedafferentfibersthatliewithinthesmoothmusclelayerofconductingairways.lThestretchreceptorssensechangesinlungvolume.lThestretchreceptorsmediatelunginflationrefelx(Hering-Breuerreflex).Lung Stretch ReflexeslPulmonaryinflationreflex(Hering-Breuerinspiratory-inhibitoryreflex)lInflationoflungsorstretchofairwaysswitchesfrominspirationtoexpiration.Asaresult,inspirationisshortenedwithincreasedbreathingrate.lPulmonarydeflationreflex:Deflationoflungspromotesinspirationiscalledpulmonarydeflationreflex.lBotharemediatedbythevagalfibers;cuttingofvagalnerveeitherunilaterallyorbilaterallycoulddeepenandprolonginspiration.More about the Hering-Breuer Inspiratory-Inhibitory ReflexlTheHering-Breuerinspiratory-inhibitoryreflex(pulmonaryinflationreflex)isstimulatedbyincreasesinlungvolume.lThisstretchreflexismediatedbyvagalfibers;itsreceptorsarelocatedinairwaysmoothmuscles.lThisreflexresultsinthecessationofinspirationbystimulatingtheoff-switchneuronsinthemedulla.lItisinactiveduringquietbreathinganditplaysaroleonlyinventilatorycontrolinadultswhenVTisgreatthan1L.lItmaybemoreimportantinnewborns.Irritant ReceptorslTheirritantreceptorsaresensoryterminalsofmyelinatedafferentfibersthatarefoundinthelargerconductingairways.lTheyarerapidadaptingreceptors.lTheyareinvolvedincoughing,gasping,andprolongedinspirationtime.J ReceptorslThesereceptorsarecalledjuxtapulmonarycapillaryreceptorsorJreceptors.lTheyareC-fiberendings.