神經(jīng)遞質(zhì)和受體

NeurotransmittersandReceptors

Theneurotransmittersarethechemicalsubstanceswhichbringtheinformationfromoneneurontoanother.Thenerveendingshavebeencalledbiologictranducers,thatconvertelectricalenergy

intochamicalenergy.Thisconversionprocessinvolvestheneurotransmitters.Asubstanceisatransmitterifitis1.distributedinthesynapticknob,anditsdistributionparallelsthatitreceptorsinpostsynpticcell,2.Therearethesyntheticenzymesinpresynapticneuronandthecatabolizingenzymesinthesynapse.Cduceseffectsontargetneuronswhenappliedtotheirmembrancebymesnsofamicropipette(微電泳).5.Theagonistcanproducethesameeffects;butantagonistcanblocktheroleoftransmitters.AcetycholineandcholinergicreceptorsSynthesisandcatabolismCholineAcetyl-CoAAcetylcholineCholineacetyltransferaseAcetylcholinesteraseCholineAcetateAcetylcholinergicreceptors

Muscrinicreceptors(M-receptor)smoothmuscle,glandandcardiacmuscle

Atropineinhibitingthecardiacmuscle,excitingthesmoothmuscle&gland

Nicotinicreceptors(N-receptor)motorending-plate(N2),postsynapticmembrane(N1),

N1:hexamethonium(六烴季胺),N2:decame-thoniumN2:excitingskeletalmuscle,N1excitingthepostsynapticneuroningangliaLocationsAntagonistNorepinrphrineNorepinephrineBiosynthesisTyrosineDopaDopamineNorepinephrineTyrosinehydroxylaseDopadecarboxylaseDopamineβ-hydroxylasePhenylalamineNorepinrphrinergicReceptors

α-receptors

α1&α2

Deoxynorepinephrinephentolamine(α)

prazosin(α1)yohimbine(α2)β-receptorsβ1,β2,β3Isoproterenolpropranonol(β)atenolol(β1)butoxamine(β2

Theraretwotypesofthenorepinephrinergicreceptorsbindedwithnorepinephrineandepinephrine.AgonistAntagonistTypesDopamineDopamineandit’sreceptorsarelocatedmainlyincentralsystem.Itissecretedbyneuronsthatoriginateinthesubstantianigra.Theterminationsoftheseneuronsaremainlyinthestraitalregionofthebasalganglia.Theeffectofdopamineisusuallyinhibitory.Thereare5sub-typesofdopaminergicreceptors;D1,D2,D3,D4,D5form.SerotoninItissecretedbynucleithatoriginateinthemedianrapheofthebrainstemandprojectstomanybrainareas,especiallytothedorsalhornsofthespinalcordandtothehypothalamus.Serotoninactsasaninhibitorofpainpathwaysinthecord,anditiaalsobelievedtohelpcontrolthemoodoftheperson,perhapseventocausesleep.OpioidPeptides

EnkephalinandendorphinsTheyareprobablysecretedbynerveterminalinthespinalcord,thebrainstem,thethalamus,andthehypothalamus.Theseprobablyactasexcitatorytransmitterstoexciteanothersystemthatinhibitsthetransmissionofpain.Threeopiatereceptorsareestablished:μκδreceptorReflexConcept:Areflexisanautomaticresponsetoastimulus,carriedoutbyarelativelysimpleneuronalnetwork.Form:Unconditionedreflex,ConditionedreflexUnconditionedreflex:protectivereflex;feedingreflex;sexualreflexConditionedreflexesa.form:classicconditionedreflex,electrocorticalconditioning,operantconditioningb.mechanism:afunctionalpathwayisdevelopedduringtheconditioningperiod.notes:conditionedstimulus,unconditionedstimulus,internalandexternalinhibition,positiveandnegativereinforcement,habituationReflexArcSensoryFunctionOfNervousSystemSensoryPathwaysPosteriorcolumnpathwayStep1:Thetouchandproprioceptionimpulsesreachthespinalcordthroughthedorsalrootsofspialnerves.Insidethespinalcord,theaxonsasendinthedorsalcolumntothemudulla.Step2:Theysynapseinthegracileandcuneatenucleiinthemudulla,andtheaxonofthenervesinthesenucleiscrossovertotheoppositesideofthebrainstemandasendtothethalamus.Touch,vibration,pressure,andproprioceptionNucleiinmedullaoblongataNucleiinthalamusLateral&ventralspino-thamictracts1.Thepainandtempreturefibersthatenterthedorsalcolumnspasstothedorsalhorn,wherethefiberssynapseonsecond-orderneurons.2.Theaxonsfromtheseneuronscrossthemidlineandasendintheanterolateralcolumnofthespinalcordtothethalamus,andsynapseonthespecificsensoryrelaynucleiofthethalamus.3.Thereisamajorinputfromtheanterolateralsystemintothemesencephalicreticularformation.Thussensoryinputactivitiesthereticularactivitinysystem,whichinreturnmaintainsthecortexinthealertatate.Lateral&ventralspino-thamictractsNucleiinthalamusLateralspino-thalamictractVentralspino-thalamictractThalamus

Allsensoryinformationsenterthethalamusbeforetransmissiontothecereberalcortex(exceptiontoolfactorysignals).Thethalamicfunctionsisavitalwaystationforthereceiptofsensoryimpulsesfromthebody.Fromthethalamus,thissensoryinformationisrelayed(projected)toappropriateareasofthecerebralcortex.Inaddition,thethalamusintegratesandtransmitsnerveimpulsestosubcorticalareas,andreceivesafferentimpulsesthatoriginateinthecerebralcortex,cerebellum,andbasalganglia.ThamamicNucleisThethalamicnucleiscanbedividedinto3groups:Sense-relaynucleiThespecificsense-relaynuclei,whichrelayauditory,visualandsomatestheticimpulsetotheauditory,visualcortexandpostcentralgyrus.2.Associatednuclei

Whichareconcernedwiththeintegrationofmovement,andtheconnectionoftheallsenses.3.Intralaminarnuclei:Thesenucleusdon’tprojectdirectlytocentralareasofthecortex.Theintralaminarnucleitransmitsnerveimpulsestosubcorticalareasbeforetransmissiontothecereberalcortex.andthenprojectediffuselytothecortexandmaintainwakefulness.ThalamusThethalamusisthefinalrelaypointforallasendingsensoryinformation,otherthanolfaction,thatwillreachourconsciousawareness.Itactsasafilter,passingontotheprimarysensorycortexonlyasmallportionofthearrivingsensoryinformation.Thethalamusalsoplaysaroleinthecoordinationofvoluntarymotorcommands.ProjectionSystemSpecificprojectionsystemfromthesensoryrelayandconnectivenucleisprojectingtothespecificareasofcortexinducingthespecificsensory.Non-SpecificprojectionsystemfromthethirdthalamicnucleisprojectingdiffuselytothecortexmantainingtheawarenessstateCorticalRepresentionSomaticsensoryareaIislocatedthepostcentralgyrus..SomaticSensationFunctionalCharacteristicsofSomaticsensoryareaI1.Thepartsofthebodyarerepresentedinorderalongthisarea,withthelegsonthetopandtheheadatthefeetofthegyrus.2.Thesizeofthecorticalreceivingareaforimpulsefromaparticilarpartofthebodyisproportionaltothenumberofreceptorsinthepart.3.Thelegsandtrunkarerepresentedbytheoppositesideofthepostcentralgyrus.SomaticsensoryareaII

The

somaticsensoryareaIIislocatedinthesuperiorwallofsylvianfissure（大腦側(cè)裂）.Theheadisrepresentedattheinferiorendofthepostcentralgyrus,andthefeetatthebottomoftheslyvianfissure.Therepresentionofthebodypartsisnotascompleteordetailedasitisinthepostcentralgyrus.Propriocepton(本體感覺）Proprioceptiveinformationistransmittedupthespinalcordinthedorsalcolumn.Agooddealoftheproprioceptiveinputgoestothecerebellum,butsomepassesviathemediallemniciandthalamicradiationtothecortex.TemperatureThetemperaturesenseorgansarenakednerveendings.Coldreceptorsrespondfrom10to38oC.Warmreceptorsrespondfrom30to45oC.Theimpulsesfromtheserecetorsrelayinformationtothepostcentralgyrusviathelateralspinothalamictractandthethalamicradiation.PainPainisaveryunpleasantfeelingproducedbytheharmfulstimulations.Thesenceorgansforpainarethenakednerve-endings.Painimpulsesaretrainmittedtothecentrolnervoussystemby2fiberssystems,smallmyelinatedAδfibersandunmyelinatedC.

FastPainSlowPain“bright”sharplocalizedfollowedbyadull,intense,diffuse,andunpleasurefeeling.trainsmittedbyAδfibers“cautery”slowpoorlylocalizedfollowedbynausea,throwup,cardiovescularandrespiratorychanges.trainsmittedbyCfibersVisceralPain&ReferredPainVisceralpainistheslowpainthatispoorlylocalized,unpleasant,andassociatedwithnauseaandautonomicsymptoms.ReferredpainIrriationofaviscusfrequentlyproducespaininsomesomaticstructurethatmaybeaconsiderabledistanceaway.LocationsofReferredPainFormationofReferredPainViscusViscusSomaticstructureSomaticstructureTobrainTobrainEvokedcorticalpotentialsDefinition:Theelectricaleventsthatoccurinthecortexafterstimulationofasenceorgancanbemonitred.Component:a.prirmaryresponse(largepyramidalcells)b.afterdischarge(cortex-thalamiccircuit)WavesofEvokedCorticalPotentialsElectroencephalogram(EEG)TherecordofthevariationsinpotentialrecordedfromthebrainiscalledtheEEG.TheEEGcanberecordedwithscapeelectrodesthroughtheunopenedskullorwithelectrodesonorinthebrain.Thetermelectrocorticogram(EcoG)issometimesusedtorefertotherecordobtainedwithelectrodesonthepialsurfaceofthecortex.MethodofRecordingEEGFormsOfEEGWaves1.alphawaves(alpharhythm):Inanadulthumanatrestwithmindwanderingandeyesclosed,themostprominentcomponentoftheEEGisafairlyregularpatternofwavesatafrequencyof8~12/sandanamplitudeofabout50μVwhenrecordedfromthescalp.2.betawaves:atafrequencyof14~30/s,anamplitudeofabout50μV,recordedfromparietalandfrontalregionofthescap;3.thetawaves:Thiswaveoccursinchildren,emotionalstress,braindisorersd,andisgeneratedinhippocampusinexperimentalanimals.4.deltawaves:below3.5/s;occursindeepsleep,infancy,veryseriousorganicbraindisease.EEGWavesAlphaBlock:Whentheeyesareopened,thealpharhythmisreplacedbyfast,irregularlow-voltagewithnodominantfrequecy.Thisphenomenoniscalledalphablock.alphawavesEyesopenEyeclosealphawaves

Sleep

Phasesofsleep(1)Slowwavesleep:Apersonasleepfirstertersthisstage,itlastsabout80~120minutes.(2)Desynchronizedsleep:lastsabout20to30minutes,andusuallyappearsontheaverageevery90minutesSWS

Slow一synchronizedeasilyFWS

Fast

irregularirregular+desynchronizeddifficutlyEyemovementBloodpressureHeartrateRespirationSenseSkeletalmusclesrelaxTensionofmuscleDreamingPatternofEEGArouseMechanismofSleepControlOfPosture&Movement-------ElementaryPrinciplesOfMovementControlMotoneuronsOfSpinalCord&MotorUnit1.Motoneuronsofthespinalcordαmotoneuronslargeαmotoneurons→fastmusclesmallαmotoneurons→slowmuscleγmotoneurons→intrafusalfibersofmusclespindle.2.Motorunit:Allthemusclefibersinnervatedbyabyasinglemotornervefiberarecalledamotorunit.StretchReflex1.Definition:Whentheskeletalmusclewithanintactnervesupplyisstretched,itcontracts.Thisresponseiscalledthestretchreflex.2.Form:tendonreflexandtonicstretchrefle(muscletonus)TendonreflexSuddenstretchofamusclecausesreflexcontractionofthesamemuscle,andthisopposesfurtherstretchofthemuscle.Tonicstretchreflex(muscletonus):Slowandconstantstretchofamusclecausestoniccontractionofthemuscle,andthismaintainsthepostureofthebody.

MuscleTonusMechanismofStretchReflexMusclespindle&GolgiorgansMusclespindle:Eachspindleisbuiltaroundthreetotensmallintrafusalmusclefibers,anditisaverysmallskeletalmusclefiber.Thecentralregionofeachfiberhaseithernoorfewactinandmyosinfilaments.Thecentralportionofthemusclespindleisthesensoryreceptorareaofthespindleandcansensethelengthofthemuscle.Golgiorgan:TheGolgiorgansensesthetensionofthemuscle,andit’safferentsaretheIbfibers.Effectsof

γ-motoneuronsTheefferentsfibersoftheγ-motoneuronsinnervatetheintrafusalmuscle,andcontrolthesensitivityofthemulsclespindlesdetectingthechangeinlengthofthemuscle.