神经科学课件

生命科学导论

神经科学简介李晓东，Ph.D.Office6008xiaodli@Mindvs.Body---ABriefIntroductiontoNeuroscienceSensations,Emotionsanditsexpression

Sensoryevents(Perceptionoftheenvironment)Motor(Physiologyandbehavior)BodilyNeedsTheintegrativefunctionoftheIndividualSatisfybodilyneeds(thirst,hunger,sleepiness….)---(homeostasisandhealth)Selfprotectionandpreservationandkeepingthespeciesgoing----reproductionBodySensorysystems

SomaticMotorsystemEndocrinesystemDigestivesystemCirculatorysystemRespiratorysystemReproductiveSystemExcretionSystemNervous

systemBrainventricularsystemsandmeningesProductionandflowoftheCSFinsidethebrainChoroidplexusVentricularsystemsVentricularforamenattheendoftheIVventricleSubarachnoidspaceSinus(vein)NeuronstructureNeuronisaspecializedkindofcellNeurites---dendritesandaxonsCellbody(soma,perikaryon)containsthenucleus,Golgiapparatus,ribosomesandalltheothersubcelluarorganelles(Nisslbodies-----ribosomes)Thesynapse----structureEndoftheaxon(specializedstructure)Containvesicles(whereneurotransmittersarepacked)Electricalpulsesfromtheaxontriggersthevesiclestoreleasetothenextcell.Thepost-synapticdensity(PSD)EMpicture

Nomenclature:PresynapticSynapticcleftPostsynapticPostsynapticdensity(darkerintheEMimage)WhatisinthepostsynapticdensityPSD

isthesitewherethepostsynapticneuronreceiveschemicalsfromthepresynapticneuronShownincoloristhereceptorproteinsonthepostsynapticmembranewherethesignaltransductionoccurInformationpropagationChemicalsElectricalpulseChemicalsSynapseNextsynapsePNS---CranialNervesandtheirassociatenucleiDermatomePNS---AutonomicNervousSystemTwoDivisions

Sympathetic(thoracolumbar)

&

Parasympathetic(craniosacral)theentericnervoussystemTwoplexuses:Myenteric&SubmucosalFunctionsindependentof,butmodulatedbytheautonomicnervoussystembyCortexSensoryandmotorhomonculusRelativeproportions(motor)AuditorycortexTheskeletalmuscle-undervoluntarycontrol,andattachedtobonesAsingleskeletalmuscle,suchasthetricepsmuscle,isattachedatitsorigintoalargeareaofbone;inthiscase,thehumerus.Atitsotherend,theinsertion,ittapersintoaglisteningwhitetendonwhich,inthiscase,isattachedtotheulna,oneofthebonesofthelowerarm.SkeletalmusclesAskeletalmusclecontainsmanyfasciculuswhicharethebundlesofmusclefibers.MusclesarespecializedintermsofenergystorestheyrelyonforactionBasedonoxidativeenzymeactivity,thereare3distinctskeletalmusclefiber(cell)types.FlashThekneejerkreflexThereisahierarchicalsystemofneuronsthatcontrolvoluntary(somatic)muscleactivityLowermotorneuronshavecellbodiesintheanterior(ventral)graycolumnofthespinalcord,andsynapsedirectlywiththemusclefibers.(Also,lowermotorneuronsinnervatingtheheadhavetheircellbodiesintherespectivecranialnervemotornucleiinthebrainstem.)

UpperMotorNeuronsUppermotorneuroneshavecellbodiesinthecerebralcortexandothersupraspinalnervecenters,andinfluencethelowermotorneuronseitherwithdirectsynapticcontactorthroughinterneurons.

Neuronsofthecerebellumandthebasalganglia

influencetheuppermotorneurons.Supra-spinalinputWithinthespinalcord,differentsupraspinalinputshavedistinctterminationzonesandinfluencemotorpoolsatdifferentlocationsoftheventralhorn.

Generallythemotorpoolsforthedistallimbmusclesarelocatedlaterallywhiletheproximalandaxialmusclemotorpoolsarelocatedmoremedially.MultiplesupraspinalsourcesCorticospinal(cortex)Rubrospinal(rednucleus)Reticulospinal(reticularformation)Vestibulospinal(vestibularnuclei)Tectospinal(tectum,superiorcolliculus,usedforheadrotationbycontrollingneckmusclestobringtargetsintofocus)Thoseinputareorganizedasmedialandlateraldivisionsthathavedistinctfunctions.1.CorticospinalpathwayAlsocalled"pyramidalsystem",whichbeginswiththelargepyramidalneuronsofthemotorcortex,travelsthroughthepyramidsofthebrainstem,andfinallyendsonornearthea-motorneurons.ThecorticospinaltractoriginatesastheaxonsofpyramidalneuronsinlayerVof(mainly)primarymotorcortex.2.Rubrospinalpathway3PontineandmedullaryReticulospinalTractThelateralvestibulospinaltractisinvolvedinposturalcontrol(especiallyrelatedtomovementsofthehead)byinhibitingaxialflexormuscles,andstimulatingaxialextensormuscles.Themedialvestibulospinaltract(alsocalledthemediallongitudinalfasiculus)isinvolvedinthecoordinationofheadandeyemovements.4.VestibulospinalTractThekneejerkreflexStimulus:tappingthetendon,thuslengtheningofthemuscleDetection:lengtheningofthemuscleAction:contractionofthemusclerelaxationoftheantagonisticmuscleMusclecontractionorlengtheningaresensedbytwosensoryorganscloselyassociatedwiththemuscleanditstendonMusclespindlesGolgitendonorgansMusclespindlesandGolgitendonorgansarethemechanicalsensorystructuresofthemuscleMotorneuronsaresusceptibletomanyinputsbesidesfromothermusclespindlesandGolgitendonorgansSuchascutaneuouspain,mechanoceptorinputs.ThosereachthemotorneuronsthroughsynapticrelaysSuchaswithdrawlreflexwhentheskinisdamagedbymechanicalorthermalstimuli,thisservesasaprotectiveresponseTheconceptofcentralpatterngeneratorsTheconceptofcentralpatterngeneratorreferstotheorganizationpatternofspinalinterneuronsthathaveeitherexcitatoryorinhibitoryeffectsonipsilateralorcontralateralspinalmotorneurons.Itisthebasisforcoordinationofactivitypatternamongdifferentmotorpoolsatthespinallevel.Thecentralpatterngeneratorsiscriticalforcoordinatedlocomotionperformance.Thetwoarms(andlegs)arealternatelyflexingandextendingduringnormalwalking,andittakesalotofefforttomakethemmoveinthesamedirectionatthesametime.BothreflexandCPGusespinalinterneurons.Theymaystructurallyoverlap.Towhatdegreetheyareincommonisnotknownindetail.

CPGisthetargetofsupraspinalinputmodulation.OnEarth,whentheheadistiltedtotheleftorright,forwardorback,theotolithstendtomovealongthegravitygradient(downwards).Evenaslightmovementoftheotolithicmembraneisenoughtobendhaircellsandsendsensoryinformationtothebrain.Asimilarinertiaandgravity-dependentprocessoccurswhenyouacceleratelinearly—upordown,forwardorbackward.CerebellumThecerebellumThecerebellumcanbedividedintotheanteriorlobe,theposteriorlobe,andtheflocculonodularlobe.CerebellarAfferentsCerebellumCerebellumCerebellarefferenttargetsincludetherednucleus,thevestibularnuclei,reticularformation,andthecortexviathalamus.Thuscerebellumaffectfuncitonalstatesofcorticospinal,vestibulospinal,rubrospinaltracts,andreticulospinaltractsMotorlearningAccordingtothetheoriesofMarrandAlbus,alteringthestrengthofcertainparallelfiber-PurkinjecellsynapseswouldselectspecificPurkinjecellstoprogramorcorrecteyeorlimbmovements.Duringamovementtheclimbingfiberswouldprovideanerrorsignalthatwoulddepressparallelfibersthatareactiveconcurrentlyandallow“correct”movementstoemerge.Withsuccessivemovementstheeffectsofparallelfiberinputsassociatedwithaflawedcentralcommandwouldincreasinglybesuppressedandamoreappropriatepatternofactivitywouldemergeovertime.BasalgangliaThebasalgangliaThebasalgangliaaffectsthecorticospinalsystem(alsootheruppermotorneuronsystemsandeyemovement).Keystructuresassociatedwiththebasalganglia-thesubthalamusandsubstantianigraSubthalamusInternalcapsulearethefiberstoandfromthecortexInterconnectionsofthebasalgangliaandrelatedstructures(1)ThefirstisadirectfeedfromtheneostriatumtotheGPi/SNr.ThispathwayusesGABAandSubstancePasco-transmitters,andisinhibitory.TheGPi/SNr-themainoutputpathwayofthebasalganglia-projectsviainhibitoryGABAergicaxons,totheVA/VLthalamus,andintralaminarnuclei,inhibitingcells(differentcellsthanthecerebellarinputs),whichprojecttotheprefrontalcortex,limbiccortex,supplementaryandpre-motorcortexprimarily.NeostriatumoutputThebasalgangliathen,appeartobeableeithertopromoteandfacilitatemotoractivityortoinhibitit-andprobablydoesboth:suppressingunwantedactionswhichmightinterferewithadesiredmovement,whilstamplifyingandfacilitatingthoseprocesseswhichcontributetowardsthegenesisofthedesiredmovement.InHuntington'sChorea,ahereditarydiseaseinwhichGABAergic/enkephalinergicandcholinergiccellsinthestriatum(Pathway2)degenerate(GlutamicAcidDecarboxylaseandCholineAcetylTransferaseactivityfall).Symptomsincludeirritability,fidgetingandclumsiness,leadingtodementia,choreicmovementsandinexorablytodeath.Inlaterstages,GABA/SubstancePcellsrelatedtoPathway1alsodegenerate,leadingtofailuretoinitiatenormalmovements.DopaminergicneuronsinthesubstantianigracompactaprojectstobasalgangliaThedopaminergicsystemParkinson'sdisease,whichresultsinthedegenerationofdopaminergicsystemsinthebasalganglia,producesadisabilitytoinitiatedesiredmovements.Onetheotherhand,Huntington'schorea,whichresultsinthedegenerationofthemajorprojectionneuronsofthebasalganglia,ischaracterizedbyuncontrolledmovements.themotorsystemThevisualsystem

Thehumanvisualsystemgeneratesthesensationofcolor,form,movement…ThehumanvisualpathwayThreecomponentsofthevisualeventsLightsourceTheobjectwhichreflectsoremittinglightTheobserver(thevisualsensationtotallydependsontheobserver,differentspecies,anddifferentindividualswithinthesamespeciesrespondtolightstimulusdifferently:wavelength,color…)physicsColorhasthreemainperceptualattributes

Qualitatively,hueiswhetheracolourisred,orange,yellow,greenetc.Colourfulnessistheextenttowhichthehueisapparent.Brightnessistheextenttowhichanareaappearstoemitlight.Colorvisionenrichesvisualperceptionbutaloneitisapoordetectorofspatialdetail

AAnormalfull-colorimagecontainsinformationaboutvariationsinbrightnessandcolor.

BAnachromaticimagecapturesbrightnessvariationsinthesceneandisformedbyweightingtheenergyofthereflectedlightbytheoverallspectralsensitivityoftheeye.Spatialdetailiseasilydiscernedinthiskindofimage.

CApurelychromaticimagecontainsnoinformationaboutvariationsinbrightnessinthescene;ratheritcontainsonlyinformationabouthueandsaturation.Spatialdetailishardtodiscern.NervesupplyingIntrinsicEyeMuscles(autonomicnervoussystem)Retinaandopticnerve(centralnervoussystem)theeyeLightpassseveralcelllayerstoreachthephotoreceptorlayer,wherelightenergyisconvertedtoelectricalsignalsbyneuronsTheretinalayersPhotoreceptors—rodsandconesOpsinsarelocatedonthedisc-membranes,andtheyabsorblightenergyThereis3typesofconeopsinscomparedtoonerhodopsininnormalhumansDifferentopsinsabsorbinglightatdifferentwavelengths,sotheyareoptimallyactivatedbylightatdifferentpartofthespectrumLateralinhibitionofreceptivefieldsofganglioncellsInthecenterofthereceptivefield,itiseither“on”and“off”,intheperipheral,itisalsoonandoff.Thatis,lightoffthemainaxisoftheganglionalsocauseittorespondtothelight.ThenextrelayfromtheRGCsisthevisualthalamus-DLGThecentralrelaystationofthebrain(andmore)Theopticchiasmasthesiteforsortingopticnervefibers

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查看原图Neuronsinlayer4Cformoculardominancecolumns(injectionofmarkerintooneeyelabeldistinctcolumnsofcells.Tangentialviewofthelayer)ReceptivefieldsofV1corticalneuronsinlayer4CSynthesisofreceptivefieldsinV1corticalneurons(thisisasimplereceptivefieldneuron).Thistypeofneuronisbeststimulatedbyabaroredgeshapedobject.

LGNneuronsV1neuronOrientationselectivityWithineachoculardominancecolumn,neuronsshoworientationselectivity:thatis,theyarebeststimulatedwithabarataparticularorientationinthevisualfield.ThisisduetoretinotopicprojectionfromtheeyetotheLGNandfromtheLGNtotheV1visualcortexNeuronsintheV1regionprojectstootherareaofthecortex,thedirecttargetisV2dorsalstream:importantforvisualspatialtasksbutarewithoutanyeffectontheabilityofanimalstorecognizeobjectsventral:importantforrecognitionofobjectsbutnotvisuospatialtasks(cellsofthisregionrespondselectivelytospecificobjectssuchashandsorfaces)hearingSoundwavepressuredrivesthetympanicmembraneThepressureistransferredviathreesmallbones-ossicles(themalleus,incus,andstapes)whichinturnsdrivetheovalwindowinthecochlearorgan,causingthefluidinsidetooscillateOuterear

middleear

innerearTwocompartmentsofthelabyrinthTheouterbonylabyrinthandtheinnermembranaouslabyrinthhelicotremaThereare3ductswithinthecochlea-theauditorystructureScalavestibuleScalamediaScalatympaniThesensoryorganoftheear----thespiralorganofCortiItisanarrowsheetofcolumnarepitheliumrunningthelengthofthecochlearduct.TheepitheliumconsistsofsupportingpillarcellsandHensen’scellsandsensoryhaircellsresemblingthoseinthevestibularapparatus.ThesearesituatedonthebasilarmembraneandcoveredbythetectorialmembraneDirectionofperilymphmovementDirectionofperilymphmovementSignaltransductionLocalizedvibrationinthebasilarmembranecausesthestereociliaofthehaircells(embeddedinthetectorialmembrane)toshearrelativethetectorialmembrane,causingperiodicdepolarizaitonandhyperpolarizaitonofthecells.Thesignalispickedupbytheafferentnervefibers.PropertiesofthebasilarmembranedeterminesthelocationofthewaveinresponsetostimulationatcertainfrequenciesThebasilarmembraneisnarrow(50um)andstiffatthebase(theovalwindowwherethestapesstrikesandwiderandlessstiffattheapex(500um).Highfrequenciescausevibrationatthebasalendwhilelowfrequenciescausevibrationtowardtheapex.PositionsoftheauditorycenterswithintheCNSCerebralasymmetryCortex—gyri,sulciandlobesThesplitbrainRogerSperry

Apatientwithasplitbrain,whenshownanimageintheleftvisualfield(thatis,thelefthalfofwhatbotheyessee),willbeunabletovocallynamewhathasbeenseen.Thisisbecausethespeech-controlcenterisintheleftsideofthebraininmostpeople,andtheimagefromtheleftvisualfieldissentonlytotherightsideofthebrain(thosewiththespeechcontrolcenterintherightsidewillexperiencesimilarsymptomswhenanimageispresentedintherightvisualfield).Sincecommunicationbetweenthetwosidesofthebrainisinhibited,thepatientcannotnamewhattherightsideofthebrainisseeing.

FunctionLeftHemisphereRightHemisphereVisonLinguisticstimuli(letters,words)

Complexgeometricpatterns

Faces

Steropsis(depthperception)

AuditionLanguagesounds

Rhythm

Nonlinguisticsounds(environmentalsounds)

Melody

Somatosensation

Tactilerecognitionofcomplexpatterns

Braille

MotorComplexsequencesofvoluntarymovement

Movementsinspatialpatterns

MemoryVerbalmemory

Nonverbalmemory

LanguageSpeech

Reading

Writing

Arithmetic

Prosody

EmotionSocialemotions

Primaryemotions

SpatialprocessesGenerationofimagery

Geometry

Spatialorientation

Manipulationofimages(rotation)

Allocationofspatialattention

LimbicsystemOlfactionMemoryEmotionsanddrivesHomeostaticfunctionsincludingautonomicandneuroendocrinecontrolHOMEEmotionsDrawingsandphotographsusedbyDarwintoillustratecross-speciessimilaritiesinemotionexpression(anger/aggression).(Anger,fear,surpriseandsadness)AnimalmodelsandFACEvalidityWalterCannon’sShamRageexperimentsandtheemotionalmotorsystem

In1928,BardandCannonreportedthefollowing:Theyremovedbothcerebralhemispheres(includingthecortex,underlyingwhitematter,andbasalganglia)inaseriesofcats.Whentheanesthesiahadwornoff,theanimalsbehavedasiftheywereenraged.Theangrybehavioroccurredspontaneouslyandincludedtheusualautonomiccorrelatesofthisemotion.Thecatsalsoexhibitedsomaticmotorcomponentsofanger,suchasarchingtheback,extendingtheclaws,lashingthetail,andsnarling.Thisbehaviorwascalledshamragebecauseithadnoobvioustarget.Acompleteshamrageresponseoccurredaslongasthecaudalhypothalamuswasintact.Emotionalbehaviorsareoftendirectedtowardself-preservationandofteninvolvesphylogeneticallyolderpartsofthenervoussystem.

AmygdalaConditionalReflex(classicalconditioning)hypothalamusAutonomicNervousSystem(ANS)(internalbodyenvironment)andLimbicSystem(emotionalbrain)arelinkedbytheHypothalamus.HippocampusThehippocampusandmemeoryThehippocam