神经元和神经胶质细胞-神经元

CellularNeurobiologyNeuroscienceResearchInstitutePekingUniversityDepartmentofNeurobiologyPekingUniversityHealthScienceCenterAlbertCheung-HoiYU于常海北京大學神經科學研究所[e-mail]’smanydrawingsofBraincircuityTheletterslabelthedifferentelementsCajalidentifiedinanareaofthehumancerebralcortexthatcontrolsvoluntarymovement.•Neurons:Excitablecells–“wiring”“SignalSenders”•Neuroglia:Support,Nurturing,InsulationCellularComponentsNerveCellsNeuronsNeuroglia•Cellbody(soma;perikaryon)•Axon:onlyone(branchesarecollaterals;terminalsareendfeet)•Dendrites:muchshorter;oneormorethanone;branchextensivelyintodendritictreesStructureofNeuronsAxonHillock(Axonalendfeet)TheAxonandAxonCollaterals•CellBody(Soma):LifeSupport–ProteinSynthesis–SingleNucleus,RER(NisslBodies)•Axon:Longestprocesstransmitsmessagesawayfromcellbody•Dendrites:Multipleprocessesoffcellbody–receivemessagesNeuronsStructure&FunctionNeuronsaresimilartoothercellsinthebodyinsomewayssuchas:1.Neuronsaresurroundedbyamembrane.2.Neuronshaveanucleusthatcontainsgenes.3.Neuronscontain:Whatareinsideofaneuron?NucleusNucleolusMicrofilaments/NeurotubulesEndoplasmicReticulum(ER)MitochondriaGolgiApparatusNisslBodiesOthers•Dendrites:–dendritetree•Axon:–axonhillock(axonorigination)–axonaltransportsystem–initialsegment(firstmyelinsheath)•actionpotentialgeneration–myelinsheathAxonandDendritesAxonsDendritesTakeinformationawayfromthecellbodyTakeinformationtothecellbodySmoothsurfaceRoughsurface(dendriticspines)Generallyonly1axonpercellUsuallymanydendritespercellNoribosomeHaveribosomesCanhavemyelinNomyelininsulationBranchfurtherfromthecellbodyBranchnearthecellbodyDifferencesbetweenAxonsandDendritesNeuronClassificationbyShape•Multipolar:“multi-”manyprocesses–Majority:Singleaxon,manydendrites(motorneuronandinterneuron)•Bipolar:“bi-”2processes–Foundinsomesensoryorgans(retina,taste,smell,innerearneuron)•Unipolar(pseudo-unipolar):“uni-”1process(withbranches)–Sensoryafferentneurons(dorsalrootganglia)ClassificationofNeuronsbyMorphologyClassificationofNeuronsbyAxonLength1.GolgitypeINeurons•Longaxons(longestfromthecortextothetipofspinalcord,50-70cm)2.GolgitypeIINeurons•Shortaxons(shortestaxonsterminateonlyafewmicronfromcellbody,interneurons)3.AmacrineNeurons•Anunusualcelltype,lackaxons–Sensoryneuron•fromreceptortoCNS;receivestimuliandtransmitafferentimpulsestoCNS–Interneurons•communicatingbetweenneurons;formcircuitsintheCNS–Motorneuron•fromCNStoeffectorcells;deliverefferentimpulsesoutthroughthePNStotheeffectorstocarryouttheactionsdirectedbytheCNSFunctionalClassificationofNeuron•EXCITABLEMembrane:Abletoregulatethemovementofions(charges)acrossandalongmembraneSIGNALTRANSDUCTION•DONOTReplicate:Damagedcellscannotbereplaced!ImportantFeaturesofNeuronsActionPotentialFourFunctionalRegionsofModelNeurons•Impulsetransmission:–electrical–chemical•Morphology:–axodendritic–axonsomatic–axoaxonic–dendrodendriticClassificationofSynapsessynapse4VesiclesreleaseNeurotransmitters•Chemicalsynapse:–presynapticknob(presynapticcomponent)•synapticvesicles–synapticcleft–postsynapticmembrane(postsynapticcomponent)•Electricalsynapse:–gapjunctionsSynapseStructuresTypesofsynapseDis-tanceCytoplasmiccontinuityUltrastruct-uralcomponentAgentoftrans-missionSynapticdelayDirectionoftrans-missionElectrical3.5nmYesGap-junctionchannelIoncurrentVirtuallyabsentUsuallybidirectionalChemical20-40nmNoPresynapticvesicleandactivezone;postsynapticreceptorsChemicaltransmittersSignificant:atleast0.3ms;usually1-5msorlongerUni-directionalDistinguishingPropertiesofElectricalandChemicalSynapsesAtachemicalsynapse,neuronstransmitinformationacrossacleft.1.SmallMoleculeNeurotransmitterSubstancesAcetylcholine(ACh);Dopamine(DA);Norepinephrine(NE);Serotonin(5-HT);Histamine2.AminoAcidsGamma-aminobutyricacid(GABA);Glycine;Glutamate;Aspartate3.NeuroactivePeptides-partiallist!!Bradykinin;beta-endorphin;calcitonin;cholecystokinin;enkephalin;dynorphin;insulin;gastrin;substanceP;glucagon;secretin;vasopressin;oxytocin,etc.ListofSomeNeurotransmitters•Axonaltransport:–intracellularcommunication•Bidirectionalmechanism:–anterogradetransport–retrogradetransport•Classifiedbytransportrates:–slowtransportsystem(0.2to1mm/day)–fasttransportsystem(200to400mm/day)AxonalTransportSystemsHitchingaRideon“Retrorail”MembranesoforganellesinvolvedinsynaptictransmissionarereturnedtothecellbodyforreuseordegradationNucleusCytoskeleton(Anterogradetransport))ComponentRate(mm/day)StructureandcompositionFasttransportAnterograde200-400Smallvesiculotubularstructures,neurotransmitters;membraneproteinsandlipidsMitochondria50-100MitochondriaRetrograde200-300LysosomalvesiclesandenzymesSlowtransportSCb2-8Microfilaments,metabolicenzymes,clathrincomplexSCa0.2-1NeurofilamentsandmicrotubulesMajorRateComponentsofAxonalTransport1.Neuronshavespecializedprojectionscalleddendritesandaxons.Dendritestakeinformationtothecellbodyandaxonstakeinformationawayfromthecellbody2.Neuronscommunicatewitheachotherthroughanelectrochemicalprocess3.Neuronscontainsomespecializedstructures(likesynapses)andchemicals(likeneurotr