神經(jīng)元和神經(jīng)膠質(zhì)細胞神經(jīng)元

OneoftheCajal’smanydrawingsofBraincircuityTheletterslabelthedifferentelementsCajalidentifiedinanareaofthehumancerebralcortexthatcontrolsvoluntarymovement.Neurons:Excitablecells–

“wiring”

“SignalSenders”Neuroglia:Support,Nurturing,InsulationCellularComponentsNerveCellsNeuronsNeuroglia二、神經(jīng)元

1.結(jié)構(gòu)

胞體樹突突起軸突胞體樹突軸突神經(jīng)末梢神經(jīng)膠質(zhì)細胞

(1)胞體

soma

是神經(jīng)元營養(yǎng)和代謝的中心，主要位于腦皮質(zhì)，脊髓的灰質(zhì)以及神經(jīng)節(jié)內(nèi)。①細胞膜cellmembrane

可興奮膜，感受刺激，傳導(dǎo)神經(jīng)沖動。

②細胞核cellnucleus

核大而圓，位于細胞中央，著色淺，核仁明顯。

③細胞質(zhì)cytoplasm

除了有一般的細胞器外，還有尼氏體、神經(jīng)原纖維

※尼氏體

Nisslbody

LM:顆粒或斑塊狀

EM：有RER、R

功能：合成蛋白質(zhì)，如結(jié)構(gòu)蛋白、酶、神經(jīng)調(diào)質(zhì)等。1.細胞膜2.細胞核3.核仁4.尼氏體5.軸丘※神經(jīng)原纖維neurofibril

銀染LM：呈棕黑色細絲

EM：神經(jīng)絲、微管功能：構(gòu)成神經(jīng)元的細胞骨架，也參與物質(zhì)運輸。

(2)突起分樹突與軸突

①樹突dendrite

一個或多個，粗短且有分支，結(jié)構(gòu)類似細胞質(zhì)。功能：接受刺激，傳向胞體。

②軸突axon

只有一條，細而長，內(nèi)無尼氏體。

※

軸丘axonhillock

：無尼氏體。功能：傳導(dǎo)興奮沖動，傳離胞體。Cellbody(soma;perikaryon)Axon:onlyone(branchesarecollaterals;terminalsareendfeet)Dendrites:muchshorter;oneormorethanone;branchextensivelyintodendritictreesStructureofNeuronsAxonHillock(Axonalendfeet)TheAxonandAxonCollateralsCellBody(Soma):

LifeSupportProteinSynthesisSingleNucleus,RER(NisslBodies)Axon:LongestprocesstransmitsmessagesawayfromcellbodyDendrites:Multipleprocessesoffcellbody–receivemessagesNeuronsStructure&Function

Neuronsaresimilartoothercellsinthebodyinsomewayssuchas:1.Neuronsaresurroundedbyamembrane.2.Neuronshaveanucleusthatcontainsgenes.3.Neuronscontain:

Whatareinsideofaneuron?NucleusNucleolusMicrofilaments/NeurotubulesEndoplasmicReticulum(ER)Mitochondria

GolgiApparatusNisslBodiesOthersDendrites:dendritetreeAxon:axonhillock(axonorigination)axonaltransportsysteminitialsegment(firstmyelinsheath)actionpotentialgenerationmyelinsheathAxonandDendritesAxonsDendritesTakeinformationawayfromthecellbodyTakeinformationtothecellbodySmoothsurfaceRoughsurface(dendriticspines)Generallyonly1axonpercellUsuallymanydendritespercellNoribosomeHaveribosomesCanhavemyelinNomyelininsulationBranchfurtherfromthecellbodyBranchnearthecellbodyDifferencesbetweenAxonsandDendritesNeuronClassificationbyShapeMultipolar:“multi-”manyprocessesMajority:Singleaxon,manydendrites(motorneuronandinterneuron)Bipolar:“bi-”2processes

Foundinsomesensoryorgans(retina,taste,smell,innerearneuron)

Unipolar(pseudo-unipolar):“uni-”1process(withbranches)Sensoryafferentneurons(dorsalrootganglia)神經(jīng)元的分類

1.按神經(jīng)元突起的數(shù)目分：

a.多極神經(jīng)元

multipolarneuron

b.雙極神經(jīng)元

bipolar

neuron

c.假單極神經(jīng)元

pseudounipolar

neuron

2.按神經(jīng)元的功能分:

a.感覺神經(jīng)元sensory

neuron:傳入神經(jīng)元

b.運動神經(jīng)元motorneuron:傳出神經(jīng)元

c.中間神經(jīng)元inter

neuron:聯(lián)絡(luò)神經(jīng)元3.按神經(jīng)元釋放的遞質(zhì)不同分：

a.膽堿能神經(jīng)元

b.腎上腺素能神經(jīng)元d.肽能神經(jīng)元

c.胺能神經(jīng)元e.氨基酸能神經(jīng)元4.按軸突的長短分：

a.高爾基I型神經(jīng)元

b.高爾基II型神經(jīng)元ClassificationofNeuronsbyMorphologyClassificationofNeuronsbyAxonLengthGolgitypeINeuronsLongaxons(longestfromthecortextothetipofspinalcord,50-70cm)GolgitypeIINeuronsShortaxons(shortestaxonsterminateonlyafewmicronfromcellbody,interneurons)AmacrineNeuronsAnunusualcelltype,lackaxonsSensoryneuron

fromreceptortoCNS;receivestimuliandtransmitafferentimpulsestoCNSInterneuronscommunicatingbetweenneurons;formcircuitsintheCNSMotorneuron

fromCNStoeffectorcells;deliverefferentimpulsesoutthroughthePNStotheeffectorstocarryouttheactionsdirectedbytheCNSFunctionalClassificationofNeuronEXCITABLEMembrane:Abletoregulatethemovementofions(charges)acrossandalongmembraneSIGNALTRANSDUCTIONDONOTReplicate:Damagedcellscannotbereplaced!ImportantFeatures

of

NeuronsActionPotentialFourFunctionalRegionsofModelNeurons突觸定義：突觸是（synapse）神經(jīng)元與神經(jīng)元之間，或神經(jīng)元與非神經(jīng)細胞之間的一種特化結(jié)構(gòu)。1.胞體2.突起3.突觸Impulsetransmission:

electricalchemicalMorphology:

axodendriticaxonsomaticaxoaxonicdendrodendriticClassificationofSynapses分類：化學(xué)性突觸、電突觸

結(jié)構(gòu)：電突觸:縫隙連接

突觸小泡:神經(jīng)遞質(zhì)神經(jīng)調(diào)質(zhì)突觸前成分突觸前膜突觸間隙

突觸后成分:突觸后膜、受體、酶化學(xué)性突觸超微結(jié)構(gòu)模式圖化學(xué)性突觸超微結(jié)構(gòu)synapse4VesiclesreleaseNeurotransmittersChemicalsynapse:presynapticknob(presynapticcomponent)synapticvesiclessynapticcleftpostsynapticmembrane(postsynapticcomponent)Electricalsynapse:gapjunctionsSynapseStructures

TypesofsynapseDis-tanceCytoplasmiccontinuityUltrastruct-uralcomponentAgentoftrans-missionSynapticdelayDirectionoftrans-missionElectrical3.5nmYesGap-junctionchannelIoncurrentVirtuallyabsentUsuallybidirectionalChemical20-40nmNoPresynapticvesicleandactivezone;postsynapticreceptorsChemicaltransmittersSignificant:atleast0.3ms;usually1-5msorlongerUni-directional

DistinguishingPropertiesofElectricalandChemicalSynapsesAtachemicalsynapse,neuronstransmitinformationacrossacleft.SmallMoleculeNeurotransmitterSubstancesAcetylcholine(ACh);Dopamine(DA);Norepinephrine(NE);Serotonin(5-HT);HistamineAminoAcidsGamma-aminobutyricacid(GABA);Glycine;Glutamate;AspartateNeuroactivePeptides-partiallist!!Bradykinin;beta-endorphin;calcitonin;cholecystokinin;enkephalin;dynorphin;insulin;gastrin;substanceP;glucagon;secretin;vasopressin;oxytocin,etc.ListofSomeNeurotransmittersAxonaltransport:

intracellularcommunicationBidirectionalmechanism:anterogradetransportretrogradetransportClassifiedbytransportrates:slowtransportsystem(0.2to1mm/day)fasttransportsystem(200to400mm/day)AxonalTransportSystemsHitchingaRideon“Retrorail”MembranesoforganellesinvolvedinsynaptictransmissionarereturnedtothecellbodyforreuseordegradationNucleusCytoskeleton(Anterogradetransport))ComponentRate(mm/day)StructureandcompositionFasttransport

Anterograde200-400Smallvesiculotubularstructures,neurotransmitters;membraneproteinsandlipidsMitochondria50-100MitochondriaRetrograde200-300LysosomalvesiclesandenzymesSlowtransport

SCb2-8Microfilaments,metabolicenzymes,clathrincomplexSCa0.2-1NeurofilamentsandmicrotubulesMajorRateComponentsofAxonalTransport1.Neuronshavespecializedprojectionscalleddendritesandaxons.Dendritestakeinformationtothecellbodyandaxonstakeinformationawayfromthecellbody2.Neuronscommunicatewitheachotherthroughanelectrochemicalprocess3.Neuronscontainsomespecializedstructures(likesynapses)andchemicals(likeneurotransmitters)4.NisslBodies

5.DONOTReplicate:Damagedcellscannotbereplaced!NeuronsdifferfromOtherCells神經(jīng)膠質(zhì)細胞

神經(jīng)膠質(zhì)細胞（neuroglialcell）數(shù)量較多，分布廣，結(jié)構(gòu)類似神經(jīng)元，突起無樹突和軸突之分。

1.中樞神經(jīng)系統(tǒng)的神經(jīng)膠質(zhì)細胞

(1)星形膠質(zhì)細胞astrocyte

分泌神經(jīng)營養(yǎng)因子和生長因子，對神經(jīng)細胞起支持、營養(yǎng)、絕緣等作用，參與構(gòu)成血－腦屏障及中樞神經(jīng)創(chuàng)傷修復(fù)。(2)少突膠質(zhì)細胞oligodendrocyteCNS的髓鞘形成細胞，參與CNS神經(jīng)纖維的形成。(3)小膠質(zhì)細胞microglia

屬于單核吞噬細胞系統(tǒng)，可轉(zhuǎn)變?yōu)榫奘杉毎?4)室管膜細胞ependymocyte

分布在脊髓中央管和腦室的表面，能分泌腦脊液。2.周圍神經(jīng)系統(tǒng)的神經(jīng)膠質(zhì)細胞(1)施萬細胞Schwan