神经元和神经胶质细胞神经元

OneoftheCajal’smanydrawingsofBraincircuityTheletterslabelthedifferentelementsCajalidentifiedinanareaofthehumancerebralcortexthatcontrolsvoluntarymovement.Neurons:Excitablecells–

“wiring”

“SignalSenders”Neuroglia:Support,Nurturing,InsulationCellularComponentsNerveCellsNeuronsNeuroglia二、神经元

1.结构

胞体树突突起轴突胞体树突轴突神经末梢神经胶质细胞

(1)胞体

soma

是神经元营养和代谢的中心，主要位于脑皮质，脊髓的灰质以及神经节内。①细胞膜cellmembrane

可兴奋膜，感受刺激，传导神经冲动。

②细胞核cellnucleus

核大而圆，位于细胞中央，着色浅，核仁明显。

③细胞质cytoplasm

除了有一般的细胞器外，还有尼氏体、神经原纤维

※尼氏体

Nisslbody

LM:颗粒或斑块状

EM：有RER、R

功能：合成蛋白质，如结构蛋白、酶、神经调质等。1.细胞膜2.细胞核3.核仁4.尼氏体5.轴丘※神经原纤维neurofibril

银染LM：呈棕黑色细丝

EM：神经丝、微管功能：构成神经元的细胞骨架，也参与物质运输。

(2)突起分树突与轴突

①树突dendrite

一个或多个，粗短且有分支，结构类似细胞质。功能：接受刺激，传向胞体。

②轴突axon

只有一条，细而长，内无尼氏体。

※

轴丘axonhillock

：无尼氏体。功能：传导兴奋冲动，传离胞体。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)神经元的分类

1.按神经元突起的数目分：

a.多极神经元

multipolarneuron

b.双极神经元

bipolar

neuron

c.假单极神经元

pseudounipolar

neuron

2.按神经元的功能分:

a.感觉神经元sensory

neuron:传入神经元

b.运动神经元motorneuron:传出神经元

c.中间神经元inter

neuron:联络神经元3.按神经元释放的递质不同分：

a.胆碱能神经元

b.肾上腺素能神经元d.肽能神经元

c.胺能神经元e.氨基酸能神经元4.按轴突的长短分：

a.高尔基I型神经元

b.高尔基II型神经元ClassificationofNeuronsbyMorphologyClassificationofNeuronsbyAxonLengthGolgitypeINeuronsLongaxons(longestfromthecortextothetipofspinalcord,50-70cm)GolgitypeIINeuronsShortaxons(shortestaxonsterminateonlyafewmicronfromcellbody,interneurons)AmacrineNeuronsAnunusualcelltype,lackaxonsSensoryneuron

fromreceptortoCNS;receivestimuliandtransmitafferentimpulsestoCNSInterneuronscommunicatingbetweenneurons;formcircuitsintheCNSMotorneuron

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

of

NeuronsActionPotentialFourFunctionalRegionsofModelNeurons突触定义：突触是（synapse）神经元与神经元之间，或神经元与非神经细胞之间的一种特化结构。1.胞体2.突起3.突触Impulsetransmission:

electricalchemicalMorphology:

axodendriticaxonsomaticaxoaxonicdendrodendriticClassificationofSynapses分类：化学性突触、电突触

结构：电突触:缝隙连接

突触小泡:神经递质神经调质突触前成分突触前膜突触间隙

突触后成分:突触后膜、受体、酶化学性突触超微结构模式图化学性突触超微结构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神经胶质细胞

神经胶质细胞（neuroglialcell）数量较多，分布广，结构类似神经元，突起无树突和轴突之分。

1.中枢神经系统的神经胶质细胞

(1)星形胶质细胞astrocyte

分泌神经营养因子和生长因子，对神经细胞起支持、营养、绝缘等作用，参与构成血－脑屏障及中枢神经创伤修复。(2)少突胶质细胞oligodendrocyteCNS的髓鞘形成细胞，参与CNS神经纤维的形成。(3)小胶质细胞microglia

属于单核吞噬细胞系统，可转变为巨噬细胞。(4)室管膜细胞ependymocyte

分布在脊髓中央管和脑室的表面，能分泌脑脊液。2.周围神经系统的神经胶质细胞(1)施万细胞Schwan