神經(jīng)組織-組織學和胚胎學

nervetissueCNS:consistingofthebrainandthespinalcord;PNS:consistingofnerves,ganglia(collectionofnervecellbodies)andspecializednerveendings.nervoussystemCompositionofnervetissuenervetissueneurons(nervecells)supportingcellsIntheCNS:neurogliacell(gliacell)

InthePNS:SchwanncellsatellitecellFunctionofnervetissueNeuron:

toreceivestimuliandconductelectricalimpulses.Supportingcell:physicalsupport(protection)forneuronalprocesses;electricalinsulationfornervecellbodyandprocesses;metabolicexchangepathwaysbetweenvascularsystemandneuron.neuron

Neuronisthefunctionalunitofthenervesystem.Itcanreceivestimuliandconductelectricalimpulses.

Structureofneuron

Neuronismadeupofcellbody(somaorperikaryon),dendriteandaxon.

1.

Soma：whereribosomes,mitichondria,andothersubcelluar

partsdothemetabolicworkofcells

Cellmembrane:

Therearesomeion-channelsandreceptorsinit.

Cytoplasm:

Nisslbodies,neurofibrils,ribosomes,

mitochondria,etc.

Nucleus:

central,largeandround,lightlystained,withanobviousnucleolus.neuronNisslbodyinthesoma：Basophilicgranules.EachNisslbodyismadeupofastackofRERandfunctionsinproducingproteins.

2.Dendrite：numeroustaperingbranchesformthedendritic

trees,whichincreasethereceptorsurfaceareaofaneuron.ThereareNisslbodiesinthedendrites.

Function:receivingstimuliandconductingthemtothecellbody.neuron3.Axon:thinandlong,similarindiameter.fewbranches.withoutNisslbodies.Functionastransmittingstimulitootherneuronsor

effectorcells.

Hillock:continuouswiththeaxon,theareaofcellbodywhereisfreeoflargecytoplasmic

organells:RERandsoon.

Axonaltransportsystem：Amodeofintercellularcommunicationbetweencellbodyandtheterminalofaxon.①Anterogradetransport：fromcellbodytotheterminalofaxon（materialssynthesizedinthesoma)②Retrogradetransport：(metabolicproductsandetc.)neuralstructureAxonHillockAxonaltransportsystem

Theclassificationofneurons1.Basedonthenumberofitsprocesses①multipolarneuron：oneaxonandtwoormoredendrites

②bipolarneurons：oneaxonandonedendrite.(limitedtotheretinaandetc.)③unipolar(pseudo-unipolar)neuron：oneprocess,whichdividesclosetothecellbodyintotwolongprocesses.threetypesofneurons2.Basedonthefunctionoftheneuron①sensoryneuron：conveyimpulsesfromreceptors(unipolar)toCNS-------afferentneuron.②motorneuron：conveyimpulsesfromtheCNSor

(multipolar)gangliatoeffectorcellsandcontroltheactivityofmuscleandthesecretionoftheglands------efferentneuron.③interneuron:formacommunicatingandintegrating

(multipolar)

networkbetweensensoryandmotorneurons--------intercalatedneuron.synapse

synapseissomespecialcelljunctionbetweenneuronsorbetweenneuronanditseffectorcell(musclefiberorglandularcell).synapseelectricalsynapsechemicalsynapsegapjunction:two-directiontransmissionindependentofneurotransmittersconsistsofpresynapticelement,synapticcleftandpostsynapticelement;one-directiontransmissionmediatedbyneurotransmitters;chemicalsynapse1.presynapticelement:bulb-likeenlargementsoftheaxonterminalswhichiscalledterminalbuttonorsynapticbag.

presynapticmembrane：presynaptic

cellmembranewith

voltagesensitivecalciumchannels.

synapticvesicles：membraneboundvesicleswhichcontainneurotransmitters.2.synapticcleft：thespacebetweenthepresynapticandpostsynapticmembranes.3.postsynapticelement：postsynaptic

cellmembranewithchemicalsensitiveionchannelsandreceptorsoftheneurotransmitters.synapticbagsynapsethetransmissionofthenerveimpulseNerveimpulsearrivesatpresynapticcellmembraneinfluxofthecalciumionsthroughthepresynapticmembraneSynapticvesiclespourtheneurotransmittersintothesynapticcleftNeurotransmittersreachandbindontocorrespondingreceptorsThepostsynapticmembranebecomesdepolarized.synapsesynapseseveralmorphologicalkindsofsynapsesaxodendritic:

occurringbetweenaxonsanddendrites;axosomatic:

occurringbetweenaxonandsoma;axoaxonic:

occurringbetweenaxonandaxon;dendrodentritic:

occurringbetweendendritesanddendrites.kindsofsynapsessupportingcellssupportingcellsInthePNS:SchwanncellsatellitecellIntheCNS:neurogliacell:astrocyte

(gliacell)oligodendrocyte

microglia

ependymalcell

nonconductivecells.function:insulatetheneuronsfromeachother,protecttheneurons

supportingcellsinthePNS

1.Schwanncell2.satellitecell1Schwanncellandmyelinsheath

profile:flatsacinshape

nucleus:flattened,stainsdarkly.function:surroundingtheaxonandconstitutingtheneurilemmaandmyelinsheath.

myelinsheath-formingcellinthePNS.formationofmyelinsheath

myelinsheath:

composedofmultiplelayersofSchwanncellmembranewrappedconcentricallyaroundtheaxon.EachSchwanncellinitiallysurroundssomepartofanaxon;Itwrapsashortsegmentofaxon,formingmultipleSchwanncelllayers,andcytoplasmissqueezedoutfrombetweenthemembraneoftheconcentriclayers;Theinnerleafletsoftheplasmamembranethenfuse.formationofmyelinatedaxonmyelinatedaxonmyelinsheathmyelinatedaxon（SEM）longitudinalandcrosssectionsofmyelinsheathmyelinatedaxon:

surroundedbymyelinsheath

unmyelinatedaxon:

withoutmyelinsheath

inthePNS

(

1)myelinatedaxoninthePNSanditsmyelinsheath

ThemyelinsheathissegmentedbecauseitisformedbynumerousSchwanncellsarrayedsequentiallyalongtheaxon.These"breaks"inmyelinationallowforsaltatoryconduction.neurilemma(thesheathofSchwann):ItispartofSchwanncellwhichisexternalto,contiguouswith,themyelinsheath.myelinsheath:composedofmultiplelayersofSchwanncellmembranewrappedconcentricallyaroundtheaxon.Ranviernode:ThejunctionwheretwoadjacentScheanncellsmeetisdevoidofmyelin.ThissiteiscalledRernode(internodalsegment):

themyelinbetweentwosequentialRanviernodes.ItiscomposedofpartofaxonanditsmyelinsheathwhichisformedbyoneSchwanncell.

(2)UnmyelinatedaxoninthePNS

TheSchwanncellsareelongated,andaxonsfitintothegroovesinthesurfaceofthecell.AsingleaxonoragroupofaxonsmaybeenclosedinthesurfaceofoneSchwanncell.

2.satellitecell

alayerofcuboidalorlowcolumnarcellsthatsurroundtheneuronalcellbodyoftheganglia.

Function:

providingelectricalinsulationandphysicalprotectionoftheneuronalbody.satellitecellsatellitecellsupportingcellsintheCNS1.neuron2.oligodendrocyte3.bloodvessel4.Axon5.astrocyte6.ependymalcell7.microglia1.astrocyte(fibrousandprotoplasmic)profile:largest,star-shapedglialcellsoftheCNSthathavenumerousprocesses.Manyoftheseprocessesextendtobloodvessels.Theexpandedendingsoftheastrocyteprocessesareknownasend-feet.

blood-brain-barrier:Itisformedbytightjunctionsbetweenendothelialcells,theend-feetfunctiontoinduceandmaintaintheblood-brainbarrier.

supportingcellsintheCNSendfeetofastrocytesandBBBBBB:torestrictthematerialpermeationbetweenbloodandbrain.astrocyteastrocyte（1）fibrousastrocyte：morecommoninwhitematter.Fewerprocesseswhicharerelativestraight.（2）protoplasmicastrocyte：moreprevalentingraymatterTheyhavenumerous,short,branchingprocesses.

2.oligodendrocyte

Profile:smallerthanastrocyte,processesareshorterandlessthanthoseoftheastrocyte.Nucleus:smallerandstaineddarkly.Function:involvedintheformationofthemyelinsheathintheCNS.oligodendrocyte

andthemyelinsheathintheCNS(1)myelinatedaxonintheCNS

2.oligodendrocyte4.Axon(1)myelinatedaxonintheCNSIntheCNS,myelinsheathisformedbyoligodendrocytes.eachprocessoftheoligodendrocytescansurroundsomepartofoneaxon:Processesofoneneuroncansurroundtheaxonsofseveralneurons.

(2)TheunmyelinatedaxonintheCNS

Theaxonisthinner.Usuallythereisnogliasurroundingit.

3.microgliaprofile:thesmallestgliacell.roundorthinandlonginshape.withfewerandshorterprocesses.nucleus:triangleinshapeorlookslikeapole.function:similartothatofmacrophage.

microglia4.ependymalcell：column-shapedcellsthatlinetheventriclesofthebrainandcentralcanalofthespinalcord.itisanimportantpartofthebarrierbetweenthebrainandcerebrospinalfluid.supportingcellsintheCNSmyelinatedaxonaxonsinthePNS

nervefiberandnervenervefiber:Itiscomposedoftheaxonwithorwithoutthemyelinsheath.

Basedon

thepresenceofmyelinsheath,nervefibersaredividedintotwocategories:

myelinatednervefiberandunmyelinatednervefiber.

nerve

nerve:abundleofnervefibersheldtogetherbytheconnectivetissue(C.T.).

epineurium：CTsurroundinganerve.

perineurium：CTsurroundingeachnervefiberfascicle.

endoneurium：CTsurroundingeachindividualnervefiber.

peripheralnerve

epineuriumendoneurium

perineurium5.nerveendingsensorynerveendingtheterminalpartoftheperipheralarborizationofthesensoryneuron.Itcanformkindsofsensoryreceptorsinthetissueororgan.1.freenerveending2.tactilecorpuscle

3.lamellarcorpuscle

4.musclespindle

1.Freenerveending

terminalbranchesofthemyelinatedsensorynervefiber.Itisdevoidofmyelinsheath.Distribution:betweenthecellsofepidermis,cornealepitheliumorintheC.T.ofdermisandhairfollicles,etc.Function:

receptorofpain.2.tactilecorpuscle(Meissner’scorpuscle)ellipse,freenerveendingswithacapsuleofC.T.Distribution:lieinthedermalpapillae.Function:servingastouchreceptors.

3.lame