Hermopäätteet

Peruskonseptit

Hermostuneisuus (4 kuvaa)

Thefiberterminalpartoftheperipheralnerveterminatesintheuniquestructureformedinothertissues,Callednerveending(nerveending).Accordingtotheirfunctions,nerveendingscanbedividedintotwocategories:sensorynerveendingsandmotornerveendings.

Aistihermopäätteet-rengassolut,ovaalinmuotoiset,sisävarsi,aistihermokuidut,vaippaelimet.

Motornerveendings-motorendplates,myelinatednervefibersbranchrepeatedlytoskeletalmusclebundlesandextendtomusclefibers.Nervefibersapproachthesarcolemmaandbranchrepeatedly,withabutton-likeend.Thisiscalledthemotorendplate

Toiminto

Tunne

Aspecificstructureformedbytheterminalpartoftheprocesssurroundingasensory(afferent)neuronandothertissuestructuresiscalledareceptor.Itcanfeelvariousstimuliinsideandoutsidethehumanbody,andtransformitintonerveimpulses,whicharetransmittedtothecenter.Sensorynerveendingscanbedividedintofreenerveendingsandtunicatesensorynerveendingsaccordingtotheirstructure.

Vapaa

(freenerveending)Thiskindofterminaliswidelydistributedintheepidermis,cornea,serosalmembrane,muscleandconnectivetissue,andthestructureisrelativelysimple.Themyelinsheathoftheperipheralprocessdisappearsneartheterminalend,anditsexposedfinebranchesbranchrepeatedly,anddispersefreelyacrossepithelialcellsorconnectivetissues,andcanfeelthestimulationofpainandcoldandheat.

Liike

Motornerveending(motornerveending)istheendoftheefferentnervefiberofthemotorneuron

,endinginSkeletalmuscle,myocardium,smoothmuscleandglandsformeffectors,whichinnervatemusclecontractionorglandularsecretion.Therearetwotypesofefferentnervefibers:oneisthesomaticefferentnervefiberwithmyelinsheath,whichisacomponentoftheperipheralnerve,anditsendformsthemotorendplateintheskeletalmusclefiber;theotheristhevisceralefferentnervefiber,Nomyelinsheath,sentoutfromtheautonomicganglion,endinginthemyocardium,smoothmuscleandglandularepithelium,thenerveendingsareswollennodules.

Luokittelu

On tunicatettavia aistillisia hermoja

(encapsulatenerveendig)Therearemanyformsofthiskindofsensorynerveendig,andthesizeisdifferent.One,butthenerveendingsarecoveredwithconnectivetissuecapsules.Thecommononesare:

(1)Tactilecorpuscle:alsoknownasMeissnercorpuscle,distributedinInthedermalpapillaoftheskin,thepalmsofthefingersandtheundersidesofthetoesarethemostcommon.Thecorpuscleiselliptical,withadiameterofabout30-100μm,surroundedbyconnectivetissuetoformacapsule,andtherearemanyrowsofflattactilecells.Myelinatednervefiberslosemyelinsheathatthetunicateandpenetrateintothetunicate,andthebranchesarecoiled.Themainfunctionistofeelthesenseoftouch.

(2)Lamellarcorpuscle:alsoknownasPaciniancorpuscle,thistypeofcorpuscleiswidelydistributed,morecommoninthedeepdermis,subcutaneoustissue,mesentericandpancreasConnectivetissue.Thecorpusclesaremostlyroundorelliptical,withdifferentsizesandadiameterofabout0.5-3mm.Thecapsuleofthecorpuscleisaconcentriclamellaformedbyflatconnectivetissuecellsandfibers,andthelamellaisfilledwithgel-likesubstances.Thecentralaxisofthecorpuscleisahomogeneouscylinder.Itissaidthattheinnerbulbnervefiberlosesmyelinandenterstheinnerbulb,mainlyforfeelingpressure,vibrationandtension.

(3)Musclespindle:Aslenderspindle-shapedbodywidelydistributedintheskeletalmusclesofthewholebody,about2～5mminlength,withaconnectivetissuecapsuleonthesurface,whichcontains3～10thinnerskeletalmusclefibersarecalledintrafusalmusclefibers.Therearetwotypesofsensorynervefibersthatenterthemusclespindle:onesensorynervefiberisathickmyelinatednervefiber.Thehumanmusclespindlelosesmyelinsheathinfrontofthemusclespindle,andentersthemusclespindleinthemiddleofthemusclespindle.Itwrapsaroundthenucleus-containingpartoftheinnerspindlemuscle;theotherisathinmyelinatednervefiber,whichhasaflowerbranchshapeafterlosingmyelinsheath,andisdistributedatbothendsofthenerveterminal.Inaddition,thereisathinmotornervefiberinthemusclespindle,whichcomesfromthesmallneuron(γneuron)intheanteriorhornofthespinalcord.Themusclespindleislocatedbetweenthemusclefiberbundles.Whenthemusclecontractsorstretches,theinnerspindlemusclefibersareforcedtostimulatethenerveendingsandgeneratenerveimpulses,whicharetransmittedtothecentertoproducesensations.Therefore,themusclespindlesarethemainbodythatsensesthemovementofmusclesandchangesinthepositionofthelimbs.Receptors.Thestructureoftendonspindleissimilartothatofmusclespindle.

Moottoripään levyneuroliitin

(motorendplate)ItcomesfromtheaxonterminalofthemotorneuronintheanteriorhornofthespinalcordorbrainstemandreachesThemusclemembraneofskeletalmusclefiberslosesmyelinsheath,andthendividesintoclaw-shapedfinebranches.Theterminalswellsandformsanellipticalplate-shapedbulgeonthesurfaceoftheskeletalmusclefiber,withadiameterof10to80μm.Mitochondriaandsphericalsynapticvesiclesinthesphericalterminaloftheaxoncontainacetylcholine.Theaxonmembraneofthesphericalterminalisthepresynapticmembrane,andthemusclemembranecorrespondingtotheanteriormembraneisthepostsynapticmembrane.ThereareNreceptorsinthemembrane.Thesurfaceareaof​​therearmembrane.Betweenthepre-synapticandposteriormembranesisasynapticgapwithawidthofabout40-60nm.Itcanbeseenthatthemotorendplateisaneuromuscularjunction(neuromuscularjunction).AcetylcholinereleasedbysynapticvesiclesactsontheNreceptorsofthepostsynapticmembrane.Itcausesthemusclemembranetobeexcitedandisconductedtotheentiremusclefiberthroughthetransversetubulesystem,causingthemusclefibertocontract.Eachbranchofprefilledmotorneuronaxoncaninnervate100to2000skeletalmusclefibers.

Themusclefibersinnervatedbytheaxonanditsbranchesofeachmotorneuronarecalledamotorunit.Thesizeofthemotorunitisthenumberoffiberlinesinnervatedbythemotorneuron.Thereisabigdifferenceinthenumberofmotorunitsofeachmuscleinthehumanbody.Usuallythenumberofmotorunitsoflimbmusclesislarge;themotorunitsofsmallmusclessuchashandsandfeetarefew.Forexample,thehumantibialisanteriormusclehas443motorunits,andthenumberofmusclefiberspermotorunitis562.Thevermiformmuscleofthehandhasonly96motorunits,andthenumberofmusclefibersineachmotorunitis108.Muscleatrophyoccurswhenfronthornmotorneurondiseaseorperipheralnerveinjuryoccurs,whichwillinvolvechangesinthenumberofvarioustypesofmusclefibersandeachsportsshoeunit.

Viskeraalimotoriset hermot

(visceralmotornerveending)Thevisceralmotornerveendingisinnervatedbyautonomicneurons,usuallypassingthroughtwoneurons,passingthroughAutonomicganglia.Thefirstneuroniscalledthepreganglionicneuron,thecellbodyislocatedinthelateralgraymatterhornofthespinalcordorthebrainstemnucleus,anditsaxoniscalledthepreganglionicfiber;thesecondneuroniscalledthepostganglionicneuron,andthecellbodyislocatedintheautonomicganglionornerveplexusInside,itsaxonsarecalledpostganglionicfibers.Thesepostganglionicnervefibersaredistributedonthesmoothmuscle,myocardiumandglandcellsofthevisceraandbloodvessels,formingvisceralmotornerveendings.Thesevisceralefferentfibersaremostlyunmyelinatednervefibers,withverythinaxons,withadiameteroflessthan1μm.Theaxonterminalstructureissimple.Afterrepeatedbranching,theterminalbranchisenlargedinabeadedshape.Theenlargedterminalpartiscalledthenerveendingnodule,whichisattachedtosmoothmusclecellsorglandcells.Theterminalbranchisabeadedenlargedpart,calledvaricosity,withadiameterof1to2μm.Thebulgeisthepartthatestablishesasynapsewiththeeffectorcell.Theaxonofanautonomicneurondoesnotbranchattheendcanformabout30,000bulges.Thisstructureincreasestheareaorsurfaceareawhereneuronsreleaseneurotransmitters.Undertheelectronmicroscope,itcanbeseenthattherearemanysynapticcisternsandmitochondriainthebulge.Theexpandedaxonmembraneisthepresynapticmembrane,andthecorrespondingeffectorcellmembraneisthepostsynapticmembrane,withneurotransmitterreceptorsonthemembrane.Thesynapticcleftis15-20nm.Thegapbetweensomebulgingandeffectorcellsisabove80nm,evenuptoseveralmicrometers.Thecorrespondingpartdoesnothavethespecializedstructureofpostsynapticmembrane.Therefore,thisformofsynapseiscalleddistantsynapse(distantsynapse).synapse)ornon-synapticchemicaltransmission(non-synapticchemicaltransmission),whichproduceseffectsintheformofdispersion.Themaintransmittersofautonomicneuronsareacetylcholine,norepinephrineandpeptides.Whennerveexcitementspreadsnervefibersalongthevisceratotheends,itleadstothereleaseofneurotransmitters,causingsmoothmuscleandcardiacmusclecontractionandglandularsecretion.