Overview:
Thepartwheretheactivitiesofthenervecenterareconductedbynervefibersandfinallyproduceeffects,suchasmuscles,secretoryglands,etc.Theexcitementofthecentralnervoussystemreachestheeffectorthroughthenerve,causingittoundergocorrespondingactivities,suchasmusclecontractionandglandsecretion.
Anatomicalfeatures
Itisthelastlinkofthereflexarc,theterminaldeviceofthemotor(effect)neuronaxon,andthenerveimpulsetransmittedfromthecentertotheeffectoroccurshereTransformation,andspreadtovariousorgans,musclesorglands,whichmanifestsitselfincertainactivities,soitiscalledaneffector.Themotornerveendingsdistributedtotheskeletalmusclearecalledsomaticmotornerveendings;themotornerveendingsdistributedtotheinternalorgansarecalledvisceralmotornerveendings.Thecontactpointbetweenthesomaticmotornerveterminalandthemusclefiberiscalledthemotorend-plate(motorend-plate),whichiscomposedofthemotornerveterminalandthecontactedmusclefiberarea,alsoknownastheneuromuscularjunction.Theaxonlosesmyelinbeforeenteringthemotorendplate,andbranchestoformsomeprotrusionsattachedtothemusclemembrane.Here,sarcoplasmisabundant,andmitochondriaandnucleiareincreased.Eachmyelinatedfibercancontrolseveraloreventhousandsofmusclefibers.Thevisceralmotornerveendingsaredistributedinthesmoothmusclesoftheinternalorgansandbloodvessels,aswellasglandularepithelialcells.Thefibersarethin,withoutmyelin,andtheterminalbranchesarebeadedorswollenandattachedtothesmoothmusclefibersorrunthroughtheglandcells.
Accordingtothedifferentdistributionofnerveendings,itcanbedividedintosomaticmotornerveendingsandvisceralmotornerveendings.Motornerveendingsaredistributedtotheskeletalmusclefibersandcloselyadheretothemusclefiberstoformthemotorendplate.
Thevisceralmotornerveendingsaredistributedinthesmoothmuscleandglandularepithelialcellsoftheviscera.Nervefibersarethin,withoutmyelinsheath,andtheperipheralbranchesareplexiform;theendsswellintonodulesorbuckles,wrappingaroundmusclefibersorpassingbetweenglandcells.
Nerveendingstransmitimpulsestomusclefibersbecausetheaxonterminalswellingofnervefibersreleasesachemicalmedium(acetylcholine),whichpassesthroughthefissureandactsonthemusclemembranetogeneratemembranepotentialinthemusclemembrane.
Motornerveendingsandthemusclesorglandstheyinnervatearecalledeffectors.Theeffectorispartofthereflectionarc.Thereflexarcisdividedintofiveparts:receptors,afferentnerves,nervecenter,efferentnerves,andeffectors.Iftheeffectorisdamaged,whenthehumanbodyisinjuredorstimulatedfromoutside,thenervecenterofthehumancerebralcortexwillfeelpain,butitwillnotbeabletomakeanymovements.