Vestibular system: Anatomy, pathway and function | Kenhub

The vestibular system is a somatosensory portion of the nervous system that provides us with the awareness of the spatial position of our head and body ... Connectionlost.Pleaserefreshthepage. 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GoPremium Vestibularsystem Author: JanaVaskovićMD • Reviewer: RobertoGrujičićMD Lastreviewed:December21,2021 Readingtime:18minutes VestibularsystemanatomyThevestibularsystemisasomatosensoryportionofthenervoussystemthatprovidesuswiththeawarenessofthespatialpositionofourheadandbody(proprioception)andself-motion(kinesthesia). Itiscomposedofcentralandperipheralportions. Theperipheralportionofthevestibularsystemconsistsofthevestibularlabyrinth,vestibularganglion,andvestibulocochlearnerve(CNVIII).Thevestibularlabyrinthiscomprisedofproprioceptivecomponentslocatedintheinnerear;  Thesemicircularcanals,whichcontainthecellsthatdetectangularaccelerationofthehead; Theutricleandsaccule,whichcontainthecellsthatdetectthelinearaccelerationoftheheadandpositionoftheheadinspace(spatialorientation).  Thestimulifromthesereceptorsareconveyedtothevestibularganglion.Fromhere,theytravelthroughthevestibularportionofthevestibulocochlearnerve(CNVIII)intothecentralportionofthevestibularsystem;thevestibularnucleiinthebrainstem.Thevestibularnucleisendprojectionsintothecerebellum,spinalcord,thalamus,andnucleioftheoculomotor(III),trochlear(IV)andabducens(VI)nerves.Viatheseconnections,thevestibularsystemcontributestotheadjustmentsoftheheadandneckmovements,aswellasthepostureandbalanceofthewholebody,vestibulo-ocularreflexandeyemovements.Thisarticlewilldiscusstheanatomyandfunctionofthevestibularsystem. Keyfactsaboutthevestibularsystem Definition Aproprioceptivesomatosensorysystemwhichmediatesthesenseofbalanceandpositionoftheheadrelativetootherbodypartsandthesurroundings. Parts Central:vestibularnuclei Peripheral:Semicircularcanals,otolithicorgans,vestibularganglion,vestibulocochlearnerve(CNVIII) Functions Reflexeyemovements(vestibulo-ocularreflex),postureandbalanceofheadandneck Contents Labyrinthandsemicircularcanals Semicircularcanals Otolithicorgans Haircells Function Vestibularganglion Vestibularnerve Vestibularnuclei Connectionswiththenucleiofthecranialnerves Vestibulo-ocularreflex Connectionswiththespinalcord Connectionswiththecerebellum Connectionswiththecortex Clinicalanatomy Motionsickness  Vertigo Meniere’sdisease Caloricreflextest Sources +Showall Labyrinthandsemicircularcanals Thevestibularlabyrinthisabonycavitylocatedwithinthepetrousportionofthetemporalbone.Itconsistsofthebonyframeworkforthecochleaaswellasthethreesemicircularcanals.Thebonylabyrinthhousesthethreesemicircularcanalsandthetwootolithicorgans(theutricleandsaccule).Moreover,itcontainsthecochleawhichisapartofthehearingapparatus. Semicircularcanals Thesemicircularcanalsarethethreemembranouschannelslocatedwithinthebonysemicircularductsofthelabyrinth.Theyarelocatedinthreeplanes,witheachcanalmakinganangleofapproximately90degreeswiththeother.Thus,thesemicircularcanalsarethe: Anterior(superior),locatedinthesagittalplane Lateral(horizontal),locatedinthetransverseplane Posterior(inferior),locatedinthefrontalplane Theterminalpartofeachcanalendswithadilationcalledtheampulla,whichopensintothevestibule.Theampullaofeachsemicircularcanalcontainsaclusterofmechanoreceptorcellscalledthecristaampullaris.Eachcristaiscomposedofthespecialsensoryreceptorcells,calledthehaircells.Giventhatthesemicircularcanalsarefilledwithendolymph,themovementsofthisfluidstimulatethehaircells.Inthisway,eachsemicircularcanaldetectswhentheheadmovesduringtherotationalaccelerationalongitscorrespondingplane.Inotherwords,thesemicircularcanalsdetectheadmovementssuchasnoddingupanddown,shakingsidetoside,ortiltingleftandright. Otolithicorgans Theotolithicorgansarethetwomembranouscavitiesthatlieinthebonyvestibuleoftheinnerear.Namely,theyaretheutricleandsaccule.  Theutricleliesintheposteriorpartofthevestibule.Ononeend,itcommunicateswiththesemicircularcanals,whilstontheoppositeendformsautriculosaccularductwiththesaccule.Thisductpassesthroughthetemporalboneandreachestheposteriorsurfaceofthepetrouspartofthetemporalbone. Thesacculeliesanteriortotheutricleandissignificantlysmallerthanit.Besidesjoiningtheutriculosaccularduct,thesacculecommunicateswiththecochleabyductusreuniens. Theutricleandsacculecontaintheclustersofhaircellsaswell,exceptthatinthem,theclustersarecalledthemaculaoftheutricleandthemaculaofthesaccule.Theseneurosensoryareasrespondtothestimulationfromtheendolymphtodetectthelinearmovementsofthehead,aswellasitspositioninspacewhiletheheadisnotmovingbuttherestofthebodyis.Thecellsoftheutriclearespecializedtodetectmovementinthehorizontalplane,whilethesacculedetectsverticalmovement. Haircells Thehaircellsarethemotionreceptorsoftheinnerear,embeddedwithinthewallsofthesemicircularcanalsandotolithicorgans.Theyarecylindricalinshapeandfeaturemanystereociliaontheirapicalends.Eachcellalsohasasinglekinocilium,whichsitsonthelateralmostendoftheapicalsurface.  Inthesemicircularcanals,thehaircellsprojectfromthecristaeampullarestowardsthecavityofthecanals.Theapicalliningofthehaircellsinthesemicircularcanalsiscoveredbyagelatinousmasscalledthecupula.  Thecupulaoftheutricleandsacculehasanadditionalsuperficialfibrouslayercalledtheotolithicmembranewhichcontainsnumerouscrystalsofcalciumcarbonatecalledotolithsorotoconia.  Thehaircellswithinthevestibularorgansareorientedinawaythatthewholevestibularapparatusissensitivetomovementsinalldirections. Function Therotationalmovementsoftheheadinoneoftheplanescausestheendolymphwithinthesemicircularcanalstomoveintheoppositedirectionbyinertia.Theendolymphthenflowsagainstthecupula,whichdistendsacrosstheapicalsurfaceofthehaircells,movingthestereociliatowardthekinocilium.Theseciliarymovementsopenthetransductioncellchannels,triggeringtheexcitationofthecells.Themovementofstereociliaintheoppositedirectionreducesthecellactivity.Thereasonwhythelinearmovementsdon’tstimulatethecristaeampullaresisthatthelinearmovementshappenintheplanesinwhichtheendolymphalwayshitsthecupulafrombothsides,eventuallynotcausinganydisplacementnorhaircellstimulation. Lookingforwaysonhowtolearnandunderstandanatomyfaster?Tryoutour8stepstocreateyourownanatomyflashcards! Thehaircellsoftheotolithicorgansfunctionslightlydifferently.Theotolithicmembranemakesthelayeroverthehaircellsalotheavierthanthecupulainthesemicircularcanal.Oncetheheadislinearlytilted,thegravitycausestheotolithicmembranetoshearfromtheapicalsurfaceoftherelevantmacula.Theshearingmovementstimulatestheciliaandtriggersanactionpotential.Thereasonwhytherotationalmovementsdon’tstimulatethemaculaeoftheotolithicorgansisthattheflowoftheendolymphaloneisnotenoughtocausetheshearingoftheotolithicmembrane,thusitnevermovesthecilia. Anteriorampullarynerve Nervusampullarisanterior 1/5 Synonyms: Superiorampullarynerve,Nervusampullarissuperior Theactionpotentialsfromthecristaeandmaculaearecarriedbythecorrespondingbranchofthevestibularnerve; Cristaampullarisoftheanteriorducttransmitssignalsviatheanteriorampullarynerve. Cristaampullarisoftheposteriorducttransmitssignalsviatheposteriorampullarynerve. Cristaampullarisofthelateralducttransmitssignalsviathelateralampullarynerve. Maculaoftheutricletransmitssignalsviatheutricularnerve. Maculathesacculetransmitssignalsviathesaccularnerve. Theutricular,anteriorampullary,andlateralampullarynervesjointoformtheutriculo-ampullarynerve.Ultimately,theutriculo-ampullary,saccularandposteriorampullarynervessynapsewithinthevestibularganglion.  Learnmoreaboutthestructuresoftheinnerearwithourvideos,quizzes,labelleddiagramsandarticles. Internalear Explorestudyunit Vestibularganglion Superiorpartofvestibularganglion Parssuperiorgangliivestibularis 1/2 Synonyms: Superiorbranchofvestibularnerve,Ramussuperiornervivestibularis Thevestibularganglion(ganglionofScarpa)lieswithinthefundusoftheinternalauditorymeatus.Itisaclusterofbipolarsensoryneurons,thatarethefirst-orderneuronsofthevestibularpathway. Theperipheralprocessesofvestibularganglioncellscomprisethenervefibersthatreceivethestimulifromthehaircellsoftheotolithicorgansandsemicircularcanals,respectively.Thecentralprocessesofthevestibularganglioncomprisethefibersofthevestibularportionofthevestibulocochlearnerve(CNVIII). Vestibularnerve Vestibularnerve Nervusvestibularis 1/1 Synonyms: Nervusstaticus Thevestibularnervetransmitstheequilibriumimpulsesfromthevestibularapparatus.Itleavestheinnerearthroughtheinternalauditorymeatusandenterstheposteriorcranialfossa.Then,itsynapseswiththevestibularnucleiinthebrainstem.  Moreover,someofthefiberssynapsedirectlywiththecerebellumaswell.Thismakesthevestibularnerveunique,asitistheonlycranialnervewhosefirst-orderneuronssynapsewiththecerebellumdirectly. Masterthevestibulocochlearnerveanatomyandfunctionhere. Vestibulocochlearnerve(CNVIII) Explorestudyunit Vestibularnuclei Vestibularnuclei Nucleivestibulares 1/5 Thevestibularnucleiarethefournucleithatliewithintherhomboidfossaofthebrainstem.Theycontainthesecond-orderneuronsofthevestibularpathwaythatsynapsewiththevestibularportionofthevestibulocochlearnerve.Namely,thevestibularnucleiare: Thesuperiorvestibularnucleus(ofBechterew) Thelateralvestibularnucleus(ofDeiters) Theinferiorvestibularnucleus(ofRoller) Themedialvestibularnucleus(ofSchwalbe) Thesuperiorandmedialvestibularnucleireceivemostoftheinputsfromthecristaeampullaresofthesemicircularcanals.Theinferiorandlateralnucleireceivetheremainingfibersfrominferiorsemicircularcanals,aswellasfromtheutricleandsaccule.Thevestibularnucleiintegrateinputsfromtheperipheralvestibularstructures,contralateralvestibularnuclei,cerebellumandtheothersensorysystems(thevisualandsomatosensorysystems). Connectionswiththenucleiofthecranialnerves Mediallongitudinalfasciculus Fasciculuslongitudinalismedialis 1/1 Thesuperiorandmedialvestibularnucleisendfibersthatjointhemediallongitudinalfasciculus(MLF).Viathispathway,theysynapsewiththemotornucleioftheoculomotor(CNIII),trochlear(CNIV)andabducens(CNVI)nerves,includingtheinterstitialnucleusofCajalandthenucleusofDarkschewitsch.  Thisway,thevestibularsystemmediatesthereflexiveactivityoftheextraocularmuscles.Moreprecisely,thevestibularsystemmediatesthevestibulo-ocularreflex,inwhichthemovementsoftheeyesareadjustedtothemovementsofthehead. Vestibulo-ocularreflex Thevestibulo-ocularreflexisaninvoluntarymotoractivitymediatedbythevestibularsystemwhichservesforadjustingtheeyemovementswhiletheheadmovesinthehorizontalplane.Itservesforfixingthegazeduringheadrepositioning.Thereflexarcismediatedbythemediallongitudinalfasciculus(MLF)inthefollowingway; Oncetheheadisturnedsideways(e.g.totheleft),theendolymphinthevestibularorgansfallsbehindtotherightduetoinertiaandstimulatesthehaircellsofthelefthorizontalsemicircularcanal. Theinformationisconveyedtothevestibularnucleiviatheipsilateralvestibulocochlearnerve. TheneuronsfromthesuperiorandmedialvestibularnucleijointheMLFandreachthenucleusofthecontralateralabducensnerve.Thisway,thecontralaterallateralrectusmusclecontractsandpullstheeyesintheoppositedirectiontothatofthehead. Simultaneouslytotheabducensstimulation,someMLFfiberscrossthemidlineandsynapsewiththeoculomotornucleus.Thisstimulatesthemedialrectusmuscleontheoppositeeye,resultingwiththeconjugatedmovementofbotheyesinthehorizontalplane.  Atthesametime,theipsilateralmedialrectusmuscleisinhibitedsothatitdoesn’tcompetewithitscontralateralcounterpart. Toreiterate,onceapersonturnstheirheadwhilewantingtofixthegazeonastaticobject,thevestibulo-ocularreflexenablestheeyestoturnintheoppositedirectionsothatthepersoncanmaintainfocusontheperceivedobject. Connectionswiththespinalcord Vestibulospinaltract Tractusvestibulospinalis 1/1 Thelateralvestibularnucleussendsaxonsviathelateralvestibulospinaltract.Thistractsynapseswithinterneuronsalongtheentirelengthofthespinalcord,adjustingthepostureofthebodyandtoneofextensorsaccordingtothevestibularstimuli(vestibulo-spinalreflex). Themedialandinferiorvestibularnucleiprojecttheirfibersviathemedialvestibulospinaltract.Thistractterminateswithinthecervicalspinalcord,adjustingthepostureoftheheadandneck(vestibulo-cervicalreflex). Connectionswiththecerebellum Thevestibularinputsconnectwiththecerebellumintwoways; Inferiorcerebellarpeduncle Pedunculuscerebellarisinferior 1/2 Thesecond-orderneuronsfromthevestibularnucleiprojecttotheinferiorolivarynucleusviathevestibulo-olivarytract.Fromhere,thevestibularinputsarerelayedviathelateralpartoftheinferiorcerebellarpeduncle(restiformbody)intotheipsilateralcerebellarvermis,flocculusandnodulus.Thisconnectionenablesthejointmodulationofbalancebythecerebellumandvestibularsystem. Aportionofthefirst-orderneuronsfromthevestibularganglionofScarpapassthroughthemedialpartoftheinferiorcerebellarpeduncle(juxtarestiformbody).Theyenterthecerebellumasthemossyfibersandsynapsedirectlywiththeipsilateralvestibulocerebellum,vermisandfastigialnucleus.Theseconnectionsenablecerebellarawarenessofthevestibularsensationsandpromotenecessarymovementmodificationsbythecerebellum. Connectionswiththecortex Brodmannarea3 AreaBrodmann3 1/2 Synonyms: BA3 Thesuperiorandlateralvestibularnucleiprojecttotheventralposteriornucleiofthethalamustosynapsewiththethird-orderneuronsofthevestibularpathway.Thethalamusthenrelaysthesignalstotheprimaryvestibularcortex(Brodmannarea3a),locatedinthecortexoftheparietallobeadjacenttotheprimarymotorcortex.Thisareaintegratestheinformationfromthevestibularsystemwithotherproprioceptivesystemsandpassesthatinformationdirectlytotheprimarymotorcortex(Brodmannarea4).Fromhere,themotorresponsetotheproprioceptivestimuliisgenerated. Otherconnectionsbetweenthevestibularsystemandthecortexarestillbeinginvestigated.Sofar,thetwoparticularlyinterestingcorticalareashavebeenidentified; Oneofthemliesposteriortotheprimarysomatosensorycortex; Thesecondoneliesbetweenthesomatosensorycortexandmotorcortex Thesecorticalareasprocessthevestibularandvisualstimuli,andtheyareparticularlyactivewhenapersonundergoesrotatorymovementswitheyesclosed. Clinicalanatomy Motionsickness  Motionsicknessisaconditioncharacterizedbynauseaandvomitingduetothetravelling,itismostoftenseeninsomepeopletravellingbyvehicle.Itisduetofluctuationsinthemaculae. Vertigo Vertigoisaconditioninwhichapersonhasafalsesensationthateitherhimorsurroundingsareinmotion.Itcancausenausea,dizziness,sweatingandvomiting.Thisconditionisassociatedwithvestibularmalfunction.VertigoisthecommonsymptomofVestibularneuritis(labyrinthitis),Meniere’sdiseaseandVIIInervedamage. Meniere’sdisease Thisiscausedbyblockageinthecochlearaqueductandsymptomsaretinnitus,hearinglossandvertigo,senseofpressureintheear,sounddistortionsandnoisesensitivity.Thisdiseaseresultsinendolymphaticvolumewithballooningofthecochleaduct,utricle,andsaccule. Caloricreflextest Thisisatestofthevestibulo-ocularreflex.Itisdonebypouringcoldorwarmwaterintotheexternalauditorycanalusingasyringe.Thetemperaturedifferencebetweenthebodyandthewatercreatesaconvectivecurrentintheendolymphofthehorizontalsemicircularcanal.Hotandcoldwaterproducecurrentsinoppositedirectionsandthereforeaquickhorizontaleyesmovementintheoppositedirections.Ifthewateriswarm,theendolymphintheipsilateralhorizontalcanalrises,therebyincreasingthefiringrateoftheafferentvestibularnerve.Thiswillresulttotheeyesturningtowardsthecontralateralear,withaquickhorizontaleyesmovementtotheipsilateralear.Ifthewateriscold,theendolymphinthesemicircularcanalfalls,therebydecreasingthefiringrateoftheafferentvestibularnerve.Thiswillresulttotheeyesturningtowardstheipsilateralearandaquickhorizontalmovementoftheeyestothecontralateralear.Ifthecalorictestisdoneonpatientswithcerebraldamage,thefastphaseofquickhorizontaleyesmovementwillbeabsentasthisiscontrolledbythecerebrum.Alsopouringcoldwaterintotheexternalauditorycanalofbrain-damagedpatientswillresultinquickhorizontaleyesmovementtowardthecontralateralear. Sources AllcontentpublishedonKenhubisreviewedbymedicalandanatomyexperts.Theinformationweprovideisgroundedonacademicliteratureandpeer-reviewedresearch.Kenhubdoesnotprovidemedicaladvice.Youcanlearnmoreaboutourcontentcreationandreviewstandardsbyreadingourcontentqualityguidelines. References: Augustine,G.J.,Fitzpatrick,D.(2004).Neuroscience(3rded.).Sunderland,MA,USA:SinauerAssociates. Blumenfeld,H.(2018).Neuroanatomythroughclinicalcases(2nded.).Sunderland,MA:Sinauer. Haines,D.E.,Mihailoff,G.A.(2018).Fundamentalneuroscienceforbasicandclinicalapplications.Philadelphia,PA:Elsevier. Haines,D.E.(2014).Neuroanatomyinclinicalcontext:Anatlasofstructures,sections,systemsandsyndromes(9thed.).Philadelphia,PA:LippincottWilliams&Wilkins. Mancall,E.L.,Brock,D.G.,&Gray,H.(2011).Gray’sclinicalneuroanatomy:theanatomicbasisforclinicalneuroscience.Philadelphia,PA:Elsevier. Moore,K.L.,Dalley,A.F.,&Agur,A.M.R.(2014).ClinicallyOrientedAnatomy(7thed.).Philadelphia,PA:LippincottWilliams&Wilkins. Netter,F.(2019).AtlasofHumanAnatomy(7thed.).Philadelphia,PA:Saunders. Patestas,M.A.,Gartner,L.P.,&Patestas,M.A.(2009).ATextbookofNeuroanatomy.Oxford,UK:BlackwellPublishing. Standring,S.(2016).Gray'sAnatomy(41tsted.).Edinburgh:ElsevierChurchillLivingstone Illustrators: Vestibularsystemanatomy-PaulKim Labyrinth(diagram)-PaulKim Vestibularsystem:wanttolearnmoreaboutit? Ourengagingvideos,interactivequizzes,in-deptharticlesandHDatlasareheretogetyoutopresultsfaster. Whatdoyouprefertolearnwith? Videos Quizzes Both “IwouldhonestlysaythatKenhubcutmystudytimeinhalf.” – Readmore. KimBengochea,RegisUniversity,Denver ©Unlessstatedotherwise,allcontent,includingillustrationsareexclusivepropertyofKenhubGmbH,andareprotectedbyGermanandinternationalcopyrightlaws.Allrightsreserved. Registernow andgrabyourfreeultimateanatomystudyguide! Learninganatomyisn'timpossible.We'reheretohelp. Learninganatomyisamassiveundertaking,andwe'reheretohelpyoupasswithflyingcolours. Createyourfreeaccount➞