Know Your Brain: Vestibular System - Neuroscientifically ...

The vestibular system is a sensory system that is responsible for providing our brain with information about motion, head position, and spatial ... NEUROSCIENTIFICALLYCHALLENGEDNEUROSCIENCEMADESIMPLERSubscribeKnowYourBrain:VestibularSystemNovember15,2015ViewfullsizeThevestibularlabyrinth.Whereisthevestibularsystem?Thevestibularsystemiscomprisedofseveralstructuresandtracts,butthemaincomponentsofthesystemarefoundintheinnerearinasystemofinterconnectedcompartmentscalledthevestibularlabyrinth.Thevestibularlabyrinthismadeupofthesemicircularcanalsandtheotolithorgans(alldiscussedbelow),andcontainsreceptorsforvestibularsensations.Thesereceptorssendvestibularinformationviathevestibulocochlearnervetothecerebellumandtonucleiinthebrainstemcalledthevestibularnuclei.Thevestibularnucleithenpasstheinformationontoavarietyoftargets,rangingfromthemusclesoftheeyetothecerebralcortex.Whatisthevestibularsystemandwhatdoesitdo?Thevestibularsystemisasensorysystemthatisresponsibleforprovidingourbrainwithinformationaboutmotion,headposition,andspatialorientation;italsoisinvolvedwithmotorfunctionsthatallowustokeepourbalance,stabilizeourheadandbodyduringmovement,andmaintainposture.Thus,thevestibularsystemisessentialfornormalmovementandequilibrium.Vestibularsensationsbeginintheinnerearinthevestibularlabyrinth,aseriesofinterconnectedchambersthatarecontinuouswiththecochlea.Themostrecognizablecomponentsofthevestibularlabyrintharethesemicircularcanals.Theseconsistofthreetubes,positionedapproximatelyatrightanglestooneanother,thatareeachsituatedinaplaneinwhichtheheadcanrotate.Thisdesignallowseachofthecanalstodetectoneofthefollowingheadmovements:noddingupanddown,shakingsidetoside,ortiltingleftandright.Thesemovementsoftheheadaroundanaxisarereferredtoasrotationalacceleration,andcanbecontrastedwithlinearacceleration,whichinvolvesmovementforwardorbackward.Watchthis2-MinuteNeurosciencevideotolearnmoreaboutthevestibularsystem.Thesemicircularcanalsarefilledwithafluidcalledendolymph,whichissimilarincompositiontotheintracellularfluidfoundwithinneurons.Whentheheadisrotated,itcausesthemovementofendolymphthroughthecanalthatcorrespondstotheplaneofthemovement.Theendolymphinthatsemicircularcanalflowsintoanexpansionofthecanalcalledtheampulla.Withintheampullaisasensoryorgancalledthecristaampullaristhatcontainshaircells,thesensoryreceptorsofthevestibularsystem.Haircellsgettheirnamebecausethereisacollectionofsmall"hairs"calledstereociliaextendingfromthetopofeachcell.Haircellstereociliahavefinefibers,knownastiplinks,thatrunbetweentheirtips;tiplinksarealsoattachedtoionchannels.Whenthestereociliaofhaircellsaremoved,thetiplinkspullassociatedionchannelsopenforafractionofamillisecond.Thisislongenoughtoallowionstorushthroughtheionchannelstocausedepolarizationofthehaircells.Depolarizationofhaircellsleadstoareleaseofneurotransmittersandthestimulationofthevestibulocochlearnerve.Thehaircellsassociatedwiththesemicircularcanalsextendoutofthecristaampullarisintoagelatinoussubstancecalledthecupula,whichseparateshaircellsfromtheendolymph.Whentheendolymphflowsintotheampulla,however,itcausesthedistortionofthecupula,whichleadstomovementofhaircells.Thispromptsstimulationofthevestibulocochlearnerve,whichtransmitstheinformationaboutheadmovementtothevestibularnucleiinthebrainstemaswellastothecerebellum.Thevestibularsystemusestwootherorgans,knownastheotolithorgans,todetectlinearacceleration,gravitationalforces,andtiltingmovements.Therearetwootolithorgansinthevestibularlabyrinth:theutricleandthesaccule.Theutricleisspecializedtodetectmovementinthehorizontalplane,whilethesacculedetectsmovementintheverticalplane.Theprocessofsensationintheotolithorgansbearssomesimilaritytotheprocessinthesemicircularcanals,buttherearealsosomedistinctdifferences.Likethesemicircularcanals,theotolithorgansalsocontainasensoryorganwherehaircellscanbefound;inthiscase,however,itiscalledthemacula.Asinthesemicircularcanals,thereisagelatinouslayerabovethehaircells;intheotolithorgans,however,thereisanotherfibrousstructurecalledtheotolithicmembraneabovethegelatinouslayer.Theotolithicmembranehassmallcrystalsofcalciumcarbonatecalledotoconiaembeddedwithinit.Thesecrystalsmaketheotolithicmembraneheavierthantherestofthestructure;whenlinearaccelerationoccurs,itcausestheotolithicmembranetoshiftrelativetothemacula,whichleadstothedisplacementofhaircellsandthusthereleaseofneurotransmittersfromthesecells.Thestructureoftheotolithorgansmakesthemespeciallysensitivetomovementslikelinearaccelerationandheadtilts.Thevestibularsystemusesthisinformationaboutmovementobtainedviathesemicircularcanalsandotolithorganstomaintainbalance,stability,andposture;onewayitdoesthisisthroughitsinvolvementinreflexactions.Forexample,thevestibulo-ocularreflex(VOR)isamechanisminvolvingconnectionsbetweenthevestibularsystemandthemusclesoftheeyesthatallowsourgazetoremainfixedonaparticularpointevenwhenwemoveourheads.Disruptionofthevestibularsystem,whetherduetosomeinherentpathologyortoatransientstatelikealcoholintoxication,caninvolvesymptomslikevertigo,lossofbalance,andnauseaandcanrangeinseverityfrommildtoincapacitating.Reference:KhanS,ChangR(2013).Anatomyofthevestibularsystem:AreviewNeuroRehabilitation,32(3),437-443ReceiveNewContentbyEmailOrderNowYOURBRAIN,EXPLAINEDSleep.Memory.Pleasure.Fear.Language.Weexperiencethesethingseveryday,buthowdoourbrainscreatethem?YourBrain,Explainedisapersonaltouraroundyourgraymatter.BuildingonneuroscientistMarcDingman’spopularYouTubeseries,2-MinuteNeuroscience,thisisafriendly,engagingintroductiontothehumanbrainanditsquirksusingreal-lifeexamplesandDingman’sown,hand-drawnillustrations.PreviousSlideNextSlideReadinglikeacollectionofdetectivestories,YourBrain,Explainedcombinesclassiccasesinthehistoryofneurologywithfindingsstemmingfromthelatesttechniquesusedtoprobethebrain’ssecrets.-StanleyFinger,PhD,ProfessorEmeritusofPsychological&BrainSciences,WashingtonUniversity(St.Louis),author,OriginsofNeuroscience...ahighlyreadableandaccessibleintroductiontotheoperationofthebrainandcurrentissuesinneuroscience...awonderfulintroductiontothefield.-FrankAmthor,PhD,ProfessorofPsychology,TheUniversityofAlabamaatBirmingham,author,NeuroscienceforDummiesDingmanweavesclassicstudieswithmodernresearchintoeasilydigestiblesections,toprovideanexcellentprimerontherapidlyadvancingfieldofneuroscience.-MohebCostandi,author,Neuroplasticityand50HumanBrainIdeasYouReallyNeedtoKnowAninformative,accessibleandengagingbookforanyonewhohaseventheslightestinterestinhowthebrainworks,butdoesn’tknowwheretobegin.-DeanBurnett,PhD,author,HappyBrainandIdiotBrainOrderNow