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Renad Zakaria

Enas Ajarma

Mohammad Alsalem

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Westartedtalkingaboutthemidbrain,

Twotransversesectionsofthemidbrainwillbediscussed:

1-Theleveloftheinferiorcolliculus.

2-Thelevelofthesuperiorcolliculus.

**Inthepreviouslecture&intheLABwetalkedaboutthetrochlearnervethatinnervatesonlyasinglemuscle:thesuperiorobliquemuscleoftheeye,theoriginofitanditsrelationwiththelevelofinferiorcolliculus,alsowetalkedaboutthelevelofinferiorcolliculus.

Nowwewillgoalevelupandstarttalkingaboutthelevelofsuperiorcolliculus……

Wewillfirstconsiderthattherearecommonfeaturestoseeinthesetwolevelsandtherearesomedifferences:

**Theyhavesameshape,cavity,cruscerebri,substantianigra,mediallongitudinalfasciculus(sinceitsdestinationthemotornucleusofocculomotor)andcerebralaqueduct.

**Themajordifferencebetweenthetwois:

1-ThepresenceoftherednucleusthatfoundinthelevelofsuperiorcolliculusandifnotpresentwewillbeinthelevelofinferiorcolliculusthathasDecussationofsup.cerebellarpedunclethatcomposedoffibersfromcerebellar,cerebellothalamictractandcerebellorubraltract.

**NOTE:thedecussationofsup.Cerebellarisimmediate,youseeitatthelevelofthenucleus.

2-AtthelevelofinferiorcoliculusPosteriortoSubstantianigratherearemedial,spinal,trigeminal&lateralleminisci,whereasatthelevelofsuperiorcoliculusyouwillnoticethatthereisnolateralleminiscus,why?

Weknowitcarriesinformationaboutsound(auditory)fromthecochlearnucleustovariousbrainstemnucleiandultimatelythecontralateralinferiorcolliculusofthemidbrain,andsinceweareatthesuperiorlevelyouwon’tfounditbecauseitsfibersendintheinferiorcolliculus(actinauditoryreflexes).

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**trytoidentifywhatweweretalkingabout,payattentionandkeeprefertothispicturetomakesurethateverythingisclear:

**Inthissectionatthelevelofsuperiorcolliculustherewillbemotorocculomotornucleusinsteadoftrochlearnucleus(ininferiorlevel)sincewearelevelabove,let’stalkaboutit:

Oculomotor Nerve (III)

-Isitpuremotor?

Yes,butithastwotypesofmotor:

a)Motorforskeletalmuscles.

b)Motorforsmoothmuscleslikeciliaryandconstrictorpupillaemuscles,itsparasympatheticregulation.

-It’sthefirstcranialnervetoleavethebrainstem.

-Ithastwonuclei:motorandparasympathetic,theyareposteriortoMediallongitudinalfasciculus.

Mainoculomotornucleus:

-Location:ifyougopostriolateralyouwillseethemainmotornucleusofocculomotor.

Levelofsuperiorcolliculus

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-receivebilateralstimulationfromthecortex,itreceivesfrom:

a)Corticonuclearfibers.

B)Tectobulbarfibers:Infofromvisualcortex(refertothepreviouslectures).

c)Mediallongitudinalfasciculus:connectedtothenucleioftheIV,VI,andVIIIcranialnerves.

**Insomeresourcesit’swrittenthatthismotornucleusdoesn’treceivefromthecortex,itreceivesindirectlyfrommediallongitudinalfasciculusandsuperiorcolliculusandotherregions.

Accessoryparasympatheticnucleus(Edinger-Westphalnucleus):

-Location:youwillfinditnearthemotornucleus.

-Receivesfrom:

a)FromgazecenterofthecortexthroughCorticonuclearfibers:it’sforaccommodationreflexwhichisareflexactionoftheeye,inresponsetofocusingonanearobject,thenlookingatadistantobject(andviceversa),comprisingcoordinatedchangesinvergence,lensshapeandpupilsize(thelensbecomemoresphericalwhenlookingatnearobject),italsonamedaccommodation-convergencereflex.

**flatlensisbettertorecognizefarobjects,whereassphericallensisbetterfornearobjects.

b)Pretectalnucleus:directandconsensuallightreflexes.

**pretectalnucleus:closetothelateralpartofthesuperiorcolliculus.Thesecellsreceiveinputfromretinalganglioncells(viatheoptictract)andprojectbilaterallytotheEdinger-Westphalnucleus.It’sresponsiblefor:

1- Directreflex:Thisreflexisresponsiblefortheconstrictionofthepupilsbyconstrictorpupillaemuscleuponlight'senteringtheeye,intheeyethatacceptthelight.

2-consensuallightreflex:ifanindividual'srighteyeisshieldedandlightshinesintothelefteye,

Thereflexafteraskingthispersontolookatafarobjectthentoanearone.

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constrictionoftherightpupilwilloccur,aswellastheleftbecausethepretectalnucleusgivesbothparasympatheticnuclei.

##Suchdetailsonthesereflexeswillbediscussedinphysiology.Identifythepreviousstructuresinthisfigure:

**Courseofocculomotornerve:

Thefibersfromthetwonucleiwillpassthroughrednucleuswithoutsynapse.Fromtherednucleusfibersthenpassviathesubstantianigraexitingthroughtheinterpeduncularfossa.Thenthenerveentersthelateralaspectofthecavernoussinus.Withinthecavernoussinus,itreceivessympatheticbranchesfromtheinternalcarotidplexus.Thesefibersdonotcombinewiththeoculomotornerve–theymerelytravelwithinitssheath.Thenerveleavesthecranialcavity(middlecranialfossa)viathesuperiororbitalfissurewheretheydividetotworemaisuperiorandinferior,seethefigurebelow.

NOTE:theparasympethaticfiberssynapseintheciliaryganglion,andcomeoutaspostganglionicthroughshortciliarynerve.

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**oculomotornerveinnervate:

1-Extrinsicmusclesorextraoccular(Innervatedbythemainmotornucleus):

Thelevatorpalpebraesuperioris,superiorrectus,medialrectus,inferiorrectus,andinferioroblique.

*allthemusclesexceptsuperioroblique(innervatedbythetrochlearnerveandhaslateralrotationactionanddownwordmovement)

andlateralrectus(suppliedbytheabducensnerveandhasabductionmovement)

2-Intrinsicmuscles(innervatedbytheparasympatheticnucleus):

Theconstrictorpupillaeoftheirisandciliarymuscles(parasympathetic).

-Action:Liftingtheuppereyelid;turningtheeyeupward,downward,andmedially;constrictingthepupil;andaccommodatingtheeye.

OculomotorNerveinjury

1-Completelesion,lowermotorneuronallesion:

-Allofthemusclesareparalyzedexceptlateralrectusandsuperioroblique.

–Symptoms:

•Externalstrabismus

•Diplopia(doublevision)

•Ptosis:droopingoftheuppereyelidbecauseoflevatorpalpebraesuperiorisaction.

•Thepupiliswidelydilatedandnonreactivetolight,dilationisoverriding.

•Accommodationoftheeyeisparalyzed.

2-Incompletelesions:

-Internalophthalmoplegia:lossoftheautonomicinnervationofthesphincterpupillaeandciliarymuscle(Symptoms:thepupiliswidelydilatedandnonreactivetolightonly).

Thispatientisatrestingposition,whathappenherethatattheaffectedeyetheoverridingmuscleisthelateralrectussoitwillshifttolateralaspect(diplopia)

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-Externalophthalmoplegia.:paralysisoftheextraocularmuscles,paralysisinmotorpart.(Symptoms:Externalstrabismus,diplopaandptosisonly)

**Butisthereapossibilityforthemotorfunctiontodefectwithouttheparasympatheticaction(youknowtheyrunthroughsameconnectivetissue)?

Yesitcanhappen,thetheoryimplythattheparasympatheticfibersrunsuperficialinthenervesoifapressureappliedonthenervetheparasympatheticwillbeaffectedwithoutmotor(soit’smoresusceptibletoinjurythanthemotor).AnotherpossibilitylikeIndiabeticneuropathythataffectthemotorfiber.

TOSUMUP:youmayhaveexternalophthalmoplegiaifthemotorpartisaffected,ORinternalophthalmoplegiaiftheautonomicpartisaffected,ORbothifthewholenerveisaffected.

Red nucleus

-Roundedmassofgraymatter

-Situatedbetweencerebralaqueductandsubstantianigra.

-Reddishblueincolorwhichisattributedtothehighvascularityofthestructureinadditiontothehighlevelofironpigments.

-receiveAfferentsfrom:

Cerebralcortex,cerebellum,substantianigra,thalamicnuclei,spinalcord.

-giveEfferentto:

Spinalcord,reticularformation,thalamusandsubstantianigra.

-involvedinmotorcoordination.

Substantia nigra

-Largemotornucleus.

In cases of (diabetic neuropathy), the autonomic fibers are unaffected, whereas the nerves to the extraocular Muscles are paralyzed.

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-Itisabrainstructurelocatedinthemidbrain.

-playsanimportantroleinreward,addiction,andmovement.

-SubstantianigraisLatinfor"blacksubstance"duetohighlevelsofmelanin.

-Ithasconnectionswithbasalganglia,cerebralcortex.

-ItsConcernedwithmuscletone.

-Parkinson'sdiseaseiscausedbythedeathofneuronsinthesubstantianigra.

DON’Tforget!!Therednucleusandsubstantianigraaresubcorticalcentersoftheextrapyramidalmotorsystem.

Trochlear nerve

-Ithasonenucleus,it’samotornucleus.

-Locationofthenucleus:it’sfoundanteriortothecerebralaqueduct,justbelowtheinferiorcolliculus.

-Receivesfrom:

a)Corticonuclearfibers

b)Tectobulbarfibers:Infofromvisualcortex

c)Mediallongitudinalfasciculus:connectedtothenucleioftheIII,VI,andVIIIcranialnerves.

d)Frombothside.

-Courseofthenerve:

Itgoesposteriorlyaroundthecentralgraymatterthenimmediatelydecussates,it’stheonlynervethatemergingfromtheposterioraspectofthemidbrain.Thenervethenmovesalongthelateralwallofthecavernoussinus(alongwiththeoculomotornerve)beforeenteringtheorbitoftheeyeviathesuperiororbitalfissuretoinnervatethesuperiorobliquemuscle.

**Superiorobliquemusclehasauniquestructureit’sapulley-likestructure(tackle),thispulleysystemwhatgivessuperiorobliqueitsactions,causingdepressionoftheeyeballdespitebeinginsertedonthesuperiorsurfaceanditsturntheeyelaterally(downward&laterallymovementoftheeye).

TrochlearNerveinjury:-Symptoms:1-Diplopia

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2-Difficultyinturningtheeyedownwardandlaterally,soatrestingStatethepatienteyewillgoupward&medially.

3-Difficultyindescendingstairssopatientwilltilthisheadtothesideoppositetheparalyzedeye(compensatoryadjustment).

**lookatthefigurebelow;trytoidentifythenucleusanditslocation:

Abducent Nerve

-hasonemotornucleusfoundunderneaththefourthventricle,atthelevelofthefacialcolliculus.Axonsfromthefacialnervelooparoundtheabducentnucleus,creatingaslightbulge(thefacialcolliculus)thatisvisibleonthedorsalsurfaceofthefloorofthefourthventricle;it’sclosetothemidline.

-Receivesfrom:

a)Corticonuclearfibers.

b)Tectobulbarfibers:Infofromvisualcortex.

c)Mediallongitudinalfasciculus:connectedtothenucleioftheIII,IV,VIIIcranialnerves.

**Courseofthenerve:

Theabducentnerveleavesthebrainstemanteriorlyatthejunctionoftheponsandthemedullaoblangata,medialtothefacialnerve.Thenenterthecavernoussinusbelowandlateraltotheinternalcarotidartery,thenitenterstheorbitthroughthesuperiororbitalfissureandinnervatesthelateralrectusmuscleoftheeyethatturningtheeyelaterally.

**AbducentNerveinjury

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-Symptoms:1-Diplopia.

2-Difficultyinturningtheeyelaterallywhichiscalledinternalstrabismus,thishappensbecausetheeyeatrestispulledmediallybytheoverridingofmedialrectus.

**Identifythenucleus&itslocationinthisfigure:

In the figure below try to identify the course of the nerves that we discussed: Trigiminal nerve

-Wetalkedaboutitbeforesowewilljustsummarizeit.

Ithas4nuclei,3sensoryand1motor:

v Mainsensorynucleus:-FoundonthePosteriorpartofthepons(lateral).-Foundbetweenspinalandmesencephalicnuclei.

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v Motornucleus:

FoundonthePosteriorpartofthepons(Medial).v Spinalnucleus:

-Foundthemedulla.-Superiorly:mainsensorynucleus.–Inferiorly:C2segment.

v Mesencephalicnucleus:

-FoundintheLateralpartofthegraymatteraroundthecerebralaqueduct.

-Inferiorlymainsensorynucleus.

Sensory Components -Ascendingbranches:mainsensorynucleus.

-Descendingbranches:spinalnucleus.

**Trigiminalnervehasthreedivisionsfromsuperiortoinferior:ophthalmic,maxillaryandmandibular.Thefibersofthesedivisionswillgotooneofthesenucleisoifthesensation:

-TouchandpressurefiberswillgototheMainsensorynucleus.

-PainandtemperaturefiberswillgototheSpinalnucleus.

-Proprioceptiveimpulsesfromthemusclesfiberswillgotothemesencephalicnucleus.

**Butwhathappentothefibersofthesedivisionswhengotothedestinationnucleusthattheirarrangementwillbedifferentandbelike:

• Ophthalmicwilltakeinferiorpartofthespinalnucleus.• MaxillarywilltakethemiddlepartoftheSN.• MandibularwilltakethesuperiorpartoftheSN.

**ThelocationofthecellbodyisinthegangliaexceptFormesencephalicnucleus,wherethecellbodyofthe

1storderneuronisfound,thefibersofitwilljustgo

throughtheGanglia,youwon’tfindthecellbodyofProprioception

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Fibersintheganglia,it’sinthenucleusitself.

Note:Proprioceptioncomefrommusclesofmasticationinthejawevenfrommusclesoffacialexpression,itsfibersrunsinthetrigeminalnerve.Fibersgofrommesencephalicnucleustohighercentersinthecortex,youwillfindinotherresourcesthatthisnucleusjustforreflexeslikesjawjerkreflexofthemandible(normallythisreflexshouldn’thappen).Butifthereisuppermotorlesion,exaggeratedandtheclosureofthemouthwillhappen.

Ifyoulikethislinkhavefurtherinformationaboutthisreflexanditstest:

http://neuroexam.med.utoronto.ca/cranial_5d.htm

Motorcomponent-Motornucleusreceives:

a)Corticonuclearfibersb)Rednucleus

c)Reticularformationd)Tectum

-Suppliesthroughmandibular:

-Musclesofmastication(masseter,temporalis,medialpterygoid,andlateralpterygoid).

-Tensortympani.

-Tensorvelipalatine.

-Mylohyoid.

-Anteriorbellyofthedigastricmuscle.

**Thefiguresbelowsummarizesthesensoryandmotorpathways&structuresthattheysupply:(youhavetomemorizethem)

Thisfigureshows:

-Fibersandpathwayofeachtypeofsensation.

-trigeminalGangliaanditscellbodies.

-mesencephalicnucleus&itscellbody.

-2ndorderneuron&trigeminallemniscus.

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CourseofthetrigeminalnerveThetrigeminalnerveoriginatesfromthreesensorynucleiandonemotor,attheleveloftheponsanteriorly,thesensorynucleimergetoformasensoryroot.Themotornucleuscontinuestoformamotorroot(motorruninferiortosensory).ThenInmiddlecranialfossatheyexpandintothetrigeminalganglion.

Thisfigureshowsthepartsofthefacethatsupplybytrigeminalsensorynerve:

Redpartbyophthalmic:forehead(fromthescalpasfarasthevertex)

Bluepartbymaxillary:upperlip&zygomaticpart

Greenpartbymandibular:lowerlip&mentalarea.

**Asyounoticetheangleofthemandibleistheonlyareathatnotsuppliedbythetrigeminal,it’ssuppliedbyGreatauricularnerve.

**unfortunatelyyouhavetomemorizethem.

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-Trigeminalganglionlocatedlateraltothecavernoussinus,Uppersurfaceoftheapexofthepetrousboneinadepressionofthetemporalbone,ithasapouchintheduramaterknownasMeckelcave.

Thedivisionofthisnervewillgooutthrough:

–Ophthalmic:throughsuperiororbitalfissure.

–Maxillary:throughforamenrotundumtopterygopalatinefossa.

–Mandibular:throughforamenovaletoinfratemporalfossa.

Facial nerve

1-MainMotorNucleus

•FoundDeepinthereticularformationofthelowerpartofthepons.

•Thepartofthenucleusthatsupplies:

–Upperpartofthefacereceivescorticonuclearfibersfrombothhemispheres.

Exceptthatthelowerpartofthefacereceivesonlycorticonuclearfibersfromtheoppositecerebralhemisphere.

2-ParasympatheticNuclei(superiorsalivatorylacrimatory):

•Location:Posterolateraltothemainmotornucleus.**It’salsonamedsalivatorylacrimatorynucleusbecauseithas:-Superiorsalivatory:

Mainlybysubmandibularandlingual,receivesfromthehypothalamus.-Lacrimalnucleus:

Receivesfrom:–Hypothalamus(Emotional),it’sthemajoroutputoflimbicsystemthatappearasresponsesbyautonomicnervoussystemlikeifyoufeelsadyouwillcry(lacrimalglandwillbestimulatedtoproducetears).–Sensorynucleiofthetrigeminal(reflex),likewhenaforeignbodyentertheeyeasareflextheeyestarttearing(lacrimation).

3-SensoryNucleus:**Remember:therearetwotypesofsensationinthefacialnerveoneisgeneralsensoryandtheotherrelatedtothetaste.

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**Tastesensation:

•Location:upperpartofthenucleusofthetractussolitaries.-Thetastefibersoffacialnervewillgotothenucleusoftractussolitaries.*TheCellbodiesfoundingeniculateganglion.-Fromthenucleusofthetractussolitariesthe2ndorderneuronwillmakeacrossandgoesuptotheVPM,andthenitwillgofromventralposteriomedialtothePrimarygustatorycortex(area43),thisareafoundintheparitallobejustsuperiortothelateralfissure.

Courseoffacialnerve

*Againwewillexplaintheintracranialpathway.

Let’stalkaboutitsgeneralpathwaythenwewilltalkaboutitsbranches:→Facialnervewillgooutfromtheanteriorsurfacebetweentheponsandthemedullaoblongata,aftercomingoutfromthebrainstemitwillfaceacanalwithinthepetrouspartofthetemporalboneoftheskullwhichistheinternalacousticmeatus.

-Internalacousticmeatusgivespassagetotwocranialnervesthefacialandvestibulocochlearnerves,thefacicalnervewillrunlaterallythroughthecavityofinnerearonthemedialwallthenitgoestotheposteriorwallofthetympaniccavityandfinallyEmergesfromthestylomastoidforamen.

*Inthisfigure:

-trytoidentifyfacialnervenucleus.

-Thepathwayofthetastefibers.

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**followthepathwayofthenerveinthesefigures:

Remember:fromMSSwelearnedabouttheextracranialcourseofthenerve,whereitendsintheparotidglandandwithintheparotidgland,thenerveterminatesbysplittingintofivebranches:

Temporalbranch,Zygomaticbranch,Buccalbranch,MarginalmandibularbranchandCervicalbranch.

Thesebranchesareresponsibleforinnervatingthemusclesoffacialexpression.

**Nowlet’stalkaboutfacialnervebranchesandtheirpathways(intracranial):

→Whenthefacialnervewasinthepetrouspartofthetemporalbone(inthecavityofmiddleear),itwillgivetwobranches:

1-Greaterpetrosalnerve2-chordatympaninerve

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**Howaboutlearningmoreaboutgeniculateganglionbeforetakingthebranches!

→thegangliawherethefacialnervecurvecalledgeniculateganglion(geniculatemeancurve)

*Ifyounoticethefacialnervehastwocurves,thefirstwherethemotorfiberscurveonthefloorofthe4thventricletheotherinthegeniculateganglion.

geniculateganglionissensoryganglia,hasthecellbodyofthesensorymainlyfortastefibers(Don’tsayforchordatympani,sinceithasfibersotherthantastefibers),Becareful!It’snotanautonomicganglionthereisnosynapse.

1-Greaterpetrosalnerve:

**Itcarriespreganglionicparasympethaticfibersthatwillreachthelacrimalgland.

Wesaidthatitsfoundinthecavityoftheinnerear,thenitwillleavethecavitytotheMiddlecranialfossathroughthegreaterpetrosalforamen(orhiatus),inthemiddlecranialfossaitPassesoverForamenlacerum,whereitjoinsthePostganglionicsympatheticfibersthatfoundontheinternalcrotidthatgotothemiddlecranialfossathroughthecarotidcanal.

ThesePostganglionicsympatheticfibersarethedeeppetrosalnerve(theyaremainlyoriginatedinthesuperiorcervicalsympatheticganglionintheneck).Greaterpetrosaljointhedeeppetrosaltoformthe Vidian nerve (nervetopterygoidcanal).Pterygoidcanalisapassagewaybetweenmiddlecranialfossaandpterygopalatinefossawithanotherpassagewaywhichistheformenrotundumwheremaxillarynervecomesfrom.

Sothedeepandgreaterpetrosalnervewillleavethemiddlecranialfossaandinterthepterygopalatinefossawhereaparasympatheticautonomicgangliafoundwhichispterygopalatineganglion.Followthenerve’spathwayinthisfigure:

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Finallyhowthesetwonervessupplythelacrimalgland?

Aftertheyenterthepterygopalatineganglionthatissuspendedbythemaxillarynerve,thefibersofthegreaterpetrosalwillsynapseandgivepostganglionicparasympethaticfibers(itentersthepterygoidcanalaspreganglionicparasympethaticfibersandleavethepterygopalatineganglionaspostganglionicparasympethaticfiberssftersynapse),thedeeppetrosalwillgothroughthepterygopalatineganglionwithoutsynapse(theyalreadysynapseinthesuperiorcervicalsympatheticganglionandleaveitasPostganglionicsympatheticfibers),thesefibersthenruninthemaxillarynervetothezygomaticnerve(branchfrommaxillarynerve),thentheywillgotozygomaticotemporalnerve(branchfromzygomaticnerve).Zygomaticotemporalnervewilljointhelacrimalnerve(rememberlacrimalnerveisabranchfromopthalmicnervethatisabranchfromtrigeminalnerve).AndthatwhatwemeanwhenwesaidthatsomeautonomicfibersSnoopinabranchesfromtrigeminalwhichislacrimalnerve.Thensupplythelacrimalgland.

**paymoreattentiontopreandpost,andwhereeverynervesynapses.

**Tosummarizeitall:

a)Thelacrimalnerveisamajorgeneralsensorybranchoftheophthalmicnervefromtrigeminal.

b)Parasympatheticinnervation:originallyfromgreatpetrosalnervebranchoffacialnerve.

c)Sympathaticinnervation:originallyfromdeeppetrosalnervefromcarotidplexus,superiorcervicalganglia.

##Thefigurebelowsummarizesitall:

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2-chordatympaninerve:

-Throughautoscopeitappearsasaline,keepinmindthroughdiscussionofthenervescoursesthesensorywillgoinandthemotorwillgooutthebrainstem.

-chordatympanihastwoparasympatheticfibersandtaste.

→ItOriginatesfromthefacialnerve,thenittravelsthroughthemiddleear,whereitrunsfromposteriortoanterioracrossthetympanicmembrane.Itpassesbetweenthemalleusandtheincus,onthemedialsurfaceoftheneckofthemalleus.Itwillgooutthroughthepetrotympanicfissure(alsocalledglaserianfissure)afterwhichitemergesfromtheskullintotheinfratemporalfossa,itsooncombineswithlingualnerve.

-Lingualnervefoundontheposteriorborderofmylohyoidnearthedeeppartofsubmandibularglandwherethesubmandibularganglionfound(oryoucansaysubmaxillaryganglion),thefiberthatcomefromSuperiorsalivatorynucleuswillmakesynapseinthisganglion(Preganglionicparasympatheticfibers)andthetastefiberswillcontinuewiththelingualnervethatgivetastesensorytoAnterior2/3oftongue.

**keepinmindthatthechordatympanihavetwofibersparasympatheticandtaste.

##Rememberwhenwetalkedaboutgeniculateganglion,wesaidit’sasensoryganglionthathasthecellbodyforthetaste.

**wetalkedabouttaste,motorandparasympatheticbutwhataboutthegeneralsensorythatsupplyasmallareawhichistheskinoftheexternalacousticmeatus?

Actuallyfacialnervedoesn’thaveanucleusforgeneralsensation.Thefibersofthisgeneralsensationcomefromspinaltrigeminalnucleusthatitscellbodylocatedinthegeniculateganglionwhichgivefiberscarriedbyfacialnervetotheskinoftheexternalacousticmeatusforgeneralsensation.

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Facial Nerve injury *It’simportanttoknowifitloweroruppermotorlesionsincetheydifferintheirsymptoms.

*Rememberwhenwetalkedaboutfacialmotornucleusandwelearnedthatitsuppliestheupperpartandthelowerpartofthefacedifferentlysinceitgives:

-Upperpartofthefacereceivescorticonuclearfibersfrombothhemispheres(figureA).

-thelowerpartofthefacereceivesonlycorticonuclearfibersfromtheoppositecerebralhemisphere(figureB).

*Iflowermotorneuroninjuryoccurlikefractureintemopralboneorinjurytothenervewhenitcomeoutfromstylomastoidforamen,therewillbeparalysisinthesamesideofthefaceupperandlowerpart,droppingintheangleofthemouth(sadding),difficultyinclosingtheeyeandexcessivelacrimation.(closureoftheeyeisdonebyorbicularisoculimusclewhichissuppliedbyfacialnerve.)

*Ifuppermotorneuroninjuryintheleftoccur,theupperpartwillbeintactsinceitsuppliedbytheleftandrightnucleussotherightwillcompensateontheleftsonosymptomontheupperpart(patientcanclosehiseyeontheleft).Whileonthelowerparttheangleofthemouthwilldropcontralaterally(ontheright).

Inthisfigure:

-followthetastefibersandtheircellbodyinthegeniculateganglion(greenline)

*Cellbodyiscirculated

-followtherootofthegeneralsensationfromtrigeminalnucleustotheskinoftheexternalacousticmeatus(pinkline)

*Cellbodyofgeneralsensationinthegeniculateganglionsurroundedbysquare

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Locationofthelesion:-Abducentandthefacialnervesarenotfunctioning:thismeansthatthelesioninthepons.(thisistheplacewherebotharefoundclosetoeachother)

FigureB:Inthisfiguretheblacklineshowsthattherightnucleusgivesonepathwaytothelowerpartofthefaceintheleft.(Theoppositeonthelowerrightside).

FigureA:Inthisfiguretheblacklineshowsthattheupperpartofthefaceontheleftreceive2fibersonefromtheleft&theotherfromtheright.(Theoppositeontheupperpartontheright)

Thisfigureshow:

Ifaninjuryhappenhereitwillbeuppermotorlesion,symptomswillappearlikewesaid.

Ifaninjuryhappenshereitwillbelowermotorlesion,symptomswillappearlikewesaid.

**headNO.1showthesymptomsofuppermotorlesion.

**headNO.2showthelesionoflowermotorlesion.

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-Vestibulocochlearandthefacialnervesarenotfunctioning:lesionintheinternalacousticmeatus(againherewheretheyarefoundclosetoeachother)

-Lossoftasteovertheanteriortwo-thirdsandparasympatheticofsalivaryglands:damagedtothechordatympanibranch.

**MoredetailswillbediscussedintheLAB.

Bell’s palsy -Usuallyunilateral.

-Lowermotorneurontypeoffacialparalysis.

-Causeisnotknown,mayoccurdueto:

a)Exposureofthefacetoacolddraft?

b)Complicationofdiabetes?

c)CanoccurasaresultoftumorsorAIDS?

d)ifthedentistmakeinferiordentalnerveblock,andbymistakeifhegoesalittleposterior,hemayanesthetizethefacialnerveandtheparotidgland,symptomsofBell’spalsyitwilllastfor2daysmaximallyandrecoverbyitself.

-Insomecasesitrecoverswithouttreatment.

___________________________________________

Sorryforanymistakes

رثكألا يھ طقف ىلوألا ةوطُخلا ،مھی ال ةفاسملا دُعب

.ةبوعص