Cranial Nerves Flashcards
GSA
GeneralSomaticAfferent
Somatosensory
Sensationfromskin,external ear, oralandnasalcavities
CarriedbyCNV, VII,IX,X
GSE
GeneralSomaticEfferent Somatomotor To skeletalmuscleofeye,tongue;SCMandtrapzeius mm.
CarriedbyCNIII,IV,VI,XI,XII
GVA
GeneralVisceralAfferent
Viscerosensory
Sensationfrompharynx;stretchreceptorsofthegut,
baroreceptorsofthecarotidandaorticbodies,
chemoreceptorsofgutandcarotidbody
Carried byCNVII,IX,X
GVE
General VisceralEfferent
Visceromotor
CN onlycarryparasympathetic innervationtosmoothand
cardiacmm.,salivaryandlacrimalglands,mucusglands
CarriedbyCNIII,VII,IX,X
SSA
SpecialSomatic Afferent
Vision,hearing,balance(CNII,VIII)
SVA
SpecialVisceral Afferent
Smell andTaste(CNI,VII,IX,X)
SVE
SpecialVisceralEfferent
Branchiomotor
Toskeletalmusclederivedfromthebranchialarches;
e.g.:mmofmastication,facialexpression,pharynx
(swallowing),larynx(speech)
CarriedbyCNV,VII,IX,X
Spinal nerves from forebrain
CNI‐II
Spinal nerves from midbrain
CNIII‐IV
Spinal nerves from pons
CNV‐VIII
Spinal nerves from medulla
CNIX‐XII
Spinal nerves from upper cervical spinal cord
CNXI
sensory and motor nuclei in midbrain
Sensory- trigeminalmesencephalic
(GSA; CNV)
Motor- occulomotor (GSE;CNIII)
Edinger‐Westphal (GVE; CNIII)
trochlear (GSE;CNIV)
sensory and motor nuclei in pons
Sensory- principal trigeminal (GSA;CN V,VII,IX,X), trigeminalspinal (GSA/GVA; CNV,VII,IX,X), vestibulocochlear (SSA;CN VIII)
Motor- abducens (GSE;CN VI), trigeminalmotor(SVE;CNV), facial (SVE;CNVII), superiorsalivatory (GVE;CNVII), inferiorsalivatory (GVE; CNIX)
sensory and motor nuclei in medulla
Sensory- trigeminalspinal
(GSA/GVA; CNV,VII,IX,X),
solitary (GVA/SVA;CNVII,IX,X),
vestibulocochlear (SSA;CNVIII)
Motor- ambiguus (SVE;CNIX,X),
dorsalmotor(SVE;CNX),
hypoglossal (GSE;CNXII)
sensory and motor nuclei in upper cervical spinal cord
Sensory- trigeminalspinal
(GSA/GVA; CNV,VII,IX,X)
Motor- spinalaccessory(GSE;CNXI)
TrigeminalMesencephalicNucleus
Containscellbodiesforproprioceptive
neuronscarriedbyCNV. From the midbrain
• Mechanoreceptors in the periodontalligaments ofteeth
• Golgitendonorgans,musclespindlesinthe
musclesofmastication
• Function:managejawopeningandclosing
reflexesduringchewing;preventdamageto
teethandotheroralstructures(tongue,cheeks,
etc.)duringchewing
Jawclosingreflex
UsedtotestCNVintegrity
• Tappingonthechinforcesthemandible
downwardsandstretchesthemasseter
• Reflexshouldbeabrisk,symmetricalclosingof
thejaws
TrigeminalPrincipalNucleus
Locatedinthepons • Synapsebetween1° and2° neurons carryingthesensationsoffinetouch and vibration • Nucleuscontainthecellbodiesof the2° neurons. • Theseaxonswillprojecttothe thalamusinthetrigeminothalamic tracts.
TrigeminalSpinalNucleus
• Locatedinthepons,medulla,and
uppercervicalspinalcord(approx.C1‐
C3levels).
• CNV enters the brainstem at pons; fibers will descend tothe spinalnucleus asthe trigeminal spinaltract.
• Parsoralis iscontinuous superiorlywith
thetrigeminalprincipalnucleus.
• Parscaudalis iscontinuousinferiorly
withthedorsalhornnucleiofthe
spinalcord.
• Synapsebetween1° and2° neurons
• Parsoralis mediatessensationsoffine
touchandvibration
• Parsinterpolaris andcaudalis mediate
sensationsofpain,deep touchand
temperature
• Nucleuscontain thecellbodies ofthe2° neurons.
• Theseaxonswillprojecttothe
contralateralthalamusinthe
trigeminothalamic tracts.
Nucleussolitarius
(medulla)
• GVA afferents from middle ear, pharynx, respiratory &GI tracts
• CN VIIfromnasopharynx,softpalate
• CNIX frommiddle ear, oropharynx
• CNX fromlarynx, thoracic andabdominal viscera
• SVAafferentsfortaste
• CN VII from oral (anterior2/3) tongue
• CNIX from pharyngeal (posterior1/3) tongueandvallate papillae
• CNX from epiglottis and rootof tongue
FacialMotorNucleus
Upper(dorsal)partofthefacialmotornucleus
• LMNsprojecttotheuppermotorbranchesofCNVII
(e.g.temporalbr.)
•Innervatesthemusclesoffacialexpressionoftheupperface(e.g.frontalisandorbicularisoculimm.)
Lower(ventral)partofthefacialmotornucleus
•LMNsprojecttothelowermotorbranchesofCNVII
(e.g.buccalandmandibularbr.)
•Innervatesthemusclesoffacialexpressionofthelowerface(e.g.zygomaticusmm.risorius m.,orbicularisoris m.)and the stapedius*
ReticularFormation
The“core”ofthebrainstem
• Intrinsic (transverse) projections connect sensory and motor
nuclei inthe brainstem, creating polysynaptic reflexes
• Intrinsicprojectionsare
bilateral,sothatreflexesare
bilateral(e.g.cornealblink
reflex– botheyesblink)
Glabellar reflex
instruct the patient to try not to blink. Tap lightly on the forehead
between the eyebrows. The first few taps should elicit blinks, then the blinking
should stop as the frontal lobe overrides the efferent limb. If blinking does not
stop, this is known as Myerson’s sign, and is an indication of frontal lobe
dysfunction (called frontal release) that may occur with diseases such as
Parkinson’s.
Afferent: CN V
Efferent: CN VII
PupillaryLightReflex
Afferentfibersfromopticnerve(CNII,SVA). Goes to the pre-tectal nucleus, then through the reticular formation interneuron and to the Edinger-Westphal nucleus, then toconstrictorpupillae m.(CNIII,GVE)
Directpupillarylightreflex:constrictionofipsilateraleyetostimulus(light)
Consensual pupillarylightreflex:constrictionofcontralateraleyetostimulus(light)
CornealBlinkReflex
- IrritationtothecorneaissensedbyGSAfibersinCNV1(opthalmic n.)
- Thissensationisrelayedtothespinaltrigeminalnucleus.
- A reticular formation interneuron carries the signalto thefacial motornucleus bilaterally.
- Motor fibersin CNVII cause blinking (contractionoforbicularisoculimm.).
TearingReflex
IrritationtothecorneaissensedbyGSAfibersinCNV1(opthalmic n.)
2. Thissensationisrelayedtothespinaltrigeminalnucleus.
3. Areticularformationinterneuroncarriesthesignaltothesuperiorsalivatory
nucleus.
4. Secretomotor fibersinCNVIIsynapseinthepterygopalatineganglion,then
stimulatelacrimation.
Example:youcrywhilecuttingonions.
Gustatory‐salivaryreflex
stimulationoftastebuds(CNVII,IX,X)produces
salivation(CNVII,IX)
- StimulationoftastebudsistransmittedbySVAfibersinCNVII,IX,X
- Thissensationisrelayedtothesolitarynucleus
3.Areticularformationinterneuroncarriesthesignaltothesuperiorandinferior
salivatory nuclei. - Secretomotor fibersinCNVIIandIXsynapseinthesubmandibularandotic
ganglia(respectively),thenstimulatesalivation.
Swallowingreflex
stimulationoftheoropharynxbysalivaand/orfood(CNIX)
causestheinitiatingofthemotorswallowingcascade(CNX)
Gagreflex
touchontheposteriortongueororopharynx(CNIX)causes
contractionofthepharyngealconstrictormuscles(CNX)
1.IrritationtotheposteriortongueororopharynxissensedbyGSAfibersinCNIX
(pharyngealplexus).
2. Thissensationisrelayedtothesolitarynucleus.
3. Areticularformationinterneuroncarriesthesignaltonucleusambiguous.
4. BranchiomotorfibersinCNX(pharyngealplexus)causecontractionofthe
pharyngealconstrictormuscles.
Coughingreflex
irritantstotheliningofthetrachea/bronchi(CNX)causes
contractionofpharyngealandlaryngealmuscles(CNX),diaphragmm.,abdominal
mm.
Gustatory‐gastricreflex
AKAthecephalicphaseofdigestion;stimulationofthe
tastebuds(CNVII,IX,X)causestheproductionofdigestivesecretionsinthe
stomach(CNX)
Vomitingreflex
irritationoftheGItractepithelium(CNX)causescontractionof
thesmoothmuscleofstomachandloweresophagus,skeletalmuscleofupper
esophagus,closureofglottisandsoftpalate(CNX)
Carotidsinusandbodyreflex
lowbloodpressureorlowO2content(respectively)
inthecommoncarotidartery(CNIX)causesanincreaseinheartrate,cardiac
output(CNX);highbloodpressurecausesadecreaseinheartrate,cardiacoutput
- LowbloodpressureissensedinthecarotidsinusbyCNIX.
- Thissensationisrelayedtothesolitarynucleus.
3.AreticularformationinterneuroncarriesthesignaltodorsalmotornucleusofX. - Secretomotor fibersinCNXsynapseinintramuralgangliaoftheheart,causing
increaseinheartrateandcardiacoutput,andraisingbloodpressure.
Conversely,highbloodpressureinthecarotidsinusiscommunicatedtothe
sympatheticnervoussystem,whichwilldecreaseheartrateandcardiacoutput.
Pathway of OculomotorNerve
GSA:motortoextraocularmuscles
LMNhascellbodyinoculomotornucleus(midbrain)
• CNIIIexitsmidbrainbetweenposteriorcerebralandsuperiorcerebellar
arteries
• CNIIIpassesthroughwallofcavernoussinus
• CNIIIexitscraniumthroughsuperiororbitalfissure
• Supplieslevator palpebralsuperioris m.,superiorrectusm.,medialrectusm.,
inferiorrectusm.,inferiorobliquem.
Pathway of OculomotorNerve
GVE:parasympathetictoconstrictorpupilae m.,ciliarybody
• Pre‐ganglionicneuronhascellbodyinEdinger‐Westphalnucleus
• CNIIIexitsmidbrainbetweenposteriorcerebralandsuperiorcerebellararteries
• CNIIIpassesthroughwallofcavernoussinus
• CNIIIexitscraniumthroughsuperiororbitalfissure
• GVEfiberssynapseinciliaryganglion
• Post‐ganglionicneuronhascellbodyinciliaryganglion,axonsinshortciliarynerves.
• Function:constrictspupil(pupillarylightreflex),changeslensshape
(accommodationreflex)
Pathway of TrochlearNerve
GSE:motortosuperiorobliquem.ofeye
• LMN(lower motor neuron) hascellbodyintrochlearnucleusof
midbrain
• CNIVexitsmidbrainonitsventralaspect
• CNIVpassesthroughwallofcavernoussinus
• CNIVexitscraniumthroughsuperiororbital
fissure
Pathway of CNV1:Opthalmic Nerve
GSA:sensorytoskinoverupperorbitandforehead;frontalandethmoidsinuses;uppernasal
cavity;eyeandconjunctive
• Branches:frontaln.(supraorbital,supratrochlearnn.),lacrimaln.,nasociliary n.(anterior
ethmoidaln.).
• CNV1 enterscranialcavitythroughsuperiororbitalfissure,passesthroughwallof
cavernoussinus
• 1° neuronhascellbodyintrigeminal(semilunar)ganglion,locatedinmiddlecranialfossa
• CNVentersbrainstematpons
• Fiberscarryinglighttouch&vibrationsynapseinthetrigeminalprincipalnucleus(pons)
andtrigeminalspinalnucleusparsoralis (ponsandmedulla)
• Fiberscarryingpain&temperaturedescendtothemedullaanduppercervicalspinalcord
asthetrigeminalspinaltract,synapseintrigeminalspinalnucleusparscaudalis
CNV2:MaxillaryNerve
GSA:sensorytoskinoverzygoma,nasalcavity;maxillarysinus;hardpalateandmaxillary
dentition
• Branches:zygomaticn.,infraorbitaln.
• CNV2enterscranialcavitythroughforamenrotundumfromthepterygopalatinefossa,
passesthroughwallofcavernoussinus
• 1° neuronhascellbodyintrigeminal(semilunar)ganglion,locatedinmiddlecranialfossa
• CNVentersbrainstematpons
• Fiberscarryinglighttouch&vibrationsynapseinthetrigeminalprincipalnucleus(pons)
andtrigeminalspinalnucleusparsoralis (ponsandmedulla)
• Fiberscarryingpain&temperaturedescendtothemedullaoruppercervicalspinalcordas
thetrigeminalspinaltract,synapseintrigeminalspinalnucleusparsoralis (teeth)orpars
caudalis
Pathway of CNV3:MandibularNerve sensory
GSA:sensorytoskinanteriortoearandovermandible;mandibulardentition,gingiva,
andoraltongue;meningesinmiddlecranialfossa
• Branches:inferioralveolarn.(mentaln.),lingualn.,buccaln.,middlemeningealn.
• CNV3enterscranialcavitythroughforamenovale
• 1° neuronhascellbodyintrigeminal(semilunar)ganglion,locatedinmiddlecranial
fossa
• CNVentersbrainstematpons
• Fiberscarryinglighttouch&vibrationsynapseinthetrigeminalprincipalnucleus
(pons)andtrigeminalspinalnucleusparsoralis (ponsandmedulla)
• Fiberscarryingpain&temperaturedescendtothemedullaoruppercervicalspinal
cordasthetrigeminalspinaltract,synapseintrigeminalspinalnucleusparsoralis
(teeth)orparscaudalis
Pathway of CNV3:MandibularNerve motor
SVE:motortomusclesofmastication,anteriordiastric m.,mylohyoidm.,tensor
veli palatini m.,tensortympanim.
• LMNhascellbodyinthetrigeminalmotornucleus(pons)
• CNVexitsthebrainstematthepons
• CNV3 exitsthecranialcavitythroughtheforamenovale andpassesinto
infratemporalfossa
Pathway of CNVI:AbducensNerve
GSE:motortolateralrectusm.ofeye
• LMNhascellbodyinabducensnucleusofpons
• CNVIexitspons,nearjunctionofbasilarand
anteriorinferiorcerebellararteries
• CNVIpassesthrough thecavernoussinus
• CNVIexitscraniumthroughsuperiororbital
fissure
Pathway of CNVII:FacialNerve GSA
GSA:sensorytopinnaofexternalear
• 1° neuronhascellbodyingeniculateganglioninfacialcanal
• CNVIIenterscranialcavitythroughinternalacousticmeatus
• CNVIIentersbrainstematpons
• Fiberscarryinglighttouch&vibrationsynapseinthetrigeminalprincipal
nucleus(pons)andtrigeminalspinalnucleusparsoralis (ponsandmedulla)
• Fiberscarryingpain&temperaturedescendtothemedullaoruppercervical
spinalcordasthetrigeminalspinaltract,synapseintrigeminalspinalnucleus
parscaudalis
Pathway of CNVII:FacialNerve GVA
GVA:sensorytosoftpalateandnasopharynx
• 1° neuronhascellbodyingeniculateganglioninfacialcanal
• CNVIIenterscranialcavitythroughinternalacousticmeatus
• CNVIIentersbrainstematpons
• GVAfiberssynapseinthesolitarynucleus(medulla)
Pathway of CNVII:FacialNerve SVA
SVA:tastefromoral(anterior2/3)tongue
• 1° neuronaxonsfoundinchordatympani
• 1° neuronhascellbodyingeniculateganglioninfacialcanal
• CNVIIenterscranialcavitythroughinternalacousticmeatus
• CNVIIentersbrainstematpons
• SVAfiberssynapseinthesolitarynucleus(medulla)
Pathway of CNVII:FacialNerve SVE
SVE:motortomusclesoffacialexpression,stapediusm.,posteriordigastricand
stylohyoidmm.
• LMNhascellbodyinthefacialmotornucleus(pons)
• Musclesoffacialexpressionthatmovethemouthoriginateinlower(ventral)partoffacial
motornucleus
• CNVIIexitsthebrainstematthepons
• CNVIIexitsthecranialcavitythroughtheinternalacousticmeatusandpassesinto
thefacialcanal
• SVEbranchesoffacialn.tomusclesoffacialexpressionexitthestylomatoid
foramen,passthroughtheparotidgland
• Branches:temporal,zygomatic,buccal,mandibular,cervicalbr.ofCNVII
Pathway of CNVII:FacialNerve GVE
GVE:parasympathetic,secretomotor tolacrimalglandandnasalmucosa
• Pre‐ganglionicneuronhascellbodyinsuperiorsalivatory nucleus
• CNVIIexitsmidbrainatpons
• CNVIIexitscraniumthroughinferioracousticmeatus,passesintofacialcanal
• Greaterpetrosaln.(CNVIIGVE)joinswithdeeppetrosalnerve(sympathetic)toformnerve
ofthepterygoidcanal
• GVEfiberssynapseinpterygopalatineganglion
• Post‐ganglionicneuronhascellbodyinpterygopalatineganglion
• AxonstolacrimalglandtravelwithbranchesofCNV1 andV2throughinferiororbitalfissureintoorbit
• AxonstonasalmucosatravelwithbranchesofCNV2throughsphenopalatineforamen
• Function:lacrimation,mucousproduction
GVE:parasympathetic,secretomotor tosubmandibularandsublingualglands
• Pre‐ganglionicneuronhascellbodyinsuperiorsalivatory nucleus
• CNVIIexitsmidbrainatpons
• CNVIIexitscraniumthroughinferioracousticmeatus,passesintofacialcanal
• Pre‐ganglionicaxonsfoundinchordatympani,travelwithCNV3 (lingualn.)
intosublingualspace
• GVEfiberssynapseinsubmandibularganglion,axonstraveltoglands
• Function:salivation
Pathway of CNIX:Glossopharyngeal GSA
GSA:sensorytopharyngeal(posterior1/3)tongue
• 1° neuronhascellbodyinsuperior(jugular)ganglion
• CNIXenterscranialcavitythroughjugularforamen
• CNIXentersbrainstematmedulla
• Fiberscarryinglighttouch&vibrationsynapseinthetrigeminalprincipal
nucleus(pons)andtrigeminalspinalnucleusparsoralis (ponsandmedulla)
• Fiberscarryingpain&temperaturedescendtothemedullaoruppercervical
spinalcordasthetrigeminalspinaltract,synapseintrigeminalspinalnucleus
parscaudalis
Pathway of CNIX:GlossopharyngealNerve
GVA:sensorytooropharynxandmiddleear
• CNIXformstympanicplexusinmiddleear
• 1° neuronhascellbodyininferior(petrous)ganglion
• CNIXenterscranialcavitythroughjugularforamen
• CNIXentersbrainstematmedulla
• GVAfiberssynapseinthesolitarynucleus(medulla)
Clinicaltest:
• Afferentlimbofgagreflex
Pathway of CNIX:GlossopharyngealNerve SVA
SVA:tastefrompharyngeal(posterior1/3)tongueandvallate papillae
• 1° neuronhascellbodyininferior(petrous)ganglion
• CNIXenterscranialcavitythroughjugularforamen
• CNIXentersbrainstematmedulla
• SVAfiberssynapseinthesolitarynucleus(medulla)
Pathway of CNIX:GlossopharyngealNerve SVE
SVE:motortostylopharyngeus m.
• LMNhascellbodyinthenucleusambiguus (medulla)
• CNIXexitsthebrainstematthemedulla
• CNIXexitsthecranialcavitythroughthejugularforamen
Pathway of CNIX:GlossopharyngealNerve GVE
GVE:parasympathetic,secretomotor toparotidgland
• Pre‐ganglionicneuronhascellbodyininferiorsalivatory nucleus
• CNIXexitsmidbrainatmedulla
• CNIXexitscraniumthroughjugularforamen,formstympanicplexusinmiddleear
• Lesserpetrosaln.(CNIXGVE)re‐enterscranialcavity,exitsthroughforamenovale
• GVEfiberssynapseinotic ganglionininfratemporalfossa
• Post‐ganglionicneuronhascellbodyinotic ganglion,axonstravelwithCNV3
(auriculotemporaln.)toparotidgland
• Function:salivation
Pathway of CNX:Vagus Nerve GSA
GSA:sensorytopinnaofexternalearandexternalearcanal
• 1° neuronhascellbodyinsuperior(jugular)ganglion
• CNXenterscranialcavitythroughjugularforamen
• CNXentersbrainstematmedulla
• Fiberscarryinglighttouch&vibrationsynapseinthetrigeminalprincipal
nucleus(pons)andtrigeminalspinalnucleusparsoralis (ponsandmedulla)
• Fiberscarryingpain&temperaturedescendtothemedullaoruppercervical
spinalcordasthetrigeminalspinaltract,synapseintrigeminalspinalnucleus
parscaudalis
Pathway of CNX:Vagus Nerve GVA
GVA:sensorytolaryngopharynx,larynx,visceraofthoraxandabdomen
• 1° neuronhascellbodyininferior(nodose)ganglion
• CNXenterscranialcavitythroughjugularforamen
• CNXentersbrainstematmedulla
• GVAfiberssynapseinthesolitarynucleus(medulla)
Pathway of CNX:Vagus Nerve SVA
SVA:tastefromrootoftongueandepiglottis
• 1° neuronhascellbodyininferior(nodose)ganglion
• CNXenterscranialcavitythroughjugularforamen
• CNXentersbrainstematmedulla
• SVAfiberssynapseinthesolitarynucleus(medulla)
Pathway of CNX:Vagus Nerve SVE
SVE:motortomusclesofpharynx,softpalate,andlarynx
• LMNhascellbodyinthenucleusambiguus (medulla)
• CNXexitsthebrainstematthemedulla
• CNXexitsthecranialcavitythroughthejugularforamen
• Branches:pharyngealplexus,superiorlaryngealn.,recurrentlaryngealn.
Clinicaltest:
• Say“ah”,uvuladeviatesawayfromsideoflesion
• Phonation
• Efferentlimbofgagreflex
Pathway of CNX:Vagus Nerve GVE
GVE:parasympathetic,secretomotor topharynxandthoracic/abdominal
viscera
• Pre‐ganglionicneuronhascellbodyindorsalmotornucleus(medulla)
• CNXexitsmidbrainatmedulla
• CNXexitscraniumthroughjugularforamen
• Post‐ganglionicneuronhascellbodyinintramuralgangliafoundinwallsof
targetorgan
Pathway of CNXI:SpinalAccessoryNerve
GSE:motortotrapeziusandsternocleidomastoidmm.
• LMNhascellbodyinspinalaccessorynucleus(ventralhornofC1‐C5spinal
segments).
• CNXIexitsthroughtheventralrootsofthecervicalspinalcord.
• CNXIenterscraniumthroughforamenmagnum
• CNXIexitscraniumthroughjugularforamen
• CNXIdescendstothetrapeziusm.,passingthroughtheposteriortriangleof
thenecktoreachthesternocleidomastoidm.
Pathway of CNXII:HypoglossalNerve
GSE:motortoextrinsicandintrinsicmusclesoftongue
• LMNhascellbodyinhypoglossalnucleusofmedulla
• CNXIIexitsventromedialmedulla,lateraltothemedullarypyramids
• CNXIIexitscraniumthroughhypoglossalcanal
• CNXIIpassesinferiorintoneckwithC1spinalnerve,appearinginferiortothe
posteriorbellyofthedigastricm.,superficialtothecarotidsinus
• CNXIIpassessuperiorlyintothetongue.
Clinicaltest: • tongueprotrusion • tonguedeviates towardssideof lesion.
