Cranial Nerves

Question 1

sensory/afferent fiber types: GSA vs GVA vs SSA vs SVA

Answer 1

sensory info from skin –> external environ vs sensory info from viscera & blood vessels –> internal environ vs sensory info from retina, auditory/vestibular apparatus –> see/hear vs sensory info from taste buds, olfactory mucosa –> taste, smell

Question 2

motor/efferent fiber types: GSE vs GVE vs SV/BE

Answer 2

innervates striated skel muscle vs sm muscle, viscera innervated by CN 3/7/9/10 vs innervates skel muscle from pharyngeal/branchial arches –> structures innervated by CN 5/7/9/10

Question 3

CN1/olfactory n: central vs peripheral process. injury?

Answer 3

bipolar. SVA axons at cribriform plate in ethmoid –> synapse w/ mitral cells in olfactory bulb vs mitral axons to olfactory tract –> med/lat striae –> forebrain. hyposmia, anosmia

Question 4

CN2/optic n. injury?

Answer 4

SSA axons of retinal ganglia form optic n –> optic canal w/ ophthalmic a –> nasal retinas decussate at optic chiasm, not temporal retinas –> optic tract –> lat geniculate bodies/nuclei of thal –> primary visual cortex of occ lobe. visual field deficits

Question 5

where is CN3/oculomotor n? what type of axons?

Answer 5

in interpeduncular fossa –> sup orbital fissure –> orbits; GSE axons in oculomotor nucleus (sup/med/inf rectus m & inf oblique m for eyeball, lev palpebrae superioris m for upper eyelid); GVE axons in Edinger-Westphal nucleus/accessory oculomotor nucleus; presynaptic parasympathetic axons in ciliry ganglion in orbit, postsynaptic parasympathetic axons in sphincter pupillae m for constricting pupil & ciliary muscle for accommodation

Question 6

CN4/trochlear n

Answer 6

GSE axons trochlear nucleus of midbrain –> cavernous sinus wall –> sup orbital fissure; sup oblique m for eyeball; only LMN decussating, only cranial n to exit dorsal midbrain

Question 7

CN5/trigeminal branches: V1 vs V2 vs V3

Answer 7

GSA transmits info from bridge/tip nose, eye, upper eyelid, forehead, dura of ant/med cranial fossa, falx cerebri, tentorium cerebelli; cavernous sinus wall to sup orbital fissure vs GSA transmits info lower eyelid, cheek, upper lip, maxillary teeth, dura ant/med cranial fossa; cavernous sinus wall to foramen rotundum vs GSA transmit info from sideburns, jaw, lower lip, mandibular teeth, ant 2/3 tongue, dura ant/med cranial fossa; SVE innervates muscles from pharyngeal arch & mastication

Question 8

CN5/trigeminal nuclei: mesencephalic vs principle/chief sensory trigeminal nucleus vs motor trigeminal nucleus vs spinal trigeminal nucleus

Answer 8

GSA for proprioception of masticating muscles; primary afferents vs GSA for fine/discrim touch & pressure; 2ndary afferents vs SVE innervating masticating muscles, LMN vs GSA for crude touch, pain, temp; 2ndary afferents

Question 9

CN5/trigeminal pathway lesion to nucleus vs VTT, corticobulbar tract cause?

Answer 9

ipsi vs contralat deficits. Lec 15, slide 13

Question 10

CN6/abducens n. fxn? injury? how to test?

Answer 10

GSE axons in abducens nucleus in pons –> pontomedullary jxn –> cavernous sinus wall –> sup orbital fissure. lat rectus m –> eye abduction. medial strabismus. H-test (put eye in abducted position)

Question 11

CN7/facial n

Answer 11

SVE axons in motor nucleus wrapping around abducens nucleus –> stylomastoid foramen –> innervate skel muscle for facial expression; 1st order GVE parasympathetic axons in sup salivatory nucleus, 2nd order GVE parasympathetic axons in submandibular & pterygopalatine ganglia –> innervate submandibular/ sublingual salivary glands for saliva & lacrimal gland for tears and mucosal glands in nasal cavity/palate for mucus; SVA axons in geniculate ganglion –> relay taste from ant 2/3 tongue –> solitary nucleus –> thal

Question 12

know how CN7 innervates face and when it decussates

Answer 12

bil innervates superior half of face. lesion to UMN –> paralyze contralat lower half of face => hemi-Bell’s palsy; lesion to LMN –> paralyze ipsi face => Bell’s palsy

Question 13

CN8/vestibulocochlear n

Answer 13

SSA in vestibular & cochlear nuclei in pons –> internal acoustic meatus; vestibular n gets input from vestibular apparatus for bal, cochlear n gets input from cochlea for hearing

Question 14

CN9/glossopharyngeal n

Answer 14

SVE axons in nucleus ambiguus of medulla –> innervate stylopharyngeus m; GVE parasympathetic axons in inf salivatory nucleus in medulla –> innervate parotid gland; SVA axons in sup/inf CN9 ganglia –> relay taste from post 1/3 tongue –> solitary nucleus –> thal vs GSA axons in sup/inf CN9 ganglia –> relay sensory from post 1/3 tongue & pharynx –> spinal trigeminal nucleus –> thal; GVA axons in sup/inf CN9 ganglia –> relay sensory from carotid body (chemorecept) & carotid sinus (barorecept) in ICA –> solitary nucleus –> thal

Question 15

CN10/vagus n

Answer 15

SVE axons in nucleus ambiguous in medulla –> innervate larynx & pharynx; GVE parasympathetic axons in dorsal motor nucleus –> innervate thoracic & abd viscera; SVA axons in sup/inf CN10 ganglia –> relay taste from epiglottis –> solitary nucleus –> thal; GSA axons in sup/inf CN10 ganglia –> relay sensory from larynx –> spinal trigeminal nucleus –> thal; GVA axons in sup/inf CN10 ganglia –> relay sensory from aortic chemo&baroreceptors –> solitary nucleus –> thal

Question 16

CN11/spinal accessory n. injury?

Answer 16

GSE axons in nucleus ambiguous & accessory spinal nucleus –> jug foramen –> SCM & trap mm. shoulder droop b/c trap atrophy

Question 17

CN12/hypoglossal n. injury?

Answer 17

GSE axons in hypoglossal nucleus –> hypoglossal canal –> innervate in/extrinsic tongue muscles. tongue deviates towards lesion, atrophy