Cranial Nerves Function

Question 1

CN I olfactory nerve

Answer 1

special sensory: olfaction

lesion: anosmia

Question 2

CN II optic nerve

Answer 2

special sensory: vision

lesion: anopsia

Question 3

CN III oculomotor nerve

Answer 3

somatic motor: all eye muscles except lateral rectus M. (CN VI) and superior oblique M. (CN IV)
visceral motor: parasympathetic pupil constriction
lesion:
ptosis (upper eyelid droop)
strabismus (DOWN AND OUT)
diplopia (double vision)

Question 4

CN IV trochlear nerve

Answer 4

somatic motor: superior oblique M. of eye
lesion:
strabismus (UPWARD)
diplopia (double vision)

Question 5

CN VI abducens nerve

Answer 5

somatic motor: lateral rectus M. of eye
lesion: strabismus (INWARD)
diplopia (double vision)

Question 6

CN V trigeminal nerve

Answer 6

branchial motor: mastication, tensor palatini, mylohyoid, and anterior belly of digastric MM.
general sensory: face, conjuntiva, external tympanic, mucous membranes of nose, mouth, tongue and teeth, and meninges of anterior and middle cranial fossae
lesion: trigeminal neuralgia (tic douloureux)

Question 7

CN VII facial nerve

Answer 7

branchial motor: muscles of facial expression
visceral motor: stimulation of lacrimal, submandibular, and sublingual glands
general sensory: concha of auricle, small area of skin behind ear
special sensory: taste on anterior two thirds of tongue and the hard and soft palates
lesion: decreased tearing and salivation, loss of taste sensation, Bell’s palsy

Question 8

CN VIII vestibucochlear nerve

Answer 8

special sensory: auditory information from cochlea (cochlear branch); balance information from semicircular canals (vestibular branch)
cochlear branch lesion: deafness
vestibular branch lesion: loss of balance, nausea, vomiting, and dizziness

Question 9

CN IX glossopharyngeal nerve

Answer 9

branchial motor: stylopharyngeus
visceral motor: otic ganglion (sends fibers to parotid gland)
visceral sensory: subconscious sensation from carotid body and sinus
general sensory: posterior one-third of tongue, skin of external ear, and internal tympanic membrane
special sensory: taste from posterior one-third of tongue
lesion: reduced salivary secretion, loss of taste sensations to posterior one-third of tongue

Question 10

CN X vagus nerve

Answer 10

branchial motor: muscles of pharynx, tongue, and larynx (except stylopharyngeus (CN IX) and tensor veli palati (V3))
visceral motor: smooth muscle and glands of pharynx, larynx, and thoracic and abdominal viscera
visceral sensory: larynx, trachea, esophagus, and thoracic and abdominal viscera; stretch receptors in wall of aortic arch; chemoreceptors in aortic bodies adjacent to arch
general sensory: skin at back of ear and external acoustic meatus, part of external tympanic membrane, pharynx
lesion: hoarseness, difficulty swallowing, impaired GI mobility

Question 11

CN XI accessory nerve

Answer 11

branchial motor: sternocleidomasteoid and trapezius MM.

lesion: difficulty elevating shoulder (trapezius M.) or turning head to opposite side (SCM M.)

Question 12

CN XII hypoglossal nerve

Answer 12

somatic motor: intrinsic and extrinsic MM. of tongue except the palatoglossus (CN X)
lesion: swallowing and speech difficulties, if single hypoglossal nerve a protruded tongue deviates to side of damaged nerve