Cross Species - Cranial Nerves Part 1

Question 1

what is the name & function of cranial nerve I?

Answer 1

olfactory nerve - smell

Question 2

what is the name & function of cranial nerve II?

Answer 2

optic nerve - vision, afferent fibers to the brain

Question 3

what is the name & function of cranial nerve III?

Answer 3

oculomotor nerve -

motor to the iris - parasympathetic fibers cause constriction

motor to most muscles of the eye - except for those innervated by CN IV/CN VI

Question 4

what is the name & function of cranial nerve IV?

Answer 4

trochlear nerve - motor to the dorsal oblique muscles of the eye

Question 5

what is the name & function of cranial nerve V?

Answer 5

trigeminal nerve - all 3 branches provide sensation to the face/oral cavity/corneal surface of the eye/ear

mandibular & maxillary branches - motor to the muscles of mastication

Question 6

what is the name & function of cranial nerve VI?

Answer 6

abducens nerve - motor to the lateral rectus & retractor bulbi muscles of the eye

Question 7

what is the name & function of cranial nerve VII?

Answer 7

facial nerve

motor to the muscles of facial expression

taste on the rostral 2/3 of the tongue & sensation of the concave pinna

parasympathetic fibers to the nasal glands, lacrimal glands, mandibular salivary glands, & sublingual salivary gland

Question 8

what is the name & function of cranial nerve VIII?

Answer 8

vestibulocochlear nerve

vestibular part - balance, posture, equilibrium, & muscle tone

cochlear part - hearing

Question 9

what is the name & function of cranial nerve IX?

Answer 9

glossopharyngeal nerve

sensory & motor to the pharynx & larynx

taste on the caudal 1/3 of the tongue

parotid & zygomatic salivary glands

Question 10

what is the name & function of cranial nerve X?

Answer 10

vagus nerve

sensory & motor to pharynx & larynx

sensation of the external ear canal

sensory & motor to the thoracic/gastrointestinal viscera

Question 11

what is the name & function of cranial nerve XI?

Answer 11

accessory nerve

motor to the trapezius, sternocephalic, & brachiocephalic muscles

Question 12

what is the name & function of cranial nerve XII?

Answer 12

hypoglossal nerve

motor to the tongue, sternohyoideus, & sternothyroideus muscles

Question 13

how is cranial nerve I tested?

Answer 13

may test by noting animal’s response to treats or certain chemicals

difficult to asses

Question 14

what are the ways in which you can test the function of cranial nerve II?

Answer 14

PLR test

menace response

visual tests - obstacle courses, tracking objects with the eyes

nerve fibers decussate at the optic chiasm (amount varies by species)

Question 15

what are the ways in which you can test the function of cranial nerve III? what will you see with damage/abnormality?

Answer 15

PLR

if abnormal, look for the presence of ptosis of ventrolateral strabismus

Question 16

what are the ways in which you can test the function of cranial nerve IV? what will you see with damage/abnormality?

Answer 16

really only going to look for injury causing lateral rotation of the globe

Question 17

what are the ways in which you can test the function of cranial nerve V? what will you see with damage/abnormality?

Answer 17

palpebral reflex

palpate the nasal mucosa or auricular lining & look for a reaction

if mandibular or maxillary branch is damaged - atrophied muscles of mastication

Question 18

what are the ways in which you can test the function of cranial nerve VI? what will you see with damage/abnormality?

Answer 18

corneal reflex - looking for retraction of the globe & prolapse of nictitans while keeping the eyelids open

with injury - medial strabismus

Question 19

what are the ways in which you can test the function of cranial nerve VII? what will you see with damage/abnormality?

Answer 19

menace response

palpebral reflex

tickle ear/nose & watch for a reaction

test parasympathetic function with the schirmer tear test

classic abnormal appearance - unilateral droopy lip/ear/eye, & dry eye

Question 20

what are the ways in which you can test the function of cranial nerve VIII? what will you see with damage/abnormality?

Answer 20

vestibular - with unilateral injury, see a head tilt towards the lesion, circling/falling towards the lesion, spontaneous nystagmus with the fast phase away from the lesion, & ventral strabismus when the nose is elevated

cochlear part - brainstem auditory evoked response or assessing response to loud sounds

Question 21

what are the ways in which you can test the function of cranial nerve IX? what will you see with damage/abnormality?

Answer 21

difficult to assess separately apart from CN X

damage causes dysphagia

Question 22

what are the ways in which you can test the function of cranial nerve X? what will you see with damage/abnormality?

Answer 22

look for dysphagia, laryngeal paralysis, & dysphonia

in ruminants - vagal indigestion

Question 23

what are the ways in which you can test the function of cranial nerve XI? what will you see with damage/abnormality?

Answer 23

atrophy of the trapezius, sternocephalicus, & brachiocephalicus muscles

Question 24

what are the ways in which you can test the function of cranial nerve XII? what will you see with damage/abnormality?

Answer 24

look for atrophy, weakness, or deviation of the tongue

Question 25

what are the 3 branches of major importance of cranial nerve V?

Answer 25

mandibular, ophthalmic, & maxillary branches of the trigeminal nerve

Question 26

what cranial nerves are tested by the PLR?

Answer 26

CN II is afferent

CN III is efferent - when looking at the oculomotor nerve, the efferent aspect of CN III is parasympathetic

Question 27

what cranial nerves are tested by the menace response?

Answer 27

CN II is afferent

CN VII is efferent

Question 28

what cranial nerves are tested in the palpebral reflex?

Answer 28

CN V is afferent

CN VII is efferent

Question 29

what cranial nerves are tested in the corneal reflex?

Answer 29

CN V is afferent

CN VI is efferent

Question 30

what cranial nerve is assessed by the schirmer tear test?

Answer 30

parasympathetic part of cranial nerve VII

Question 31

what two muscles of the eye are not innervated by cranial nerve III? what cranial nerves innervate them?

Answer 31

dorsal oblique muscle - trochlear, cranial nerve IV

lateral rectus & retractor bulbi muscles - abducens, cranial nerve VI