CN VIII

Question 1

Where is the vestibular nuclei? Cochlear?

Answer 1

• ponto-medullary junction

- inferior cerebellar peduncle

Question 2

Which components of the ear of vestibular? cochlear?

Answer 2

equilibrium = utricle, saccule, semicircular canals
hearing = organ of corti (has hair cells surrounding cochlea)

Question 3

Where is CN VIII?

Answer 3

lateral surface of brainstem at ponto-medullar junction

- emerges from internal acoustic meatus

Question 4

Where does CN VIII cross the posterior cranial fossa?

Answer 4

within petrous part of temporal bone

Question 5

Where do peripheral processes of primary sensory receptors extend?

Answer 5

from cochlea or vestibular apparatus to nerve cell bodies in cochlea and base of semicircular canals

Question 6

What is perilymph?

Answer 6

between bony and membranous labyrinth

- communicates with cochlear duct (scala vestibule and tympani)

Question 7

What is endolymph?

Answer 7

found in membranous labyrinth

- communicates with cochlear duct

Question 8

What are the types of vestibular component receptors?

Answer 8

macula = specialized receptors

apical surface = stereo cilia and kinocilium

Question 9

What are the functions of receptors?

Answer 9

dynamic = linear and angular
static = tilt

Question 10

What is the function of the cupula in semicircular canals?

Answer 10

evokes receptor potential in hair cells of ampullary crest

Question 11

Where are cell bodies of afferent fibers>

Answer 11

vestibular ganglion -> axons pass through internal auditory canal to reach upper medulla with cochlear n

Question 12

What senses rapid changes from semicircular canals?

Answer 12

cerebellum-flucculonodular lobe from ascending branches

Question 13

What are the coordinates synapses of vestibule-ocular pathways?

Answer 13

VI = medial vestibular nucleus for horizontal eye (horizontal semicircular canal)
III = superior s=nucleus for vertical eye (ant and post SCC)
IV

Question 14

vestibule-ocular reflexes

Answer 14

maintain gaze on target

• info comes from cerebellum and cervical spinal column
• rostral SCT

Question 15

What is the conduit between cervical spinal nn and cerebellum or vestibule-ocular reflexes?

Answer 15

accessory cuneate ligament

Question 16

What causes waves of fluid in the cochlea?

Answer 16

vibration of stapes in oval window

Question 17

Cochlear duct divisions

Answer 17

scala vestibuli (vestibular membrane) and scala tympani (basilar membrane) 
- both perilymphatic

Question 18

Where are sensory receptors found in the auditory component?

Answer 18

hair cells found in cochlear ducts with surfaces contacting basilar membrane, apical ends project cilia into tectorial membrane

Question 19

What do hair cells synapse with?

Answer 19

organ of corti (spiral organ)

Question 20

Types of 2nd order cochlear nuclei

Answer 20

posterior and ventral

Question 21

Pathway of posterior nucleus

Answer 21

dorsal acoustic striae -> contralateral lateral lemniscus (monoaural)

Question 22

Pathway of ventral nucleus

Answer 22

• intermediate striae follows dorsal (monaural)
• ventral striae terminate on ipsilateral and contralateral trapezoid body (inhibitory) and superior olivary nucleus -> lateral lemniscus (binaural)

Question 23

Where do most fibers of the cochlear nuclei run to?

Answer 23

cross and go to trapezoid body or dorsal pons

Question 24

Where are the 3rd order lateral lemniscus found?

Answer 24

tegmentum of pons and midbrain

Question 25

Where are cell bodies of lateral lemniscus found?

Answer 25

superior olivary complex and trapezoid nucleus, and nucleus of lateral lemniscus (binaural pathway)

Question 26

Where do fiber of lateral lemniscus go?

Answer 26

ascend to midbrain and terminate in tectum, specifically inferior colliculus

Question 27

Where are 4th order inferior colliculus and medial geniculate found?

Answer 27

inferior colliculus and medial geniculate body

Question 28

Where are aoustic reflexes from?

Answer 28

collateral branches from lateral lemniscus

Question 29

What nerves are involved in acoustic reflexes?

Answer 29

motor nuclei of V and VII (tensor tympani and stapediius) | - RF contributes to startled response signaled to facial n nucleus and spinal cord

Question 30

What is weber's test?

Answer 30

tuning fork in midline of forehead - conduction deafness = sound better in deaf ear - nerve deafness = better in good hear

Question 31

What is Rinne's test?

Answer 31

tuning fork on mastoid process until sound ceases then move to external auditory meatus - norma ear = sound heard again - conduction deafness = no sound

Question 32

Vestibule-Ocular reflex testing

Answer 32

- cool water irrigation to one ear drives nystagmus (white part) to opposite side - warm water draws to same side

Question 33

What happens if there is inner ear disease with vestibule-ocular testing?

Answer 33

drives exaggerated response in certain head positions

Question 34

What happens if vestibular n damage in vestibule-ocular testing?

Answer 34

exaggerated response in any head position | - absence of any reflex is criteria for brain death

Question 35

What is Rhomberg's test?

Answer 35

tests vision, proprioception - close eyes and test posture - mild lesions in proprioception and vestibular can be compensated for with vision - eye closure causes loss of position