Lecture 29: Neuroanatomy of the Auditory and Vestibular Systems

Question 1

3 functions of vestibular system

Answer 1

transduce and interpret head movements
maintain position of visual axes when head is moving = vestibulo-ocular reflex
send motor commands to trunk and limb muscles in order to maintain balance

Question 2

vestibulo ocular reflex

Answer 2

when head is moving but eyes can still look at target

Question 3

where are vestibular nuclei located

Answer 3

brainstem

Question 4

vestibular nuclei receive info from (2)

Answer 4

info on head movement from organs of balance
muscle firing from cerebellum

Question 5

which region of brainstem coordinates motor output through cortical and vestibular pathways

Answer 5

cerebellum

Question 6

cerebellum receives info from what 3 regions

Answer 6

cortex
spinal cord
vestibular system

Question 7

lesions to CN VIII or vestibular nuclei lead to disruptions in (4)

Answer 7

stance
head posture
balance
loss of extensor muscle tone

Question 8

bony labyrinth: location, definition, what is contained (general)

Answer 8

bony outer shell of deeper membranous labyrinth
within petrous portion of temporal bone
encases inner ear
organs of balance and hearing = vestibular and cochlear organs

Question 9

what are the vestibular organs (4)

Answer 9

semicircular ducts
utricle
saccule
vestibular nerve

Question 10

what are the cochlear organs (2)

Answer 10

cochlear duct
cochlear nerve

Question 11

membranous labyrinth contains

Answer 11

endolymph

Question 12

region between membranous ducts and walls of bony labyrinth contain

Answer 12

perilymph

Question 13

endolymph vs perilymph

Answer 13

endolymph = more [K+]
perilymph = more [Na+]

Question 14

vestibular and cochlear apparatuses rely on what

Answer 14

mechanical displacement of mechanoreceptors by fluid (lymph derivative)

Question 15

definition of acceleration

Answer 15

rate of change of velocity / time

Question 16

utricle: definition, function

Answer 16

vestibular organ
monitor and activate response to linear acceleration of horizontal movements relative to gravity (side to side)

Question 17

saccule: definition, function

Answer 17

vestibular organ
monitor and activate response to linear acceleration of vertical movements relative to gravity (up and down)

Question 18

3 semicircular ducts: definition, function

Answer 18

vestibular organ
respond to angular acceleration (rotation) of head in all planes = anterior, lateral and posterior semicircular canals

Question 19

on each side of the head there are (6)

Answer 19

3 semicircular ducts each with 1 ampulla
1 utricle with 1 macula
1 saccula with 1 macula
1 vestibular ganglion

Question 20

ampulla =

Answer 20

dilation

Question 21

vestibular ganglion =

Answer 21

scarpa’s ganglion

Question 22

where are semicircular hair duct cells location

Answer 22

within ampulla

Question 23

effect of moving endolymph on cupula, stereocilia, kinocilium

Answer 23

bends capula
tilts stereocilia and kinocilium of hair cells

Question 24

semicircular duct hair cells general anatomy

Answer 24

cell body
stereocilia and kinocilium in contact with endolymph

Question 25

effect of displacement of specialized hair cells during movement (hint: changing membrane potentials)

Answer 25

opens mechanically gated K+ channel = depolarizes = more voltage gated Ca channels open = increases glutamate release

Question 26

depolarization vs hyperpolarization effect on channels

Answer 26

depolarization - more APs, open channels hyperpolarization - less APs, close channels

Question 27

hair cells are located in which organs/areas (5)

Answer 27

semicircular duct otolith organs = utricle, saccule otolithic membrane otoconia macula

Question 28

otolith organ displacement process

Answer 28

moving head allows displacement of gelatinous cap --> cap moves and tilts stereocilia toward kinocilium --> hair cells depolarize = opens channels

Question 29

mirrored orientation of hair cells in macular organs

Answer 29

some hair cells depolarizing while others are hyperpolarizing reversal line indicates this separation

Question 30

opposite polarity of hair cells: effect on firing rate, what side of head

Answer 30

depolarize on side of head toward which person is turning = increase firing rate of hair cells hyperpolarize on side of head from which person is turning = decreased firing rate of hair cells

Question 31

relationship between magnitudes of firing rates in semicircular canals

Answer 31

should be equal hyperpolarization = depolarization

Question 32

which nuclei compares the firing rates from each side

Answer 32

vestibular

Question 33

what must happen to redirect eyes when head rotates: vestibuloocular reflex (2)

Answer 33

motor commands to contract left lateral rectus muscle motor commands to contract right medial rectus muscle

Question 34

lesions of vestibular portion of CN VIII, vestibular apparatus or vestibular nuclei

Answer 34

imbalance of APs received by vestibular nuclei perception of moving when NOT

Question 35

function of auditory system

Answer 35

transduce and interpret vibrations due to sound

Question 36

which labyrinth contains sound transduction mechanism

Answer 36

cochlear

Question 37

position of cochlea relative to semicircular ducts

Answer 37

rostromedial

Question 38

sound transduction mechanism in cochlea

Answer 38

footplate of stapes transmits vibrations to membrane of oval window and perilymph of scala vestibuli

Question 39

fluid displacement from oval window creates

Answer 39

waves and displacements in membranes of cochlea

Question 40

scala vestibuli is filled with

Answer 40

perilymph

Question 41

what mechanism does hearing use for transduction

Answer 41

same as vestibular system = mechanoelectrical stereocilia of hair cells are displaced

Question 42

neural sensation of hearing mechanism

Answer 42

displacement of tectorial and basilar membranes move stereocilia --> transduction of hair cell

Question 43

effect of varying material properties of basilar membrane

Answer 43

allows propagation of various waves in specific regions sensitivities to certain frequencies in certain parts of basilar membranes --> brainstem nuclei

Question 44

interaural time differences used to compute location based on

Answer 44

timing differences between each side

Question 45

interaural level differences used to compute location based on

Answer 45

sound level differences received between each side (directionality)

Question 46

2 differences used to determine where sound came from

Answer 46

interaural time interaural level