5. Physiology of Auditory and Vestibular Systems

Question 1

What is the ion distribution for endolymph?

Answer 1

High [K+}

Low [Na+]

Question 2

What is the ion distribution for perilymph?

Answer 2

Low [K+]

High [Na+]

Question 3

Where do higher frequency sounds displace the basilar membrane?

Answer 3

Near oval window where basilar membrane is narrow and stiff

Question 4

Where do low frequency sounds displace the basilar membrane?

Answer 4

Near helicotrema (tip of cochlea) where the membrane is wide and flexible

Question 5

What CN transmits central axons from the primary auditory neurons of the spiral ganglion to the brainstem?

Answer 5

CN VIII (vestibulocochlear)

Question 6

What mechanoreceptors are rich in actin?

Answer 6

Hair cells

Question 7

What motion of the hair cell stereocilia causes depolarization?

Answer 7

Deflection towards the Kinocilium

Question 8

What motion of the hair cell stereocilia causes hyperpolarization?

Answer 8

Deflection away from the kinocilium

Question 9

What neurotransmitter is released by the hair cells?

Answer 9

Glutamate

Question 10

What channel on the stereocilia allows entry of K+?

Answer 10

TRPA1

Question 11

What part of the cochlea is the stria vascularis located in? What is its function?

Answer 11

Scala media

Maintains electrochemical properties of endolymph by pumping K+ in

Question 12

What cells act as the primary source of auditory information?

Answer 12

Type 1/Inner hair cells

Question 13

What is the function of the 3 rows of outer hair cells?

Answer 13

Act as amplifier, boost mechanical vibrations of basilar membrane

Question 14

What protein allows outer hair cells to be contractile?

Answer 14

Prestin

Question 15

What is the source of otoacoustic emissions?

Answer 15

Outer hair cells (Type II)

Question 16

What type of hair cells both send afferent neurons and receive efferent neurons?

Answer 16

Outer hair cells (send Type II afferents)

Question 17

What hair cells send Type I afferent neurons?

Answer 17

Inner hair cells

Question 18

What is the function of the dorsal cochlear nuclei?

Answer 18

Integrate acoustic information with somatosensory information to localize sound

Question 19

What is the function of the ventral cochlear nuclei?

Answer 19

Process temporal and spectral features of sound

Question 20

What part of the brainstem is the first site where information from both ears converge? What is this convergence called?

Answer 20

Superior olivary complex

Binaural processing

Question 21

What structure is important for generating a map of interaural intensity differences to localize sound?

Answer 21

Lateral Superior Olivary Nucleus

Question 22

What structure is important for generating a map of interaural time differences to localize sound?

Answer 22

Medial Superior Olivary Nucleus

Question 23

Which colliculus is involved in localizing sound vertically? Horizontally?

Answer 23

Superior colliculus - Vertical

Inferior colliculus - Horizontal

Question 24

What is the role of the medial geniculate nucleus of the thalamus in the auditory pathway?

Answer 24

Processing speech inflection

Question 25

What is the role of the primary auditory cortex in the auditory pathway?

Answer 25

Conscious perception of sound (volume, rate of frequency modulation)

Question 26

What region of the primary auditory cortex responds to low frequency? High frequency?

Answer 26

Rostral responds to low frequency Caudal responds to high frequency

Question 27

What areas are contained within the auditory (secondary) association cortex (A2)?

Answer 27

Broca's, Wernicke's

Question 28

Which hair cells receive medial olivocochlear efferents?

Answer 28

Outer hair cells

Question 29

What efferent fibers do the inner hair cells receive from the superior olivary complex?

Answer 29

Lateral olivocochlear efferent fibers

Question 30

What efferent input fibers are responsible for reducing the response to noise and shifting response to higher sound levels?

Answer 30

Olivocochlear Efferents

Question 31

What parts of the middle ear send efferents to the auditory system? From what cranial nerves?

Answer 31

Tensor Tympani to malleus (CN V) Stapedius to stapes (CN VII)

Question 32

What is the main function of middle ear efferents?

Answer 32

Prevent damage - decrease transmission of sound (act at low frequencies)

Question 33

Evoked otoacoustic emissions are used for what?

Answer 33

Test for hearing loss in newborns (no emissions if damage present) Tinnitus Ototoxicity

Question 34

Damage to what structures causes sensorineural hearing loss?

Answer 34

Outer hair cells, especially at the base end (high frequency) of the cochlea

Question 35

Damage to what structures will cut off sensorineural auditory input to the CNS?

Answer 35

Inner hair cells

Question 36

What is a cochlear prosthesis?

Answer 36

Electrode array threaded through the cochlea to stimulate nerve fibers and provide sound

Question 37

What types of rotation are detected by the horizontal, posterior, and anterior semicircular canals?

Answer 37

Horizontal - rotation in horizontal plane Vertical - rotation backwards in the vertical plane (falling backwards) Anterior - rotation forwards in the vertical plane (falling forward)

Question 38

When falling backward, what is the reflex of the eye muscles?

Answer 38

Posterior semicircular canal detects falling backward =\> **Superior oblique M.** is activated, inferior oblique inhibited =\> **Eyes move down** to maintain gaze on horizon

Question 39

When falling forward, what is the reflex of the eye muscles?

Answer 39

Anterior semicircular canal detects falling forward =\> **Superior rectus m.** activated, inferior rectus muscle inhibited =\> **Eyes move up** to maintain gaze on horizon

Question 40

What is the basic action of cortex and cerebellum on the vestibulooptic reflex?

Answer 40

Inhibitory - allows for voluntary motion