Physiology of Auditory and Vestibular System (Pierce)

Question 1

Describe the physical properties that contribute to deflection of the basilar membrane (LO1)

Answer 1

Near the oval window, the basilar membrane is very narrow and stiff and picks up high frequency sound

Near the helicotrema, the basilar membrane is wide and flexible and picks up low frequency sound

this preserves the tonotopy of the auditory pathway

Question 2

How does the sound from the basilar membrane affect the rest of the auditory pathway?

Answer 2

the vibration of the basilar membrane creates a pressure differential that results in a shearing force against the stationary tectorial membrane, causing the stereocilia of the outer hair cells to displace

Question 3

Describe the processes of sound waves being converted to action potentials (LO2)

Answer 3

Stereocilia embedded in the tectorial membrane are connected to eachother via tip links that are connected to springs. They are moved by sound waves as the waves move the basilar membrane, and the springs move laterally and open TRPA1 channels ( mechanoreceptors)

The open TRPA1 receptors allow K+ into the hair cell, depolarizing it.

Ca+ enters the cell then and triggers the release of glutamate NTM to the spiral ganglion.

Question 4

What is the function of the stria vascularis? (LO3)

Answer 4

Maintains the electrochemical properties of the endolymph

Maintains the endocochlear potential which forms the blood-labyrinth barrier which serves as a drug entry site for access to the inner hair cell

some things, like CO disrupt the function of the stria vascularis and will diminish the endocochlear potential and impact hearing

Question 5

Compare and Contrast Inner and Outer Hair Cells (LO4)

Inner Hair cells

Answer 5

1’ source of auditory info

single layer

synapse with peripheral terminal of primary afferent sensory neuron

efferent neuron modulates activity as well

Question 6

Compare and Contrast Inner and Outer Hair Cells (LO4)

Outer Hair Cells

Answer 6

primary amplifiers of sound waves that result in movement of basilar membrane

contractile cells, boosting vibration of basilar membrane

three rows of these cells

synapse with afferent from spiral ganglion as well as efferent neurons

Question 7

What are otoacoustic emissions?

Answer 7

Backwards sound.

the movement of the outer hair cells causes the basilar membrane to move, pushing the oval window and ossicles toward the TM producing sound

Can be measured with microphone tool to screen newborns for sensorineural hearing loss, but not auditory neuropathy

Question 8

How do the Olivochoclear efferents protect the cochlea from intense sounds? (LO5)

Answer 8

reduces electromotility of outer hair cells

decreases basilar membrane motion

reduces resposne of inner hair cells and auditory nerve fibers

Question 9

How do middle ear efferents protect the cochlea from intense sounds? (LO5)

Answer 9

Tensor tympani M. and Stapedius M. dampen sound bilaterally

act at low frequnecies

aim is to prevent damage, protect hair cells, prevent low frequency masking

implicated in tinnitus

Question 10

How do autonomic efferents protect the cochlea from intense sounds? (LO5)

Answer 10

arises from 8th cranial nerve

sympathetic adrenergic fibers

regulates vascular tone in blood supply to cochlea

Question 11

What is the role of the dorsal and ventral cochlear nuclei? (LO6)

Answer 11

Dorsal Cochlear Nuclei integrates the acoustic information with somatosensory information

Ventral Cochlear Nuclei begins processing the temporal and spectral features of the sound, rudimentary processing

Question 12

What is the role of the medial superior and lateral superior olivary complex in auditory processing? (LO6)

Answer 12

both receive glutameteric (excitatory) input

MSO: generates a map of interaural TIME differences to help localize sound

LSO: generates a map of interaural INTENSITY differences to help localize source of sound

tonotopic map is maintained

Question 13

What is the role of the inferior colliculus in auditory processing (LO6)

Answer 13

supresses information related to echoes which would interfere with localization

arrives at a final estimation of localization of sound along the horizon

info about time and intensity converge here to create a precise origin of sound location

Question 14

What is the role of the medial geniculate nucleus in auditory processing

Answer 14

part of thalamus

converges from distinct spectral and temporal pathways allowing for processing features of speech inflections

precise information regarding intensity, frequency and binaural properties of sound are integrated and relayed onward

tonotopic map maintained

more subtle, nuanced, and sophisticated processing

Question 15

What is the role of the primary auditory cortex in auditory processing? (LO6)

Answer 15

Essential in conscious perception of sound

higher order processing of sound (loudness, volume modulation, frequency of modulation)

tonotopic map maintained

Question 16

What is the role of the secondary auditory association cortex A2? (LO6)

Answer 16

composed of multiple areas (Broca’s, Wernicke’s, Etc. )

less specifically organized in the tonotopic arrangement than the primary auditory cortex

thought to respond to more complex sounds, like music, naming sound, and speech

Question 17

Describe the purpose of the cochlear prosthesis (LO7)

Answer 17

internal component: electrode array and receiver which decodes the signal and delivers the electrical signals to the array

the electrode array is inserted into the cochlea thru the oval window where it sits in the cochlear duct along afferents from CN 8.

electrical signals along the electrode will stimulate the nerve and the array mimics the tonotopy of the basilar membrane allowing stimulation of specific frequencies

Question 18

What does the anterior semicircular canal detect? LO8

Answer 18

rotation in the vertical plane forwards (falling forward)

Question 19

What does the horizontal semicircular canal detect?

Answer 19

rotation in the horizontal plane (spinning in a circle)

Question 20

What does the posterior semicircular canal detect?

Answer 20

Rotation in a vertical plane backwards (trust fall)

Question 21

What does the utricle detect?

Answer 21

linear acceleration forward and backward (running)

Question 22

What does the saccule detect?

Answer 22

linear acceleration up and down (jumping)

Question 23

Outer hair cells receive afferent innervation from:

efferent innervation comes from:

Answer 23

aff: spiral ganglia
eff: superior olivary complex