Auditory physiology

Question 1

What constitutes the outer ear?

Answer 1

Pinna, auditory canal and tympanic membrane.

Question 2

What is the purpose of the outer ear?

Answer 2

To transmit sound waves via vibration of eardrum

Question 3

What constitutes the middle ear?

Answer 3

Air-filled space with three bones called the ossicles.

Question 4

What are the ossicles?

Answer 4

Malleus, incus, stapes.

Question 5

What is the purpose of the middle ear?

Answer 5

Conduct and amplify sound from tympanic membrane to inner ear

Question 6

What causes ossicles to move? Which bones are where?

Answer 6

Back and forth movement of the tympanic membrane from sound waves. Malleus in contact with TM, then incus, then staples in contact w/ oval window.

Question 7

What constitutes the inner ear?

Answer 7

Snail-shaped, fluid filled cochlea.

Question 8

What are the three chambers of the cochlea?

Answer 8

Scala vestibuli (perilymph) (upper)
Scala media (endolymph) (middle)
Scala tympani (perilymph) (lower)

Question 9

What is the difference between perilymph and endolymph?

Answer 9

Ion concentrations! Endolymph is filtrate of CSF. Gets secreted via endolymphatic duct and is slowly absorbed by scala media cells, creating slow turnover. Perilymph also experiences slow turnover. Voltage potential between endolymph and and perilymph = +80mV in scala media.

Question 10

What is the role of the scala vestibuli?

Answer 10

Incoming portion of vibrations from footplate (stapes via oval window).

Question 11

What is the role of the scala media?

Answer 11

Hair cells of organ of corti located in scala media; sound waves vibrate the basilar membrane, vibration is transduced by specialized hair cells.

Question 12

How are vibrations conducted through the inner ear?

Answer 12

Movement of the stapes footplate produces pressure waves in the fluids of the inner ear, and these cause a deflection of the basilar membrane, which in turn deflects the hair bundle. Basilar membrane moves up and down, which leads to a deflection of the stereocilia outward and inward, thus opening and closing the transduction channels via the tip links. This communicates to auditory nerves –> brain stem.

Question 13

What is tonotopy?

Answer 13

Each frequency leads to vibration at specific location on basilar membrane.

Question 14

Where are low frequency sounds heard best?

Answer 14

Apex, which is wide and flexible. (Near helicotrema)

Question 15

Where are high frequency sounds heard best?

Answer 15

Base of cochlea, which is thin and rigid.

Question 16

What are the labyrinths?

Answer 16

Set of channels carved into the temporal bone during development, contains vestibular (dorsal) segment and cochlear (ventral) segment.

Question 17

What is conductive hearing loss?

Answer 17

Due to blocked conduction of sound.

Question 18

What will be Rinne test show with conductive hearing loss?

Answer 18

Will be abnormal - louder hearing at bone than air. (because air pathway is blocked).

Question 19

What will Weber test findings be with conductive hearing loss?

Answer 19

Louder in the affected ear. (Like covering ear w/ hand)

Question 20

What is sensorineural hearing loss?

Answer 20

Hearing loss caused by nerve damage.

Question 21

What does the rinne test show w/ sensorineural hearing loss?

Answer 21

Normal. Air>bone.

Question 22

What does the weber test show with sensorineural hearing loss?

Answer 22

Louder in the unaffected ear.

Question 23

What is the pathogenesis of noise-induced hearing loss?

Answer 23

Damage to steriociliated cells in the organ of Corti. Loss of high frequency hearing 1st.

Question 24

How can suddenly extremely loud noises produce heairng loss?

Answer 24

Rupture of tympanic membrane.

Question 25

What it is called when there is overgrowth of desquamated keratin cells in the middle ear space?

Answer 25

Cholesteatoma

Question 26

What does cholesteatoma cause?

Answer 26

Conductive hearing loss. May erode ossicles.