7) Hearing

Question 1

What does the oval window of the cochlea interact with?

Answer 1

Fluid above basilar membrane in scala vestibuli

Question 2

What does the round window of the cochlea interact with?

Answer 2

Fluid below basilar membrane in scala tympani

Question 3

What happens to hair cells when the fluid of the cochlea vibrates?

Answer 3

Hair cells move laterally and cilia move which cause changes in ion channels in hair cells, activating the cells and impulses are sent down cochlear nerve fibres

Question 4

What is tonotopy?

Answer 4

Different frequencies of sound are represented at different points along the basilar membrane
Low freq = distal, high freq = proximal

Question 5

How many rows of each hair cells are there?

Answer 5

One row of inner hair cells, three rows of outer hair cells

Question 6

What are the functions of the inner and outer hair cells?

Answer 6

IHC = sense sounds
OHC = amplifiers

Question 7

How are the hair cells mechanical and electrically tuned?

Answer 7

Mechanically tuned by their location along the cochlea

Electrically tuned by expression of particular ion channels

Question 8

What cells support and surround the hair cells?

Answer 8

Deiter’s cells

Question 9

How does vibration in the fluid cause electrical impulse in the hair cells?

Answer 9

Bending of stereocilia opens mechano-transducer K+ channels causing depolarisation of hair cells. The depolarisation opens voltage gated Ca2+ channels triggering transmitter release onto spinal ganglion

Question 10

What system regulates the amplification of outer hair cells?

Answer 10

Olivocochlear system

Question 11

Where do action potentials propagate to along CN VIII?

Answer 11

Cochlear nucleus and auditory brainstem

Question 12

What is the function of the medial superior olive?

Answer 12

Sound localisation by interoral time difference

Question 13

What is the function of the lateral superior olive?

Answer 13

Sound localisation by interoral level difference

Question 14

List the auditory pathway:

Answer 14

Cochlea -> spiral ganglion cells -> cochlear nucleus -> superior olivary complex -> inferior colliculus -> medial geniculate nucleus -> auditory cortex

Question 15

Give examples of some causes of hearing impairment:

Answer 15

Loud noise (sound damage)
Congenital
Infections (rubella, glue ear)
Trauma
Age
Ototoxicity (aminoglycosides)

Question 16

How can hearing function be assessed?

Answer 16

Otoscopy
Audiograms
Otoacoustic emissions
Auditory brainstem response

Question 17

What are otoacoustic emissions and when can they be used in testing?

Answer 17

Sound generated by OHC
Diasapper when inner ear is damaged
Used to test babies and children

Question 18

Give examples of conductive hearing loss:

Answer 18

Blockage
Ruptured eardrum
Fluid accumulation
Otosclerosis

Question 19

Give examples of sites damaged in sensory hearing loss:

Answer 19

Hair cell destruction (physical, noise related)

Hair cell death (ototoxic)

Question 20

Give examples of neural hearing loss:

Answer 20

Spiral ganglion damage - acoustic neuroma
Age related hearing loss
Tinnitus
Auditory neuropathy
Monaural deafness

Question 21

Where can congenital deafness mutations affect?

Answer 21

Hair cells
Tectorial membrane proteins
Non-sensory cells
Mitochondrial proteins

Question 22

What are some treatments for hearing impairments?

Answer 22

Hearing aides
Cochlea implants
Hair cell regeneration
Cochlear nucleus implants

Question 23

Describe how cochlea implants work:

Answer 23

Receiving unit detects sound of all frequencies and processor splits it into its different frequency components. Receiver connects to wire passed through round window into scala tympani. Has electrodes along its length that only switch on if given frequency is in sound being heard