Week 1.2 - Physiology of hearing

Question 1

What is the transport of sound from beginning to inner ear?

Answer 1

pinna - external auditory meatus - tympanic membrane - ossicles - oval window - round cochlea - round window

Question 2

What are the ear ossicles?

Answer 2

malleus, incus and stapes

Question 3

What does the inner ear consist of?

Answer 3

vestibule and cochlea

Question 4

What is the purpose of the middle ear?

Answer 4

amplifies sound.

Question 5

How does the middle ear amplify sound?

Answer 5

• ratio of tympanic membrane to stapes footplate is 17:1, raising pressure
• lever action of ossicular chain raises pressure going directly into iner ear - 1.3:1

Question 6

What is conductive hearing loss?

Answer 6

when sound is unable to get through to middle ear due to an outer or middle ear issue

Question 7

What are examples of conductive hearing loss?

Answer 7

• fluid buildup
• osteosclerosis
• inflammation
• perforated tympanic membrane

Question 8

How does perforated tympanic membrane affect hearing?

Answer 8

• small perforation , sound still goes through. only indication for repair is recurring infections
• subtotal perforation - some sound waves still hits ossicles and gets through. max loss of 60dB

Question 9

What is otosclerosis?

Answer 9

ossicles are fixed, so cant vibrate, due to trauma or otosclerosis. upsets lever action so movement of sound doesn’t go into inner ear. conductive.

Question 10

Where does the inner ear begin and what are the roles of its 2 constituents?

Answer 10

• begins at oval window.
• ends at round window
• has vestibule which transmits balance, head movements and positioning in space
• has cochlea which transmits frequency and tone

Question 11

What type of fluid is found in the inner ear?

Answer 11

• endolymph found in the vestibule and scala media
• perilymph found in the scala vestibuli and scala tympani

Question 12

What are the components of the cochlea?

Answer 12

• scala vestibuli, scala media and scala tympani - 3 fluid filled canals.
• basilar membrane, base of scala media
• organ of corti on basilar membrane
• tectorial membrane above organ of corti

Question 13

What is the movement of pressure waves along the cochlea?

Answer 13

• pressure wave travels through oval window, then along fluid of entire scala vestibuli, up to the helictotrema, then back down the scala tympani.
• along the way the pressure waves hit the scala media
• pressure wave come sback out the round window

Question 14

How are impulses transmitted in the cochlea?

Answer 14

ossicles depress the oval window. this causes pressure waves to travel through the fluid and this hits the scala media basilar membrane, causing it to move. the vibration causes hair cells and their cilia to move, opening ion channels, leading to cations from endolymph entering into hair cells. this leads to depolarisation and an impulse sent to cochlear nerve

Question 15

What is the structure of the organ of corti?

Answer 15

• lays on basilar membrane
• has inner and outer hair cells, which connect hair bundles/cilia to the tectorial membrane above it

Question 16

How is frequency detected in the cochlea?

Answer 16

tonotopic arrangement. different parts of the basilar membrane along the cochlea are sensitive to a specific frequency.
the base of the cochlea sensitive to the highest frequency and the apex sensitive to the lowest.