the auditory system

Question 1

what is frequency?

Answer 1

number of compressed or rarefied patches of air that pass by our ears each second (Hz)

Question 2

what is intensity?

Answer 2

air pressure difference between peaks and troughs (dB)

Question 3

the ossicles of the middle ear

Answer 3

• stapes (stirrup) - pushes into oval window into cochlea
• incus (anvil) connected to stapes and malleus
• malleus (hammer) connected to tympanic membrane

Question 4

how does the middle ear transfer sound?

Answer 4

ossicles act as lever system, transferring pressure from tympanic membrane to cochlea
they

Question 5

chambers of the cochlea

Answer 5

• scala vestibuli = begins at oval window, filled with fluid called perilymph
• scala media = responsible for auditory transduction, filled with endolymph (high K+ conc.)
• scala tympani = filled with perilymph

Question 6

how does fluid move around the cochlea

Answer 6

oval window pushes against scala vestibuli, thus pushing fluid to top of coil which then moves into scala tympani and down the cochlea

this causes basilar membrane to move up and down

Question 7

anatomy of the basilar membrane

Answer 7

narrow and thick at the base, not easily moved
wide and thin at the apex, more easily moved

distorted by high frequency sounds at base but low frequency sounds at apex

Question 8

how does basilar membrane displacement affect hair cells?

Answer 8

• stapes moves outward, BM moves upwards, hair cells depolairse
• stapes moves inward, BM moves downwards hair cells hyperpolarise

Question 9

how do hair bundles create action potentials?

Answer 9

1. movement of fluid pushes taller inner hair cells
2. this pulls on tip links between individual hairs (stereocilia)
3. opens up mechanoelectrical transducer channels (TMC1) non selective cation channel