13-4: Physiology of Hearing

Question 1

How do sound waves travel from outer to middle ear?

Answer 1

directed by the auricle into the external acoustic meatus

cause tympanic membrane to vibrate

malleus > incus > stapes

movement of stapes pushes oval window in and out

Question 2

How do sound waves travel from the oval window through the cochlea?

Answer 2

movment of oval window > pressure in the perilymph

down the scala vestibuli > to the scala tympani > round window bulges into middle ear

Pressure wave presses down on and increase pressure of endolymph in the cochlear duct

Pressure causes basilar membrane to vibrate and hair cells in the organ of corti to bump into the tectorial membrane

Question 3

How does sound travel from the organ of corti to the brain?

Answer 3

as a result of bumping against the tectorial membrane

hair cells depolarize > nerve impulse generated

Carried by cochlear branch of vestibulocochlear nerve to the medulla of the brainstem, where some axons cross over

Question 4

How does sound travel from the medulla to perception of hearing?

Answer 4

from the medulla, axons travel through midbrain (inferior colliculi) to the thalamus

thalamus relays them to the auditory cortex on temporal lobe

Then you hear!

Question 5

We are born with 40,000 hair cells, but the number decrease when: ____

Answer 5

they are damaged by loud noises, disease, or drugs

Question 6

presbycusis

Answer 6

hair cell deterioration due to aging - ability to hear high pitched sounds goes first