8 - Mechanisms of Hearing and their Pathologies

Question 1

What do you use to measure frequency and magnitude of sound?

Answer 1

frequency - hertz

magnitude - decibels

Question 2

Describe how sound is transmitted to the inner ear

Answer 2

Goes to outer ear then to tympanic membrane. Vibrates middle ear bones and reaches the oval window. Oval window vibrates the perilymph within the scala vestibule and then out the scala tympani and then the round window. This vibration causes oscillatory movements in the basilar membrane which causes the movements of the tips of the stereocilia.

Question 3

What is the function of the inner and outer hair cells?

Answer 3

Inner - sense sound

Outer - amplify sound

Question 4

What happens to hair cells in order to sense sound?

Answer 4

stereocilia disrupted results in K influx and depolarising of hair cell. Influx of calcium results in neurotransmitter release.

Question 5

Where is high and low frequencies in the ear sensed?

Answer 5

high - near oval window

low - near end of scala vestibuli

Question 6

State the central auditory pathway of the vestibulocochlear nerve

Answer 6

cochlea –> spiral ganglion cells –> cochlear nucleus –> superior olivary complex –> inferior colliculus –> medial geniculate nucleus –> auditory cortex

Question 7

What is a conductive hearing los and what can cause it?

Answer 7

problem in transmission of sound from outer to inner ear

e.g. osteosclerosis, glue ear

Question 8

what is a sensorineural hearing loss and what can cause it?

Answer 8

damage to the cochlea, cochlear nerev or central auditory pathway.
e.g. ototoxic drugs, excessive noise