Physiology of hearing + balance

Question 1

What is amplitude?

Answer 1

loudness

Question 2

What is higher frequency than range of hearing called?

Answer 2

ultrasound

Question 3

What is lower frequency than range of hearing called?

Answer 3

infrasound

Question 4

How is sound measured?

Answer 4

decibels
logarithmic scale
0 decibels does not mean 0 sound, humans just cannot hear it

Question 5

What do the bones of the inner ear do?

Answer 5

amplify the force (do not amplify the volume of the sound)

Question 6

What is the attenuation reflex?

Answer 6

reflex to loud sounds
causes contraction of the tensor tympani and stapedius muscles
causes rigidity in the ossicular system, reducing transmission of low frequency sounds
protects cochlear from damage (but delay of 50-100ms)
also reduces sensitivity to own speech

Question 7

What happens at the cochlea during hearing

Answer 7

waves travel along cochlea and cause maximum vibration of the organ of corti where it has a natural resonance
high frequency near base, low frequency near helicotrema

Question 8

What role does the organ of corti have in hearing?

Answer 8

generates nerve impulse in response to vibration of basilar membrane

contains specialised nerve cells called inner and outer hair cells

synapses with the spiral ganglion of corti then the cochlear nerve

Question 9

What is the role of outer hair cells?

Answer 9

involved in sound amplification

prestin - a motor protein in outer hair cells which contracts and elongates, amplifying sensitivity to sound wave

when outer hair cells amplify response, the inner hair cells bend more, increasing response in auditory nerve

Question 10

What is presbycusis?

Answer 10

age-related hearing loss

Question 11

What can cause presbycusis?

Answer 11

loss of hair cells
loss of spiral ganglia neurones
atrophy of the stria vascularis
stiffening of the basal membrane

oxidative stress (ROS) leading to mitochondrial dysfunction and increased cell death - cochlea hypersensitive to ROS

Question 12

What is NIHL?

Answer 12

noise-induced hearing loss

Question 13

Describe the auditory pathway

Answer 13

spiral ganglion of corti
auditory part of CNVIII
superior olivary nucleus
lateral leminiscus
medial geniculate nucleus
auditory cortex of temporal lobe

Question 14

What do otolith organs detect?

Answer 14

detect linear head tilting and gravity

utricle = horizontal
saccule = vertical

Question 15

What do semicircular canals detect?

Answer 15

detect head rotation

Question 16

What is thought to cause Meniere’s disease?

Answer 16

thought to be due to excessive secretion of endolymph with acute swelling in vestibular and cochlear duct

Question 17

What are the semicircular canals filled with?

Answer 17

endolymph

Question 18

What is the enlargement at one end of the semicircular canals called?

Answer 18

ampulla

Question 19

What is the vestibular-ocular reflex?

Answer 19

stabilising eyes, while head moves