Topic 9 - the auditory system

Question 1

What is the definition of frequency?

Answer 1

Number of compressed or rarefied patches of air that pass by our ears each second, expressed as Hertz (Hz)

Question 2

What is the defintion of intensity (or amplitude) in auditory hearing?

Answer 2

Air pressure difference between peaks and troughs, expressed as decibels (dB)

Question 3

What is the human hearing range?

Answer 3

20 Hz to 20,000 Hz

Question 4

What are the 3 main regions of the ear?

and what are the ossicles of the middle ear?

Answer 4

outer ear - middle ear - and inner ear.

The ossicles of the middle ear:
Hammer = malleus
Anvil = Incus
Stirrup = stapes

Malleus to incus has a rigid connection but incus to stapes has a flexible connection.

Question 5

How does the middle ear transfer sound?

Answer 5

it concentrates sound so that no enery is lost.

Ossicles amplify sounds to exert ~ 20 times more pressure on the oval window than on the tympanic membrane - overcoming the greater impedance of cochlear fluid.

Question 6

Describe the structure of the cochlea.

Answer 6

has outer and inner hairs.

if you unroll the cochlea would have the basilar membrane.

Question 7

How does the basilar membrane displacement affect hair cells?

Answer 7

• Stapes moves outward
• BM moves upwards
• Hair cells depolarise
• Stapes moves inward
• BM moves downwards
• Hair cells hyperpolarise

Question 8

Hair bundles are connected by tip links.

describe the role of inner and outer hair cells.

Answer 8

IHCs are primary sensory receptors.

OHCs are electromotile and act as the cochlear amplifier - so can hear sounds ar a lower intensity