the ear

Question 1

sound frequency ?

Answer 1

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

Question 2

intensity or amplitude meaning?

Answer 2

Intensity (or amplitude): Air pressure difference between peaks and troughs, expressed as decibels (dB)

Question 3

human hearing range

Answer 3

Human hearing range = 20 Hz to 20,000 Hz

Question 4

Pinna structure and role

Answer 4

Pinna = latin for ‘wing’
More sensitive to sounds from in front than behind
Convolutions of pinna play a role in sound localisation
Fixed in humans but mobile in other animals.

Question 5

Auditory canal -

Answer 5

Auditory canal extends ~ 2.5 cm into skull.

Question 6

The ossicles of the middle ear

Answer 6

Malleus to incus has a rigid connection

Incus to stapes has a flexible connection

Question 7

how does middle ear transfer sound

Answer 7

Inward movement of the tympanic membrane due to the compression phase of the sound wave

Outward movement of the tympanic membrane caused by the rarefaction phase of sound waves

The middle ear must amplify sound to overcome the increased impedance of fluid within the cochlea

Question 8

impedance

Answer 8

Impedance matching is one of the important functions of middle ear. The middle ear transfers the incoming vibration from the comparatively large, low impedance tympanic membrane to the much smaller, high impedance oval window. Middle ear is an efficient impedance transformer.

Question 9

inner hair cells

Answer 9

The inner hair cells transform the sound vibrations in the fluids of the cochlea into electrical signals that are then relayed via the auditory nerve to the auditory brainstem and to the auditory cortex.
inner hair cells have much denser innervation and the auditory system receives more afferent input from the inner than outer hair cells.

Question 10

Outer hair cells

Answer 10

are electromotile and act as the cochlear amplifier

In a:
BM moves upwards
Hair bundles move towards taller stereocilia
OHC depolarises
OHC contracts
OHC becomes shorter 
Amplifies upwards movement of BM

Question 11

endolymph?

Answer 11

Hair bundles are surrounded by endolymph within the scala media
has high potassium concentration

Question 12

How does basilar membrane displacement affect hair cells?

Answer 12

Stapes moves outward
BM moves upwards
Hair cells depolarise

Stapes moves inward
BM moves downwards
Hair cells hyperpolarise

Question 13

corti organ

Answer 13

The organ of Corti contains the hair cells and sits on the basilar membrane