Q:
What two mechanisms are involved in sound amplification in the middle ear?

A:
* Mechanical advantage of supplied by the lever system of the ossicles gives a 1.3 times amplification 
* The piston action due to sound being transmitted from the large surface area of the tympanic membrane to the small area of the oval window (16 times amplification).

Q:
What is the tympanic (acoustic) reflex?

A:
Contraction of tensor tympani and stapedius mm resulting in stiffening of the ossicle chain and attenuation of the transmitted sound by up to 40dB.
Threshold for onset is about 70db and latency for response is 15-40ms.
This reflex also operates during speech to reduce hearing sensitivity.

Q:
Describe the basilar membrane.

A:
The basilar membrane is a membrane separating the scala tympani and the scala media in the cochlea of the inner ear. 
Along it's length it increases in both width and compliance going from base (oval window end) to apex (helicotrema end). 
Sound waves set up a travelling wave of displacement in the basilar membrane. High frequency sounds produce maximal displacement of the membrane near the oval window, where as low frequency sounds produce maximal displacement closer to the apex.

Q:
Greater than 90% of information coming from the cochlear is associated with which group of hair cells?

A:
Inner hair cells.

Q:
What is the theoretical function of the outer hair cells?

A:
The outer hair cells are thought to have membrane proteins containing myosin and thereby be able to change length. This it is thought would allow outer hair cells to actively change the physical relation the basilar membrane and tectorial membrane and effectively amplify the response of inner hair cells to a sound.

Q:
How is 'loudness' coded for?

A:
Volume coding is by total impulse traffic, both as a result of the number of fibres stimulated, and the rate of firing of those fibres.

On low-volume stimulation, only a few fibres fire, and they fire more slowly.
On high-volume stimulation, individual fibres fire more, and more fibres in the region fire.

Q:
Where is the auditory area of the cerebral cortex?

A:
Mainly buried in the lateral fissure on top of the superior temporal gyrus.

Q:
How is the auditory area of the cerebral cortex tonotopically organised?

A:
High frequency represented posteriorly, low frequency represented anteriorly.