Ear 2

Question 1

Organization of the Auditory System

Answer 1

pinna = external auditory canal = tympanic membrane = ossicles = oval window = scala vestibuli = scala media = scala tympani = round window

Question 2

Windows

Answer 2

Oval = separate stapes and cochlea (perilymph moves)
Round = bulges out when stapes move

Question 3

Basilar Membrane

Answer 3

• btwn cochlear duct and scala tympani
• stiff membrane at start (swings @ high frequency)
• flexible at apex (swings @ low frequency)

Question 4

The Cochlea

Answer 4

Scala vestibuli (perilymph)
Reissner’s membrane
Cochlear duct (endolymph - stria vascularis)
Basilar membrane (Organ of Corti)
Scala tympani (perilymph)
Spiral ganglion – cell bodies of sensory neurons

Question 5

Organ of Corti

Answer 5

• basilar membrane
• sensory and motor neurons (innervate hair cells)
• supporting cells
• hair cells (3 rows outer, 1 row inner)
• tectorial membrane

Question 6

Shearing Forces

Answer 6

up and down movement of Organ of Corti
- stereocilia bends –> activate ion channels –> signals

Question 7

Hair Cells

Answer 7

• stereocilia – with actin cuticular plate
• kinocilium (one per cell, lost during development)

Question 8

Inner vs Outer Hair Cells

Answer 8

Inner = sensory fibres (ear –> brain)
Outer = efferent fibres (brain –> ear)
- phalangeal cell
- amplify basilar membrane swinging = hair cell contract