The Auditory System 08/02/24

Question 1

What four components make up the auditory system? State whether the first free consist of Water or air?

Answer 1

Outer ear- Air
Middle ear- Air
Inner Ear- Fluid
Central Auditory Pathways

Question 2

What is the Structure and function of the Pinna and Ear Canal?

Answer 2

Pinna-Cartilaginous structure
Directs soundwaves towards ear canal

Question 3

What is the Pinna formed from? (2) What week is it formed from birth?

Answer 3

Pharyngeal arches 1&2
Forms between 10th and 18th week

Question 4

What is the role of The middle ear? What does this mean?

Answer 4

Acoustic Impedance match
Transference of energy from air to fluid

Question 5

How much energy is lost when energy is transferred from the air to fluid in the inner ear?

Answer 5

97%

Question 6

What are two Features of the Middle ear that allow it to amplify sound? How many decibles does the middle ear increase your hearing by?

Answer 6

1.Ratio area of TM:Stapes = 14:1
-Lever action of Ossicles
2. 20-35 dB

Question 7

How much does the structure of the middle ear increase the energy transfer from air to fluid by?

Answer 7

200 times

Question 8

What is the role of muscles in the middle ear?
How do they do this?

Answer 8

1. Protection of the inner ear
2. Stiffen the ossicular chain

Question 9

How is the Stapedius stimulated? How long does it take for it to react?

Answer 9

Acoustically
25ms

Question 10

What is the apparatus of the inner ear called? What nerve innervates it?

Answer 10

Vestibulocochlear apparatus
Vestibulocochlear nerve (CN 8)

Question 11

What are the three sections of the cochlea called? How many turns does the cochlea have?

Answer 11

Scala Tympani, Scala Media and Scala Vestibuli
2.5 turns

Question 12

What are the two ionic fluids called in the Cochlea? Where is each one found?

Answer 12

Endolymph- Scala media
Perilymph- Scala vestibuli/ tympani

Question 13

What are the Endolymph and Perilymph rich in respectively?

Answer 13

K+ (Endolymph)
Na+ (Perilymph)

Question 14

Why is it important gradients are maintained in the Cochlea?

Answer 14

Abnormalities will cause deafness

Question 15

What is the connecting channel between the scala vesitbuli and the scala tympani called?
What does it allow and why?

Answer 15

Helicotrema
Allows fluid to move between the two which slightly impedes the travel of sound

Question 16

What separates the scala vestibuli from the scala media?

Answer 16

Basilar membrane

Question 17

What happens to the Basilar membrane as impulses move up the scala vestibuli?

Answer 17

It moves

Question 18

What are three properties of the Basilar membrane at the base of the cochlea?

Answer 18

Narrow
Stiff
High frequencies detected

Question 19

What are three properties of the Basilar membrane at the Apex of the cochlea?

Answer 19

Wide at apex
Floppy at apex
Low frequencies detected at apex

Question 20

What cells are responsible for Mechanical transduction when the basilar membrane is displaced? Where are they found and what afferent never are they attached to?

Answer 20

Inner hair cells
In the Basilar Membrane
Attached to Auditory nerve

Question 21

What is the function of Outer hair cells?

Answer 21

Stiffen the Basilar membrane to prevent inner hair cells on other parts of the basilar membrane from getting stimulated

Question 22

What is the pathway of sound?

Answer 22

Auditory fibre- spiral ganglion - cochlear nerve- central auditory pathway