Auditory

Question 0

What range can humans hear? And what does it decrease with?

Answer 0

20-20,000 hz

This decreases with age and exposure to noise

Question 1

What is sound?

Answer 1

Audible variations in air pressure

Question 2

What does the outer ear consist of?

Answer 2

Pinna collects sound from in front

And auditory cannal

Question 3

What does the middle ear consit of?

Answer 3

Linked to outer ear by tympanic membrane
Ossicles malleus, ossicles, stapes
Tensor tympani muscle
Stapedius muscle
Oval window links inner and middle ear

Question 4

What does the middle ear consist of?

Answer 4

Cochlea and labyrinth

Auditory vestibular nerve

Question 5

Pathway from av nerve to cc

Answer 5

Vestibular and cochlea Nuclei in pons medulla
Also inferior colliculus in midbrain
Medial geniculate nuc in thal

Question 6

What is the role of the ossicles?

Answer 6

To act as amplifiers

Fluid in inner ear resists being compressed more than air, therefore thr vibrations need to be amplified

Question 7

Where is tensor tympani muscle

Answer 7

Anchored to bone in cavity of middle ear and malleus

Question 8

Where is stapedius muscle?

Answer 8

Fixed anchor of bone and stapes

Question 9

Role of tensor tympani and stapedius muscle

Answer 9

Contract when there is a loud noise
Causing chain of ossicles to become rigid
Therefore sound from iuter to inner ear is diminished

Question 10

Structure of the cochlea

Answer 10

Scala vestibular, media, tympani
Reissners membrane
Tectorial membrane
Organ of corti
Basilar membrane

Question 11

Role of round window

Answer 11

To compensate pressure changes caused by oval window

Question 12

Perilymph found where?

Answer 12

Low k and high na

Tympani and vestibuli

Question 13

Endolymph found where?

Answer 13

S. Media

Hugh k and low na

Question 14

What is the endocochlear potential?

Answer 14

Endolymph has electrical potential of +80mv more positive than perilymph

Question 15

What is the physiology of the cochlear?

Answer 15

Inward motion at oval window pushes perilymph into scala vestibuli
Compensated for by movement at round window (because its liquid filled and to adjust pressure)
Basilar membrane (strcuture like a flipper) bends near its base due to movement of endolymph

Question 16

How is frequency of sound mapped?

Answer 16

Depends on distance it travels on basilar membrane

Question 17

Describe organ of corti

Answer 17

Auditory rceptor cells (hair cells with sterocilia)
Convert mechanical energy into a change in membrane potential
Rods of corti provide structural support
Inner and outer hair cells

Question 18

How is concentration difference in cochlear achieved?

Answer 18

Active transport at stria vascularis

Question 19

Role of outer hair cells

Answer 19

3 rows
Amplification
Not well innervated
Shorten when depolarised

Question 20

Role of inner hair cells

Answer 20

Highly innervated
Pitch detection
One row
Nearer modiolus

Question 21

General role of hair cells

Answer 21

Synapse onto vestibular cochlear neurones

Cell bodies located in spiral ganglion within modiolus

Question 22

What type of channels are found on tips of sterocilia

Answer 22

TRPA1
Induced to open and close by bending of stereocilia
Each channel is connected to an elastic filament (TIP LINK) to a wall on adjacent cilia

Question 23

What is the principle of tonotopy?

Answer 23

Pitch is coded by the position on the basilar membrane at which the traveling waves reaches its peak

High pitch travels shorter distance than low pitch

Question 24

How do cochlea implants work?

Answer 24

Processor breaks sound down into components
Different freq channels are transmitted to implant receiver
Signal conducted along wires that end elecrodes in cochlea
Electrodes stimulate neurones under appropriate region in cochlea to stimulate spiral ganglion neurones

Question 25

How does noise lead to hearing loss?

Answer 25

Metabolic overactivity 
Excitotoxicity due to increased ca
Blood supply not sufficient
Mamalian hair cells do not regenerate
Push hair cells too much and tiplinks break

Question 26

Arrangement of hair cells

Answer 26

In a v like structure

Move in direction of point, where degenerated kinocilium is

Question 27

What is the missing fundamnetal illusion

Answer 27

If an incomplete harmonic series is presented the brain can still attribute it to a pitch of the full harmonic series.

Question 28

What are the descending pathways of the auditory system?

Answer 28

Sensitivity of the hair cells can be controlled by descending feedback from aud cortex and superior olivary complex in medulla.
Ie. supress background noise

Question 29

What is interaural time delay?

Answer 29

Sound waves will reach one ear faster than the other
Delay is detected in superior olivary nucleus determining sound source position.
Only works for long wavelengths

Question 30

What is interaural intensity differences

Answer 30

Sounds with shorter wavelengths, loudness of the sound reaching ears is compared
Sound shadow created

Question 31

What is information about sound source position used for?

Answer 31

Drive auditory reflexes which turn head and eyes towards origin of sound so it can be identified visually.
Using tectospinal tract