Auditory system

Question 1

What is sound

Answer 1

The displacement of air particles following a sinusoids pattern of compression and rarefaction

Question 2

How would you distinguish between a quiet and loud sound wave diagram

Answer 2

Greater displacement from the baseline in loud sounds ( greater amplitude)

Question 3

What is the pinna formed from (embryology)

Answer 3

Pharyngeal arches 1 & 2 ( 6x hillocks of His)

Question 4

What’s the range of human hearing

Answer 4

20Hz - 20 KHz

Question 5

Give the 4 main components of the auditory system

Answer 5

Outer ear - air
Middle ear - air
Inner ear - fluid
Central auditory pathways - electrical

Question 6

What’s the purpose of the folds in our ears

Answer 6

Filter out lower pitch sounds which are less functionally important

Question 7

What’s the function of the pinna

Answer 7

Direct sound waves towards the ear canal

Question 8

What is the bone and cartilage composition of the ear canal

Answer 8

Medial 2/3 is bone and lateral 1/3 is cartilage

Question 9

What type of epithelium is the tympanic membrane made of

Question 10

Name the top 1/3 and bottom 2/3 of the tympanic membrane and explain the difference

Answer 10

Top - pars flaccida
Bottom - pars tensa

Bottom contains endoderm, ectoderm and mesoderm but top only has ectoderm and endoderm so the top is much more delicate

Question 11

What 3 bones (ossicles) does the middle ear contain. Give them in order of size

Answer 11

Incus
Malleus
Stapes

Question 12

What 2 muscles does the middle ear contain

Answer 12

Tensor tympani

Stapedius

Question 13

Where is the Eustachian tube found

Answer 13

Middle ear

Question 14

How much energy is lost when it is transferred from air to fluid

Answer 14

99.9% loss of energy

Question 15

What is the role of the middle air and how do the ossicles faciliate this

Answer 15

Amplification of the airbone sound vibration

Question 16

How do components of the mid ear facilitate its function

Answer 16

Area difference between tympanic membrane and stapes ceates large pressure difference
Ossicles are connected and act together to create a lever mechanism

The amplification gain is 18x or 20-35 dB

Question 17

What’s the role of muscles in the middle ear and how do they carry out this role

Answer 17

Protection of the inner ear from acoustic trauma

Reflex arc of 3/4 neurones that stiffen the ossicular chain in the presence of loud sounds

Question 18

How are the stapedius and tensor tympani stimulated

Answer 18

Stapedius - stimulated acoustically

TT - voluntary and involuntary control

Question 19

What does the eustachian tube connect

Answer 19

Middle ear cavity to nasopharynx

Question 20

Whats the purpose of the E tube

Answer 20

Ventilate the middle ear space and drain secretions

Question 21

Where is the vestibulocochlear apparatus found and what innervates it

Answer 21

Set of fluid filled sacs encased in bone in the Inner ear

CN VIII - vestibulocochlear nerve

Question 22

What is the cochlea responsible for

Answer 22

Hearing

Question 23

What is the labyrinth responsible for

Answer 23

Balance

Question 24

What are the 3 compartment of the cochlea and which is not connected to the other

Answer 24

Scala tympani
Scala media - independent from the others
Scala vestibuli

Question 25

How many turns does the cochlea have

Answer 25

2.5 turns

Question 26

Guve the 2 openings on the cochlea

Answer 26

Round window | Oval window

Question 27

The cochlea contains ionic fluids. Give their names, locations and compisitions

Answer 27

Endolymph - scala media , hight in K+ Perilymph - scala tympani and vestibuli, rich in Na+

Question 28

How are gradients of cochlear fluids maintained

Answer 28

Na, K ATPase | Chlorine channels

Question 29

Describe the movement of sound in the cochlea

Answer 29

Stapes footplate presses on the oval window which develops a pressure wave within the scala vestibuli Wave progresses round through the helicotrema and into the scala tympani The wave then hits the round window

Question 30

Compare the base of the basillar membrane with the apex

Answer 30

Base: narrow, stiff and detects high frequencies Apex: wide, floppy and detects low frequencies

Question 31

Where in the cochlea does fluid energy start moving to electrical energy

Answer 31

Organ of corti - sits above basillar membrane and contains hair cells

Question 32

Desribe what occurs when the inner hair cells move

Answer 32

Mechanically gated K+ channels opened causing depolarisation (K influx from endolymph) Depolarisation resukts in opening of voltage gated calcium channels This results in naurotransmitter release - usually glutamate Repolarisation occurs through K+ efflux into perilymph

Question 33

What is meant by single nerve fibre response

Answer 33

Each nerve responds maximally at a specific frequency

Question 34

Whats the role of outer hair cells in the scala media

Answer 34

Alter the stiffness of the basillar membrane to ensure maximal stimulation at one site and dampened response at another site Increased resolution

Question 35

How are frequency, intensity and amplification encoded

Answer 35

Frequency - in nerves by location along the basillar membrane Intensity - in nerves by numbers responding and firing rate Amplification - oute hair cells

Question 36

Give the central auditory pathway

Answer 36

``` Eight CN Vestibulocochlear nerve Cochlear nucleus Olive ( sup,med, inf olivart nucleus ) Lateral leminiscus Inferior colliculus ``` ECOLI