auditory system

Question 1

What is the range of human hearing

Answer 1

20Hz-20KhZ

Question 2

Key components of the auditory system

Answer 2

1. ) Outer ear
2. ) Middle ear
3. ) Inner ear
4. ) Central auditory pathways

Question 3

Outer ear structure: what is the pinna

Answer 3

It is a cartilaginous structure

Question 4

What is the pinna formed from

Answer 4

Formed from pharyngeal arches 1 & 2 (6x Hillocks of His)

Question 5

When is the pinna formed in gestation

Answer 5

Formed between 10th and 18th week in utero

Question 6

What is the function of the pinna

Answer 6

It directs soundwaves towards ear canal

Question 7

What is the ear canal made up of

Answer 7

1/3 cartilage and 2/3 bone

Question 8

What is the middle ear made of

Answer 8

Bones/muscles/tubes

Question 9

What are the bones (ossicles) of the middle ear

Answer 9

Malleus/Incus/Stapes

Question 10

What are the muscles of the middle ear

Answer 10

Tensor tympani and stapedius

Question 11

What are the tubes of the middle ear

Answer 11

Eustachian tube

Question 12

What are the size of the bones

Answer 12

1. ) Malleus: 23mg
2. ) Incus: 27mg
3. ) Stapes: 2.5mg

Question 13

What is the role of the middle ear

Answer 13

• Acoustic impedance match between air and fluid-filled inner ear
• Amplification of the airborne sound vibration

Question 14

What takes place when energy transfers energy from outer ear to inner ear?

Answer 14

• There is a 200 fold increase boost in pressure from TM to inner ear
• This is the ossicular chain

Question 15

What is the role of muscles in the middle ear?

Answer 15

• Protects the inner ear from acoustic trauma
• Stiffens the ossicular chain
• Stapedius stimulated acoustically
• Tensor tympani is for voluntary and involuntary control and chewing

Question 16

What is the role of the eustachian tube

Answer 16

1. ) Ventilation of the middle ear space

2. ) Drainage of secretions

Question 17

Key facts about the cochlea

Answer 17

1. ) It has 2 openings: round and oval window
2. ) A fluid filled bony tube
3. ) 3 compartments: scala tympani/scala media/scala vestibuli
4. ) Has two ionic fluids

Question 18

What are the ionic fluids in the cochlear

Answer 18

1. ) Endolympth: high K+

2. ) Perilympth: Na+ rich

Question 19

How are gradients maintained

Answer 19

1. ) Na+ & K+ ATPase pump
2. ) NKCCI and CIC-K chlorine channels
   - If you have ion channel abnormalities: get deafness

Question 20

Cochlear components: the basilar membrane features

Answer 20

1. ) Narrow at base
2. ) Wide at apex
3. ) Stiff at base
4. ) Floppy at base
5. ) High frequencies detected at base
6. ) Low frequencies at apex

Question 21

What happens when the basilar membrane

Answer 21

Causes movements of specialised mechanical transducing cells

Question 22

What are the two types of hair cells

Answer 22

1. ) Inner hair cells: mechanical transduction

2. ) Outer hair cells: fine tuning

Question 23

Inner ear: how it goes from waves to sparks

Answer 23

1. ) Sterocilia moves and a rapid response is required

2. ) Mechanically gates K+ channels open which causese depolarisation

Question 24

Inner ear: how it goes from waves to sparks

Answer 24

1. ) Sterocilia moves and a rapid response is required
2. ) Mechanically gates K+ channels open which causes depolarisation
3. ) The depolarisation will result in voltage gated Ca2+ channels being opened
4. ) Releases neurotransmitter: Glutamate
5. ) Repolarisation through K+ efflux (Into K+ poor perilympth)

Question 25

Tonopothy and the role of the outer hair cells

Answer 25

- each nerve responds maximally at a specific frequency - outer hair cells can alter the stiffness of the basilar membrane to ensure max stimulation at one site and dampened response at another - increase resolution

Question 26

How is sound information encoded?

Answer 26

- encoded in formation for neural transmission - Frequency (pitch): encoded in nerves by location along the basilar membrane - Intensity (loudness): enoded in nerves by numbers responding and by firing rate - Sound transduction: inner hair cells - Amplification: outer hair cells

Question 27

How do the signals travel from neuron to brain

Answer 27

1. ) Auditory fibres: spiral ganglion 2. ) Spiral ganglion to cochlear nerve (VIII) 3. ) Central auditory pathway

Question 28

What are MSO neurons

Answer 28

They are coincident detectors. They respond only when excitatory signals arrive simultaneously - Anatomical differences in conncectivity allow each MSO neuron to be sensitive to sound source from location

Question 29

What is the central auditory pathway

Answer 29

Eight nerve-> cochlear nucleus-> olive-> lateral leminiscus-> inferior colliculus

Question 30

Types of hearing loss

Answer 30

1. ) Conductive hearing loss | 2. ) Sensorineural hearing loss

Question 31

Conductive hearing loss

Answer 31

Defective outer/middle ear

Question 32

Sensorineural hearing loss

Answer 32

Defective inner ear