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SYS I > L5 + L6 - Audition > Flashcards

L5 + L6 - Audition Flashcards

1
Q

What is the function of the pinnea?

A

To amplify sound

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2
Q

What is the auricle?

A

The ear lone

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3
Q

What did the middle ear evolve from?

A

the branchial arch skeleton

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4
Q

What did the quadratum and articulare from primitive reptiles develop into?

A

The malleus and incus

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5
Q

What did the columella from primitive reptiles develop into?

A

The stapes

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6
Q

Outline Saunder’s compared transfer function experiment

A

He tested the difference between the 3 ossicle middle ear model belonging to mammals and the 1 ossicle middle ear model belonging to birds. He tested the relative dB that could be detected at certain frequencies. He found that generally mammals can hear much higher frequencies up to 100kHz were as birds could only hear up to 10kHz. Humans are an exception to this as out hearing is limited to a maximum of 10-20kHz.

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7
Q

What is the function of the middle ear?

A

To enable transfer of airborn sound into the fluid filled inner ear, acting as an impedence transformer.

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8
Q

How does the impedence transformer function of the middle ear work?

A

The ratio between the tympanic membrane and stapes footplate surface area i very large and the lever action of the malleus to the incus is 1.3:1, this amplifies the pressure to the footplate by another 30dB.

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9
Q

What happens if the stereocilia are pushed towards the kinocilia?

A

Excitation occurs as the transduction links are stretched

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10
Q

What happens if the kinocilia is pushed towards the steroeocilia?

A

Inhibition as the transduction links are compressed

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11
Q

What happens when the transduction links are stretched?

A

The apical ion channels at the tip links re opened letting K into the cell. This opens VGCC which then open both ligand gated and VG potassium channels, extruding potassium into the Scala Tympani. Calcium is also pumped out. Meanwhile NTs are being released which stimulate the auditory afferent nerve fibres, where the sound is converted into an AP travelling to the brain.

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12
Q

What are the 2 types of spiral ganglion cells that afferently innervate the cochlea?

A

Large myelinated cells which innervate Inner hair cells

Small unmyelinated cells which innervate outer hair cells

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13
Q

What are ribbon synapses in the cochlea specialized for?

A

High precision temporal sound coding over a wide range of intensities and time periods

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14
Q

What is the main function of the outer hair cells?

A

They act as a cochlear amplifier

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15
Q

What are otoacoustic emissions?

A

Sounds emitted from the ear due to the motility of outer hair cells. They can be used to check outer hair cell function.

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16
Q

Outline spontaneous otoacoustic emissions (SOAE)

A

These occur without a sound stimulus
Present in 20-40% of normal hearing ears
Not used clinically

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17
Q

What are the two types of evoked otoacoustic emissions?

A

Transitions evoked otoacoustic emissions (TEOAE)

Distortion product otoacoustic emissions

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18
Q

Outline transitions evoked oto acoustic emissions

A

They are stimulated by a short click
They are fast but have low frequency selectivity
They are absent at hearing loss >30-40 dB
Used to test new-borns hearing

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19
Q

Outline distortion produced oto acoustic emissions

A

To elicit must use a probe with a mini microphone and two speakers inserted into the ear canal. These then emit two frequencies f1 and f2. these cause overlapping waves on the basilar membrane.In the region of the overlap a distortion with a frequency 2f1-2f2 occurs. This can then be measured by the microphone.

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20
Q

What is the driving force for K influx in the cochlear?

A

The positive endocochlear potential of 80mV

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21
Q

Where does K recycling take place in the cochlear?

A

In the supporting cells of the organ of corti, the fibrocytes of the lamina spiralis and the stria vascularis

22
Q

In the auditory at low frequencies are the action potentials timelocked to the stimulus?

A

Yes

23
Q

Is there a smaller frequency detection at high volume?

A

No there is a larger frequency detection

24
Q

Is the volume threshold the same for different frequencies?

A

No it changes

25
Q

What are the low SR fibres useful for?

A

Decoding human speech

26
Q

What are the 3 response components of the cochlea

A

Cochlear microphones - generated by transduction current through the OHC and follow closely the time course of the stimulus
Summating Potential - a dc potential generated by hair cells
Compound action potential - synchronised response of the auditory nerve fibres to onset of the stimulus

27
Q

Outline the ascending auditory pathway

A

Auditory nerve fibres –> Cochlear nucleus –> superior olivary complex –> lateral lemniscus –> inferior colliculus –> medial geniculate nucleus —> auditory cortex

28
Q

Outline the descending auditory pathway

A

Inferior colliculus –> cochlear nucleus –> spiral ganglion within bony

29
Q

What is processed in the acoustic parallel pathways?

A

Dorsal stream = sound identification

Ventral stream - binaural sound localization

30
Q

Where do the auditory parallel pathways combine?

A

The inferior colliculus

31
Q

What are the two methods of binaural sound localisation?

A

Interaural level difference

Interaural temporal difference

32
Q

What is interaural level difference (ILD)?

A

The difference in volume between the two, due to the acoustic shadow of the head. The minimus difference detectable is 1-2dB

33
Q

What is the interaural temporal difference (ITD)?

A

The time between both ears. The minimum difference that can be detected is

34
Q

Where is ILD processed?

A

The lateral superior olive (LSO)

35
Q

How is ILD processed?

A

Direct excitatory input from the ipsi-lateral spherical cells of the AVCN.
Indirect inhibitory input from the contra-lateral globular cells of the AVCN through the MNTB.
These converge in the LSO.
this is then projected to the inferior colliculus.

36
Q

Where is ITD processed?

A

Medial superior olive (MSO)

37
Q

How is ITD processed?

A

Direct excitatory input from the ipsi-lateral and contra-lateral spherical bushy cells of th AVCN to the MSO.
Indirect inhibitory input from the ipsi-lateral globular bushy cells of the AVCN via the LNTB
Indirect inhibitory input from the contra-lateral globular bushy cells of the AVCN via the MNTB.
MSO neurons then project to the inferior colliculus

38
Q

Which hemisphere is speech limited to?

A

The left

39
Q

What are on the axes for an audiogram?

A

On the y axis is he threshold in dBSPL and on the x axis is the frequency

40
Q

How is air conduction stimulated?

A

The inner ear is stimulated via a headphone

41
Q

How is bone conduction stimulated?

A

Via a bone conduction transducer

42
Q

What is the presentation for conductive hearing loss on an audiogram?

A

Normal bone conduction

Air conduction hearing loss

43
Q

What is the presentation for sensorineural hearing loss on an audiogram?

A

Air an bone conduction are similarly reduced.

44
Q

What is the presentation for combined hearing loss on an audiogram

A

Both have hearing loss however air conduction hearing loss is more severe.

45
Q

What are the possible causes of conductive hearing loss?

A

Ear canal blocked
Middle ear infection
Rupture of the ear drum
Pathology of the ossicles e.e. cholesteatome or ostosklerosis

46
Q

What are the possible causes of sensorineural hearing loss?

A

Damage and loss of hair cells
Loss of auditory nerve fibres and spiral ganglion cells
Auditory nerve neuropathy/synaptopathy
Pathology of the Stria vascularis

47
Q

What is an EAS?

A

A new type of hearing aid which uses acoustical amplification at low frequencies and electrical stimualtion at high frequencies

48
Q

How does a cochlear implant work?

A

It stimulates the auditory nerve directly

49
Q

How do you identify that the gerbil heard a sound?

A

Use a natural behaviour e.g. jumping on an elevate platform and train it so that when it hears the sound it will jump off

50
Q

Gerbils to test hearing loss

A

Tested their ability to notice a gap in the acoustic stimulus at varying volumes. It was found that the older gerbils were worse at this.

SYS I (9 decks)

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