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Neuro > Hearing > Flashcards

Hearing Flashcards

1
Q

What is pitch?

A

The perception of frequency (speed of vibrations - horizontally)

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2
Q

What is timbre?

A

It distinguishes between two sounds of the same frequency and intensity

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3
Q

What is the human range of frequency?

A

20Hz-20kHz

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4
Q

What is the amplitude of sound?

A

The size of the vibration (vertically) (volume of sound)

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5
Q

What is sound intensity?

A

How many Joules of energy passes through one square meter per second

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6
Q

How do we measure the ear’s response to sound intensities?

A

Using the deciBel scale (logarithmic)

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7
Q

How is sound intensity perceived?

A

As volume

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8
Q

What is the role of the middle ear?

A

To transmit the vibrations of the tympanic membrane to the fluid
To match the impedance and reduce any loss in energy

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9
Q

What is impedance?

A

The reluctance of a system to receive energy

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10
Q

What do you call the frequency at which the impedance is minimal?

A

Resonant frequency

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11
Q

What is resonant frequency?

A

The frequency at which the impedance is minimal

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12
Q

Why is resonant frequency important?

A

The transfer of energy is optimal when a system is stimulated at its resonant frequency (i.e. when there’s low resistance to receiving the energy)

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13
Q

What can affect impedance and resonant frequency?

A

The mechanical properties

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14
Q

List seven causes of hearing loss

A 
Earwax 
Otitis (infections)
Tumours
Fluid accumulation in inner ear
Perforated tympanic membrane 
Abnormal growth of bone (otosclerosis) 
Barotrauma (change in air pressure)
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15
Q

Give a common cause of hearing loss in children

A

Fluid accumulation in the air

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16
Q

What is hearing loss?

A

When sound is not appropriately transmitted into the cochlea

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17
Q

What is the technical name for a change in air pressure?

A

Barotrauma

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18
Q

What is the technical name for earwax?

A

Cerumen

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19
Q

What is the order of the ossicles in the ear from outer to inner?

A

Malleus
Incus
Stapes

I always MIStake the order.

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20
Q

Describe the impedance of the basilar membrane and why this occurs

A

The impedance varies along the length of the BM due to changes in its mechanical properties (narrow and tough at the stapes end, broad and floppy at the other end)

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21
Q

What are the implications of varied impedance of the BM?

A

It means that the local resonant frequency varies, and therefore only the part of the BM will which matches the frequency of the stimulus will vibrate!

22
Q

What does a varied impedance and varied local resonant frequency give rise to along the basilar membrane?

A

The tonotopic map

23
Q

What type of hair cells lie along the basilar membrane?

A

Stereocilia

24
Q

What do the basilar membrane and stereocilia form part of?

A

The organ of corti

25
Q

List the structures of the Organ of Corti

A

Basilar membrane
Tectorial membrane
Hair cells
Supporting cells

26
Q

Describe a cross section of the cochlea

A 
Perilymph
- divided by Reissner's membrane
Endolymph
- divided by Organ of corti
Perilymph
27
Q

Explain how the hair cells transmit signals to the brain

A

Opening of ion channels relaxes tip links between hair cells, allowing them to move. This is an active process

28
Q

Describe the two types of hair cells and their projections

A

Outer hair cells - most of the efferent projections from brain to ear
Inner hair cells - 95% of afferent projections from cochlea to brain

29
Q

Describe another phenomenon which suggests that transmission of info from hair cells to the brain is an active process.

A

The cell body of outer hair cells shorten and elongate when their internal voltage is changed (electromotility).

30
Q

The outer hair cells are thought to be the origin of two things. What are these?

A

Cochlear amplification

Otoacoustic emissions

31
Q

Which protein contributes towards the electromotility of outer hair cells?

A

Prestin

32
Q

Which cells synapse with hair cells in the organ of Corti?

A

Spiral ganglion cells of the cochlear ganglion

33
Q

What is special about the spiral ganglion cells?

A

They also have a tonotopic map; particular areas respond best to various resonant frequencies.

34
Q

What is sensorineural hearing loss?

A

When the problem originates in the inner ear or vestibulocochlear nerve.

35
Q

Which type of antibiotics are toxic for hair cells?

A

Aminoglycoside antibiotics

36
Q

List specific conditions causing sensorineural hearing loss

A 
Rubella - congenital
Toxoplasmosis - congenital 
Acoustic neuroma (tumour on the cochlear nerve)
Ageing - presbycusis 
Multiple sclerosis (loss of myelin)
37
Q

Explain how cochlear implants work

A

They bypass the ear and directly stimulate the cochlea using electrodes which respond to different frequencies.

38
Q

Describe the pathway of nerves from the cochlea to the brain

A

Cochlear hair cells -> spiral ganglion ->
cochlear nucleus in medulla ->
Superior olivary nucleus in pons ->
inferior colliculus of midbrain -> superior colliculus ->
medial geniculate nucleus of thalamus -> auditory cortex

39
Q

Explain the tonotopic map of the cochlea nucleus in the medulla

A

Low frequencies are transmitted ventrally

High frequencies are transmitted dorsally

40
Q

Which nucleus locates sounds in vertical plane?

A

Dorsal cochlea nucleus, using spectral cues

41
Q

Which nucleus computes sound localisation in the horizontal plane?

A

Superior olive of the superior olivary complex

42
Q

Explain the two different parts of the SOC and how they localise sound

A

Medial superior olive - uses interaural time difference (compares WHEN the sounds were detected by both ears)

Lateral superior olive - uses differences in intensity between the two ears

43
Q

A stimulus coming from the left would inhibit and excite which sides of the lateral superior olive?

A

A left stimulus would excite the left lateral superior olive, but inhibit the contralateral LSO.

Excitation - ipsilateral
Inhibition - contralateral

44
Q

What is important about the excitation/inhibition of the lateral superior olive?

A

The excitation ipsilaterally must arrive at the same time as the inhibition contralaterally

45
Q

Describe the axons and synapses carrying the inhibitory and excitatory signals to the lateral superior olive

A

Contralateral inhibitory signal - large axon with large synapses, the large calyces of Held

Ipsilateral excitatory signal - smaller axon, conducts slowly

Therefore the signals should be received at the same time

46
Q

Which neurons provide feedback to the cochlea?

A

Superior olivary nucleus

47
Q

Name a type of injury which disrupts the excitatory inhibitory signal

A

Blast injury

48
Q

Where do auditory and visual information converge, and is important for reflexes?

A

Superior colliculus

49
Q

Where is the auditory complex?

A

Superior part of the temporal lobe

50
Q

Describe the mapping of the auditory cortex

A

Tonotopically mapped

Loudness, rate and frequency modulation also mapped

Neuro (11 decks)

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