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eLCRS - 뉴로 > Neuro 8: Sound Conduction And Transduction > Flashcards

Neuro 8: Sound Conduction And Transduction Flashcards

1
Q

What are main causes of hearing loss?

A
  • loud, traumatic sounds
  • genetic
  • ageing
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2
Q

What is the hearing range of humans?

A

20 - 20000 hz

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3
Q

bel scale of sound defines :

A

it defines sound level

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4
Q

define pitch

A

pitch = perception of frequency

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5
Q

define timbre

A

timbre = what distinguishes 2 sounds at the same frequency + intensity

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6
Q

what does the 3 ossicles do?

what is the significance of this?

A

3 ossicles transmit vibration of tympanic memb to the conchea

  • and acts to match the impedance and to reduce loss of energy as vibration
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7
Q

define impedance

A

impedance = easier of reluctance of a system in receiving energy from a source

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8
Q

define resonant frequency

A

resonant frequency = frequency at which impedance of system is minimal

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9
Q

What might cause conductive hearing loss?

A
  • cerumen
  • infection
  • tumors
  • fluid accumulation
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10
Q

What is a cochlea

A

liquid filled snail shaped organ

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11
Q

What causes vibration of basilar membrane?

A

the motion of the stapes generates pressure difference between 2 chambers of the cochlea

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12
Q

what is a stapes?

A

3rd ossicle.

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13
Q

What are the main components of the organ of corti

A

basilar + tectorial memb + (inner and Outer) hair cells + supporting cells

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14
Q

what does the basilar memb motion do to hair bundles?

A

it deflects hair bundles of hair cells

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15
Q

What is a basilar membrane?

A

Basilar memb = elastic structure that vibrates at diff position along its length –> in response to different frequencies

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16
Q

Describe how mechano - transduction occurs.

A

bending of stereo cilia –> towards tallest causes change in the internal voltage of cell
- which produces an electrical signal that travels to the brain

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17
Q

What feature connects the stereo cilia?

A

tip links

note: acts like small springs –> stretched by stereo cilia’s sliding

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18
Q

why is mechano-transduction considered an active process?

A
  • because hair bundles have the capacity to do work
  • the hair bundles actively complies wit the direction of the stimulus
  • -> and measured stimulus becomes -ve
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19
Q

what are the 4 aspects of the active process of mechano-transduction?

A
  1. amplification
  2. frequency tuning
  3. compressive non linearity
  4. spontaneous otoacoustic emission
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20
Q

there are more / less outer hair cells than inner hair cells

A

there are more outer hair cells than inner hair cells

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21
Q

most of the afferent projection projects from outer hair cell/ inner hair cell

most efferent projection connects to the outer hair cell / inner hair cell

A

most of the afferent projection projects from inner hair cell

most efferent projection connects to the outer hair cell

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22
Q

How does electromobility occur?

A

due to reorientation of protein pristine, cell body shortens + elongates when their internal voltage is changed

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23
Q

Inner hair cell synapses with sensory neuron in the ______ ______

A

Inner hair cell synapses with sensory neuron in the spiral (cochlear) ganglion

24
Q

the change in response to change of presynaptic voltage is proportional to the rate of _______ ________

A

the change in response to change of presynaptic voltage is proportional to the rate of neurotransmitter release

25
Q

How might you deal with sensorineural hearing loss?

A
  • cochlear implants
26
Q

What is special about the cochlear nucleus?

A
  • its the region where different neurons are arranged tonotopically

low frequency = ventral
high frequency = dorsal

27
Q

What are the 2 main neurons in cochlear nucleus ?

A

a) T- stellate cells

b) bushy cells

28
Q

what does the T-stellate cells do?

A
  • it encodes sound freq + intensity of narrow band stimuli
29
Q

what do bushy cells do?

A
  • it carries information on timing of the inputs at every cycle

–> it provides resolution for encoding relative time of arrival of inputs to the 2 ears

30
Q

What are the 2 mechanisms at which you know where the sound is coming from?

A
  1. time difference

2. interneuronal level difference

31
Q

The superior olivary complex consists of what 2 main areas?

A
  1. medial superior olive

2. lateral superior olive

32
Q

What is the function of the medial superior olive in hearing?

A
  • it computes the interneuronal time difference
33
Q

What is the function of the lateral superior olive in hearing?

A
  • allows detection of intensity difference between the 2 ears

neurons are EXCITED by ipsilateral sound
neurons are INHIBITED by contralateral sound

34
Q

neurons are EXCITED/INHIBITED by ipsilateral sound

neurons are INHIBITED/ EXCITED by contralateral sound

A

neurons are EXCITED by ipsilateral sound

neurons are INHIBITED by contralateral sound

35
Q

what does the interneuronal level difference do?

A

it computes localization of sounds in the horizontal plane

36
Q

Neurons from the MSO feedback to the hair cells (ipsilaterally /bilaterally)

neurones from the LSO feedback to the hair cells (ipsilaterally / bilaterally)

A

Neurons from the MSO feedback to the hair cells (bilaterally)

neurones from the LSO feedback to the hair cells (ipsilaterally)

37
Q

With regards to hearing, what happens at the inferior colliculus? What does it do?

A

inferior colliculus:

  • site where responses from diff frequency merges
  • closer to the cortex –> it is more responsive to complex sounds
38
Q

With regards to hearing, what happens at the superior colliculus? What does it do?

A

superior colliculus:

  • site where auditory + visual maps merge
  • neurons turn to respond to stimuli with specific sound directions

–> so helps orientate head + eye reflex movements in response to acoustic stimuli

39
Q

note:

at primary auditory cortex :

  • loudness / rate / frequency modulation is mapped
  • also TONOTOPICALLY mapped
A

-

40
Q

what allows location of sound in the vertical plane?

A

dorsal cochlear nucleus

41
Q

what allows location of sound in the horizontal plane?

A

interneuronal level difference

42
Q

Describe how the cochlea functions.

how is sound conducted through the cochlea? (step by step)

A
  • Tympanic membrane vibrates
  • Vibration is conducted + amplified to oval window
  • This vibration induces pressure wave in perilymph (in scala Vestibuli)
  • Which in turn causes scala Media to vibrate
  • Which causes basilar membrane to vibrate
  • The round window then vibrates  to equalise pressure in the cochlea
43
Q

What is the function of organ of corti?

A
  • Organ of Corti = sense organ of cochlea

- Converts sound signals into nerve impulse that are transmitted to the brain via cochlear nerve

44
Q

What is the function of the inner hair cells

+

are they in contact with tectorial memb?

A
  • Not in contact with tectorial memb
  • Sends impulse to brain
  • Has stereocilia –> which moves in response to movement of endolymph in scala media
45
Q

Describe the features and function of outer hair cells.

+

are they in contact with tectorial memb?

A
  • Found in groups of 3
  • In contact with tectorial memb
  • They receive input from the brain
  • Can expand + contract to amplify amount of vibration
  • Damage = sensorineuronal hearing loss.
46
Q
  1. Describe what happens when the basilar membrane is displaced upwards.
A
  • When basilar memb = displaced upwards
  • Causes depolarisation
  • Stereocilia moves away from modiolus
  • K+ channels open
  • K+ enters from endolymph
47
Q
  1. Describe what happens when the basilar membrane is displaced downwards.
A
  • When basilar memb = displaced downwards
  • Hyperpolarisation occurs
  • Sterocilia moves towards modiolus
  • K+ channels close
48
Q
  1. Describe the difference in K+ and Na+ concentration in the different compartments of the cochlea.
A
  • Scala media = High K+ / Low Na+

- Scala Tympani = High Na+ / Low K+

49
Q
  1. Describe the auditory pathway from the cochlea to the primary auditory cortex
A 
Spiral ganglion -->
 cochlear nuclei -->
 superior olive -->
inf colliculus -->
medial geniculate nucleus -->
primary auditory cortex
50
Q
  1. What is the secondary auditory cortex responsible for?
A
  • Responsible for sounds coming on/ off

- Responsible for duration of sound

51
Q

How do you localise short sound burst?

A

Interneural time delay

52
Q

How do you localise continuous sound?

A

Interneural intensity difference

53
Q

What is conductive hearing loss?

A
  • Disease of middle ear –> damages ossicles / stiffens joint
  • Amplification system = affected
  • Causing conductive hearing loss
54
Q

What is sensorineural hearing loss and what can it be caused by?

A
  • Sensorineural hearing loss = cochlea / cochlear nerve is damaged
  • So signal transmitted to the primary auditory complex = reduced or lost
  • Can occur due to acoustic schwannoma/ cerebellar tumours pressing on cochlear nerve
55
Q

what is - Presbyacusis ?

A

loss of hearing due to the death of hair cells in normal ageing

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