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Fundamentals of Neuroscience > Audition > Flashcards

Audition Flashcards

1
Q

What is sound?

A

Audible vibrations in the air caused when air molecules move, compress, increase in density

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2
Q

What is the frequency of sound?

A

The number of compressed.rarefied particles that pass our ear each second.

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3
Q

What is the hamn limit of sound?

A

20kHz

Ultrasound- above limit
Infrasound - below limit

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4
Q

What is the intensity of sound?

A

Loudness

difference in pressure between compressed and rarefied particles of air

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5
Q

What is the pinna?

A

Visual part of the ear organ

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6
Q

How is the pinna adapted for its function?

A

Shape of pinna makes us more sensitive to head on sounds

Convolutions of pinna help with sound localisation

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7
Q

What is the auditory canal?

A

Enterance to the inner ear.

Extends about 1 inch into the skull before terminating

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8
Q

What is the tympanic membrane?

A

Eardrum - Where the auditory canal terminates

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9
Q

What are ossicles?

A

Little bones (smallest in body) which are connected to the medial surface of the tympanic membrane

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10
Q

what are the ossicles names?

A

Malleus
Incus
Stapes

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11
Q

What do the ossicles do?

A

Transfer movements of the tympanic membrane to a second membrane convering the oval window

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12
Q

How does the stapes ossicle work?

A

Has a footplate acting like a piston to transmit the vibrations to fluid in the cochlea

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13
Q

What is the cochlea?

A

Fluid filled space that lies behind the oval window

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14
Q

What does the cochlea do?

A

Transforms physical membrane movement into a neuronal response

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15
Q

How do soundwaves cause a neuronal response?

A
  1. soundwaves move tympanic membrane
  2. Tympanic membrane moves/vibrates ossicles
  3. Ossicles move the membrane at the oval window
  4. Fluid in the cochlea moves as a result
    Movement of fluid in the cochlea cuases a neuronal response
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16
Q

What are the divisions of the outer, middle and inner ear?

A

Outer ear - Pinna to tympanic membrane
Middle ear - tympanic membrane to ossicles
Inner ear - Ossicles to oval window

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17
Q

What is the significance of the muscles connected to the ossicles?

A

Effect on sound transmission in the inner ear

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18
Q

What does muscle contraction around the ossicles cause?

A

Makes the ossicles more rigid to lead to sound conduction in the ear being greatly diminished

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19
Q

What is the attenuation reflex?

A

Neural response causing ossicle muscles to contract upon the onset of a loud sound

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20
Q

When is the attenuation reflex greatest?

A

At low frequencies

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21
Q

What is the purpose of the attenuation reflex?

A

Adapt ear to continuous sound at high intensities
Increase dynamic range of hearing
Protec thte inner ear from damage by local sounds
Removes background noise

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22
Q

What is the Eustechian tube and its function?

A

Connection between the middle ear and the nasal cavity.

used to relieve pressure in the ears when swallowing

23
Q

What are the 3 chambers in the cochlea?

A

Scala bestibuli
Scala Media
Scala Tympani

24
Q

What is the reissners membrane?

A

Separates the Scala vestibuli from the media

25
Q

what is the Basilar membrane?

A

Separates the Scala tympani form the media

26
Q

What is special about the basilar membrane?

A

On the membrane is the organ of corti which holds the auditory receptor neurones

27
Q

What is perilymph?

A

Fluid in the vestibuli and tympani

28
Q

What are the concentrations of K and Na in the perilymph?

A

Low K concentration

High Na concentration

29
Q

What is the Endolymph?

A

Scala media fluid

30
Q

What are the concentrations of K and Na in the Endolymph?

A

High K concentration

Low Na concentration

31
Q

What is the endocochlea potential?

A

endolymph eletcrical potential > perilymph electrical potential.

32
Q

Why is the endocochlea potential important?

A

Enhances the auditory transduction

33
Q

What are the auditory receptors and their specialisations?

A

Hair cells - Found in the organ of corti

Each hair cell has 100 sterocillia

34
Q

What are the types of hair cells?

A

Outer hair cells - sound amplification

Inner hair cells - Nervous transmission

35
Q

What is the importance of the sterocilia?

A

Bending of sterocilia is a critical event in the transduction of sound to a neural signal.

36
Q

What are Tiplinks?

A

Tiplink filaments - Connect sterocilia together so they all move in conjunction with each other.

37
Q

How are the sterocilia joined by tiplinks?

A

Each adjacent sterocilia is joined to the tiplink via an ion channel

38
Q

How is an action potential generated in the 1st order neurone of the auditory pathway?

A
  1. Movement of endolymph causes sterocilia to bend
  2. Bending causes the tiplink adjacently joined to the ion channel to tug and open the channel gate.
  3. This causes the mechanically gated K cahnnel to open
  4. Endolymph has a high K concentration outside the receptor cell and hence K flows into the cell
  5. This causes depolarisation of the receptor membrane
  6. The receptor releases glutamate to the dendrites of the vestibulocochlear nerve (VIII).
  7. This is the 1st order neurone and with a strong enough EPSP an action potential will be generated.
39
Q

How does an auditory signal go from the 1st neurone to initiate a hearing response?

A
  1. Signal in 1’ neurone (VIII)
  2. Action potential
  3. Impulse sent to fibres either side of medulla oblongata to the cochlea nuclei
  4. VIII synapse with 2’ neurone which assends to the superior olivary nucleus
  5. Other 2’ neurones assend to inferior colliculi
  6. 3’ neurones lead to thalamus where they synapse with 4’ neurones
  7. 4’ neurones transmit signal to primary auditory cortex in temporal lobe
  8. Site of sound processing
40
Q

What is binaurial hearing?

A

Using both ears to determine a sounds location

41
Q

What are mono and binaural neurones?

A

monoaural - Only respond to sound presented in 1 ear

Binaural - Responses are influenced by sound at both ears

42
Q

How is sound intensity encoded?

A

By firing rates of neurones

By number of active neurones firing

43
Q

How is a more intense stimulus (louder sound) encoded?

A

Greater amplitude of vibration of the basilar membrane
Causes:
More hair cells to be firing (frequently depolarised)
Firing rates of neurones to be increased

44
Q

What is characteristic frequency?

A

Frequencies at which specific hair cells respond to

45
Q

What are the different frequency sensitivities of the basilar membrane?

A

Nerves at apical basilar membrane - Low frequency

Nerves at basal basilar membrane - High frequency

46
Q

What is tonotopy?

A

Systematic organisation of characteristic frequencies within an auditory structure

47
Q

What is phase locking?

A

Consistent firing of a cell at the same phase of a sound wave

Cant lock at higher frequencies due to action poteintials being in refractory period

48
Q

What what frequencies are phase locking and tonotopy used?

A

Low frequencies - Phase locking
Medium frequencies - Phase locking and tonotopy
High frequencies - Tonotopy

49
Q

How is sound localised in the horizontal plane?

A

Interaural time delay - sound from one direction will reach 1 ear before the opposite ear

Interaural intensity difference - Sound at higher frequency in the ear from one direction will appear at a lower frequency in the opposite ear

50
Q

How is sound localised in the verticle plane?

A

Bumps and ridges in the ear assess elevation of a source of sound and produce reflections.

The delay between the directed and reflected path changes as the sound moves vertically

51
Q

What are some clinical correlations of the ear?

A

Osteosclerosis
Nerve deafness
Tinnitus

52
Q

What is Osteosclerosis?

A

In the middle ear causes conduction deafness where sound is muffled and less clear

53
Q

What is nerve deafness?

A

Caused by damage to a nerve in the auditory pathway

Drugs may also cause this

54
Q

What is Tinnitus?

A

Outer hair cells cause membrane movement in the absence of sound leading to a patient hearing sounds which arent there.

Fundamentals of Neuroscience (16 decks)

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