Audition Flashcards

1
Q

What is the simplest sound?

A

A pure tone

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2
Q

What makes a complex sound like speech different from a pure tone?

A

Many sound components with separate frequencies and amplitudes

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3
Q

Name for ear canal

A

External auditory meatus

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4
Q

How does the outer ear amplify sound?

A

Resonance in the concha and the external auditory meatus produces an increase in pressure between 2-7 kHz.

Leads to an amplification of sound

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5
Q

Localisation of an auditory target in the vertical plate or front/back dimension requires…

A

Spectral cues

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6
Q

Spectral cues are produced by…

A

The outer ear

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7
Q

What is the principle behind spectral cues?

A

Amplitude of different frequencies is modified in different ways by the outer ear shape depending on the location of the sound source.

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8
Q

Where does the eustacian tube connect?

A

Nasopharynx with middle ear

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9
Q

What is the role of the eustacian tube?

A

Maintains atmospheric pressure in middle ear

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10
Q

What connects the tympanic membrane to oval window of the cochlea?

A

Ossicles

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11
Q

Three ossicles

A

Malleus, incus, stapes

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12
Q

What does the malleus attach?

A

Tympanic membrane to incus

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13
Q

What does incus attach?

A

Malleus to stapes

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14
Q

What does the stapes attach?

A

Incus to the oval window

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15
Q

What muscle is attached to the malleus?

A

Tensor tympani

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16
Q

What muscle is attached to the stapes?

A

Stapedius

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17
Q

What do middle ear bones prevent?

A

Prevent loss in sound pressure that would occur due to the increased density of cochlea fluids (than air)

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18
Q

How is pressure increased by the middle ear for impedance matching?

A

Eardrum has greater surface area than the stapes

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19
Q

What is the role of the middle ear muscles?

A

Contract, reduce movement of the ossicles, reduce sound transmission (middle ear reflex) when one using their own voice or sustained loud noise

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20
Q

Ascending limbs of the middle ear reflex?

A

Auditory nerve fibres

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21
Q

What bone does the inner ear lie in?

A

Petrous part of temporal bone

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22
Q

What fluid fills the membranous labyrinth?

A

Endolymph

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23
Q

What fluid fills the area between membranous labyrinth and bony margin?

A

Perilymph

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24
Q

Endolymph is similar to?

A

ICF (high potassium)

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25
Q

Perilymph is similar to?

A

ECF (low potassium)

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26
Q

Scala vestibuli

A

Oval window (above media)

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27
Q

Scala tympani

A

Round window (below media)

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28
Q

What membrane separates the scala media and scala vestibuli?

A

Reissner’s

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29
Q

What membrane separates the scala media and scala tympani?

A

Basilar

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30
Q

Endocochlea potential

A

Potential difference between the endolymph in the scala media and the perilymph of the other two chambers of about 80 millivolts - scala media is positively charged relative to the other two chambers.

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31
Q

Hair cells have

A

Stereocilia

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32
Q

Tallest stereocilia called?

A

Kinocilium

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33
Q

What contacts the stereocilia on the basilar membrane?

A

Tectorial membrane

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34
Q

Which HC contact the tectorial membrane?

A

Just OHC, IHC free

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35
Q

Do hair cells generate APs?

A

No, just GP, which leads to NT release which activates an AP in second order neuron

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36
Q

What is generated across scala media?

A

Pressure gradient

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37
Q

What makes a tuning curve look the way it does?

A

Hair cells and fibres are tonotopically organised – at any position, hair cells are sensitive to a particular frequency, namely their characteristic frequency .

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38
Q

What causes hair cell depolarisation?

A

Bundle is pushed toward the tallest, cilium it will increase the tension the tip links, open mechanosensitive gated ion channels and lead to hair cell depolarization.

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39
Q

What causes hair cell hyperpolarisation?

A

Bundle goes in the opposite direction it will reduce the tension in the tip link, close the mechanosensitive channels and lead to hair cell hyperpolarization.

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40
Q

Hair cell depolarisation leads to?

A

Influx of calcium via VGCC - leading to an increase in the probability of neurotransmitter release onto the afferent nerve fibre (CN VIII).

41
Q

What is phaselocking?

A

Hair cells are depolarised or hyperpolarised according to whether the basilar membrane moves up or down, respectively

Auditory nerve impulses become synchronised to the phase of the stimulus waveform (phaselocking).

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

42
Q

How can cochlea movements be amplified?

A

Active OHC contractions move the BM more

43
Q

Afferent fibres mostly innervate

A

Inner hair cells

44
Q

Efferent fibres mostly innervate

A

Outer hair cells (modulatory process suggested)

45
Q

Inner hair cells receive what proportion of afferent auditory nerve fibres?

A

90-95%

46
Q

Are afferents that innervate IHC myelinated or not?

A

Myelinated

47
Q

How many fibres innervate one IHC?

A

~10

48
Q

Outer hair cells receive what proportion of afferent auditory nerve fibres?

A

5%

49
Q

Are afferents that innervate OHC myelinated or not?

A

Non-myelinated

50
Q

How many fibres innervate one OHC?

A

Each fibre innervates about 20 OHC

51
Q

What gives nerve fibres a V shaped tuning curve?

A

Nerve fibres are most sensitive to a particular sound frequency (characteristic frequency) and their thresholds increase at progressively lower or higher frequencies,

52
Q

Increase in the intensity of the sound produces

A

An increase in firing rate

53
Q

Increase in sound intensity saturates when..

A

Response saturates (i.e. does not change any further) at intensities over 30-50 dB above the threshold for each fibre.

54
Q

When intensity increases what happens to tuning curve?

A

Broadens

55
Q

Above intensity threshold what happens to frequency resolution?

A

Becomes poorer

56
Q

What is two tone suppression?

A

A second frequency lying outside the tuning

curve (in shaded regions) can suppress the response to an excitatory tone.

57
Q

What is two tone supression due to?

A

Non-linear response of the basilar membrane

58
Q

CN VIII projects into the brainstem at the level of the .

A

Pons

59
Q

Does the auditory system has more or less subcortical nuclei than the visual or somatosensory pathways.

A

More

60
Q

Where is the cochlea nucleus?

A

Medulla

61
Q

What synapses at cochlea nucleus?

A

Cochlea ganglion cells

62
Q

What end of the cochlea is low frequencies ?

A

Apical end

63
Q

What end of the cochlea is high frequencies?

A

Basal end

64
Q

Basilar membrane shape and frequencies?

A

Apical end (centre) wider and less stiff for low frequencies

Basal end narrower and more stiff for high frequencies

65
Q

Fibres that carry information from apical end of cochlea (low frequencies) terminate

A

Ventrally in the cochlea nuclei

66
Q

Fibres that carry information from the basal end of the cochlea (high frequencies) terminate

A

Dorsally in the cochlea nuclei

67
Q

Where is neural inhibition seen for the first time?

A

Cochlea nucleus

68
Q

What part of the CN shows the most neural inhibition?

A

Dorsal

69
Q

Where are spectral cues analysed?

A

CN

70
Q

Area where localisation is first introduced?

A

CN

71
Q

Superior olivary complex

A

Axons from the ventral CN project to neurons in the superior olivary complex.

72
Q

Inferior olivary complex

A

Input to spinocerebellum

73
Q

How do we localise low frequency tones (up to 1500 Hz)

A

Interaural time differences

74
Q

How do we localise high frequencies (above 3 kHz)

A

Interaural intensity differences

75
Q

What is the first site of binaural convergence?

A

Superior olive

76
Q

What side cochlea nucleus does the SO receive input from?

A

Both sides

77
Q

What superior olive is sensitive to ITD?

A

Medial

78
Q

What superior olive is sensitive to IID?

A

Lateral

79
Q

What is the principle of ITD?

A

Comparison of timing of firing in response to sound from the two ears ( sound arrives at near ear before far ear)

80
Q

Do humans have delay lines?

A

Not really, mammalian MSO neurones are coincidence detectors, but no delay lines

81
Q

How do humans detect ITD?

A

MSO neurones are sensitive to phase of waveform due to phase locking so relative activity of neurones in left/right MSO reflects interaural time difference.

82
Q

LSO receives excitatory input from?

A

Ipsilateral CN

83
Q

LSO receives inhibitory input from?

A

Contralateral CN

84
Q

How do humans detect IID?

A

Convergence of excitation and inhibition means if sound coming from left side, signal more intense on left thus excitatory response, on other side the inhibitory response is active.

85
Q

Crossing of auditory fibres known as?

A

Trapezoid body

86
Q

How do auditory fibres travel up to IC?

A

In lateral lemniscus

87
Q

Inferior colliculus to the

A

Medial geniculate nucleus (thalamus)

88
Q

MGN to

A

A1 - temporal lobe of the cerebral cortex

89
Q

Cortical neurons generally respond better to

A

Complex sounds than to pure tones.

90
Q

What is pitch?

A

Rate at which a periodic sound repeats itself (so the pitch of a pure tone is defined by its frequency)

91
Q

Why does ITD only work for lower frequencies?

A

Phase ambiguity, wavelength smaller than ones head, then different ear may experience same part of wave

92
Q

Why does IID only work for high frequencies?

A

If a sound is high enough frequency, the head will alter the amplitude-quality of the sound as it passes across

In low frequency sounds, however, the wavelength is too large to interact with the head therefore the amplitude will not change between ears

93
Q

Why does IID work?

A

Acoustical shadow

94
Q

Listeners can distinguish two sounds separated by as little as

A

1° in angle

95
Q

A conductive hearing loss is caused by

A

Mechanical damage to the outer or middle ear

96
Q

Sensorineural loss is caused by

A

Damage to transduction apparatus

97
Q

Cochlear implant

A

Stimulates the remaining nerve fibres.

98
Q

Tympanic membrane shape?

A

Cones into middle ear

99
Q

What part of the stapes is inserted into the oval window?

A

Baseplate