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NSCI 201 > Auditory system > Flashcards

Auditory system Flashcards

1
Q

A sinusoidal sound wave could be characterized as biphasic. What are its two phases?

A

Condensation and rarefaction.

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2
Q

What are representing condensations and rarefactions?

A

Changes in air pressure.

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3
Q

What are the 4 sound features?

A
  • Intensity (amplitude)
  • Pitch (frequency)
  • Waveform (texture)
  • Phase (location)
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4
Q

How can a complex sound be modeled?

A

As the sum of different sinusoidal sound waves varying in their properties.

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5
Q

What is lost first in the human ear between the perception of high and low frequencies?

A

High frequencies lost more rapidly.

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6
Q

What is the principle function of the external and middle ear?

A

Amplify sound for the inner ear.

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7
Q

What is the principal role of the external ear? What are the two main structures of the external ear and their substructures? What is the role of each structure?

A

Principal role: serves as a parabolic antenna to boost sound pressure of frequencies.
Auricle: composed of pinna and concha, which filter different frequencies and provide cues about elevation of sound source = VERTICAL PLANE SOUND LOCALIZATION.
Canal: auditory meatus boosts sound pressure of frequencies.

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8
Q

What is the principal role of the middle ear? What are its two pressure-boosting mechanisms?

A

Principle role: amplification of sound for the impedance shift between air transmission and aqueous transmission.
Pressure-boosting mechanisms:
-Tympanic membrane is much larger than base of stapes in oval window →vibrations (sound) are amplified
- Lever action of ossicles

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9
Q

What are the three ossicles?

A

Malleus, incus and stapes.

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10
Q

What are the two structures regulating transmission in the middle ear?

A
  • Tensor tympani

- Stapedius

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11
Q

How can damage to external and middle ears be tested?

A

By the Weber fork test.

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12
Q

How is named the structural organization found in the basilar membrane of the cochlea for the processing of sound frequencies?

A

Tonotopy.

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13
Q

What are the perilymph chambers?

A
  • Scala vestibuli
  • Scala tympani
  • Scala media
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14
Q

With what liquid are filled the perilymph chambers?

A

Scala vestibuli and tympani -> perilymph

Scala media -> endolymph

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15
Q

How is the endolymph of the scala media moved?

A

Liquid in scala vestibuli is pushed by vibrations coming from oval window of stapes ->induces vibrations to the reissner membrane -> vibrations transmitted to scala media.

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16
Q

In the tonotopy of the basilar membrane of the cochlea, ____ pitch sounds move the ____ of the membrane, ____ oval window, whereas ____ pitch sounds move the ____ of the membrane, ____ oval window.

Words to place:

apex
high
base
low
away from
close to
A

In the tonotopy of the basilar membrane of the cochlea, high pitch sounds move the base of the membrane, close to oval window, whereas low pitch sounds move the apex of the membrane, away from oval window.

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17
Q

Hair cells are found between what membranes?

A

Tectorial and basilar membranes.

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18
Q

What are the two types of hair cells? What are they responsible for?

A

Inner hair cells: innervated by afferents from CN VIII → transmit impusles toward CNS (mechano-electric conduction).
Outer hair cells: innervated by efferents →modulate the “stiffness” of the basilar membrane to adjust the “volume” and produce otoacoustic emissions.

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19
Q

What is the ion channel responsible for depolarization in the hair cells?

A

Mechanically-gated potassium channel.

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20
Q

What are cells the “hairs” of the hair cell? What is the name of the tallest one?

A
  • Stereocilia

- Kinocilium

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21
Q

How are the stereocilia moving together in a bundle?

A

They are attached one to another by tip-links.

22
Q

Explain the mechanoelectrical transduction of the inner hair cell.

A

Movement of endolymph of scala media ->pulling the stereocilia toward the kinocilium -> opening of K+ channels and inward flow of K+ ->opening of voltage-gated Ca++ channels ->Ca++ influx -> NT release on auditory nerve ending -> APs conducted to CNS via CN VIII

23
Q

Above what frequency of sound is the frequency of electrical impulses produced by the cochlea not faithful to the frequency of the sound (phase locking lost)?

A

> 3 kHz

24
Q

What is phase locking in the auditory system?

A

Hair cells firing action potentials periodically, following the condensation frequency of the sound wave.

25
Q

What are the electrical charges (mV) of the endolymph and the perilymph?

A

Endolymph: +80mV
Perilymph: 0mV

26
Q

What is the endocochlear potential?

A

The electrical difference between potentials of endolymph and perilymph.

27
Q

Provide two functions of phase locking.

A
  • Preservation of tonotopy

- Provides temporal information that can be compared between ears to localize sound source

28
Q

What is the ratio of auditory fiber to hair cell?

A

1:1

29
Q

How can frequencies above 3 kHz be encoded?

A

The tonotopy of the basilar membrane is used by the hair cells (the membrane potential of hair cells cannot phase lock if frequency > 3 kHz).

30
Q

What is the first synaptic relay for information travelling in CN VIII from cochlea to brainstem?

A

Cochlear nucleus

31
Q

How many ascending parallel pathways preserving tonotopy are there from the cochlear nucleus? What are they?

A
  • Pathway to superior olivary complex (pons)
  • Monaural pathways
  • Pathway to inferior colliculus (midbrain)
32
Q

What is the olivary complex responsible for?

A

HORIZONTAL PLANE SOUND LOCALIZATION

33
Q

True or false: the olivary complex has a monolateral connectivity from the cochlear nucleus.

A

False: bilateral connectivity.

34
Q

How many nuclei related to the olivary complex exist? What is their distribution?

A

2 lateral superior olives
+ 2 medial superior olives
= 4 nuclei

35
Q

List 2 differences between the two systems for sound localization in the olivary complex and explain their respective mechanisms.

A

Interaural time difference (ITD) system:
-For sound frequencies ≤ 3 kHz
-In the medial olives
Mechanism: MSO neurons receive inputs both from the left and right ears (from both cochlear nuclei) →function as coincidence detectors → the position of the MSO neuron that receives inputs from both ears at the same time provides localization info. about the sound source

Interaural intensity difference (IID) system:
-For sound frequencies > 3 kHz
-In the lateral olives
Mechanism: high frequency sounds directed to one side of the head create an acoustical shadow of lower intensity to the side of the head not directed toward the sound source -> the intensity between the sound emitted and its acoustical “shadow” can provide info. about localization of sound source (excitation-inhibition balance in which the ear closest to the source sound is more excited than inhibited)

36
Q

What is one difference between the monaural pathways and the superior olivary complex pathway?

A

Monaural pathways, in contrast to olivary complex pathway, respond only to the sound arriving from one ear (monolateral connectivity).

37
Q

What is the anatomy of the monaural pathways?

A

Axons from cochlear nucleus synapse in the pons-midbrain junction to the lateral lemniscus nucleus on contralateral side of brainstem.

38
Q

What is the role of the inferior colliculus pathway for the cochlear nucleus?

A

Integration of sound processed in superior olives, lemniscal comlex and directly from cochlear nucleus to help integrate sound with reflexes (e.g. eye movements).

39
Q

What are the properties integrated in the inferior colliculus?

A
  • Timing
  • Intensity
  • Frequency
40
Q

Where does occur the integration of the three parallel ascending pathways from the cochlear nucleus?

A

In the inferior colliculus.

41
Q

Where are projecting in the thalamus the axons from the inferior colliculus? How is auditory information segregated in the thalamus?

A

In the medial geniculate complex (MGC) of the thalamus. Thalamus receives auditory inputs from spectrally and temporally seperate pathways.

42
Q

Fibres from MGC ____ region project to ____, whereas fibres from MGC ____ region project to ____.

Words to place:

belt and parabelt regions
ventral
primary auditory cortex
dorsal

A

Fibres from MGC ventral region project to primary auditory cortex, whereas fibres from MGC dorsal region project to belt and parabelt regions.

43
Q

True or false: tonotopy is preserved all the way up to the cortex.

A

True.

44
Q

True or false: primary auditory cortex and belt/parabelt are interconnected.

A

True.

45
Q

In the cortex, low frequencies are organized ____ and high frequencies are organized ____.

A

Anteriorly… posteriorly.

46
Q

Apart of tonotopy, what is another layer of organization in the primary auditory cortex?

A

Transversal dominance columns.

47
Q

What are the two types of transversal dominance columns in the primary auditory cortex?

A

EE and EI.

48
Q

Why can we say that the primary auditory cortex does active processing?

A

Because auditory cortex fills-in missing sound frequencies.

49
Q

In which auditory cortex is speech highly processed? Music?

A

Speech is highly porcessed in the left auditory cortex.

Music is highly processed in the right auditory cortex.

50
Q

True or false: Wernicke’s area continuous with secondary auditory area.

A

True.

NSCI 201 (14 decks)

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