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ZOOL 342 > Audition > Flashcards

Audition Flashcards

1
Q

Changes in _________________ from ________________ move the eardrum in and out. Air molecules are closer together in regions of ____________ pressure and farther apart in regions of ____________ pressure. (note: this is how we hear)

A

air pressure; sound waves; higher; lower

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2
Q

How is pitch affected by freqeuncy?

A

increasing frequency increases pitch

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3
Q

How is the intensity of sound waves scaled?

A

logarithmically

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4
Q

TRUE or FALSE: a high intensity sound corresponds with loud volume

A

TRUE

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5
Q

What frequencies are considered infrasound? ultrasound?

A
  • infrasound = below 20 Hz
  • ultrasound = above 20 kHz
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6
Q

What frequency range are humans most sensitive?

A

2-6 kHz (frequency of speech)

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7
Q

What are the parts of the outer ear?

A
  • pinna
  • auditory canal
  • tympanic membrane (eardrum)
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8
Q

In what vertebrates did the tympanic membrane evolve?

A

frogs and toads (–> reptiles –> mammals)

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9
Q

Where are the tympanal organs in invertebrates usually found?

A

on the feet

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10
Q

What are the parts of the middle ear?

A
  • ossicles: malleus, incus, stapes
  • oval window
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11
Q

What is the function of the middle ear (ossicles and oval window) in audition?

A
  • ossicles: lever action to amplify and transmit sound waves as mechanical waves
  • oval window: reduction of surface area to amplify sound
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12
Q

By what factor does the middle ear amplify sound?

A

20x

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13
Q

What is the difference between the mammalian and reptilian middle ear?

A
  • mammals: malleus (articular), incus (quadrate), stapes
  • reptiles: stapes in middle ear; quadrate and articular located at back of jaw and skull
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14
Q

What is the malleus, incus, and stapes called in reptiles?

A
  • malleus = articular
  • incus = quadrate
  • stapes = stapes
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15
Q

What reflects the frequency range?

A

length of cochlea

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16
Q

While the mammalian ear has a cochlea, the reptilian ear has a __________________.

A

basilar papilla

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17
Q

TRUE or FALSE: cochlear hair cells have a kinocilium

A

FALSE: cochlear hair cells LACK a true kinocilium

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18
Q

How many inner and outer hair cells are present in the cochlea?

A
  • 3,500 inner hair cells
  • 11,000 outer hair cells
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19
Q

What is the difference between outer and inner hair cells in the cochlea?

A
  • outer hair cell = 3 rows of stereocilia (outward = longer)
  • inner hair cell = shallow disk with some rows of stereocilia

(slide 14)

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20
Q

TRUE or FALSE: inner hair cell is efferent, outer hair cell is afferent

A

FALSE:
- inner = afferent
- outer = efferent

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21
Q

what internal strucure of the mammalian cochlea consists of the outer and inner hair cells, the basilar membrane, and the tectorial membrane?

A

organ of corti

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22
Q

What percentage of afferent contact inner hair cells?

A

90%

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23
Q

How many afferents per inner hair cell?

A

as many as 20

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24
Q

How many afferents per inner hair cell?

A

as many as 20

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25
Q

TRUE or FALSE: more afferents contact outer hair cells than inner hair cells

A

FALSE: fewer afferents contact outer hair cells

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26
Q

TRUE or FALSE: most efferents make contacts on outer hair cells (vs. inner hair cells)

A

TRUE

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27
Q

Where on the organ of corti do the hair cells sit?

A

on the basilar membrane

28
Q

Describe the pathway of sound waves to the basilar membrane.

A

sound waves –> tympanic membrane vibrates –> vibration transferred from malleus to incus to stapes –> oval window moves in and out, wave in the perilymph results, moving the basilar membrane –> hair cells come in contact with tectorial membrane

29
Q

Which duct is filled with perilymph? endolymph?

A
  • perilymph = vestibular duct and tympanic duct
  • endolymph = cochlear duct
30
Q

What causes depolarization in hair cells in the cochlear duct?

A
  • endolymph in cochlear duct has high k+
  • K+ go into hair cells
  • depolarization
31
Q

Where is frequency represented tonotopically in the ear? How does frequency affect vibration of this structure in the ear?

A

basilar membrane; low frequency = high vibration

32
Q

TRUE or FALSE: the basilar membrane side closest to the oval window encodes higher frequencies

33
Q

the hairs of the hair cells are embedded in the ________________________.

A

tectorial membrane

34
Q

What is the characteristic frequency that auditory nerve fibers respond best? at what threshold (dB) is this frequency?

A

10 kHz; 30 dB

35
Q

TRUE or FALSE: inner hair cells act as a cochlera amplifier

A

FALSE: OUTER hair cells

36
Q

Which substance was used to test whether outer hair cells act as a cochlear amplifier? How did it work? Draw diagram of cochlea to explain.

A

furosemide kills outer hair cells, leading to decreased cochlear amplitude displacement (slide 22)

37
Q

Describe the motile response of the outer hair cells.

A

healthy basilar membranes show that the outer hair cells respond to sound by slight tilting and changing length (shortening)

38
Q

TRUE or FLASE: outer hair cells lengthen when stimulated, pushing on basilar and tectorial membrane

A

FALSE: shortens when stimulated, pulling membrane

39
Q

How does activation of the outer hair cells affect activity of the inner hair cells?

A

activation of out hair cells INCREASES activity of inner hair cells

40
Q

Draw a diagram to show how outer hair cell activation affects inner hair cell activity.

41
Q

TRUE or FALSE: if outer hair cells are active and lengthened, there is an increase in action potentials

A

FALSE: decrease in APs (shortened = increase in APs)

42
Q

If the outer hair cells are destroyed, what happens to the characteristic frequency? Draw a graph of frequency vs threshold to explain.

A

characteristic frequency becomes much lower (with higher threshold)

43
Q

In which organism did hair cells first evolve?

A

archosaurs

44
Q

What are inner and outer hair cells in mammals synonymous with in archosaurs?

A
  • INNER hair cell = TALL hair cells
  • OUTER hair cell = SHORT hair cells
45
Q

in snakes, lizards, and turtles, bundles with tall hair respond to which frequencies? short hair?

A
  • tall hair = low frequencies (like inner hair cell)
  • short hair = high frequencies (like outer hair cell)
46
Q

TRUE or FALSE: ACh efferents from the medial superior olive excite the outer hair cells.

A

FALSE: inhibit

47
Q

What happens to the threshold for hearing when ACh efferents are activated?

A

increase threshold (by inhibiting outer hair cells)

48
Q

Why is the inhibitory effect of ACh efferents on outer hair cells evolutionarily beneficial?

A

allows us to gain control for loud sounds and prevent damage by increasing threshold

49
Q

Draw the current for ACh receptors when sound is transmitted. Explain its shape.

A

slide 30; initial transient depolarization; long-lasting hyperpolarization is due to the K+ outflow via SK2

50
Q

Describe the events that occur when ACh binds to the ACh receptor on efferents to the outer hair cells to cause hyperpolarization (inhibitory activity).

A
  • Ca2+ influx leads to opening of SK2 channel (a Ca2+-gated K+ channel)
  • outflow of K+ leads to hyperpolarization
51
Q

Where does the auditory nerve in the cochlea first synapse?

52
Q

TRUE or FALSE: lateral superior olivary has ipsilateral innervation from the cochlea, whereas the medial superior olivary has bilateral innervation

53
Q

TRUE or FALSE: tonotopy continues from the cochlea, to the superior olivary complex, to the inferior colliculus, to the thalamus, to the cortex

54
Q

What is sound localization based on?

A

difference in time and intensity at the 2 ears

i.e. inter-aural time difference (ITD) and inter-aural intensity difference (IID)

55
Q

At what azimuth is ITD greatest? Draw a graph to demonstrate

A

90 degrees (slide 35)

56
Q

At what azimuth is IID greatest?

A

90 degrees (slide 35)

57
Q

At which level of the central pathway for audition does frequency become less important?

A

cerebral cortex

58
Q

How many ears are needed to localize sound?

59
Q

What does the Jeffress circuit compute?

60
Q

Describe how the Jeffress circuit works when sound is coming from straight ahead. Draw a diagram.

A
  • signals coming from left and right ear start travelling at same time
  • neural coincidence detector fires when the 2 signals arrive at the same time

(diagram a and b on slide 36)

61
Q

Describe how the Jeffress circuit works when sound is coming from the right. Draw a diagram

A
  • signals from the right ear start travelling first
  • neural coincidence detector fires when the signal from right ear and left ear arrive at the same time

(diagram c and d on slide 36)

62
Q

What detects time difference in audition?

A

bilateral input to the medial superior olive

63
Q

TRUE or FALSE: the medial superior olive (MSO) computes ITD, whereas the jeffress circuit detects ITD

A

FALSE:
- MSO = DETECT ITD
-Jeffress circuit = COMPUTE ITD

64
Q

TRUE or FALSE: when ITD is 0, MSO neurons have the lowest rate of firing

A

FALSE: they have the greatest rate of firing

(note: ITD of 0 means that sound is from straight ahead)

65
Q

TRUE or FALSE: lateral superior olive (LSO) detects IID and MSO detects ITD

66
Q

TRUE or FALSE: neurons in the LSO are excited by the contralateral ear and inhibited by the ipsilateral ear

A

FALSE: inhibited by contralateral, excited by ipsilateral

ZOOL 342 (21 decks)

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