ZOOL 342 > Audition > Flashcards

Audition Flashcards

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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
TRUE or FALSE: more afferents contact outer hair cells than inner hair cells
FALSE: fewer afferents contact outer hair cells
26
TRUE or FALSE: most efferents make contacts on outer hair cells (vs. inner hair cells)
TRUE
27
Where on the organ of corti do the hair cells sit?
on the basilar membrane
28
Describe the pathway of sound waves to the basilar membrane.
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
Which duct is filled with perilymph? endolymph?
- perilymph = vestibular duct and tympanic duct - endolymph = cochlear duct
30
What causes depolarization in hair cells in the cochlear duct?
- endolymph in cochlear duct has high k+ - K+ go into hair cells - depolarization
31
Where is frequency represented tonotopically in the ear? How does frequency affect vibration of this structure in the ear?
basilar membrane; low frequency = high vibration
32
TRUE or FALSE: the basilar membrane side closest to the oval window encodes higher frequencies
TRUE
33
the hairs of the hair cells are embedded in the ________________________.
tectorial membrane
34
What is the characteristic frequency that auditory nerve fibers respond best? at what threshold (dB) is this frequency?
10 kHz; 30 dB
35
TRUE or FALSE: inner hair cells act as a cochlera amplifier
FALSE: OUTER hair cells
36
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.
furosemide kills outer hair cells, leading to decreased cochlear amplitude displacement (slide 22)
37
Describe the motile response of the outer hair cells.
healthy basilar membranes show that the outer hair cells respond to sound by slight tilting and changing length (shortening)
38
TRUE or FLASE: outer hair cells lengthen when stimulated, pushing on basilar and tectorial membrane
FALSE: shortens when stimulated, pulling membrane
39
How does activation of the outer hair cells affect activity of the inner hair cells?
activation of out hair cells INCREASES activity of inner hair cells
40
Draw a diagram to show how outer hair cell activation affects inner hair cell activity.
slide 25
41
TRUE or FALSE: if outer hair cells are active and lengthened, there is an increase in action potentials
FALSE: decrease in APs (shortened = increase in APs)
42
If the outer hair cells are destroyed, what happens to the characteristic frequency? Draw a graph of frequency vs threshold to explain.
characteristic frequency becomes much lower (with higher threshold)
43
In which organism did hair cells first evolve?
archosaurs
44
What are inner and outer hair cells in mammals synonymous with in archosaurs?
- INNER hair cell = TALL hair cells - OUTER hair cell = SHORT hair cells
45
in snakes, lizards, and turtles, bundles with tall hair respond to which frequencies? short hair?
- tall hair = low frequencies (like inner hair cell) - short hair = high frequencies (like outer hair cell)
46
TRUE or FALSE: ACh efferents from the medial superior olive excite the outer hair cells.
FALSE: inhibit
47
What happens to the threshold for hearing when ACh efferents are activated?
increase threshold (by inhibiting outer hair cells)
48
Why is the inhibitory effect of ACh efferents on outer hair cells evolutionarily beneficial?
allows us to gain control for loud sounds and prevent damage by increasing threshold
49
Draw the current for ACh receptors when sound is transmitted. Explain its shape.
slide 30; initial transient depolarization; long-lasting hyperpolarization is due to the K+ outflow via SK2
50
Describe the events that occur when ACh binds to the ACh receptor on efferents to the outer hair cells to cause hyperpolarization (inhibitory activity).
- Ca2+ influx leads to opening of SK2 channel (a Ca2+-gated K+ channel) - outflow of K+ leads to hyperpolarization
51
Where does the auditory nerve in the cochlea first synapse?
medulla
52
TRUE or FALSE: lateral superior olivary has ipsilateral innervation from the cochlea, whereas the medial superior olivary has bilateral innervation
TRUE
53
TRUE or FALSE: tonotopy continues from the cochlea, to the superior olivary complex, to the inferior colliculus, to the thalamus, to the cortex
TRUE
54
What is sound localization based on?
difference in time and intensity at the 2 ears i.e. inter-aural time difference (ITD) and inter-aural intensity difference (IID)
55
At what azimuth is ITD greatest? Draw a graph to demonstrate
90 degrees (slide 35)
56
At what azimuth is IID greatest?
90 degrees (slide 35)
57
At which level of the central pathway for audition does frequency become less important?
cerebral cortex
58
How many ears are needed to localize sound?
2
59
What does the Jeffress circuit compute?
ITD
60
Describe how the Jeffress circuit works when sound is coming from straight ahead. Draw a diagram.
- 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
Describe how the Jeffress circuit works when sound is coming from the right. Draw a diagram
- 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
What detects time difference in audition?
bilateral input to the medial superior olive
63
TRUE or FALSE: the medial superior olive (MSO) computes ITD, whereas the jeffress circuit detects ITD
FALSE: - MSO = DETECT ITD -Jeffress circuit = COMPUTE ITD
64
TRUE or FALSE: when ITD is 0, MSO neurons have the lowest rate of firing
FALSE: they have the greatest rate of firing (note: ITD of 0 means that sound is from straight ahead)
65
TRUE or FALSE: lateral superior olive (LSO) detects IID and MSO detects ITD
TRUE
66
TRUE or FALSE: neurons in the LSO are excited by the contralateral ear and inhibited by the ipsilateral ear
FALSE: inhibited by contralateral, excited by ipsilateral
ZOOL 342
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