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Flashcards in The Auditory System Deck (142):
1

What does the basilar membrane (BM) separate?

the scala media and scala tympani

2

What ion's movement underlies hair cell depolarization?

K+ influx

3

What are otoacoustic emissions (OAEs)?

sounds created by active OHCs

4

The inner hair cells (IHCs) are attached to the _____.

basilar membrane (BM)

5

This is a Na+-rich fluid that fills the scala vestibuli and bathes the basal end of the hair cells.

perilymph

6

What do patients with auditory neuropathy use for sound localization?

interaural level difference (ILD)

7

The basilar membrane (BM) vibrates best to low frequencies near ______.

the apex of the cochlea

8

This is a K+-rich fluid that fills the scala media and bathes the apical ends of the hair cells.

endolymph

9

This is caused by the head forming an acoustic shadow between the 2 ears.

an interaural level difference (ILD)

10

When does the hair cell hyperpolarize?

when the stereocilia bundle is pushed towards the direction of the shortest stereocilia

11

What comprises the external ear?

pinna --> external auditory meatus --> tympanic membrane

12

Human hearing spans frequencies of ____ to ____ Hz with a peak sensitivity around _____.

20-20,000; peak = 3000

13

What comprises the middle ear?

the ossicles

14

What is the function of the medial olicocochlear neurons (MOCs)?

they're feedback control to change the cochlear sensitivity

15

The ____ of sound increases when the air is compressed more forcefully, resulting in increased density of air.

intensity

16

What is presbycusis?

a loss of high frequency hearing

17

Where are the inner and outer hair cells found?

in the organ of Corti

18

What causes vertical displacement of the basilar and tectorial membranes?

cochlear fluid waves

19

What is the function of the stria vascularis?

pump K+ into the endolymph --> create (+) potential inside the scala media (the endocochlear potential)

20

What is the cochlear amplifier?

the mechanical amplification of the displacement of the basilar membrane (BM) by the outer hair cells (OHCs)

21

_____ lesions rostral to the cochlear nuclei produce bilateral deafness.

Unilateral

22

Movements of the basilar membrane (BM) are translated by _____ into electrical signals.

inner hair cells (IHCs)

23

Movements of the basilar membrane (BM) are translated by inner hair cells (IHCs) into ______.

electrical signals

24

Are there more type I or type II ANFs?

type I

25

From the inferior colliculus, fibers project mainly to the ____.

ipsilateral medial geniculate in the thalamus

26

_____ are innervated by efferent neurons called medial olicocochlear neurons (MOCs).

Outer hair cells (OHCs)

27

What comprises the inner ear?

  • the cochlea
  • the semicircular canals

28

Unilateral lesions in the inferior colliculus (IC) or more central cause ______ deafness.

bilateral

29

What are auditory nerve fibers (ANFs)?

the 8th CN (spiral ganglion) innervating the inner and outer hair cells

30

What are the 2 primary qualities of sound?

  1. amplitude (intensity)
  2. frequency

31

What do the cochlear fluid waves cause?

vertical displacement of the basilar and tectorial membranes

32

The frequency is the number of times/sec that a sound wave ______ (or ______).

reaches the peak of rarefaction; compression

33

Unilateral lesions rostral to the cochlear nuclei produce ____ deafness.

bilateral

34

What is perilymph?

a Na+-rich fluid that fills the scala vestibuli and bathes the basal end of the hair cells

35

The OHCs contribute up to ____ dB of the cochlea's sensitivity to sound.

50

36

What is the excitatory NT in the hair cell?

glutamate

37

What is sensorineural hearing loss? Examples?

  • damage to/loss of hair cells or nerve fibers
  • ex:
    • excessively loud sounds
    • ototoxic drugs
    • age (presbycusis)

38

Where is the Organ of Corti located?

in the scala media on top of the basilar membrane (BM)

39

What might cause a collapse of the endocochlear potential? What is the functional result?

a mutation in the gap junction subunit, connexin 32 --> decreased active transport of K+ in the stria vascularis --> congenital sensorineural deafness

40

This is the name for the mechanical amplification of the displacement of the basilar membrane (BM) by the outer hair cells (OHCs).

the cochlear amplifier

41

The dorsal acoustic stria and trapezoid body regroup to form the ______ and ascend to the _____ of the midbrain.

lateral lemniscus; inferior colliculus

42

What is located in the scala media on top of the basilar membrane (BM)?

the organ of Corti

43

What are the 3 flexible elements of the cochlea?

  1. oval window
  2. basilar membrane (BM)
  3. round window

44

What is the perceptual correlate of intensity?

loudness

45

Some axons from cells in the cochlear nucleus cross the midline to the _____ and _____.

dorsal acoustic stria and trapezoid body

46

This is a hole in the basilar membrane (BM) at the apex of the cochlea that connects the scala vestibuli to the scala tympani.

the helicotrema

47

What separates the scala vestibuli from the scala media?

Reissner's membrane

48

The ____ is an obligatory relay and integration center for ascending auditory information.

inferior colliculus

49

The intensity of sound increases when _____, resulting in increased density of air.

the air is compressed more forcefully

50

Where are the nuclei of the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN) found?

on the dorsal and lateral aspects of the inferior cerebellar peduncle

51

During and oscillatory sound wave the basilar membrane (BM) will move up towards the scala vestibuli during rarefaction and down towards the _____ during _____.

scala tympani; compression

52

Where do the 2 bifurcations of the ANF cell bodies in the spiral ganglion relay to?

  • the ventral cochlear nucleus (VCN)
  • the dorsal cochlear nucleus (DCN)

53

Movements of the ______ are translated by inner hair cells (IHCs) into electrical signals.

basilar membrane (BM)

54

Why are otoacoustic emissions (OAEs) significant?

they're the main method to test newborn hearing

55

What innervates the inner and outer hair cells?

CN8 (spiral ganglion)

56

Where do the axons of the auditory nerve fibers (CN8) go to?

the cochlear nucleus of the brainstem

57

What separates the scala media and scala tympani?

the basilar membrane (BM)

58

Name the 2 types of auditory nerve fibers (ANFs) and their differences.

  1. type I (innervate the IHCs, myelinated, 95% of total)
  2. type II (innervate the OHCs, not myelinated, 5% of total)

59

During and oscillatory sound wave the basilar membrane (BM) will move up towards the _____ during ______ and down towards the scala tympani during compression.

scala vestibule; rarefaction

60

What does damage to Wernike's Area cause?

Wernike's aphasia (impairment in language comprehension but not production)

61

The basilar membrane (BM) vibrates best to ____ near the apex of the cochlea.

low frequencies

62

Dx?

  • normal OAEs
  • normal tone thresholds
  • deficits in discriminating or understanding speech

auditory neuropathy

63

What is endolymph?

a K+-rich fluid that fills the scala media and bathes the apical ends of the hair cells

64

How can OHCs change their length?

the motor protein, prestin

65

This is an epi on the side of the scala media that actively pumps K+ into the endolymph.

the stria vascularis

66

This is different timing of the arrival of noises to each ear.

an interaural time delay (ITD)

67

Where are interaural level differences (ILDs) processed?

in the lateral superior olive (LSO)

68

What is an interaural level difference (ILD)?

the acoustic shadow btw the 2 ears bc of the head

69

What is the endocochlear potential?

the +80mV potential inside the scala media

70

Sound above ____ can result in permanent hearing loss.

120 dB

71

The frequency is ______ that a sound wave reaches the peak of rarefaction (or compression).

the number of times/sec

72

What are sounds created by active OHCs called?

otoacoustic emissions (OAEs)

73

The basilar membrane (BM) vibrates best to high frequencies near ______.

the base of the cochlea

74

What is the helicotrema?

a hole in the basilar membrane (BM) at the apex of the cochlea that connects the scala vestibuli to the scala tympani

75

How do OHCs respond to changes in voltage?

they change their length (electromotile)

76

What is the hearing threshold?

the smallest dB that the subject can detect

77

This isa thread-like connection btw adjacent stereocilia.

a tip link

78

The _____ are attached to the basilar membrane (BM).

inner hair cells (IHCs)

79

How does the middle ear alleviate the impedance mismatch btw the fluid and air?

  1. decreased area being pushed on by the sound waves (from tympanic membrane to stapes footplate)
  2. increased force (ossicles form a levering action)

80

Why is the cochlear amplifier important?

sensorineural deafness can be caused by damage to the OHCs by blocking the transduction channel or by prolonged exposure to loud sounds

81

OHCs are innervated by ____ neurons called medial olicocochlear neurons (MOCs).

efferent

82

Unilateral lesions in the inferior colliculus (IC) or above results in deficits in sound source localization for sources _____ to the lesion.

contralateral

83

Which hair cells are more sensitive to loud sounds?

outer hair cells (OHCs)

84

Lesions _____ to and including the cranial nerve produce unilateral deafness.

caudal

85

What is the stria vascularis?

an epi on the side of the scala media that actively pumps K+ into the endolymph

86

How will a pt with auditory neuropathy present?

normal OAEs normal tone thresholds deficits in discriminating or understanding speech

87

What happens when the hair cell is depolarized and the transducer channel opens?

voltage-dependent Ca++ channels open in the basolateral membrane --> NT released --> excitation of afferent axon

88

What is the tonotopic arrangement/map of the basilar membrane (BM)?

a frequency-wise arrangement of vibrational properties of the BM; each inner hair cell (IHC) responds best to a certain frequency determined by the mechanical properties of the BM at that location

89

What is the function of the pinna?

collect sound --> directional amplification --> filtering of sound

90

What does the stapes contact?

the oval window

91

Unilateral lesions _____ to the cochlear nuclei produce bilateral deafness.

rostral

92

What is the function of the helicotrema?

to relieve pressure in the inner ear

93

OHCs are innervated by efferent neurons called _____.

medial olicocochlear neurons (MOCs)

94

Lesions caudal to and including the cranial nerve produce ______ deafness.

unilateral

95

What is a type II ANF?

innervate the OHCs, not myelinated

96

The _____ is the number of times/sec that a sound wave reaches the peak of rarefaction (or compression).

frequency

97

When the stereocilia bundle is pushed towards the direction of the longest stereocilia, the membrane potential becomes _____.

more positive (depolarizes)

98

What is the normal membrane potential of a hair cell?

-50mV

99

What are the 3 fluid-filled compartments in the cochlea?

  1. scala vestibuli
  2. scala media
  3. scala tympani

100

What is the purpose of the outer hair cells (OHCs)?

to amplify the movements of the basilar membrane (BM)

101

What are the 2 important response properties of the auditory nerve fibers (ANFs)?

encoding sound intensity (rate code) temporal coding of timing (phase locking)

102

The perceptual correlate of frequency is _____.

pitch

103

What is a tip link?

a thread-like connection btw adjacent stereocilia

104

The hair cell potential follows, almost exactly, the ____.

movement of the basilar membrane (BM)

105

When does the hair cell depolarize?

when the stereocilia bundle is pushed towards the direction of the longest stereocilia

106

The basilar membrane (BM) vibrates best to ______ near the base of the cochlea.

high frequencies

107

Auditory neuropathy results from problems with neural transmission from ____ to ____, or in the ANF function itself.

inner hair cell (INH) to auditory nerve fibers (ANFs)

108

What is an interaural time delay (ITD)?

different timing of the arrival of noises to each ear

109

What do hair cells do?

transduce sound into electrical signals

110

At the basal end, the hair cell is contacted by ____, whose cell bodies are located in _____.

auditory nerve fibers (CN 8); spiral ganglion

111

What is Reissner's membrane?

the separation btw the scala vestibule and the scala media

112

Where are interaural time delays (ITDs) processed?

in the medial superior olive (MSO)

113

What is the function of the ossicles?

to translate airborne pressure waves into motion of the fluid of the inner ear

114

How much hearing loss results from conductive hearing loss?

10-60 dB

115

How do audiologist quantify hearing loss?

measure the threshold in each ear = the smallest dB that the subject can detect

116

What is conductive hearing loss? Examples?

  • degraded mechanical transmission
  • ex:
    • fluid from otitis media
    • otosclerosis
    • atresia
    • perforation/rupture of the tympanic memb
    • interruption of ossicle chain
    • static pressure

117

Name 4 ototoxic drugs.

  1. diuretics
  2. aminoglycoside Abxs
  3. aspirin
  4. CA therapy

118

When the stereocilia bundle is pushed towards the direction of the shortest stereocilia, the membrane potential becomes _____.

more negative (hyperpolarizes)

119

These innervate the OHCs and are not myelinated.

type II ANFs

120

Patients with auditory neuropathy cannot use ____ for sound localization because it relies on phase locking.

interaural time delays (ITDs)

121

How many auditory nerve fibers (ANFs) are found in each ear?

30,000

122

These innervate the IHCs and are myelinated.

type I ANFs

123

Sound radiates from vibrating sources as a series of ____ of alternating ___ and _____ of air molecules.

pressure waves; compression; rarefaction

124

Within each XC of the organ of Corti, there are ____ inner hair cells (IHCs) and _____ outer hair cells (OHCs).

1 inner; 3 outer

125

What is found in the organ of Corti?

the inner and outer hair cells

126

A 300-Hz sound results in an oscillating membrane potential of ____.

300 Hz

127

What is a loss of high frequency hearing?

presbycusis

128

An OHC changing its length causes the BM to be _____.

pulled towards or away from the tectorial membrane --> change the mechanical frequency selectivity of the BM

129

What is a type I ANF?

innervate the IHCs, myelinated

130

What is the function of the tip link?

they pull on the top of the stereocilia --> mechanical opening of the transduction channels --> depolarization of the hair cells OR pull --> close channels --> hyperpolarize

131

The mechanical force of the stereocilia acts directly upon the ______.

transduction channel gating mechanism

132

The medial geniculate sends projections to the ______.

primary auditory cortex (A1)

133

How is conductive hearing loss distinguished from sensorineural hearing loss?

hold tuning fork in air vs against skull- in conductive, the sound will be heard when against the bone when it wasn't heard in the air

134

What does impedance mismatch mean?

water has high impedance (it's more resistant to movement than air); air has low impedance

135

What does a collapse of the endocochlear potential cause? Why?

sensorineural deafness bc of the loss in driving force for transduction

136

How many hair cells are there per cochlea? How are they arranged?

16,000; 4 rows (1 row of IHCs and 3 rows of OHCs)

137

During and oscillatory sound wave the _____ will move _____ towards the scala vestibule during rarefaction and _____ towards the scala tympani during compression.

basilar membrane (BM); up = rarefaction; down = compression

138

How many type I ANFs innervate a single inner hair cell?

10-30

139

The intensity of sound increases when the air is compressed more forcefully, resulting in ______.

increased density of air

140

_____ results from problems with neural transmission from inner hair cell (INH) to auditory nerve fibers (ANFs), or in the ANF function itself.

Auditory neuropathy

141

What kind of channel is the transduction channel found at the tips of the hair cells?

a non-specific cation channel that is voltage-INsensitive

142

What is the most common cause of hearing loss?

age