The Auditory System Flashcards
1
Q
What does the basilar membrane (BM) separate?
A
the scala media and scala tympani
2
Q
What ion’s movement underlies hair cell depolarization?
A
K+ influx
3
Q
What are otoacoustic emissions (OAEs)?
A
sounds created by active OHCs
4
Q
The inner hair cells (IHCs) are attached to the _____.
A
basilar membrane (BM)
5
Q
This is a Na+-rich fluid that fills the scala vestibuli and bathes the basal end of the hair cells.
A
perilymph
6
Q
What do patients with auditory neuropathy use for sound localization?
A
interaural level difference (ILD)
7
Q
The basilar membrane (BM) vibrates best to low frequencies near ______.
A
the apex of the cochlea
8
Q
This is a K+-rich fluid that fills the scala media and bathes the apical ends of the hair cells.
A
endolymph
9
Q
This is caused by the head forming an acoustic shadow between the 2 ears.
A
an interaural level difference (ILD)
10
Q
When does the hair cell hyperpolarize?
A
when the stereocilia bundle is pushed towards the direction of the shortest stereocilia
11
Q
What comprises the external ear?
A
pinna –> external auditory meatus –> tympanic membrane
12
Q
Human hearing spans frequencies of ____ to ____ Hz with a peak sensitivity around _____.
A
20-20,000; peak = 3000
13
Q
What comprises the middle ear?
A
the ossicles
14
Q
What is the function of the medial olicocochlear neurons (MOCs)?
A
they’re feedback control to change the cochlear sensitivity
15
Q
The ____ of sound increases when the air is compressed more forcefully, resulting in increased density of air.
A
intensity
16
Q
What is presbycusis?
A
a loss of high frequency hearing
17
Q
Where are the inner and outer hair cells found?
A
in the organ of Corti
18
Q
What causes vertical displacement of the basilar and tectorial membranes?
A
cochlear fluid waves
19
Q
What is the function of the stria vascularis?
A
pump K+ into the endolymph –> create (+) potential inside the scala media (the endocochlear potential)
20
Q
What is the cochlear amplifier?
A
the mechanical amplification of the displacement of the basilar membrane (BM) by the outer hair cells (OHCs)
21
Q
_____ lesions rostral to the cochlear nuclei produce bilateral deafness.
A
Unilateral
22
Q
Movements of the basilar membrane (BM) are translated by _____ into electrical signals.
A
inner hair cells (IHCs)
23
Q
Movements of the basilar membrane (BM) are translated by inner hair cells (IHCs) into ______.
A
electrical signals
24
Q
Are there more type I or type II ANFs?
A
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
