Test 3 Flashcards
1
Q
What electrical potentials are still present during the absence of an “auditory stimulus?”
A
- Endolymphatic potential
- Hair cell potential
2
Q
How much endolymphatic potential is present during the absence of an “auditory stimulus?”
A
- (+80mv)
3
Q
How much hair cell potential is present during the absence of an “auditory stimulus?”
A
- (-70mv)
4
Q
What is another term for hair cell potential?
A
- intracellular potential
5
Q
What electrical potentials are present in the presence of an “auditory stimulus?”
A
- cochlear microphonic (CM) & summating potential (SP)
- action potential OR all or none potential
6
Q
Where does microphonic and summating potential occur?
A
- at the level of the hair cell
7
Q
Where does action potential or all or none potential occur?
A
- at the auditory nerve
8
Q
What electrical potentials are present at the level of the hair cells?
A
- cochlear microphonic and summating potentials
9
Q
What term is synonymous with “action potential?”
A
- spike
10
Q
What kind of nerve fibers are dedicated to taking information into the brain?
A
- afferent nerve fibers
11
Q
What has to happen at the level of the hair cells before the action potential occurs? (What are the “prerequisites?”)
A
- cochlear microphonic (CM) and summating potential
12
Q
What does a cochlear implant electrode stimulate directly? Why?
A
- the auditory nerve
- because it is bypassing the non-functional hair cells
13
Q
What does AC stand for?
A
- alternating current
14
Q
What does DC stand for?
A
- direct current
- i.e. battery
15
Q
Name the 5 qualities of cochlear microphonic hair cell potential.
A
- alternating current (AC) electrical potential is both positive and negative potential-alternating
- Mimics the frequency of sound (i.e. present 1000 Hz to the outer ear get 1000Hz CM out from the hair cells). Hair cell output same as the input.
- Electrical activity is produced by the inflow K+ ions
- Graded potential (stack up in amplitude/strength)
- Sufficient CM is required before initiating an action potential (AP) at the auditory nerve level.
16
Q
What is Bekesy’s theory?
A
- frequency-place principle (explain further)
17
Q
T or F? The AP is also referred to as the “All or None Potential”
A
FALSE is action potential
18
Q
Why is it called the all or none potential?
A
- there is nothing in between
19
Q
What is CM and SM?
A
- graded potentials
20
Q
The AP travels through the auditory nerve to the auditory brainstem and finally to the what in the brain?
A
- temporal lobe
21
Q
T or F? The endolymphatic potential is + 80mv.
A
TRUE
22
Q
T or F? The CM and SP are K+ dependent stimulus potentials.
A
TRUE
23
Q
Ionic exchange is sodium moving from where to where?
A
- outside to inside
24
Q
T or F? When hair cells cilia move towards the spiral limbus, you can expect tip links to open for ionic exchange.
A
- FALSE because when they move towards the spiral limbus the tip links are closing
25
T or F? Space in between the myelin sheath of an axon is referred to as the "node of ranvier."
- TRUE
26
T or F? Between the hair cell-auditory nerve junction, glutamate is the neurotransmitter.
- TRUE
27
Where is the glutamate being stored?
- synaptic vesicles
28
Finish phrase: The lower the frequency....
- longer the time interval between AP spike (the longer the period)
29
T or F? During the relative refractory period, a neuron can fire provided the stimulus intensity is much stronger compared to the stimulus intensity at the absolute refractory period.
- TRUE
30
What is the refractory period?
- the time interval between the threshold and the resting place
31
When BM moves towards the SV, the tip links are open resulting in the hair cell depolorization.
- TRUE
32
When the BM moves toward the scala vestibuli, what is the direction of the footplate?
- away from the oval window
33
As you gradually increase the sound intensity, you can expect what with the traveling wave?
- traveling wave is wider and taller causing a lack of frequency specificity
34
T or F? When the stapes footplate move inward towards the oval window, there is an insignificant CM and SP at the hair cell level and thus no action potential generated.
- TRUE
35
T or F? At higher frequencies (above 1000Hz), our auditory system uses time interval between spikes as a cue for decoding frequency changes.
- FALSE because we use the rate of firing as the cue
36
T or F? At the axonal level, the NA+ and K+ ionic exchange happens at the "node of raniver."
- TRUE
37
Finish the phrase: The CM potential is considered as....
1. Graded potential
2. Produced by K+ inflow at the hair cell level
4. Larger in amplitude compared to SP
38
T or F? The neurotransmitter substance is contained in the cell body of an axon.
- FALSE it is the terminal end bulb
39
T or F? During the neuronal depolarization, Na+ ions move inward, K+ move outward.
- TRUE
40
Name the 5 qualities of the summating potential (SP) hair cell potential.
1. Direct current electrical potential
* either positive or negative electrical potential
2. Produced as a result of hair cells NOT perfectly moving for an incoming sound at different frequencies.
3. Graded potential (stack up in amplitude/strength)
4. In normal hearing subjects, SP is relatively small in amplitude compared to CM or AP
5. In pathological ears, SP amplitude is larger compared to CM or AP (as in Meniere's disease-too much of endolymphatic fluid in the scala media).
41
What is meniere's disease?
- too much endolymphatic fluid in the scala media causing dizziness or vertigo
42
What is electro-cochleo-graphy (ECOG)
-a technique of recording stimulus-related responses or electrical potentials of the inner ear and auditory nerve
43
What is the name of the hole on top of the cilia?
- transduction channel
44
What connects the cilia to each other?
- side links
45
When inhibition occurs in cilia, what is there less of?
- CM and SP
46
When excitation occurs in cilia, what is there more of?
- CM and SP
47
Name 3 fundamental units the nervous system contains.
1. Dendrites
2. Cell body with nucleus
3. Axon
48
Describe function the axon.
- the myelin sheath on the axon increases speed of conduction and action potential
49
When the myelin sheath on an axon speeds up the conduction of the action potential, this is done through what?
- insulation
50
What node is within an axon and what does it not include?
- the "Node of Ranvier" and it points along the axon "without" a myelin sheath
51
Describe the end of an axon.
- the terminal bulb with synaptic vesicles containing neurotransmitters
52
What 3 qualities does every neuron exhibit?
1. resting potential (-80mv)
2. "threshold" (lowest level at which a neuron triggers a "spike" or "ap"
3. the duration of AP = 1msec (referred to "Absolute Refractory Period"
53
What is 15dB equivalent to in terms of membrane potential?
- (-40mv)
54
How much time does it take to get from threshold, to spike, and back to threshold?
- Absolute Refractory Period (1ms); given, you can't change it
55
During ARP what is a is neuron unable to do?
1. can't discharge any additional spike regardless of the amount of stimulation
(the neuron can not do more work until it comes back to the threshold)
56
Under what 2 conditions can a neuron discharge again?
1. neuron comes back to normal resting potential (-80mv)
2. during the "relative refractory period" (time interval between threshold and resting potential)
8 intensity and stimulation has to be greater compared to the intensity of stimulation during the absolute refractory period
57
(ASK NIKKI) In order for a neuron to give you another spike in the relative refractory period after the absolute refractory period is HIGHER than that of the ABS
Need to break this down with Nikki.
58
How many auditory nerve fibers do we depend on when processing information?
50,000
59
The auditory action potential is what in relation to the input sound?
- it is the electrical correlate
60
Does the amplitude of AP change with sound intensity or frequency?
NO
61
AP is produced along what?
- it is produced all along the auditory pathways
62
How would you describe the 2 types of methods to record APs?
- invasive (under sedation to remove tumor, could potentially damage auditory or facial nerve)
- non-invasive (electro-carteo-graphy; auditory brain stem response)
63
Describe ALL in ALL or NONE action potential.
- has enough strength to reach the threshold
64
Describe NONE is ALL or NONE action potential.
- does not have sufficient strength to reach the threshold
65
Describe chemical concentration outside of the axon.
- higher concentration of Na+ and lower concentration of K+
66
Describe chemical concentration inside of the axon.
- higher concentration of K+ and lower concentration of NA+
67
An ionic exchange occurs to produce what?
- action potential
68
What is MS?
- an autoimmune disease that attacks your own body
69
How does MS attack your own body?
- demyelination occurs (myelin is taken away)
70
What results in ones body due to demyelination?
- without a myelin sheath there is not a node of ranvier causing a loss of conduction and ionic exchange (this is inefficient for action potentials)
71
What do synaptic vesicles contain?
- neurotransmitter substance
72
Sounds from the middle ear enter through what?
- scala vestibuli through the oval window
73
Describe Bekesy's theory.
- traveling wave starts from the base and moves towards the apex
74
What is the frequency-place principle?
- based on the frequency, there is a specific place in the cochlea, traveling wave will have maximum amplitude
75
What is disturbed during the cochlear mechanics?
- perilymphatic fluid
76
What does perilymphatic fluid disturb?
- tectoral and basilar membrane
| - hair cells
77
What happens to the thin membrane around the round window every time fluid moves in and out?
- it bulges in and out
78
How does the movement of the round window's thin membrane help the hearing process?
- it releases pressure when sound comes in
79
Look at figure 10.6 in the book.
It describes functions of the cochlea.
80
What is happening at the level of the hair cells at the auditory nerve?
- the stereocilia and cilia of hair cells move and produce the "cochlear microphonic potential"
81
What does CM potential stimulate?
- "vesicles" to release neurotransmitters into synaptic cleft
82
If CM is sufficient in "quantity" to reach the auditory nerve threshold, what will happen?
- action potential/spike is triggered
83
The action potential travels through what?
- the auditory nerve
84
Where does the action potential go?
- to the auditory brainstem and finally to the brain (temporal lobe)
85
When the stapes footplate moves inward towards the inner ear, what happens?
1. basilar membrane moves downward towards the scala tympani
2. the round window's thin membrane moves outwards
3. tip links move towards the spiral limbus
4. closes the tip links gates causing INHIBITION
5. NO ionic exchange and thus NO electrical activity at the hair cells and at the nerve
6. NO neurotransmitter substance released
7. NO action potential produced at the auditory nerve causing HYPERPOLARIZATION
86
When the stapes footplate moves outwards away from the inner ear, what happens?
1. basilar membrane moves upwards towards scala vestibuli
2. round window's thin membrane moves inwards
3. tip links move away from the spiral limbus
4. opens the tip links gate causing EXCITATION
5. more ionic exchange and more electrical activity at the hair cells
6. significant neurotransmitter substance released
7. action potential produced at the auditory nerve level causing DEPOLARIZATION
87
Note: More ionic exchange when stapes moving towards vs. moving away.
Ask Nikki
88
Note: Same logic of neurotransmitters occurs between levels of nerve cells auditory nerve fiber.
Ask Nikki
89
What is a synapse?
- a place where neurons connect with other cells
90
Why does sodium move from outside to inside?
- because particles will move from highest concentration to lowest concentration
(this is an exchange of ions; depolarization)
91
Why does potassium move from inside to outside?
- because particles will move from highest concentration to lowest concentration
(this is an exchange of ions; repolarization)
92
Name the different neurotransmitters in the central nervous system.
1. glutamate
2. gamma aminobutyric acid (GABA)
3. dopamine
4. serotonin
5. acetylcholine (ACH)
93
Describe the cochlear mechanics to account for intensity changes at the threshold place of maximum stimulation.
1. the width of the traveling wave is narrow (CP level)
2. the height of the traveling wave is smaller (CP level)
3. few number of auditory nerve fibers are active
4. the action potentials in each nerve fiber cumulatively account threshold intensity changes
94
Describe cochlear mechanics to account for intensity changes at higher intensity levels at place of maximum stimulation.
1. the width of the traveling wave is broader (CP level)
2. the height of the traveling wave is larger (CP level)
3. many auditory nerve fibers cumulatively a/c intensity changes
95
What does the time interval between spikes help us determine?
- different types of frequencies
96
How does time interval affect frequency?
- the longer the time interval the lower the frequency
97
If frequency is 250Hz, what is the period? Or time interval between spikes?
250 Hz = 4ms
500 Hz = 2ms
1000 Hz = 1msec
98
How long is the refractory period?
1 msec
99
What is the name of a device that measures oscillatory movement of the eyes in response to caloric stimulation?
- electrony-stagmo-graph
100
List three functions of the stria vascularis.
1. carries blood
2. produces a DC potential
3. produces endolymph
101
T or F? The stria vascularis supports hair cells.
FALSE
102
What is the type of cerebal palsy that is most associated with sensorinueral hearing loss?
- athetosis
103
In what unit is angular acceleration measured?
- degrees/sec^2
104
The macula is the end organ located in what?
- utricle
105
List three things that make up the wall of the cochlear duct.
1. bony shelf
2. basilar membrane
3. reissner's membrane
106
Where is endolymph found?
- scala media
107
The fluid surrounding the membranous labyrinth is called what?
- perilymph
108
What portion of the inner ear responds to angular acceleration?
- semicircular canals
109
What is the name of the central core the cochlea winds around.
- modiolus
110
What are the tips of the outer hair cells embedded in?
- the tectorial membrane
111
The most common postnatal cause of bilateral hearing loss from viral infection is what?
- rubeola (measles)
112
What unit is linear acceleration measured in?
- cm/sec^2
113
T or F? Rubella is considered a perinatal cause of hearing loss.
FALSE
114
List 3 considered causes of perinatal hearing loss.
1. anoxia
2. trauma
3. prolonged labor
115
Deprivation of oxygen, which may cause damage to the cochlea (and the brain) is called, what?
- anoxia
116
The small opening allowing passage of perilymph from scala vestibuli to scala tympani is called what?
- helicotrema
117
How many numbers of turns does the cochlea make?
- 2 1/2
118
The structure just medial to the oval window is called what?
- vestibule
119
The crista is the end organ of what?
- semicircular canals
120
Rapid back and forth movement of the eyes is called what?
- nystagmus
121
The fluid contained in the membranous labyrinth is called what?
- endolymph
122
The end organ of hearing is the what?
- organ of corti
123
The portion of the inner ear responsible for linear acceleration is what?
- the utricle and saccule
