Test 3 Flashcards
What electrical potentials are still present during the absence of an “auditory stimulus?”
- Endolymphatic potential
- Hair cell potential
How much endolymphatic potential is present during the absence of an “auditory stimulus?”
- (+80mv)
How much hair cell potential is present during the absence of an “auditory stimulus?”
- (-70mv)
What is another term for hair cell potential?
- intracellular potential
What electrical potentials are present in the presence of an “auditory stimulus?”
- cochlear microphonic (CM) & summating potential (SP)
- action potential OR all or none potential
Where does microphonic and summating potential occur?
- at the level of the hair cell
Where does action potential or all or none potential occur?
- at the auditory nerve
What electrical potentials are present at the level of the hair cells?
- cochlear microphonic and summating potentials
What term is synonymous with “action potential?”
- spike
What kind of nerve fibers are dedicated to taking information into the brain?
- afferent nerve fibers
What has to happen at the level of the hair cells before the action potential occurs? (What are the “prerequisites?”)
- cochlear microphonic (CM) and summating potential
What does a cochlear implant electrode stimulate directly? Why?
- the auditory nerve
- because it is bypassing the non-functional hair cells
What does AC stand for?
- alternating current
What does DC stand for?
- direct current
- i.e. battery
Name the 5 qualities of cochlear microphonic hair cell potential.
- 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.
What is Bekesy’s theory?
- frequency-place principle (explain further)
T or F? The AP is also referred to as the “All or None Potential”
FALSE is action potential
Why is it called the all or none potential?
- there is nothing in between
What is CM and SM?
- graded potentials
The AP travels through the auditory nerve to the auditory brainstem and finally to the what in the brain?
- temporal lobe
T or F? The endolymphatic potential is + 80mv.
TRUE
T or F? The CM and SP are K+ dependent stimulus potentials.
TRUE
Ionic exchange is sodium moving from where to where?
- outside to inside
T or F? When hair cells cilia move towards the spiral limbus, you can expect tip links to open for ionic exchange.
- FALSE because when they move towards the spiral limbus the tip links are closing
T or F? Space in between the myelin sheath of an axon is referred to as the “node of ranvier.”
- TRUE
T or F? Between the hair cell-auditory nerve junction, glutamate is the neurotransmitter.
- TRUE
Where is the glutamate being stored?
- synaptic vesicles
Finish phrase: The lower the frequency….
- longer the time interval between AP spike (the longer the period)
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
What is the refractory period?
- the time interval between the threshold and the resting place
When BM moves towards the SV, the tip links are open resulting in the hair cell depolorization.
- TRUE
When the BM moves toward the scala vestibuli, what is the direction of the footplate?
- away from the oval window
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
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
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
T or F? At the axonal level, the NA+ and K+ ionic exchange happens at the “node of raniver.”
- TRUE
Finish the phrase: The CM potential is considered as….
- Graded potential
- Produced by K+ inflow at the hair cell level
- Larger in amplitude compared to SP
T or F? The neurotransmitter substance is contained in the cell body of an axon.
- FALSE it is the terminal end bulb
T or F? During the neuronal depolarization, Na+ ions move inward, K+ move outward.
- TRUE
Name the 5 qualities of the summating potential (SP) hair cell potential.
- Direct current electrical potential
* either positive or negative electrical potential - Produced as a result of hair cells NOT perfectly moving for an incoming sound at different frequencies.
- Graded potential (stack up in amplitude/strength)
- In normal hearing subjects, SP is relatively small in amplitude compared to CM or AP
- 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).
What is meniere’s disease?
- too much endolymphatic fluid in the scala media causing dizziness or vertigo
What is electro-cochleo-graphy (ECOG)
-a technique of recording stimulus-related responses or electrical potentials of the inner ear and auditory nerve
What is the name of the hole on top of the cilia?
- transduction channel
What connects the cilia to each other?
- side links
When inhibition occurs in cilia, what is there less of?
- CM and SP
When excitation occurs in cilia, what is there more of?
- CM and SP
Name 3 fundamental units the nervous system contains.
- Dendrites
- Cell body with nucleus
- Axon
Describe function the axon.
- the myelin sheath on the axon increases speed of conduction and action potential
When the myelin sheath on an axon speeds up the conduction of the action potential, this is done through what?
- insulation