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11 Cards in this Set
- Front
- Back
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What is another term for voltage-gated channels?
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potential-dependent channels
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What is the threshold voltage for an AP?
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~ 20mV depolarization
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What are local currents relative to an AP?
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the point of depolarization reverses the relative polarity of the cell membrane at that point. the cations peripheral to the point of depolarization will be attracted to the negative charge on teh outside of the cell, whereas the cations on the inside of the cell at the point of depolarization will be attracted to the negative charges peripheral to them on the inside of the cell.
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What does the length constant depend on?
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Rin (internal propagating resistance of the axon) and Rm (membrane resistance restricting movement in and out of axon membrane)
length constant = sqrt(Rm/Rin) so a small Rin and a large Rm are the best combinations for best speed of transmission because /\ length constant is goooooood. |
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What is the principle of "inactivation" in regard to Na channels?
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they automatically inactivate themselves after being open for a moment which allows the AP to propagate and the local membrane to return to resting potential.
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What are all the events that cause repolarization in an AP?
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1. Na channels display inactivation
2. K channels open to allow K out of the cell this allows repolarization to occur VERY QUICKLY and we hyperpolarize because K channels stays open a little longer than necessary. |
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What is the difference between K channels and Na channels on how and when they open and close?
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Na two-gate channels open per onset of depolarization, then exhibit inactivation until the cell reaches Em
K one-gate channels open per completion of depolarization and slowly close after slight Em hyperpolarization |
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What is depolarization conduction block?
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flaccid paralysis that follows spastic paralysis when the cholinergic nicotinic receptors are stimulated without stopping stimulation. this happens because if axon doesn't go back to Em, Na two-gate channels won't release from inactivation
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What is the absolute refractory period?
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all of the depolarization of an AP and the entire time when there are 100% Na channels inactivated (about 1/2 of the repolarization. during this time it is IMPOSSIBLE to make another AP
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What is the relative refractory period?
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time when there are some Na channels that are no longer inactivated and an AP also cannot be able to be initiated with a normal stimulus. a bigger kick CAN cause an AP. this is about 1/2 of the repolarization and all of the hyperpolarized time period of repolarization
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What is the concept of accomodation?
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when there is a sub-threshold series of stimulus that causes enough Na channels to inactivate which causes a raise of threshold
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