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28 Cards in this Set
- Front
- Back
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What are propagated changes in the membrane potential that, once initiated, affect an entire excitable membrane? |
Action Potential |
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What is another word for the electrical events called action potential? |
Nerve impulses |
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What are abundant on the axon, its branches, and its axon terminals? |
Voltage-gated sodium channels |
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What are voltage-gated sodium channels abundant on? |
Axon, It's branches, It's axon terminals |
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What is the first step to generating an action potential? |
Opening of voltage-gated sodium at one site |
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What site does the generation of an action potential by opening a voltage-gated sodium ion channel usually happen at? |
Initial segment of the axon |
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The movement of sodium ions into the axon depolarizes adjacent sites. What does this trigger? |
The opening of additional voltage-gated sodium channels |
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What triggers the opening of additional voltage-gated sodium channels? |
The movement of sodium ions into the axon depolarizing adjacent sites |
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The movement of sodium ions into the axon depolarizes adjacent sites, triggering the opening of additional voltage-gated sodium channels. What does this result in? |
A chain reaction that spreads across the surface of the membrane like a line of falling dominoes |
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The chain reaction is essentially the action potential being propagated along what? |
The length of the axon |
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What does this action potential ultimately reach? |
Axon terminals |
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What is the membrane potential at which an action potential begins called? |
Threshold |
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What is the threshold for an axon in mV? |
Between -60mV and -55mV |
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Threshold for an axon is typically between -60 mV and -55 mV. What does this correspond to? |
A depolarization of 10 to 15 mV |
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A stimulus that shifts the resting membrane from -70 mV to -62 mV will not produce what? |
An action potential |
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What stimulus that shifts from the resting membrane potential from -70 mV to -62 mV will only produce what? |
A graded depolarization |
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What happens when a stimulus shifting the resting membrane potential from -70 mV to -62 mV is removed? |
The membrane returns to the resting level |
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What is the depolarization of the initial segment of the axon caused by? |
local currents resulting from the graded depolarization of the axon hillock |
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What do local currents resulting from the graded depolarization of the axon hillock cause? |
The depolarization of the initial segment of the axon |
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The initial depolarization acts like what? |
The trigger of a gun |
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In the case of an axon or another area of excitable membrane, a graded depolarization is similar to what on the gun? |
The pressure on the trigger. |
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What action of the gun is the action potential similar to in the case of an axon or another area of excitable membrane? |
The firing of the gun |
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What brings the membrane to threshold? |
Stimuli |
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What does all stimuli that brings the membrane to threshold generate? |
Identical action potentials |
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What are the properties of the action potential independent of? |
Relative strength of the depolarizing stimilus |
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That stimulus exceeds the threshold |
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The concept that a given stimulus either triggers a typical action potential, or non at all is known as what? |
All-or-none principle |
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What principle applies to all excitable membranes? |
All-or-none |
