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52 Cards in this Set
- Front
- Back
E - hyperpolarization
B - depolarization A - rest C - initiation of repolarization D - repolarization |
Which part of the graph to the right corresponds to the following:
hyperpolarization depolarization rest initiation of repolarization repolarization |
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D
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Which part of the graph to the right corresponds to:
A time when voltage-gated sodium channels are inactivated, then reset to the closed state. Potassium channels continue to open. |
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A
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Which part of the graph to the right corresponds to:
A time when voltage-gated sodium and potassium channels are closed. |
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C
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Which part of the graph to the right corresponds to:
A time when voltage-gated sodium channels begin to inactivate and voltage-gated potassium channels begin to open. |
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B
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Which part of the graph to the right corresponds to:
A time when voltage-gated sodium channels open rapidly, resulting in movement of sodium into the cell. |
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A. rest
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Which phase of the action potential does the diagram below best correspond to?
a. rest b. depolarization c. peak d. repolarization e. hyperpolarization |
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A. rest
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Which phase of the action potential does the diagram below best correspond to?
a. rest b. depolarization c. peak d. repolarization e. hyperpolarization |
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C. Peak
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Which phase of the action potential does the diagram below best correspond to?
a. rest b. depolarization c. peak d. repolarization e. hyperpolarization |
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D. repolarization
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Which phase of the action potential does the diagram below best correspond to?
a. rest b. depolarization c. peak d. repolarization e. hyperpolarization |
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E. hyperpolarization
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Which phase of the action potential does the diagram below best correspond to?
a. rest b. depolarization c. peak d. repolarization e. hyperpolarization |
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B
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What letter on this graph to the right corresponds to the absolute refractory period?
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C
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What letter on this graph to the right corresponds to the relative refractory period?
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nerve impulse
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What is another name for an action potential?
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A large membrane potential change
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What does an action potential consist of?
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axon hillock
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Where is the action potential generated?
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when it receives signals from dendrites & the cell body.
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What causes an axon potential to occur at the axon hillock?
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They open rapidly to increase permeability to Na+
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What happens to ion channels when the membrane depolarizes at the axon hillock?
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15 mV
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How much does the axon hillock have to depolarize to reach threshold?
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threshold
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An action potential is generated.
Weak stimuli that DO NOT reach _________ do no produce action potentials. The action potential is an "all or none" event. |
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the action potential is NOT produced.
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What happens if there is a weak stimulus at the axon hillock and threshold is not reached?
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yes
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Do action potentials always have the same amplitude and the same duration?
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This means a positive feedback loop is established.
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Threshold is a special membrane potential where the process of depolarization becomes regenerative. What does this mean?
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It opens more Na+ voltage-gated channels
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What happens to sodium voltage-gated channels at threshold?
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The more Na+ flow into the cell causes the cell to depolarize further and open more Na+ voltage-gated channels.
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Explain how the positive feedback loop maintains the rising phase of the action potential.
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1. Inactivation of Na+ voltage-gated channels
2. The opening of voltage gated K+ channels |
The rising phase of the action potential ends when the positive feedback loop is interrupted. What two processes break the loop?
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1. voltage-sensitive gatd
2. time-sensitive inactivation gate |
What are the names of the two gates on the voltage-gated sodium channels?
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When the cell is depolarized
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When does the voltage-sensitive gate open?
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it stops the movement of Na+ through the channel after the channel has been open for a fixed time.
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What is the function of the time-sensitive inactivation gate?
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They begin to inactivate the inward flow of Na+ decreases, and positive feedback loops are interupted.
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What happens to the voltage gated sodium channels at the peak of the action potential?
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when action potential reaches it peak
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When do the voltage-gated potassium channels open?
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depolarization ends and positive feedback loop is interupted.
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What happens when the voltage-gated potassium channels open and the potassium moves out of the cell?
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When Na+ moving into the and more K+ moving out of the cell.
Membrane pot. becomes more -, moving toward the resting value. |
When does repolarization occur? What happens to the membrane potential?
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hyperpolarization
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Process by which the membrane potential of a cell changes to become more - than its resting membrane potential.
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Because K+ keeps moving out of the cell, making it -.
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Why does hyperpolarization occur?
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B. During the rising phase of the action potential
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During the action potential, when does sodium permeability increase rapidly?
a. during repolarization b. during the rising phase of the action potential c. during hyperpolarization d. during repolarization |
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A. during repolarization
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During the action potential, when does sodium permeability decrease rapidly?
a. during repolarization b. during the rising phase of the action potential c. during hyperpolarization d. during repolarization |
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a. during repolarization
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During the action potential, when is potassium permeability the greatest?
a. during repolarization b. during the rising phase of the action potential c. during hyperpolarization d. during repolarization |
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C. during hyperpolarization
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During the action potential, when does potassium permeability decrease slowly?
a. during repolarization b. during the rising phase of the action potential c. during hyperpolarization d. during repolarization |
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C. the rising phase of the action potential
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The rapid increase in sodium permeability is responsible for _____.
a. the repolarization of the cell b. the hyperpolarization c. the rising phase of the action potential |
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A. the repolarization of the cell
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The rapid decrease in sodium permeability and simultaneous increase in potassium permeability is responsible for _____.
a. the repolarization of the cell b. the hyperpolarization c. the rising phase of the action potential |
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B. The hyperpolarization
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The slow decline in potassium permeability is responsible for _____.
a. the repolarization of the cell b. the hyperpolarization c. the rising phase of the action potential |
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absolute refractory period
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The period of time following an action potential when an excitable cell cannot generate another action potential no matter how large a stimulus it receives.
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Because Na+ can't move in through inactive channels & because K+ continues to move through open voltage gated channels.
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Why can't a neuron generate another action potential during the absolute refractory period?
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relative refractory period
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The period of time following an action potential when an excitable cell can generate another action potential only if it receives a stimulus stronger than normal.
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It is more difficult because it has to be depolarized to a value more positive than normal threshold.
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Why is it more difficult for a neuron to generate another action potential during the relative refractory period?
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1. the diameter of the axon
2. How well the axon is insulated w/myelin. |
What two factors does conduction velocity depend on?
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As the axon diameter increases, the internal resistance to the flow of charge decreases
The potential travels faster. |
What is the effect of axon diameter on conduction velocity?
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It makes the action potential travel faster down the axon.
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What is the effect of myelin on conduction velocity?
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More speed is gained by insulating an axon w/myelin than by increasing the axon diameter.
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Why do myelinated axons conduct action potentials faster than non myelinated axons?
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it is propogated down the axon
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What happens after an action potential is generated at the axon hillock?
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+ charges flow along axon
depolarizing adjacent areas of membrane reaches the threshold generate an action potential (which moves along the axon as a wave of depolarization traveling away from the cell body.) |
How is an action potential propagated down the axon?
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conduction velocity
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The speed with which an action potential is propagated along an axon.
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