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Glossary of 3 - Nervous System 1: Action Potential

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Which part of the graph to the right corresponds to the following:
hyperpolarization
depolarization
rest
initiation of repolarization
repolarization
E - hyperpolarization
B - depolarization
A - rest
C - initiation of repolarization
D - repolarization

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
D

Which part of the graph to the right corresponds to:

A time when voltage-gated sodium and potassium channels are closed.
A

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.
C

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.
B

Which phase of the action potential does the diagram below best correspond to?
a. rest
b. depolarization
c. peak
d. repolarization
e. hyperpolarization
A. rest

Which phase of the action potential does the diagram below best correspond to?
a. rest
b. depolarization
c. peak
d. repolarization
e. hyperpolarization
A. rest

Which phase of the action potential does the diagram below best correspond to?
a. rest
b. depolarization
c. peak
d. repolarization
e. hyperpolarization
C. Peak

Which phase of the action potential does the diagram below best correspond to?
a. rest
b. depolarization
c. peak
d. repolarization
e. hyperpolarization
D. repolarization

Which phase of the action potential does the diagram below best correspond to?
a. rest
b. depolarization
c. peak
d. repolarization
e. hyperpolarization
E. hyperpolarization

What letter on this graph to the right corresponds to the absolute refractory period?
B

What letter on this graph to the right corresponds to the relative refractory period?
C
nerve impulse
What is another name for an action potential?
A large membrane potential change
What does an action potential consist of?
axon hillock
Where is the action potential generated?
when it receives signals from dendrites & the cell body.
What causes an axon potential to occur at the axon hillock?
They open rapidly to increase permeability to Na+
What happens to ion channels when the membrane depolarizes at the axon hillock?
15 mV
How much does the axon hillock have to depolarize to reach threshold?
threshold
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.
the action potential is NOT produced.
What happens if there is a weak stimulus at the axon hillock and threshold is not reached?
yes
Do action potentials always have the same amplitude and the same duration?
This means a positive feedback loop is established.
Threshold is a special membrane potential where the process of depolarization becomes regenerative. What does this mean?
It opens more Na+ voltage-gated channels
What happens to sodium voltage-gated channels at threshold?
The more Na+ flow into the cell causes the cell to depolarize further and open more Na+ voltage-gated channels.
Explain how the positive feedback loop maintains the rising phase of the action potential.
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?
1. voltage-sensitive gatd
2. time-sensitive inactivation gate
What are the names of the two gates on the voltage-gated sodium channels?
When the cell is depolarized
When does the voltage-sensitive gate open?
it stops the movement of Na+ through the channel after the channel has been open for a fixed time.
What is the function of the time-sensitive inactivation gate?
They begin to inactivate the inward flow of Na+ decreases, and positive feedback loops are interupted.
What happens to the voltage gated sodium channels at the peak of the action potential?
when action potential reaches it peak
When do the voltage-gated potassium channels open?
depolarization ends and positive feedback loop is interupted.
What happens when the voltage-gated potassium channels open and the potassium moves out of the cell?
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?
hyperpolarization
Process by which the membrane potential of a cell changes to become more - than its resting membrane potential.
Because K+ keeps moving out of the cell, making it -.
Why does hyperpolarization occur?
B. During the rising phase of the action potential
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
A. during repolarization
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
C. during hyperpolarization
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
C. the rising phase of the action potential
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
A. the repolarization of the cell
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
B. The hyperpolarization
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
absolute refractory period
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.
Because Na+ can't move in through inactive channels & because K+ continues to move through open voltage gated channels.
Why can't a neuron generate another action potential during the absolute refractory period?
relative refractory period
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.
It is more difficult because it has to be depolarized to a value more positive than normal threshold.
Why is it more difficult for a neuron to generate another action potential during the relative refractory period?
1. the diameter of the axon
2. How well the axon is insulated w/myelin.
What two factors does conduction velocity depend on?
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?
It makes the action potential travel faster down the axon.
What is the effect of myelin on conduction velocity?
More speed is gained by insulating an axon w/myelin than by increasing the axon diameter.
Why do myelinated axons conduct action potentials faster than non myelinated axons?
it is propogated down the axon
What happens after an action potential is generated at the axon hillock?
+ 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?
conduction velocity
The speed with which an action potential is propagated along an axon.

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