Deck 5: Generation and Conduction of Action Potentials

Question 1

The length constant of an unmyelinated axon increases as the diameter of the axon increases.This is primarily a result of:

A)Increasing membrane capacitance.
B)Decreasing membrane capacitance.
C)Increasing membrane resistance.
D)Decreasing membrane resistance.
E)Decreasing axoplasmic resistance.

Answer 1

E

Question 2

Which of the following events is common to all types of sensory receptors?

A)The generation of a receptor potential.
B)The generation of an action potential.
C)The binding of a stimulus to a receptor.
D)The binding of a stimulus to a membrane channel.
E)Membrane depolarization.

Answer 2

A

Question 3

The axon membrane responds to an intracellular injection of a subthreshold positive current with:

A)Transient depolarization only in the region where the current is injected.
B)Maintained depolarization until negative current is injected.
C)Maximal depolarization locally and attenuated depolarization along the axon.
D)Immediately opening K⁺ channels to maintain resting potential.
E)Firing an action potential.

Answer 3

C

Question 4

Which of the following is not a true statement about the conduction of action potentials (APs)in axons?

A)The inward Na⁺ current of an AP generates an AP in the neighboring node of a myelinated axon.
B)All APs in a given axon typically are identical in magnitude and duration.
C)An action potential experimentally generated by a depolarization in the middle of an axon is conducted in only one direction from the site of initiation.
D)The velocity of AP conduction is positively correlated with axon diameter.
E)The frequency of APs is limited by the length of the refractory period.

Question 5

At the threshold for generating an action potential:

A)The membrane is at the K⁺ equilibrium potential.
B)The conductances for Na⁺ and K⁺ are equal.
C)There is a rapid opening of voltage-gated Na⁺ channels.
D)K⁺ conductance is maximal.
E)The transmembrane voltage is zero.

Question 6

The afterhyperpolarization that follows the action potential:

A)Results primarily from to the inactivation of voltage-gated Na⁺ channels.
B)Makes it easier to trigger another action potential.
C)Is the main cause of the relative refractory period.
D)Makes it impossible to fire another action potential.
E)Is the consequence of continuing K⁺ influx.

Question 7

Which of the following stimulus parameters is not encoded in the pattern of action potentials in a sensory axon?

A)Threshold
B)Frequency
C)Modality
D)Duration
E)Intensity

Question 8

Myelination increases AP conduction velocity by:

A)Increasing the axonal diameter.
B)Increasing membrane capacitance.
C)Limiting voltage-gated K⁺ channels to the nodes.
D)Decreasing the membrane resistance.
E)Increasing the length constant and decreasing the membrane capacitance between the nodes.

Question 9

Which of the following statements about a compound action potential recording is not true?

A)Each peak represents a group of axons of similar conduction velocity.
B)Each peak represents a group of axons of similar diameter.
C)The magnitude of each peak reflects the number of axons in that category.
D)The magnitude of a peak is negatively correlated with axonal conduction velocity.
E)The profiles of peaks are characteristic of and different for different peripheral nerves.

Question 10

Which of the following is responsible for the repolarization of the membrane after the peak of the action potential?

A)The membrane potential reaches the Na⁺ equilibrium potential.
B)The voltage-gated Na⁺ channels begin to inactivate.
C)The slowly opening voltage-gated K⁺ channels allow K⁺ to enter.
D)The influx of Na⁺ and the outflow of K⁺ are equal.
E)There is no longer a gradient to drive K⁺ out of the cell.