Question 1

Which of the following best explains why action potentials only propagate in one direction along an axon?

Accepted Answer

The inactivation gates of voltage-gated Na+ channels close in the segment that just fired, creating a refractory period.

Question 2

A patient is exposed to a neurotoxin that blocks voltage-gated Na+ channels. What is the most likely effect on neuronal function?

Accepted Answer

The neuron will only be capable of producing graded potentials.

Question 3

Which of the following events occurs first during the generation of an action potential in response to a threshold stimulus?

Accepted Answer

Voltage-gated Na+ channels change shape and their activation gates open.

Question 4

If the permeability of a resting axon to sodium ions increases, what will be the immediate effect on the membrane potential?

Accepted Answer

The membrane will depolarize as Na+ moves inward.

Question 5

Which of the following best describes the effect of multiple sclerosis (MS) on action potential propagation?

Accepted Answer

MS destroys myelin, decreasing internode membrane resistance and preventing local currents from reaching adjacent nodes.

Question 6

Which equation best represents the electrochemical gradient for an ion across a membrane?

Accepted Answer

$$E = E_{chemical} + E_{electrical}$$

Question 7

A neuron is exposed to a drug that prevents the closing of voltage-gated Na+ channels. What would be the effect on the absolute refractory period?

Accepted Answer

It would last indefinitely.

Question 8

Which of the following is true regarding the resting membrane potential ($$RMP) of a $$typical neuron?

Accepted Answer

The $$RMP is $$maintained by the Na+-K+ ATPase and leak channels.

Question 9

Which of the following best describes saltatory conduction?

Accepted Answer

Action potentials 'jump' from node to node along a myelinated axon.

Question 10

A neuron receives two excitatory postsynaptic potentials (EPSPs) in rapid succession at the same synapse. What is this phenomenon called?

Accepted Answer

Temporal summation

Question 11

Which of the following is the correct sequence of events at a cholinergic synapse?

Accepted Answer

Action potential arrives, Ca2+ enters, acetylcholine released, acetylcholine binds to receptors, chemically-gated Na+ channels open

Question 12

Which of the following factors does NOT influence the speed of nerve impulse transmission?

Accepted Answer

Whether or not the impulse begins in the CNS

Question 13

During the repolarization phase of an action potential, which of the following occurs?

Accepted Answer

Voltage-gated K+ channels open, allowing K+ to move out of the cell.

Question 14

Which of the following best describes the effect of opening chemically-gated Cl- channels on the postsynaptic membrane?

Accepted Answer

It causes hyperpolarization and decreases the likelihood of an action potential.

Question 15

Which of the following is true regarding the propagation of action potentials in unmyelinated axons?

Accepted Answer

Action potentials are regenerated at every segment of the axon.

Question 16

Which of the following best explains why the resting membrane potential is typically -70 mV?

Accepted Answer

The inside surface of the plasma membrane is much more negatively charged than the outside surface.

Question 17

Which of the following is the main ion responsible for depolarizing the membrane during an action potential?

Accepted Answer

Sodium (Na+)

Question 18

A postsynaptic neuron will have an excitatory postsynaptic potential (EPSP) when:

Accepted Answer

Chemically regulated sodium channels are open and sodium is diffusing into the cell.

Question 19

Which of the following best describes the role of the Na+-K+ ATPase in neurons?

Accepted Answer

It actively transports Na+ out and K+ into the cell, maintaining their gradients.

Question 20

Which of the following types of nerve fibers possesses the fastest speed of impulse propagation?

Accepted Answer

Type A fibers

Neurophysiology Study Guide – Action Potentials, Synaptic Transmission, and Nerve Fiber Properties

Study Guide - Practice Questions