Question 1

Which type of gated channel is primarily responsible for initiating an action potential in a neuron?

Accepted Answer

Voltage-gated channel

Question 2

A graded potential is recorded at the site of a stimulus and at the axon hillock. The magnitude of the potential is smaller at the axon hillock. What property of graded potentials does this illustrate?

Accepted Answer

Decremental conduction

Question 3

During which phase of the action potential are voltage-gated sodium channels inactivated and incapable of opening, regardless of the stimulus strength?

Accepted Answer

Absolute refractory period

Question 4

If a neuron receives two subthreshold stimuli in rapid succession at the same location, which process may allow the neuron to reach threshold and fire an action potential?

Accepted Answer

Temporal summation

Question 5

Which of the following best describes the 'all-or-none' principle of action potentials?

Accepted Answer

Once threshold is reached, an action potential of fixed size is generated.

Question 6

A patient has a genetic mutation that causes their myelin sheaths to degrade. Which of the following is most likely to occur as a result?

Accepted Answer

Saltatory conduction will be impaired, slowing neural transmission.

Question 7

Which equation best represents the change in membrane potential during depolarization?

Accepted Answer

$$\Delta V_m = V_{final} - V_{rest}$$, where $$V_{final} \u003e V_{rest}$$

Question 8

Which of the following is a key difference between graded potentials and action potentials?

Accepted Answer

Graded potentials can sum, while action potentials cannot.

Question 9

A neuron is exposed to a chemical that keeps sodium channels open longer than normal. What effect would this have on the action potential?

Accepted Answer

The action potential would have a prolonged depolarization phase.

Question 10

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

Accepted Answer

The absolute refractory period prevents backward propagation.

Question 11

If the diameter of an axon increases, what is the expected effect on the speed of action potential propagation, and why?

Accepted Answer

Speed increases due to decreased resistance.

Question 12

Which of the following scenarios would most likely result in hyperpolarization of a neuron?

Accepted Answer

Opening of ligand-gated potassium channels

Question 13

A neuron receives two simultaneous stimuli at different locations on its dendrites. What is this process called?

Accepted Answer

Spatial summation

Question 14

During the after-hyperpolarization phase of an action potential, which ion movement is primarily responsible for the membrane potential becoming more negative than the resting potential?

Accepted Answer

Efflux of potassium ions

Question 15

Which of the following best describes saltatory conduction?

Accepted Answer

Action potentials jump from one node of Ranvier to the next.

Question 16

A neuron is exposed to a toxin that blocks voltage-gated potassium channels. What is the most likely effect on the action potential?

Accepted Answer

Repolarization will be delayed.

Question 17

Which of the following is true regarding the refractory periods of a neuron?

Accepted Answer

During the relative refractory period, a second action potential can be generated with a stronger stimulus.

Question 18

Which of the following best explains why graded potentials are important for neural communication?

Accepted Answer

They determine whether the threshold for an action potential is reached.

Question 19

A neuron is at rest with a membrane potential of $$-70\ \mathrm{mV}. If a $$stimulus causes the membrane potential to reach $$-55\ \mathrm{mV}$$, what will most likely occur?

Accepted Answer

An action potential will be triggered.

Question 20

Which of the following best describes the role of the inactivation gate of the voltage-gated sodium channel during an action potential?

Accepted Answer

It closes during depolarization, stopping sodium influx.

Electrical Signals in Neurons: Graded and Action Potentials

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