Question 1

Which ion is primarily responsible for the depolarization phase of an action potential in a neuron?

Accepted Answer

Sodium (Na$$^+) $$influx

Question 2

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

Accepted Answer

K$$^+$$ channels open and K$$^+$$ flows out

Question 3

What is the primary effect of opening voltage-gated sodium channels in the axon membrane?

Accepted Answer

The membrane potential moves toward zero (depolarization)

Question 4

Which of the following best describes the sequence of ion channel activity during an action potential?

Accepted Answer

Na$$^+$$ channels open first, then K$$^+$$ channels

Question 5

If a toxin blocked voltage-gated K$$^+$$ channels, what would most likely happen to the action potential?

Accepted Answer

The neuron would not repolarize efficiently

Question 6

Which graph best represents the change in membrane potential during the depolarization phase of an action potential?

Accepted Answer

An upward curve above resting potential

Question 7

What is the role of voltage-gated ion channels in the propagation of an action potential?

Accepted Answer

They allow for rapid changes in membrane potential by opening in response to voltage changes

Question 8

A neuron is exposed to a drug that keeps Na$$^+$$ channels open longer than normal. What is the most likely effect on the action potential?

Accepted Answer

The depolarization phase will be prolonged

Question 9

Which of the following best explains why the action potential is unidirectional along the axon?

Accepted Answer

The refractory period prevents backward propagation

Question 10

If the extracellular concentration of Na$$^+ is $$decreased, what would be the effect on the action potential amplitude?

Accepted Answer

The amplitude would decrease

Question 11

Which of the following equations best represents the Nernst equation for calculating the equilibrium potential for an ion?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$$

Question 12

A patient presents with a genetic mutation that causes voltage-gated Na$$^+$$ channels to inactivate more slowly. Which symptom would most likely be observed?

Accepted Answer

Prolonged depolarization and possible muscle spasms

Question 13

Which of the following best describes the resting membrane potential of a typical neuron?

Accepted Answer

$$-70 mV$$, with the inside of the cell negative relative to the outside

Question 14

Which process restores the original ion distribution after an action potential?

Accepted Answer

Active transport by the Na$$^+/K$^+$$ ATPase pump

Question 15

A neuron is unable to fire a second action potential immediately after the first. This is due to:

Accepted Answer

The absolute refractory period

Sketch #2

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