MCAT Biology Question 48: Answer and Explanation

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Question: 48

3. Which of the following is true with regard to the action potential?

  • A. All hyperpolarized stimuli will be carried to the axon terminal without a decrease in size.
  • B. The size of the action potential is proportional to the size of the stimulus that produced it.
  • C. Increasing the intensity of the depolarization increases the size of the impulse.
  • D. Once an action potential is triggered, an impulse of a given magnitude and speed is produced.

Correct Answer: D

Explanation:

As in the previous question, the action potential is often described as an all-or-nothing response. This means that, whenever the threshold membrane potential is reached, an action potential with a consistent size and duration is produced. Neuronal information is coded by the frequency and number of action potentials, not the size of the action potential, eliminating choices (B) and (C) and making choice (D) the correct answer. Hyperpolarizing (inhibitory) signals are not transmitted to the nerve terminal, eliminating choice (A).

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