Question

During a nerve action potential, a stimulus is delivered as indicated by the arrow shown in the following figure. In response to the stimulus, a second action potential will ________.

1) occur with a smaller magnitude
2) occur with a normal magnitude
3) occur with a normal magnitude, but will be delayed
4) occur, but will not have an overshoot
5) not occur

Answer 1

A second action potential will occur with a normal magnitude if the threshold is reached and it is not in the refractory period.

Step-by-step explanation:

During a nerve action potential, if the depolarization threshold is reached, an action potential will occur with the same magnitude every time, regardless of the strength of the stimulus. This is due to the fact that action potentials are all or none events. Since all action potentials peak at the same voltage (+30 mV), a second action potential, in response to a stimulus, will occur with a normal magnitude. However, if an action potential is already in progress, another one cannot be initiated due to what is known as the refractory period, which is divided into absolute and relative phases. During the absolute refractory period, no new action potential can begin, while in the relative refractory period, a new action potential can only start with a stronger stimulus.