Question

Which of the following is FALSE in regards to the refractory period of an action potential?

A. The refractory period limits the number of action potentials that a neuron can produce during a certain period of time.
B. This period inhibits action potentials to flow back to sites that had recently been stimulated
C. The movement of potassium (K+) back to resting levels causes the refractory period.
D. The movement of sodium (Na+) back to resting levels causes the refractory period.
E. When the membrane potential is restored to about -60mV, the refractory period is over and the resting period is resumed.

Answer 1

The false statement regarding the refractory period of an action potential is that the movement of potassium (K+) back to resting levels causes the refractory period; instead, it is the inactivation of Na+ channels that primarily contributes to this period.

Step-by-step explanation:

The statement that is FALSE in regards to the refractory period of an action potential is: C. The movement of potassium (K+) back to resting levels causes the refractory period. During the refractory period, a neuron's membrane cannot generate another action potential, which ensures proper direction of nerve impulse propagation and maintains the polarity of the neuron.

The absolute refractory period is caused by the inactivation of voltage-gated Na+ channels, preventing any new action potential from starting. During the relative refractory period, a higher than normal stimulus is required to initiate an action potential due to the ongoing outflow of K+. Eventually, the sodium-potassium pump (Na+/K+ ATPase) restores the resting membrane potential by moving Na+ out of the cell and K+ back into it, signaling the end of the refractory period.

The fallacy in the statement C arises because it is not merely the movement of K+ back to resting levels that directly causes the refractory period; it is the inactivation of Na+ channels during the action potential that is primarily responsible for the absolute refractory period. Moreover, statement D is also misleading, as the movement of sodium (Na+) back to resting levels is facilitated by the Na+/K+ ATPase during the restoration of resting potential, not during the refractory period itself.