Final answer:
The movement of positive ions outside the membrane after depolarization to return the cell to its resting state is known as repolarization; it involves closing sodium channels and opening potassium channels to restore the resting membrane potential.
Step-by-step explanation:
The movement of positive ions outside of the membrane after depolarization in order for the cell to return to its resting state is known as repolarization.
During an action potential, depolarization occurs when the membrane potential moves toward zero as sodium ions (Na+) rush into the cell due to a higher concentration outside compared to the inside. This makes the inside of the cell less negative relative to the outside. Repolarization follows depolarization, and it is the process by which the cell returns to its resting state; the membrane potential moves back toward the -70 mV value of the resting membrane potential.
This happens as potassium ions (K+) move out of the cell, taking positive charges with them, and voltage-gated sodium channels close. The Na+/K+ pump helps maintain the gradient by moving Na+ back out of the cell and K+ into the cell. The continuous leakage of K+ out of the cell leaves behind a negative charge, thus ensuring that the cell can depolarize again in the future. Hence, repolarization is essential for restoring the resting membrane potential and allows the neuron or muscle cell to be ready for the next action potential.