Final answer:
Potassium ions rapidly diffuse out of the cell after an action potential, restoring the cell's resting potential. Potassium channels open, allowing K+ to leave the cell, while sodium channels close. This repolarization process is part of the action potential cycle in neurons.
Step-by-step explanation:
Immediately after an action potential is propagated, potassium ions (K+) rapidly diffuse out of the cell into the tissue fluid. During the action potential, the membrane potential rises due to the influx of sodium ions (Na+), and once the peak is reached, the sodium channels close while the potassium channels open. This allows potassium to exit the cell, leading to repolarization, where the cell membrane potential returns to the resting level.
The proper function of the sodium-potassium pump is also crucial in maintaining the resting potential after action potentials. For every ATP consumed, this pump moves two potassium ions into the cell and removes three sodium ions, keeping the inside of the cell negatively charged compared to the outside. Chloride ions (Cl-), on the other hand, are typically found outside the cell and do not play a direct role during the repolarization phase of the action potential.