repolarization - this happens when potassium ion channel opens up and the action potential ends. This is called the repolarization.

Resting potential is the difference in electrical charge across the plasma membrane of a neuron that is not actively transmitting a nerve impulse

Sodium-potassium pump is the active transport mechanism in which sodium ions are pumped out of a cell and potassium ions are pumped into the cell with the help of a carrier protein and energy from ATP

Thus, ATP is the higher energy form (the recharged battery) while ADP is the lower energy form (the used battery). Think of it as the “energy currency” of the cell. If a cell needs to spend energy to accomplish a task, the ATP molecule splits off one of its three phosphates, becoming ADP (Adenosine di-phosphate) + phosphate.

potential difference

nerve impulse - electrical signal transmitted by the nervous system