Potassium absorption and sodium excretion are processes that belong to the process of active cellular restoration of resting potential in the late phase of the action potential, which belongs to the process of primary active operation. Primary active operation is the process of running ions against a concentration gradient or potential gradient. Normally, in the resting state, the concentration of sodium ions outside the cell membrane is greater than that inside the membrane, so there is a tendency for sodium ions to diffuse into the membrane. At the action potential, when the cell is stimulated, the permeability of the cell membrane to sodium ions suddenly increases and exceeds that to potassium ions, resulting in a large inward flow of sodium ions and the formation of the rising branch of the action potential; At the falling branch of the action potential, because the sodium channel opening time is very short, it quickly enters the inactivation state, thus the membrane permeability to sodium ions becomes smaller. After the action potential, a large number of sodium ions inward flow, so the cell to return to the resting state, we need to rely on the primary active operation of the physiological sodium and potassium pump, the action potential into the cell during the sodium ion transfer to the outside of the cell, at the same time will be outflow of potassium ions into the cell, so as to make the membrane inside and outside of the distribution of ions back to the original resting level, the process is required to consume energy.