Now, at this point, our permeability of the membrane to potassium is actually higher than normal. And this is exactly what causes our voltage of the cell to drop below the resting voltage in this period, when our voltage of the membrane drops slightly below the resting membrane potential. This is known as the hyperpolarization period. Now, to return the neuron to return the membrane of the neuron back to the resting membrane potential, which is equal to about negative 70 millivolts. Now, we have to use energy, we have to use ATP, and we have to use a special type of pump, a special type of ATPase pump ATPase pump known as the sodium potential or the potassium sodium ATPase pump. And what the potassium sodium ATPase pump does is it actively pumps three sodiums out of the cell, so against electrochemical gradient and two potassium into the cell against the electrochemical gradient.