So our resting potential is about negative 90 millivolts. And let's suppose we have some type of stimulus that reaches the threshold voltage of about negative 70 millivolts. So what happens next? Our sodium voltage gated channels on the membrane are very quick to open and basically they allow for the rapid movement of the sodium ions inside the cell and that causes the inside of the cell to become positive. And that leads to our depolarization period. Now, when we reach about positive 30 millivolts, the sodium voltage gated channels close, while the potassium voltage gated channels begin to open.