Now, we know that outside of the cell, we have a higher concentration of sodium ions than on the inside of the cell. So as soon as our stimulus reaches our threshold value, that will open up our sodium, our sodium voltage gated channels. And when they open up, this is known as our depolarization period. So what will begin to happen is the sodium ions will begin to move down their electrochemical gradient. So because they contain a positive charge and the inside is negatively charged, they will move this way from the outside to the inside. And because our concentration is high on the outside and low on the inside, they will move into our cell.