Now, as soon as our sodium ions rush inside the cell, they will reverse the polarity of the cell. And this is known as the depolarization period. So that basically means because we have positively charged sodium ions flowing into the cell, that will make the inside of the cell momentarily positive and the outside of the cell will become momentarily negative in the region where the stimulus is applied. So that is shown in the following diagram, the sodium channels open up and our sodium ions move into the cell, as shown. And that will cause the inside of the cell membrane to become positively charged and the outside to become negatively charged. Now, notice, the adjacent region of the cell membrane still contains a negative charge on the inside and the positive charge on the outside.