Let's suppose the stimulus basically reaches the threshold potential of around negative 70 millivolts. If this takes place, then we have the opening of our sodium voltage gated channels down on the cell membrane. So these voltage gated sodium channels are known as time dependent channels. And what time dependent means is they only open for a very small fraction of a second and they close immediately afterwards. So as soon as our threshold potential is reached, all these sodium voltage gated channels open up very quickly. And because they open up so quickly, we have the movement of the sodium channels from the outside of the sodium ions from the outside to the inside, down their electrochemical gradient.