Now, when the signal arrives at the AV node, the AV node, what it does is it delays that signal by about zero of a second. And what that does is it gives the atria enough time to fully contract and move all that blood into the fully relaxed ventricles. So we see along our P waves, our atria begins to contract at the tip while the ventricles are actually fully relaxed. Now let's move on to our PR segment. This PR segment basically has no voltage difference. We have a zero voltage difference.