 The last stage is ventricular diastole. Now our ventricles are going to relax. The muscle itself has finished its contraction, and now we're going to repolarize and relax. Now in our EKG, think about it, ventricular repolarization is an electrical event. There are charges moving. And we have potassium particles leaving, which brings the membrane potential back down to a negative place. That is an electrical thing that's going on. You don't think of it as being electrical because you think of the contraction as being a bigger electrical thing, but the relaxation is actually just the opposite. And so you can see the T-wave is associated with ventricular repolarization. Remember, the P-wave was atrial depolarization. So when the atria begin to contract, that's associated with the P-wave. QRS is ventricular depolarization. In this space right here, we actually are having atrial repolarization. The atria are repolarizing, but you can't really see it because it gets lost in the giant ventricular depolarization. And then our ventricles repolarize, and that's the T-wave. That's what's happening right now. This is another moment where all of a sudden, guess who? We've pushed out the blood. The ventricles start to relax. What's the blood going to want to do? Dude, the blood is going to rush back into the ventricles. There's a low pressure space in there. Everybody's relaxing. That's awesome. Let's go in there. They accept the semi-lunar valves now do their thing, and they say, uh-uh, you're not going back in, my friend. You have to keep going in the direction that we sent you. The snapping of the semi-lunar valves during this moment of relaxation, this is the dup of the heartbeat. Lub, it-lub is AV valve. Dup is semi-lunar valve snapping together. And when you look at the anatomy of a valve, like that's just not possible. That snapping together can create the sound that we hear. It's incredible. Okay, so all your valves, notice this. Everything is closed. All the valves are, we're not going to change volume right now. However, our ventricles are relaxing, and we're almost back to where we started, where the ventricles, as they relax, the pressure in there decreases, and we have more room for blood from the body to come in. And so that you relax and make space for that blood, and this whole thing just keeps us going. Yeah, yeah, yeah, yeah, yeah. Dude, how awesome is that? All right, so there are a couple of numbers to describe the blood that is being pumped during the cardiac cycle, and that's what we're going to talk about next.