 This is Carl Wager. And Carl was one of our dead white guys who is definitely considered a father of physiology. In fact, I went and looked him up because I was curious, like, what's Carl's scoop? And I found this article about his life as a young man in search of excellence. Apparently he played a huge role in understanding pulmonary circulation. Fantastic. You can understand that the heart and all the pressures and the volumes and how everything fits together in this beautiful diagram that we're going to look at in a second, which hopefully you do appreciate its loveliness. He took all of that information and integrated it together, and that is why the Wiggers diagram gets to have his name on it. So let's look at the Wiggers diagram. It's a diagram that if you don't unpack it, you might have crossing eyes and want to cry. What I'm going to tell you is that if you understand the cardiac cycle, unpacking the Wiggers diagram isn't crazy. Like, it really isn't crazy if you understand how the heart beats and what happens to blood as we go. And that's actually something that you should have in your back pocket from anatomy. So you can see that, yes, we're going to look at pressures here, pressures in the atria, pressures in the ventricles. I included a copy of this diagram, which also came from the OpenStacks textbook. I included it in your lecture notes so that you can draw on this thing as you would like. And I'm going to bring another copy to lecture so that you can have another view of it that puts your pieces together. You might want to combine this visual with this one. So as we work through the Wiggers diagram and we unpack all these layers and put together like the whole big picture, be sure you're keeping in mind the actual events in the heart muscle itself, the atria and the ventricles, what's actually happening. Okay, so we're going to start this whole thing. I've been all over the place. Do I start with, I mean, I've literally thought of a million different ways of organizing this lecture. And I have decided to organize it by event. I could organize it by, you know, we'll talk about everything that happens during systole. We'll talk about everything that happens during diastole. And I've decided not to go that route. I've decided to look at all. We're going to start out with the electrical events. We're going to look at the whole cardiac cycle. What's happening with the electrical events? Because that really starts the whole process. The electrical activity of the heart is measured in this electrocardiogram line of Wiggers diagram. And we're going to break that out and look at it more closely.