 Now, all of these little pieces, AB nodes, SA nodes, auto-rhythmic cells, contractile cells, who cares, potassium, calcium, what? Nobody cares unless we put it into context of an actual heart beat. And I think it's important at this point to tie up today's lecture just a little preview of the cardiac cycle because otherwise these details can float in the middle of pointless detail land, and they're way too important. We can't have them floating in pointless detail land. So look at this picture. This is from your textbook. A complete cardiac cycle is the series of events that result in blood being pumped from the atria into the ventricles and from the ventricles out to the body or the lungs and back into the atria again. We have a complete pathway. And what I want you to remember is that, yes, the message is going to begin. We're going to break this down in detail next time, but the message is going to begin. Oh, oh, it doesn't show up. Okay, let's do black. There's my SA node. Here's my AV node. The message is traveling out. At each point of this process, we're going to have different events that are stimulated by my electrical conduction system. So the fact that we can pump blood, you have to keep in mind that it's happening because the electrical conduction system is sending the messages. The auto-rhythmic cells are sending the messages saying, hey, dude, let's contract. The other thing we're going to look at in detail next time is this bad boy. This is the ECG or the EKG. And that, take a deep breath because that is a sum of all the action potentials that are happening in the heart during a single cardiac cycle. So there's pressure issues. There's volume issues. There's heart sounds. Where do, why are you loving and dubbing? It's because your valves are flipping and flapping. And all of that is happening thanks to our auto-rhythmic cells, which set the tone and make it happen and the contractile cells that follow the instructions that they receive. How are you? Make sure that you are totally comfortable with today's content before moving on, before going to class for the next topic because we definitely are building. So next time, this is where we're headed in great detail. All right. See you next time, doggies.