 Hello everybody. I have to tell you that it's a little bit of an accomplishment right now to be recording a video lecture and I also have to tell you that it's a double accomplishment because I'm recording a video lecture hopefully successfully and it isn't the middle of the night. This is amazing. So this might actually be a remotely coherent lecture that we're about to embark upon. In the last lecture we talked about the cardiovascular system from, we did heart anatomy and then we dove into the kinds of cells that make up the myocardium or the muscle of the heart itself. And we sort of looked at how those particular cells, there were two types of cells that we looked at and we examined how they function. We looked at the contractile cells which really make up the bulk of the heart muscle itself. 99% of your heart muscle is made of contractile cells and then there's this 1% which is the auto-rhythmic cells which are super cool and they generate their own action potentials and thereby initiate contraction of the cardiac muscle in a rhythmic way for forever without even having any neural input necessary at all. In this lecture we're going to take that information, we're going to take like all those little cellular details and we're going to sort of zoom out and look at the big picture. And I tend to be a small part to big part thinker but this big piece thinking part might actually be really helpful for you in understanding the small bits that we did in the last lecture. So we're going to start out by looking at the cardiac cycle as a whole and what qualities we look at when we talk about the cardiac cycle which is basically one heartbeat, all the events that take place in one heartbeat. We're going to link all those little processes, all those little mechanisms to big heartbeat function that you can hear, that you can feel and that we can appreciate never ever stops. And then we're going to break it down and we're going to look at the volume that we see different volumes. We're going to look at the electrical activity. We're going to look at heart sounds and then we're going to talk about some clinically relevant measurements that we can make using heart function. And then those of you in my face to face class, actually I'm not going to say that part because next semester it will be a different schedule. So how awesome is that? I just totally made this a reusable video. And it would have been super cool if I hadn't just said all that but that's just the way it goes. So let's start with the definition of the cardiac cycle and that will get us rolling.