Systole and Diastole – Cardiac Cycle

The cardiac cycle. Here in the cardiac cycle, we need to break it down into its two most basic forms – that is systole and diastole. So, in terms of systole, what really are we talking about? We’re talking about what's occurring with ventricular contraction. So, contraction is one of the biggest components of systole. Interestingly, though, also, is the ejection of blood comes along with contraction. So, the majority of the time, during the ejection phase of the blood, there will be within systole. However, a little bit of it translates over into diastole. There is a relaxation phase that transitions between systole and diastole. So, what do I mean by relaxation? It is the muscles themselves – cardiac muscle – that is relaxing. So, it's interesting to think about, even when the muscle is relaxing a little bit, you still could be in systole, i.e. pushing blood out because blood being pushed out of the left ventricle is simply a matter of the pressure differential. The other times in which you are in diastole are during the filling phases. And you notice we have some numbers attached to things like ejection and filling. That is because there's a rapid and a reduced ejection and a rapid and a reduced filling. So, all of those kind of items come out when we look at the cardiac cycle. ...