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.