00:02
The cardiac cycle.
00:04
Here in the cardiac cycle,
we need to break it down into
its two most basic forms –
that is systole and diastole.
00:13
So, in terms of systole,
what really are we talking about?
We’re talking about
what's occurring with ventricular contraction.
00:20
So, contraction is one of the
biggest components of systole.
00:25
Interestingly, though, also, is
the ejection of blood
comes along with contraction.
00:31
So, the majority of the time,
during the ejection phase of the blood,
there will be within systole.
00:40
However, a little bit of it
translates over into diastole.
00:46
There is a relaxation phase that transitions
between systole and diastole.
00:52
So, what do I mean by relaxation?
It is the muscles themselves
– cardiac muscle –
that is relaxing.
01:00
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.
01:16
The other times in which you are in diastole
are during the filling phases.
01:21
And you notice
we have some numbers
attached to things like ejection and filling.
01:27
That is because
there's a rapid and a reduced ejection
and a rapid and a reduced filling.
01:35
So, all of those kind of items come out
when we look at the cardiac cycle.