00:08
So, let’s start by following the
heart through its contraction phase.
00:14
What you see here on the
next three slides show
the entire cycle that results in contraction
and relaxation and filling of the heart.
00:25
What we see here in numbers
1, 2, 3, 4 and 5
is we see atrial systole on the
right atrium and the left atrium,
the tricuspid and
mitral valves open,
blood flows into the ventricles, and you
can see the ventricle swelling and filling.
00:46
What you see now in
number 6 through 10
is the ventricles
begin to contract,
the thin walled right ventricle and
the thicker walled left ventricle.
00:57
tricuspid and
mitral valves close,
and the pulmonary valve and the aortic
valve open as the two ventricles contract.
01:07
And then in the final sequence,
they begin to relax again
and the tricuspidand
mitral valves open
as blood flows into the
ventricles to start another cycle.
01:21
And here, we see in this
little motion diagram,
the heart contracting.
01:27
You can see a little green pattern,
that’s the electrical wave,
passing down,
starting at the right atrium,
passing to the left atrium,
down through the ventricular septum
and out into the
ventricular walls.
01:41
Can you see that the mitral and tricuspid
valves open during diastole and then close
and then the pulmonary
and aortic valve are open
during systole when the
ventricles contract?
Let’s talk a little bit
about ventricular systole.
02:00
Ventricular systole is
particularly important
because that is, in fact,
the pumping time of the heart.
02:08
Ventricular systole
lasts for 0.3 seconds,
every beat is the
same 0.3 seconds.
02:15
So, you can see that when
the heart rate accelerates,
in each minute there becomes
less time for diastole.
02:22
The ideal balance between
systole and diastole occurs
generally between heart
rates of 60 to 90 per minute.
02:30
As we start to get above
heart rates over a 100,
we have the problem
that diastole is
progressively shortened,
particularly at heart rates of 130, 140,
150 and unless you are a trained athlete,
you may not fill the
ventricles adequately
and cardiac output- that is the pumping
ability of the heart per minute,
may actually go
down a little bit.
02:54
The same thing happens with
very, very slow heart rates.
02:57
The ventricles can
only fill so much
and therefore,
you need a sufficient number of systoles
during a minute to produce a good
blood flow and a good blood pressure.
03:10
Here we see, actually,
the start of ventricular systole on
the right side with the blue blood
and on the left side with
the oxygenated red blood.
03:20
You can see that the
right ventricular wall
is much thinner than the
left ventricular wall
because it’s doing
mostly volume work.
03:29
It’s pumping volumes of blood
to the pulmonary
artery at low pressure
while on the left side,
the piston like left ventricle is
pumping the same volume of blood,
but at a high pressure in order to get
the blood to profuse throughout the body.