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Diastole (relaxation of the heart):

Atrioventricular Valves: between the left atrium and
ventricle
...
Closure of these valves ensures that, when the ventricles contract , blood within
them moves to the aorta and pulmonary artery rather
than back to the atria
...
As the
atria fill, the pressure in them rises
...
The passage of blood is aided by gravity
...


Semi-Lunar valves: in the aorta and pulmonary artery
...
This arises when the elastic walls of the vessels recoil increasing the pressure within them and
when the ventricle walls relax reducing the pressure
within the ventricles
...
This causes
the pressure to be lower than that in the aorta and the pulmonary artery, and so the semi-lunar valves in the aorta
and the pulmonary artery close, accompanied by the characteristic ‘dub’ sound of the heart
...
Throughout this stage the muscle of the ventricle walls remains relaxed
...
These ensure that when veins are
squeezed, blood flows back towards the heart rather
than away from it
...
When pressure is greater on the
Blood is kept flowing through one direction of the convex side, they move apart to let blood pass between
Ventricular Systole (contraction of the ventricles):
heart and around the body by the pressure created the cusps
...
Blood will always move from collects within the ‘bowl’ of the cusps, pushing them
After a short delay to allow the ventricles to fill with blood,
together to form a tight fit that prevents the passage of
their walls contract simultaneously
...

pressure within them, forcing the atrioventricular valves shut Valves are designed so that they open whenever blood
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With these the difference in blood pressure either side of
closed, the pressure in the ventricles rises further
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When pressure differences are refrom the ventricles into these vessels
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Left
close
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Valves in the control of blood flow:

Pressure and volume changes of the heart:

The Cardiac Cycle

Because blood is confined to vessels, the pressure within
them can be maintained and regulated
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These are related to the waves of electrical activity
created by the sinoatrial node and the hearts response to these
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Cardiac Output:

This is the volume of blood pumped by one ventricle of the
heart in one minute
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Cardiac Output = heart rate x stroke volume



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