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The cardiac cycle - heart beat, One full cardiac cycle - one heart beat. -…
The cardiac cycle - heart beat
When the heart muscles are relaxed the heart is in diastole.
When the heart is in
diastole
, the atria at the top are relaxed and blood can flow into the atria freely from the
vena cavae
and the
pulmonary vein
. The
AV valves
prevent the blood from flowing into the
ventricle
.
The atria will not contract
(systole)
to force blood through the
AV valves
and into the
ventricles
.
The
atria
will then relax and go back into
diastole
and the
ventricles
contract to go into
systole
.
Contraction of the ventricles forces blood out of the heart and into the relevant artery.
The
ventricles
will
diastole
. The entire heart is relaxed.
The
atria
prepare for
systole
again.
No noise - everything is relaxed.
complete diastole
Dupp noise- made by movement of semi-lunar valves.
ventricle systole
Lubb noise
Atrial systole
When the ventricles are contracted the heart is in systole.
What causes this?
A message is sent from the cardiovascular centre in our brain - the medulla oblongata - to tell us to continue triggering our heart to contract.
To begin atrial systole, cells in the sinoatrial node (SA) creates an ACTION POTENTIAL. This ACTION POTENTIAL is pulled down through the nerves and into the sinoatrial node(SA). The surrounding cells depolorise and the atria contract.
This action potential moves through the heart.
Every so often the cardiovascular centre will send another ACTION POTENTIAL down.
Current moves down from the SA node to the AV node then from the AV node to the septum/ bundle of His then divides into left and right branches into something called purkinje fibres in the ventricular muscle.
This process triggers ventricular systole/ contraction.
Noise of heart
Lubb/ Dupp/ no noise / Lubb Dupp/ no noise / Lubb Dubb
One full cardiac cycle - one heart beat.