Cardiac Cycle
                     CARDIAC CYCLE
WHAT IS CARDIAC 
CYCLE?
The cardiac cycle attributes to a 
comprehensive heartbeat from its 
production to the commencement of 
the next beat. It comprises diastole, 
the systole, and the intervening 
pause. 
Source: byjus.com
OCCURRENCE OF A 
CARDIAC CYCLE 
The occurrence of a cardiac cycle is 
illustrated by a heart rate, which is 
naturally indicated as beats per 
minute. A healthy human heart beats 
72 times per minute which states 
that there are 72 cardiac cycles per 
minute.
Source: byjus.com
CARDIAC CYCLE 
PHYSIOLOGY
The human heart consists of four 
chambers, comprising left and right 
halves. Two upper chambers include 
left and right atria; lower two 
chambers include right and left 
ventricles. 
Source: byjus.com
KEY FUNCTION 
The key function of the right ventricle 
is to pump deoxygenated blood 
through the pulmonary arteries and 
pulmonary trunk to the lungs. While 
the left ventricle is responsible for 
pumping newly oxygenated blood to 
the body through the aorta.
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ATRIAL DIASTOLE
In this stage, chambers of the heart 
are calmed. That is when the aortic 
valve and pulmonary artery closes 
and atrioventricular valves open, 
thus causing chambers of the heart 
to relax.
Source: byjus.com
ISOVOLUMIC 
CONTRACTION
At this stage, ventricles begin to 
contract. The atrioventricular valves, 
valve, and pulmonary artery valves 
close, but there won’t be any 
transformation in volume.
Source: byjus.com
ISOVOLUMIC RELAXATION
In this phase, no blood enters the 
ventricles and consequently, 
pressure decreases, ventricles stop 
contracting and begin to relax. Now 
due to the pressure in the aorta – 
pulmonary artery and aortic valve 
close.
Source: byjus.com
VENTRICULAR FILLING 
STAGE
In this stage, blood flows from atria 
into the ventricles. It is altogether 
known as one stage (first and second 
stage). After that, they are three 
phases that involve the flow of blood 
to the pulmonary artery from 
ventricles.
Source: byjus.com
DURATION OF CARDIAC 
CYCLE
Atrial systole: continues for about 0.1 
seconds
Ventricular systole: continues for about 
0.3 seconds
Atrial diastole: continues for about 0.7 
seconds
Ventricular diastole: continues for 
about 0.5 seconds
Source: byjus.com
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