Introduction to Cardiac Cycle
Hello and Welcome friends in our new blog of Cardiac Cycle.
So firstly we know that Cardiac Cycle is related to our Heart Function and How does the Heart play an important role in our body? let us understand.
What is Heart?
- Heart a visceral or important organ of our body who does its work restlessly without stopping, we can take it as a inspiration that doing your work without stopping or taking no rest as heart if it stops that means we are over life over.
- Heart does rythmic work during one full heartbeat , it is a stepwise process or pattern of rythmic contraction and relaxation of heart to flow the blood in body or the sequential event in the heart which is cyclically repeated known as cardiac cycle. The CARDIAC CYCLE is of total 0.8sec.
Function of Heart
It act as a pump ,insuring Oxygen-rich blood to the body to circulate and Deoxygenated blood(DOB) to lungs to make it again oxygenated blood(OB) ,without any interuption in Cardiac cycle.
The phases of Cardiac Cycle
There are two main phases SYSTOLE(contraction phase) and DIASTOLE(relaxation phase ) in CARDIAC CYCLE let’s elaborate one by one:
- Systole(contraction phase): In this phase the heart contracts, and pumps the blood out to the body or to the heart chambers (Atria and ventricle contraction simultaneously but a phase surprisingly when both atria and ventricle are relaxed ;known as JOINT DIASTOLE.
- Diastole(relaxation phase): In this phase the heart relaxes and fills the blood in atria and ventricle simultaneously. In simple way “simultaneously” means when atria relax then ventricle contracts and when ventricle relax then atria contracts.
Process of Cardiac Cycle
When the heart is in joint diastole the tricuspid valve (valve between right Atria and right ventricle) and bicuspid valve (valve between left atria and left ventricle) are open, blood from the pulmonary veins(only vein having deoxygenated blood) and vena cava(having deoxygenated blood) flows into left and the right ventricle respectively from left and right atria and for the stoppage of backflow of blood into ventricle the Semilunar valve are closed at this phase.
Now the main process begins, the SAN, the pacemaker of heart generates action potential which stimulates both atria to contracts as signals conducts in sequence explained below:
signal -> SAN(Sino-atrial node) -> AVN(Atrio-ventricular node)-> BOH(Bundle of his) -> Purkinje fibre
- Atrial systole: At this stage the both atria contracts which represents by “P” WAVE in ECG graph ,the ventricles are in diastole at this time. This increases the flow of blood in ventricle and fills it 30% with blood .This phase is of 0.1sec.
- Ventricle systole: Now the action potential conducts in way to AVN to AV BUNDLE to BOH to purkinje fibres transmits the signal through entire ventricle side causing ventricle muscle contraction now the pressure increases in it causing the closure of tricuspid and Bicuspid valve(atrio-ventricular valve) (LUB sound) to prevent the backflow of blood in atria from ventricle. This phase is of 0.3 sec and the both atria are in diastole phase .This phase represents as “QRS complex” in ECG graph. Now the contraction causes more pressure increase causing the opening of SEMILUNAR VALVES guarding pulmonary artery(right side) and Aorta(left side). The DOB from right ventricle to lungs through pulmonary artery to make it oxygenated and OB to heart through pulmonary vein from lungs(only vein carrying OB).
Now the ventricles diastole causing the closure of semilunar valve(DUB sound) preventing the backflow of blood into the ventricle. As the ventricular pressure declines and the tricuspid and bicuspid valve opens by the pressure in atria due to the blood emptied in it by the vein ,the blood present in atria are freely move in ventricles once again causing remaining 70% blood filling . Both atria and ventricles are in relaxed stage known as JOINT DIASTOLE is of 0.4sec .The atria systole or ventricle diastole (0.1sec) + atria diastole or ventricle systole(0.3sec) + joint diastole (0.4sec) = 0.8sec. Soon the new action potential will be generated by SAN and the process will be continue similarly explained above.