Cardiac Cycle

The human heart is a muscular organ that is about the size of a fist that pumps blood all the way through a set of connections between arteries and veins. It is known as the cardiovascular system. It involves systemic and pulmonary circulation.

What is Cardiac Cycle?

The cardiac cycle attributes to a comprehensive heartbeat from its production to the commencement of the next beat. It comprises of diastole, the systole, and the intervening pause. 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. The cardiac cycle involves a complete contraction and relaxation of both the atria and ventricles and the cycle lasts approximately 0.8 seconds.

Also Refer: Structure & Functions of Human Heart

Cardiac Cycle Physiology

The human heart consists of four chambers, comprising of left and right halves. Two upper chambers include left and right atria; lower two chambers include right and left ventricles.  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.

Also Read: Cardiac Output

Cardiac Cycle Phases

cardiac cycle

A human Heartbeat Comprises of 5 Stages :

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.

Atrial Systole: At this phase, blood cells flow from atrium to ventricle and at this period atrium contracts.

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.

Ventricular Ejection: Here ventricles contract and emptying. Pulmonary artery and aortic valve close.

Isovolumic Relaxation: In this phase, no blood enters the ventricles and consequently forth pressure decreases, ventricles stop contracting and begin to relax. Now due to the pressure in the aorta – pulmonary artery and aortic valve close.

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.

Explore more: Regulation Of Cardiac Activity

Learn more in detail about the Cardiac Cycle,  Its Anatomy, Physiology and other related topics @ Byju’s Biology

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