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Systole refers to the contraction of
A. SA node
B. AV node
C. Major arteries
D. Atria and ventricles

Last updated date: 20th Jun 2024
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Hint: The human body consists of many organs that function together to make us survive. The blood is a very important connective fluid tissue that transfers oxygen to every art of the body and the blood purification takes place in the heart.

Complete Answer:
- Heart is the muscular organ found behind the breastbone the heart pumps the blood through the network of veins and arteries considered as the cardiovascular system. The heart comprises four chambers; the right atrium, that receives the blood from the veins and transfers it to the right ventricle.
- The right ventricle the blood pumps to the lungs where it gets the oxygen, the left atrium gets the oxygenated blood from the lungs and pumps it to the left ventricle. From the left ventricle the oxygenated blood pumps to the rest of the body. The vigorous contraction by the left ventricle produces the blood pressure.
- The coronary arteries along the heart surface provide the oxygenated blood to the muscle of the heart. A web of nerve tissue also move through the heart that involve in conducting signals to control the contraction and relaxation of the cardiac muscles and considered as pericardium.
- Now, systole refers to the atria contraction that propels the blood to the ventricles and ventricular contraction that expels the blood inside the pulmonary artery and aorta. In other words, we can say that it is the contraction period of the ventricles of the heart that produce between the 1st and 2nd sound of the cardiac cycle. It causes the blood ejection inside the aorta.

Thus, the correct option is ‘D’. Atria and ventricles.

Note: The SA node of the heart is the natural pacemaker that is composed of clusters of cells that are located in the upper part of the wall of the right atrium and the impulse is produced there it is also termed as sinus node. The impulse produced by the SA node is sent inside the ventricle by AV node so that the lower chamber of heart can contract.