Grade 7, Science Olympiad (CBSE) - Heart 

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Grade 7  |   Science  |   Heart, Transportation in animals and plants, Olympiad, CBSE, ICSE, SOF, ITO


The heart is a small muscular organ present slightly towards the left side in our chest. 

It is the pumping organ which is causing the blood to flow in our body and perform its function well. The human heart has four chambers, the right auricle, the right ventricle, the left auricle, and the left ventricle. 

The upper two chambers are called atrium or auricle whereas the lower two chambers are called ventricle. 

Functions of heart

1. In the resting state, both the atria get filled with blood. The right atrium receives deoxygenated blood from all the parts of the body and the left atrium receives oxygenated blood from lungs by pulmonary veins.

2. When both atria contract, their cusp valves open up. The left atrium pours its blood into the left ventricle and the right atrium pour its blood into right atrium into the right ventricle.

3. On relaxation of the atria and contraction of the ventricle, the cuspid valves are shuttered and semilunar valves open up.

The left ventricle pumps the oxygenated blood into the aorta which distributes blood to all body parts by arteries. The right ventricle pumps the deoxygenated blood into the pulmonary aorta and is transported to the lungs by the pulmonary arteries for oxygenation.

The rhythmic contraction and relaxation of auricles and ventricles cause the beating of the heart. Our heart beats 72 times per minute. You can feel it by placing your palm on the left side of your chest.

Systole- One heartbeat includes a phase of contraction of heart muscles which we call systole.

Diastole- In one heart beat, a phase of relaxation of heart muscles or general pause is called Diastole.

Blood pressure

This is the pressure exerted by flow  the blood on the walls of blood vessels. Sphygmomanometer is an instrument used to measure it.

We can hear the heart best in two phases - lub and dub sounds. The heart beat sound caused by contraction of muscles and shutting down of valves. 

  • In the lub phase, the ventricles contract and cuspid valves close.
  • In the dub phase, the pulmonary and aortic valves close.

This lub and dub sound can be heard by an instrument called stethoscope.

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