The heart — Cambridge IGCSE Biology
Heart structure, how it pumps, monitoring heart rate, the effect of exercise, and coronary heart disease with its risk factors.
Revision notes
4 short notes, in the order of the specification. Each one in short:
The heart is a muscular pump made of cardiac muscle, with two atria that receive blood from veins and two ventricles that pump blood into arteries. A septum separates the left and right sides, one-way valves stop blood flowing backwards, and the coronary arteries supply the heart muscle itself with oxygenated blood.
How the heart pumps blood
SupplementThe heart pumps blood when the atria contract, pushing blood through the atrioventricular valves into the ventricles, and then the ventricles contract, forcing blood into the aorta and pulmonary artery through the semilunar valves. Valves shut to stop backflow. The left ventricle wall is thicker because it pumps blood at high pressure all around the body.
Heart activity can be monitored by an ECG, which records the heart's electrical activity, by the pulse rate in beats per minute, or by listening to the valves closing with a stethoscope. Heart rate rises during exercise, so blood delivers more oxygen and glucose to the respiring muscles and removes carbon dioxide faster, then returns to the resting rate.
Coronary heart disease is the blockage of the coronary arteries by fatty deposits, so the heart muscle receives less oxygen and glucose. A complete blockage causes a heart attack. Risk factors include a diet high in saturated fat, lack of exercise, stress, smoking, genetic predisposition, age and sex. A healthier diet and regular exercise reduce the risk.
Exam questions
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Quick check questions
Supplement What is the septum?
Show answer
The wall of muscle separating the left and right sides of the heart.
Name the vessels that supply the heart muscle with blood.
Show answer
The coronary arteries.
Supplement Why is the wall of the left ventricle thicker than that of the right ventricle?
Show answer
It pumps blood to the whole body at higher pressure; the right pumps only to the lungs.
State three ways of monitoring the activity of the heart.
Show answer
ECG, pulse rate, listening to the sounds of the valves closing.
State two risk factors for coronary heart disease.
Show answer
Any two of: diet, lack of exercise, stress, smoking, genetic predisposition, age, sex.
Frequently asked questions
How does the heart pump blood?
Supplement The atria contract and push blood through the open atrioventricular valves into the ventricles. The ventricles then contract, the pressure rises, the atrioventricular valves shut and the semilunar valves open, forcing blood into the aorta and pulmonary artery. When the ventricles relax, the semilunar valves shut to stop blood flowing back.
Why is the left ventricle thicker than the right?
Supplement The left ventricle has a thicker muscle wall because it pumps blood all around the body, so it must produce a high pressure. The right ventricle pumps blood only to the nearby lungs, at a lower pressure that does not damage the delicate lung capillaries. Both ventricles have thicker walls than the atria.
Why does heart rate increase during exercise?
Supplement Heart rate increases during exercise because the muscles respire faster, so they need more oxygen and glucose and produce more carbon dioxide. Blood flows faster, delivering oxygen and glucose to the muscles for aerobic respiration and removing carbon dioxide quickly. Do not say the heart beats faster to give the muscles energy.
What causes coronary heart disease?
Coronary heart disease is caused by fatty deposits blocking the coronary arteries, so less blood, oxygen and glucose reach the heart muscle. A complete blockage causes a heart attack. Risk factors include a diet high in saturated fat, lack of exercise, stress, smoking, family history, increasing age and being male.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026