The heart — Cambridge IGCSE Combined Science

Revision notes

4 short notes, in the order of the specification. Each one in short:

1. Structure of the heart

   The heart is a muscular pump with two atria, two ventricles, a septum, valves and coronary arteries that supply the heart muscle with oxygenated blood.

2. How the heart pumps blood

   Supplement

   Atria contract, then ventricles contract to force blood out while valves stop backflow; the left ventricle is thicker as it pumps blood round the body.

3. Monitoring the heart and the effect of exercise

   Practical

   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.

4. Coronary heart disease

   Supplement

   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.