IGCSE · Practice questions · The heart

Lub, dub, and what drives the rate.

Six original Cambridge-style questions on the chambers and valves of the heart, pulse rate data from an exercise investigation, coronary heart disease and the action of the heart.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Atria in, ventricles out.

Away in arteries, back in veins: aorta and pulmonary artery leave the ventricles; vena cava and pulmonary vein enter the atria.
Left side is on the right of a heart diagram; find the thick left ventricle wall.
Extended valves: AV valves shut when the ventricles contract (lub); semilunar valves shut when they relax (dub).
Exercise: more respiration, more oxygen and glucose needed, more carbon dioxide to remove, so a faster heart rate.

Recall

[4 marks]

Name the blood vessel that (a) brings blood from the body to the heart, (b) carries blood from the heart to the lungs, (c) carries blood from the heart to the body, (d) supplies the heart muscle itself.

(a) vena cava. ✓
(b) pulmonary artery. ✓
(c) aorta. ✓
(d) coronary artery. ✓

Explain

[4 marks]

Extended. Explain the difference in the thickness of the muscle walls of (a) the left and right ventricles, (b) the atria and the ventricles.

(a) The left ventricle wall is thicker because it pumps blood all round the body, against more resistance, so it must produce a higher pressure. ✓
The right ventricle pumps blood only to the lungs, which are close by; a lower pressure also avoids damaging the delicate lung capillaries. ✓
(b) The atria have thinner walls because they only pump blood a short distance, into the ventricles below. ✓
The ventricles must pump blood out of the heart into the arteries, so they need thicker, more muscular walls. ✓

Recall

[4 marks]

Extended. Describe how the contraction of the heart muscles and the action of the valves move blood through the left side of the heart.

The left atrium contracts, pushing blood through the open atrioventricular valve into the left ventricle. ✓
The left ventricle contracts; the rise in pressure shuts the atrioventricular valve, preventing backflow into the atrium. ✓
The semilunar valve at the base of the aorta is pushed open and blood is forced into the aorta. ✓
When the ventricle relaxes the semilunar valve shuts, stopping blood flowing back from the aorta into the ventricle. ✓

Data

[4 marks]

A student measured her pulse rate before and after running for 2 minutes.

Time	Pulse rate / beats per minute
at rest	68
0 min after running	148
2 min after	112
4 min after	84
6 min after	70

(a) Calculate the increase in pulse rate caused by the run. (b) Describe the pattern after the run. (c) State two ways to make the results more reliable.

(a) 148 − 68 = 80 beats per minute. ✓
(b) The pulse rate falls quickly at first, then more slowly, returning almost to the resting rate (70, close to 68) after 6 minutes. ✓
(c) Repeat the whole investigation and calculate a mean; use several students. ✓
Keep the exercise the same (same distance, speed and time) and rest until the pulse is back to resting before each repeat. ✓

Explain

[4 marks]

Extended. Explain why the heart rate increases during physical activity.

Muscles contract more, so the muscle cells respire faster to release more energy. ✓
They need more oxygen and glucose, and produce more carbon dioxide. ✓
The heart beats faster so blood flows faster, delivering oxygen and glucose to the muscles more quickly... ✓
...and removing carbon dioxide more quickly (in vigorous exercise, also supplying oxygen to remove lactic acid). ✓

Explain

[5 marks]

Describe coronary heart disease, name two risk factors that cannot be changed, and discuss how diet and exercise can reduce the risk.

Fatty deposits build up in the walls of the coronary arteries, narrowing them; a clot may block an artery completely. ✓
The heart muscle beyond the blockage gets less (or no) oxygen and glucose, cannot respire, and may die: a heart attack. ✓
Risk factors that cannot be changed: any two of age, sex (being male), genetic predisposition. ✓
Diet: eating less saturated fat (and salt) reduces the build-up of fatty deposits in the arteries. ✓
Exercise: regular exercise strengthens the heart and helps reduce body mass, blood pressure and blood fat levels. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.