Answers · Exercise and heart health

Coronary heart disease — answer key

Check meaning, not exact wording. These are teaching points, not official Cambridge marks.

1. HQ1 · Practice

Model answer. In coronary heart disease fatty deposits narrow the coronary arteries, which supply the heart muscle, and a clot can block them. The muscle beyond gets too little oxygen and glucose.

A full answer includes

I chose: fatty deposits narrow the coronary arteries, so the heart muscle gets too little oxygen.
I did not choose the blood in the chambers: the heart muscle gets its blood from the coronary arteries.

Also accept

fatty deposits narrow the coronary arteries; the heart muscle gets too little oxygen

Watch for

“Fatty deposits narrow the coronary arteries, so blood in the heart chambers cannot leave.” — The chambers still pump blood out. CHD harms the heart's own muscle, which gets its blood from the coronary arteries.
“Fatty deposits narrow the coronary arteries, so the lungs get too little blood.” — The coronary arteries supply the heart muscle, not the lungs. Blood reaches the lungs in the pulmonary arteries.
“Fatty deposits block the heart valves, so the coronary arteries get too little blood.” — CHD is a blockage in the coronary arteries themselves, not in the valves.

2. HQ2 · Practice

Options as numbered on the pupil sheet: 1 — the fatty deposit has grown overnight and closed the artery; 2 — the heart muscle beyond the block has died; 3 — a valve between an atrium and a ventricle no longer closes; 4 — a fatty deposit has left a channel too narrow for extra blood; 5 — a blood clot has suddenly blocked the narrow channel.

Model answer. At 56 a fatty deposit had narrowed the artery: at rest enough blood passed, but on the stairs the working heart muscle needed more oxygen than the narrow channel could carry, so it hurt. At 61 a blood clot formed on the deposit and blocked the channel: no blood passed, so the pain came at rest and did not stop (a heart attack). The heart muscle beyond the block got no oxygen or glucose and died, so weeks later that part no longer contracts.

A full answer includes

I matched the pain on the stairs to a channel too narrow for the extra blood.
I matched the sudden pain at rest to a blood clot blocking the narrow channel.
I matched the muscle that no longer contracts to heart muscle that has died.
I did not match the sudden pain to the deposit growing overnight: deposits build up over years.

Also accept

stairs: channel too narrow for the extra blood; sudden pain: a clot blocks the channel; no longer contracts: the muscle has died

Watch for

“At 61 the fatty deposit grew overnight and closed the artery.” — Fatty deposits build up slowly, over years. A sudden block is caused by a blood clot on the deposit.
“At 56 a valve between an atrium and a ventricle no longer closed.” — A leaking valve is heard as a whoosh through a stethoscope. Pain on the stairs comes from heart muscle short of oxygen.
“Six weeks later a clot is blocking the narrow channel.” — The clot blocked the artery at 61. Muscle that still does not contract weeks later has died.

3. HQ3 · Practice

Model answer. Smoking, lack of exercise, stress and age are risk factors for coronary heart disease (with diet, genetic predisposition and sex). Eating plenty of fibre and eating oily fish are not risk factors.

A full answer includes

I chose smoking.
I chose lack of exercise.
I chose stress.
I chose age.
I did not choose eating plenty of fibre.
I did not choose eating oily fish.

Also accept

smoking, lack of exercise, stress, age

Watch for

“Eating a lot of fibre.” — A diet high in fibre is usually lower in saturated fat; it is not a risk factor.
“Eating oily fish.” — Oily fish is not a risk factor. Eaten in place of fatty meat, it lowers the saturated fat in the diet.
“Age is not a risk factor, because nobody can change it.” — A risk factor makes the disease more likely, whether or not it can be changed. The risk rises with age.

4. HQ4 · Practice

Model answer. Eating less saturated fat lowers the cholesterol in the blood, so fatty deposits build up more slowly in the coronary arteries and they are less likely to narrow and block.

A full answer includes

I chose: it lowers blood cholesterol, so fatty deposits build up more slowly in the coronary arteries.
I did not choose "removes the deposits": a diet slows new deposits but does not clear old ones.

Also accept

less cholesterol in the blood; fewer fatty deposits in the coronary arteries

Watch for

“It lowers blood pressure, so fatty deposits in the coronary arteries dissolve away.” — Less salt is what helps to keep blood pressure down, and deposits do not dissolve away.
“It lowers blood glucose, so fatty deposits build up more slowly in the coronary arteries.” — Saturated fat raises blood cholesterol, not glucose. The deposits contain cholesterol.
“It removes fatty deposits already in the coronary arteries, so they widen again.” — A low-fat diet slows the build-up of new deposits. It does not clear the ones already there.

5. HQ5 · Practice

Model answer. The key shows yellow fatty deposit, plain red blood flowing through and a speckled dark blood clot. In M the fatty deposit leaves only a small red channel: it is narrow but still open. At rest it carries enough blood for the heart muscle, but on the stairs the heart beats faster and harder and needs more oxygen than the narrow channel can bring, so the muscle beyond hurts. In K the small disc is a clot, not blood: it closes the channel, so no blood passes even at rest, and the pain would come at rest too (a heart attack). In J the deposit is thin and the red channel stays wide, so enough blood passes even on the stairs. L is all red: a healthy artery.

A full answer includes

I chose M.
I did not choose K: the key shows a clot closing its channel, so the pain would come at rest too.

Also accept

Watch for

“J” — In J the deposit is thin and the red channel is still wide. Enough blood passes even on the stairs.
“K” — The key shows that K's small disc is a clot, not flowing blood. It closes the channel, so no blood passes and the pain would come at rest too.
“L” — L is all red: a healthy artery with a wide space, so the heart muscle gets enough blood on the stairs.

6. HQ6 · Practice

Model answer. The wall of the left ventricle is thick muscle. Oxygen and glucose from the blood inside the chamber cannot diffuse far enough to reach most of its cells, so the wall gets its supply from the coronary arteries on its surface. Beyond the clot the muscle cells get no oxygen or glucose, so they cannot respire aerobically, release no energy to contract, and may die. The blood in the chamber is rich in oxygen, but it is pumped straight out into the aorta.

A full answer includes

I chose: the wall is too thick for oxygen to diffuse in from the chamber; it relies on coronary blood.
I did not choose the electrical signal: the muscle stops because its cells cannot respire.

Also accept

the wall is too thick for oxygen to diffuse in from the chamber; it relies on coronary blood

Watch for

“The blood in the left ventricle has already given up its oxygen to the rest of the body.” — The left ventricle holds blood that has just come from the lungs, so it is rich in oxygen. The wall still cannot use it.
“The clot stops the electrical signal spreading, so that part of the wall is not told to contract.” — The electrical signal spreads through the heart muscle, not along the artery. The muscle stops because its cells get no oxygen or glucose to respire.
“The clot has moved on into the left ventricle, so the blood in the chamber cannot flow.” — The clot is in a coronary artery on the surface of the heart, not in a chamber. The ventricle still fills and empties at every beat.

7. HQ7 · Practice

Model answer. A father who had a heart attack young points to a genetic predisposition, and both brothers may have inherited it. Stress is a separate risk factor: it can raise blood pressure, so Ade's stressful job adds to his risk. Neither brother is certain to develop coronary heart disease; Femi has fewer risk factors, but not none.

A full answer includes

I chose: both may have inherited a genetic predisposition, and Ade's stress can add to his risk.
I did not choose "both will develop it": a risk factor raises the chance, it does not make the disease certain.

Also accept

both may have inherited a genetic predisposition; Ade's stress adds to his risk

Watch for

“Only Ade may have inherited a genetic predisposition, because his stress shows it, and stress can raise blood pressure.” — Both brothers have the same father, so both may have inherited it. Stress is a separate risk factor, not a sign of the genes.
“Both may have inherited a genetic predisposition, but stress cannot change the risk, because it is only a feeling.” — Stress can raise blood pressure, and high blood pressure makes coronary heart disease more likely.
“Both will develop coronary heart disease, because a genetic predisposition makes it certain, whatever their stress.” — A risk factor raises the chance. It never makes the disease certain.

8. HQ8 · Practice

Model answer. Losing body fat brings his body mass closer to healthy, which helps to keep his blood pressure lower. Lower blood pressure does less damage to the walls of the coronary arteries, where fatty deposits start, so they are less likely to narrow. His lower resting heart rate shows that regular exercise has made his heart muscle stronger: it pumps more blood with each beat, so fewer beats are needed and the heart works less hard. Less stress also helps to keep blood pressure down. These changes lower his risk; they do not remove it.

A full answer includes

I explained two of the changes, each with how it lowers the risk, from the four below.
I could write: less body fat (a healthier body mass) helps to keep his blood pressure lower.
I could write: lower blood pressure does less damage to the walls of his coronary arteries, so fatty deposits are less likely to form.
I could write: the lower resting rate shows a stronger heart muscle, which pumps enough blood with fewer beats, so his heart works less hard.
I could write: less stress helps to keep his blood pressure down.
I did not write that his coronary arteries now cannot block: exercise lowers the risk, it does not remove it.

Also accept

any two of: healthier body mass, lower blood pressure; lower blood pressure, less damage to artery walls; stronger heart muscle, fewer beats needed; less stress, lower blood pressure

Watch for

“Cycling has cleared the fatty deposits from his coronary arteries.” — Exercise slows the build-up of new deposits. It does not clear the ones already there.
“His stronger heart muscle means that his coronary arteries cannot block.” — A stronger heart does not stop deposits forming. Exercise lowers the risk; it does not remove it.

9. HQ9 · Practice

Model answer. A risk factor raises the chance of a disease across a large group. Smokers are more likely to develop coronary heart disease, but not every smoker does, and some non-smokers do. One lucky smoker does not change the pattern in many people.

A full answer includes

I chose: a risk factor raises the chance across many people; one case cannot disprove it.
I did not choose "every smoker gets it": a risk factor is not a certainty.

Also accept

a risk factor raises the chance in a group; one case cannot disprove it

Watch for

“The man must have had the disease without knowing it, because every smoker gets it.” — Not every smoker gets CHD. A risk factor raises the chance; it does not make the disease certain.
“He was protected by his age, because older people are less likely to develop it.” — The risk rises with age, so his age was not protecting him.
“Smoking is a risk factor only for people who also eat a diet high in saturated fat.” — Smoking raises the risk by itself. Several risk factors together raise it more.

10. HQ10 · Practice

Model answer. In every column the rate is higher at 60–69 than at 40–49; in every age group and sex smokers have a higher rate than non-smokers; and men have a higher rate than women in every group. So smoking, older age and being male are each linked to a higher rate. A risk factor raises the chance: even 18 per 1000 is under 2 %.

A full answer includes

I chose: smoking, older age and being male are each linked to a higher rate.
I checked each factor in both age groups or for both sexes.
I did not choose "every smoker": 18 per 1000 is under 2 in every 100.

Also accept

smoking, older age and being male are each linked to a higher rate

Watch for

“Every smoker aged 60–69 in the study developed coronary heart disease.” — The highest rate is 18 per 1000, under 2 %. A risk factor raises the chance; it does not make the disease certain.
“Women in the study did not develop coronary heart disease at any age.” — Women's rates are lower than men's, but they are never zero: from 1 to 11 per 1000.
“A smoker aged 40–49 has a higher rate than a non-smoker aged 60–69.” — Compare 5 with 9 for men and 3 with 5 for women. In these data age raises the rate more than smoking.

11. HT1 · Apply

Model answer. All the heart muscle beyond a block loses its blood supply. X is near the start of the artery, before its branches, so a block there cuts off the whole artery and all its branches. Y is after the last branch, so a block there cuts off only the small area at the end. A block at X leaves a much larger area of heart muscle with no oxygen or glucose, and that muscle may die.

A full answer includes

I wrote that all the heart muscle beyond a block loses its blood.
I wrote that X is before the branches, so a block there cuts off the artery and all its branches.
I wrote that a block at Y cuts off only the end of the artery.
I wrote that a larger area of heart muscle then gets no oxygen or glucose and may die.
I did not write that the blood pressure at X is the reason.

Also accept

X is before the branches, so more heart muscle loses its oxygen and glucose

Watch for

“The blood is under more pressure at X.” — What matters is how much heart muscle lies beyond the block.
“A clot at X is bigger than a clot at Y.” — The two marks are the same size. What matters is how much muscle lies beyond each block.

12. HT2 · Apply

Model answer. In a narrowed coronary artery only a small space is left for blood. Sticky platelets make a clot more likely to form on the rough fatty deposit, and even a small clot can then fill that space completely, so no blood passes. The heart muscle beyond gets no oxygen or glucose, cannot respire aerobically and may die: a heart attack.

A full answer includes

I wrote that a clot can form on the fatty deposit, where the space is already narrow.
I wrote that even a small clot can then fill the narrow space completely.
I wrote that the heart muscle beyond then gets no oxygen or glucose.
I did not write that tar from the smoke blocks the artery.

Also accept

a clot forms on the deposit; even a small one fills the narrow space; the heart muscle beyond loses its oxygen and glucose

Watch for

“Tar from the smoke collects in the coronary artery and blocks it.” — Most of the tar stays in the lungs. The danger in the artery is a clot that forms on the fatty deposit.
“Smoking makes the fatty deposits melt.” — Smoking does not remove deposits. The link is a clot that fills the narrow space left by the deposit.

13. HT3 · Apply

Model answer. (a) Meal Y has less saturated fat: 2 g instead of 12 g, a difference of 10 g, which helps to keep blood cholesterol and fatty deposits down. (b) But meal Y has much more salt (2.4 g instead of 0.3 g), and a lot of salt raises blood pressure, so neither meal is better on every count.

A full answer includes

(a) I identified meal Y.
(a) I worked out the difference: 12 − 2.
(a) I wrote 10 g.
(b) I wrote that meal X has much less salt (0.3 g instead of 2.4 g).
(b) I wrote that too much salt raises blood pressure.
(b) I did not write that meal Y is better in every way.

Also accept

(a) Y, 10 g less; (b) X has less salt; salt raises blood pressure

Watch for

“Meal Y is better in every way.” — Look at the salt as well as the fat.
“The difference is 6 times, not 10 g.” — The question asks for the difference in grams: 12 − 2 = 10 g.