A person is rushed to hospital after collapsing. Doctors find that a blockage in a coronary artery has reduced blood flow to the heart muscle. Explain why a blockage in a coronary artery is life-threatening, referring to the role of the heart and blood vessels in the cardiovascular system.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Coronary arteries supply the heart muscle itself with oxygenated blood. If a coronary artery becomes blocked, the heart muscle in that region no longer receives an adequate blood supply.
Model answer (5 marks)
1. The heart is the pump that circulates blood throughout the body.
2. Arteries carry oxygenated blood away from the heart under high pressure.
3. Coronary arteries supply the heart muscle itself with oxygen and nutrients.
4. A blockage stops oxygen and nutrients reaching the myocardium, so the heart cells cannot respire and produce ATP.
5. Without ATP the heart cannot contract, it stops pumping, and the rest of the body is deprived of oxygen – a life‑threatening situation.
2. Arteries carry oxygenated blood away from the heart under high pressure.
3. Coronary arteries supply the heart muscle itself with oxygen and nutrients.
4. A blockage stops oxygen and nutrients reaching the myocardium, so the heart cells cannot respire and produce ATP.
5. Without ATP the heart cannot contract, it stops pumping, and the rest of the body is deprived of oxygen – a life‑threatening situation.
Examiner tips
- Use the exact terms ‘myocardium’, ‘ATP’, and ‘circulate’
- Show the causal chain from blockage to loss of circulation
- Keep each point short and to the point
Common mistakes
- Confusing the coronary artery with a systemic artery
- Saying the heart stops because of a lack of blood flow to the body rather than to the heart itself
- Using vague phrases like ‘heart stops’ without explaining the loss of ATP
Mark scheme (5 marks)
- The heart is the organ that pumps blood around the body, so the heart muscle must continuously contract
- Arteries carry blood away from the heart under high pressure, and coronary arteries supply the heart muscle with oxygenated blood / oxygen and nutrients
- If the coronary artery is blocked, the heart muscle cells are deprived of oxygen / nutrients
- Without oxygen the heart muscle cells cannot respire / produce energy, so the heart cannot contract properly / stops beating
- If the heart stops pumping, blood is no longer circulated to the rest of the body / organs are deprived of oxygen, which is life-threatening
Key terms in this question
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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