1[1 mark]
Which blood vessel carries oxygenated blood from the lungs to the heart?
- Aorta
- Pulmonary artery
- Pulmonary vein
- Vena cava
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Answer: C C (pulmonary vein)
2[2 marks]
Explain the role of the valves in the heart.
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- prevent backflow of blood (1)
- so the blood flows in one direction only (1)
3[3 marks]
Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.
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- left ventricle pumps blood around the whole body (1)
- right ventricle pumps blood only to the lungs (1)
- so the left ventricle needs to produce a higher pressure / more force, so a thicker muscle wall is needed (1)
4[2 marks]
A person has a heart rate of 72 beats per minute and a stroke volume of 70 cm³. Calculate the cardiac output. Include the unit.
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- 72 × 70 (1)
- = 5040 cm³ per minute (1) allow cm³/min; correct answer with no working = 2 marks; 5040 with no unit or the wrong unit = 1 mark
5[3 marks]
A person has a cardiac output of 6300 cm³ per minute and a heart rate of 90 beats per minute. Calculate the stroke volume.
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- stroke volume = cardiac output ÷ heart rate (1)
- 6300 ÷ 90 (1)
- 70 cm³ (1)
6[2 marks]
A student counts 21 pulse beats in 15 seconds. Calculate the student’s heart rate in beats per minute.
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- 21 × 4 / 21 ÷ 15 × 60 (1)
- = 84 beats per minute (1) allow bpm
7[6 marks]
Explain how the structure of the heart and the circulatory system allow blood to be delivered to both the lungs and the rest of the body.
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| Level | Marks | What the answer does |
|---|---|---|
| 3 | 5–6 | A clear and logical explanation which follows the blood through both circuits, naming the major vessels and explaining the roles of the valves and the different wall thicknesses. |
| 2 | 3–4 | Some of the structure is described with some explanation of function, but the account of the route or the adaptations may be incomplete. |
| 1 | 1–2 | Some structures or vessels are named, with little or no explanation of how they relate to function. |
Indicative content
- double circulatory system: one circuit to the lungs, one to the body
- deoxygenated blood enters the right atrium from the vena cava, and passes to the right ventricle
- right ventricle pumps blood to the lungs through the pulmonary artery
- oxygenated blood returns in the pulmonary vein to the left atrium, then the left ventricle
- left ventricle pumps blood to the body through the aorta
- left ventricle has a thicker wall than the right ventricle because it pumps blood at higher pressure around the whole body, while the right ventricle pumps to the lungs
- valves prevent backflow so blood flows one way
- ventricle walls are thicker than atrium walls because they pump blood out of the heart