Explain why blood pressure is measured at two different values and describe what abnormally high blood pressure can indicate about a patient's health.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Blood pressure is measured using a sphygmomanometer and is recorded as two numbers, for example 120/80 mmHg.
Model answer (5 marks)
The higher value is the systolic pressure – the pressure when the heart contracts and pumps blood out.
The lower value is the diastolic pressure – the pressure when the heart relaxes between beats.
Two values are needed because blood pressure changes during the cardiac cycle and is not constant.
Abnormally high blood pressure (hypertension) means the heart must work harder, putting extra strain on it.
High blood pressure increases the risk of cardiovascular disease, stroke, heart attack and damage to blood vessels and arteries.
The lower value is the diastolic pressure – the pressure when the heart relaxes between beats.
Two values are needed because blood pressure changes during the cardiac cycle and is not constant.
Abnormally high blood pressure (hypertension) means the heart must work harder, putting extra strain on it.
High blood pressure increases the risk of cardiovascular disease, stroke, heart attack and damage to blood vessels and arteries.
Examiner tips
- Use the exact terms ‘systolic’ and ‘diastolic’. Explain the cardiac‑cycle reason for two values. Link high pressure to extra cardiac workload and disease risk.
Common mistakes
- Confusing systolic with diastolic or vice versa. Failing to mention the cardiac‑cycle reason for two readings. Omitting the health risks of hypertension.
Mark scheme (5 marks)
- The higher value is the systolic pressure / pressure when the heart contracts / pumps blood out
- The lower value is the diastolic pressure / pressure when the heart relaxes / between heartbeats
- Two values are needed because blood pressure changes / is not constant during the cardiac cycle
- Abnormally high blood pressure (hypertension) puts extra strain on the heart / makes the heart work harder
- High blood pressure increases the risk of cardiovascular disease / stroke / heart attack / damage to blood vessels / arteries
Key terms in this question
Related
- All AQA A-Level Physics (7408) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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