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Figure 9 shows the stroke volume at different heart rates of a person who has trained for a marathon and of a person who has not trained for a marathon - Edexcel - GCSE Biology - Question 8 - 2019 - Paper 1
Question 8
Figure 9 shows the stroke volume at different heart rates of a person who has trained for a marathon and of a person who has not trained for a marathon. (a) (i) Com... show full transcript
Worked Solution & Example Answer:Figure 9 shows the stroke volume at different heart rates of a person who has trained for a marathon and of a person who has not trained for a marathon - Edexcel - GCSE Biology - Question 8 - 2019 - Paper 1
Step 1
Compare the effect of heart rate on stroke volume of the person who has trained for a marathon with the person who has not trained for a marathon.
Answer
The graph indicates a clear relationship between heart rate and stroke volume for both individuals. For the person who has trained for a marathon, the stroke volume increases steadily with heart rate, reaching about 200 ml at the highest heart rates. This suggests that trained individuals can accommodate higher blood volumes per heartbeat as their heart rate increases.
Conversely, the person who has not trained for a marathon shows a less pronounced increase in stroke volume. While there is an upward trend, it peaks around 140 beats per minute at approximately 160 ml, indicating a lower efficiency in pumping capacity as heart rate increases compared to the trained individual.
Overall, trained individuals demonstrate a superior capacity to increase stroke volume in response to rising heart rates compared to those who have not trained.
Step 2
Calculate the cardiac output for the person who has trained for a marathon when the heart rate is 160 beats per minute.
Answer
To calculate cardiac output (CO), the formula is:
From the graph, at a heart rate of 160 beats per minute, the stroke volume for the trained person is approximately 180 ml.
Substituting the values:
This gives:
Thus, the cardiac output for a person who has trained for a marathon at a heart rate of 160 beats per minute is 28.8 L/min.