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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. (i) Compare... 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
When comparing the stroke volume of a person who has trained for a marathon with one who has not, it is clear that the trained individual shows a higher stroke volume across all heart rates. As the heart rate increases, the stroke volume of the trained athlete increases more significantly than that of the untrained individual.
For instance, at a heart rate of 160 beats per minute, the stroke volume of the trained person may reach around 180 ml, whereas the untrained person's stroke volume may only reach approximately 140 ml. This indicates that training enhances the heart's efficiency and ability to pump blood effectively during increased physical exertion.
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 the cardiac output (CO), we use the formula:
Given that the stroke volume for a trained person at 160 beats per minute is around 180 ml, we can substitute:
Now, converting ml to liters:
Thus, the cardiac output for the person who has trained for a marathon is 28.8 L/min.