The table below shows measurements made from a cyclist before and during a timed hill climb. Fig. 1 shows the double circulation of a human, with blood pass...
Question 1 Report
The table below shows measurements made from a cyclist before and during a timed hill climb. Fig. 1 shows the double circulation of a human, with blood passing through the lungs before it returns to the left side of the heart.
| Condition | Heart rate / beats per minute | Stroke volume / cm3 per beat |
|---|---|---|
| Resting | 72 | 70 |
| Hill climb | 150 | 105 |
(a) Complete the calculation of cardiac output at rest.
cardiac output = heart rate × stroke volume
= 72 × 70 = ........ cm3 per minute [2]
(b) Use Table 1 to calculate the increase in cardiac output during the hill climb. [2]
(c) Describe the route of blood from the right ventricle to the left atrium. [3]
(d) Explain why cardiac output increases during the hill climb. [1]
Answer Details
(a)
\[72\times70=5040\text{ cm}^3\text{ per minute}\]
The cardiac output at rest is 5040 cm3 per minute. [2]
(b) During the hill climb:
\[150\times105=15\,750\text{ cm}^3\text{ per minute}\]
\[15\,750-5040=10\,710\text{ cm}^3\text{ per minute}\]
The increase in cardiac output is 10 710 cm3 per minute. [2]
(c) Blood travels from the right ventricle into the pulmonary artery, then to the lungs and capillaries around the alveoli. It returns by the pulmonary vein to the left atrium. [3]
(d) During the hill climb, working muscle cells need more oxygen and glucose and require carbon dioxide to be removed more rapidly. Increasing cardiac output increases blood flow to meet these demands. [1]
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