A sports clinic shows a spirometer trace from a human runner before and immediately after a 400 m race. The small repeated waves show normal breathing. The ...
Question 1 Report
A sports clinic shows a spirometer trace from a human runner before and immediately after a 400 m race. The small repeated waves show normal breathing. The larger wave follows a forced breath. The technician notes that exercising muscle cells need more oxygen for respiration, and blood carries this oxygen from the lungs.
The runner had a breathing rate of 14 breaths per minute at rest and 32 breaths per minute just after the race. Her tidal volume also increased. The runner drank water before the test and had not eaten for two hours.
(a) Describe the change in breathing rate after the race. [2]
(b) Suggest why breathing rate and tidal volume both increase during exercise. [2]
(c) Name the blood cells that transport most oxygen. [2]
(d) Use the information in Fig. 1 to state which part of the trace represents the greatest change in lung volume. [2]
Answer Details
(a) Breathing rate increased from 14 to 32 breaths per minute. The increase was \(32-14=18\) breaths per minute. [2]
(b) During exercise, muscle cells respire faster to release more energy for contraction. They need more oxygen and produce more carbon dioxide, so both breathing rate and tidal volume increase to take in oxygen and remove carbon dioxide faster. [2]
(c) Red blood cells, also called erythrocytes, transport most oxygen in the blood. [2]
(d) The large forced-breath wave represents the greatest change in lung volume because it has the greatest vertical distance on the spirometer trace. [2]
Exam reminder: a faster breathing rate and a larger tidal volume both increase ventilation.
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