Cardiac output, ventilation and exerciseEdexcel International A Level Biology: Subtopic test

1. 1
   During a fitness test, a student's heart rate and stroke volume were measured at rest and during vigorous exercise. At rest: heart rate 70 beats per minute and stroke volume 75 cm³. During vigorous exercise: heart rate 150 beats per minute and stroke volume 110 cm³.

   (a)

   What is the cardiac output of the student during vigorous exercise?

   [1 mark]

   • A16.5 dm³ min⁻¹
   • B1.65 dm³ min⁻¹
   • C260 cm³ min⁻¹
   • D11.25 dm³ min⁻¹

   (b)

   By what factor does cardiac output increase from rest to vigorous exercise?

   [1 mark]

   • A2.1
   • B1.5
   • C3.1
   • D3.6

   (c)

   Explain how the change in cardiac output allows the muscles to respire aerobically at a high rate during exercise.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A researcher investigates how the body responds when blood carbon dioxide concentration rises during exercise. As the muscles respire faster they release more carbon dioxide into the blood, which lowers the blood pH. Chemoreceptors in the walls of the carotid arteries and the aorta are sensitive to this change.

   (a)

   In which part of the brain is the cardiovascular control centre located?

   [1 mark]

   • AHypothalamus
   • BCerebellum
   • CCerebral cortex
   • DMedulla oblongata

   (b)

   Which change would the cardiovascular control centre bring about to increase the heart rate?

   [1 mark]

   • AMore impulses along the vagus nerve to the SAN
   • BMore impulses along the sympathetic (accelerator) nerve to the SAN
   • CFewer impulses along the sympathetic nerve to the SAN
   • DRelease of adrenaline by the vagus nerve

   (c)

   Explain how a rise in blood carbon dioxide concentration leads to an increase in heart rate.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student breathes in and out of a spirometer containing soda lime, first at rest and then during vigorous exercise on a cycle ergometer. The results were: at rest, tidal volume 0.50 dm³, breathing rate 12 breaths per minute and oxygen consumption 0.30 dm³ per minute; during exercise, tidal volume 2.0 dm³, breathing rate 30 breaths per minute and oxygen consumption 2.4 dm³ per minute.

   (a)

   Calculate the respiratory minute ventilation at rest and during exercise, and the percentage increase on exercising.

   [3 marks]

   (b)

   Explain how a spirometer trace is used to find oxygen consumption, and why oxygen consumption increases during exercise.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   During a 400 m race, an athlete's muscle cells respire much faster, so the concentration of carbon dioxide in her blood rises and the blood pH falls. In the minutes before the race she was very nervous, and her adrenal glands released adrenaline into the blood.

   (a)

   Explain how the athlete's heart rate and ventilation rate are controlled and increased in response to the rise in blood carbon dioxide concentration.

   [6 marks]

   (b)

   Explain how the adrenaline released before the race prepares the athlete's body for the race.

   [6 marks]

   Total for question 4: 12 marks

End of questions