2.10 Heart rate and cardiac output
6 exam questions worth 14 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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A student has a heart rate of 75 beats per minute and a stroke volume of 68 cm3.
Calculate the student's cardiac output. Give the unit.
Mark scheme
- 75 × 68 (1)
- = 5100 (1)
- cm3 per minute (1)
Model answer
cardiac output = 75 × 68 = 5100 cm3 per minute.
During exercise, an athlete's cardiac output was 21 000 cm3 per minute and their heart rate was 150 beats per minute.
Calculate their stroke volume.
Mark scheme
- 21 000 ÷ 150 (1)
- = 140 (cm3) (1)
Model answer
stroke volume = 21 000 ÷ 150 = 140 cm3.
Define stroke volume.
Mark scheme
the volume of blood pumped (out of the left ventricle) in one (heart)beat
Model answer
Stroke volume is the volume of blood pumped out of the left ventricle in one heartbeat.
Explain why cardiac output increases during exercise.
Mark scheme
- muscles respire faster / more respiration (1)
- need more oxygen and glucose (1)
- need more carbon dioxide removed (1)
- heart rate and stroke volume increase so more blood delivered per minute (1)
Model answer
During exercise the muscles respire faster to release more energy. They need more oxygen and glucose, and more carbon dioxide must be removed. The heart rate and stroke volume both increase, so more blood is pumped to the muscles every minute.
A student counts 18 pulse beats in 15 seconds.
Calculate their heart rate in beats per minute.
Mark scheme
- 18 × 4 (1)
- = 72 (bpm) (1)
Model answer
18 × 4 = 72 beats per minute.
Trained athletes often have a lower resting heart rate than untrained people.
Suggest why their cardiac output at rest can still be the same.
Mark scheme
- athletes have a larger stroke volume (1)
- so the same volume of blood is pumped per minute with fewer beats (1)
Model answer
Their hearts pump more blood in each beat, so they have a larger stroke volume. The same cardiac output can be reached with fewer beats per minute.
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