Control of heart rateEdexcel A-Level Biology B: Mind map

Exam questions on Control of heart rate

1. A 17-year-old runner has a resting heart rate of 62 beats per minute. During a 5 km race her heart rate rises to 170 beats per minute and the carbon dioxide concentration in her blood increases. After she finishes, both gradually return to normal.
   Explain how the rise in carbon dioxide concentration in the runner's blood leads to an increase in her heart rate.2 marks
2. A woman stands up quickly from lying down and feels dizzy for a few seconds. Blood pools in her legs, so the blood pressure in her aorta and carotid arteries briefly falls. Within seconds her heart rate rises and her blood pressure returns to normal.
   Explain why the woman's heart rate falls back to normal once her blood pressure has been restored.2 marks
3. A student is walking home when a dog suddenly runs at her. Within seconds her heart rate rises from 70 to 120 beats per minute. The raised rate persists for several minutes after the dog has left.
   Explain how the nervous system brings about the immediate rise in the student's heart rate.3 marks