Control of heart rateEdexcel A-Level Biology B: Flashcards

What these 12 flashcards ask

Where is the cardiac centre?
Where are baroreceptors found?
Where are chemoreceptors that monitor blood CO₂ and pH found?
What is the SAN?
What is the SAN's intrinsic rate?
What does the sympathetic nerve release at the SAN, and what is the effect?
What does the parasympathetic (vagus) nerve release at the SAN, and what is the effect?
Which branch dominates at rest?
How does a rise in blood CO₂ increase heart rate?
How does a rise in blood pressure reduce heart rate?
Which hormone raises heart rate and where does it come from?
Why does adrenaline's effect last longer than a nerve impulse's?

Exam questions on Control of heart rate

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
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
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

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).