Exercise causes an increase in heart rate - AQA - A-Level Biology - Question 1 - 2017 - Paper 1
Question 1
Exercise causes an increase in heart rate.
Describe the role of receptors and of the nervous system in this process.
[4 marks]
Worked Solution & Example Answer:Exercise causes an increase in heart rate - AQA - A-Level Biology - Question 1 - 2017 - Paper 1
Step 1
Chemoreceptors detect rise in CO₂/H⁺/acidity
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Chemoreceptors in the body detect increases in carbon dioxide (CO₂) levels, changes in pH, and the concentration of hydrogen ions (H⁺). This rise in acidity is a critical signal during exercise.
Step 2
Signal transmission to cardiac centre
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Once the chemoreceptors have detected the changes, they send impulses to the cardiac center located in the medulla of the brain.
Step 3
Increase in sympathetic activity
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
This information is then relayed to the SAN (sinoatrial node) through the sympathetic nervous system, leading to an increase in heart rate.
Step 4
Parasympathetic inhibition
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Alternatively, if needed, the parasympathetic nervous system can downregulate these signals, preventing excessive heart rate increases during less intense activities.
