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/carbonic acid/fall in pH
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Answer
Chemoreceptors play a crucial role in detecting changes in the blood composition, specifically an increase in carbon dioxide (CO₂) levels or a decrease in pH. This detection is vital in initiating physiological responses such as an increased heart rate.
Step 2
Send impulses to cardiac centre/medulla
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Once chemoreceptors detect the changes, they send electrical impulses to the cardiac centre located in the medulla oblongata of the brain. This area is responsible for regulating heart function.
Step 3
More impulses to SAN
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The cardiac centre responds by sending more impulses to the sinoatrial node (SAN), which is the natural pacemaker of the heart. This increase in impulses results in a higher heart rate.
Step 4
By sympathetic nervous system
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Additionally, the sympathetic nervous system becomes activated during exercise. This branch of the autonomic nervous system further enhances the heart rate by stimulating the SAN and increasing the force of heart contractions.
