Exercise causes an increase in heart rate - AQA - A-Level Biology - Question 1 - 2017 - Paper 2
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 2
Step 1
Role of Chemoreceptors
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Answer
Chemoreceptors detect a rise in carbon dioxide (CO₂) levels, an increase in hydrogen ions (H⁺), or a fall in blood pH. This triggers a physiological response to increase heart rate.
Step 2
Blood Pressure Receptors
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Answer
Baroreceptors detect changes in blood pressure. An increase in blood pressure sends signals to the medulla oblongata to regulate heart rate accordingly.
Step 3
Nervous System Impulses
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Answer
The information from these receptors is relayed to the cardiac center in the medulla, which generates impulses to the sinoatrial node (SAN), leading to an increased heart rate.
Step 4
Response of the Autonomic Nervous System
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Answer
The sympathetic nervous system is activated, which enhances the heart rate by releasing neurotransmitters like norepinephrine that increase the conduction rate through the heart.
