Explain how the nervous system controls the secretion of adrenaline and describe two effects that adrenaline has on the body to prepare a person for sudden physical activity.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
During a sudden emergency, such as narrowly avoiding a collision whilst cycling, a person's heart rate increases rapidly and they feel a surge of energy. This response is triggered by a hormone released into the bloodstream.
Model answer (4 marks)
The sympathetic nervous system sends nerve impulses to the adrenal medulla, stimulating it to release adrenaline into the blood.
Adrenaline then travels through the bloodstream to target organs.
It increases heart rate and the force of contraction.
It also dilates the pupils (or increases blood glucose, diverts blood to muscles, etc.).
Adrenaline then travels through the bloodstream to target organs.
It increases heart rate and the force of contraction.
It also dilates the pupils (or increases blood glucose, diverts blood to muscles, etc.).
Examiner tips
- Use the phrase "sympathetic nervous system" and "adrenal medulla" for the control part. Mention "bloodstream" for transport. Give two distinct effects, e.g. heart rate and pupil dilation. Keep sentences short and use exam terminology.
Common mistakes
- Confusing the adrenal cortex with the adrenal medulla. Failing to mention the bloodstream as the transport route. Giving only one effect or repeating the same effect twice.
Mark scheme (4 marks)
- The nervous system (via nerve impulses) stimulates the adrenal glands to release adrenaline
- Adrenaline travels in the bloodstream to target organs
- Adrenaline increases heart rate (accept: increases the rate and force of heartbeat)
- Adrenaline causes one further correct effect: e.g. dilates the pupils / increases blood glucose concentration / diverts blood to muscles / causes faster / deeper breathing / inhibits digestive activity
Key terms in this question
Related
- All Pearson Edexcel International GCSE Biology (4BI1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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