Explain how adrenaline prepares the body for the fight or flight response.

Edexcel GCSE Biology (1BI0) — 7.1 Hormonal coordination · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

During a stressful situation, such as encountering danger, the adrenal glands release a hormone into the bloodstream.

Model answer (4 marks)

Adrenaline is released by the adrenal glands during stress.
1. It increases heart rate and blood pressure.
2. It causes vasoconstriction of blood vessels to the skin and gut and vasodilation to the skeletal muscles.
3. The increased muscle blood flow delivers more oxygen and glucose for rapid contraction.
4. It stimulates glycogenolysis, raising blood glucose levels to supply extra energy for the fight‑or‑flight response.

Examiner tips

Use the exact terms ‘adrenaline’, ‘heart rate’, ‘blood pressure’, ‘blood flow to muscles’, ‘blood glucose’
Show the cause–effect chain: adrenaline → physiological changes → energy supply
Keep each point brief and to the point

Common mistakes

Confusing adrenaline with cortisol or other hormones
Omitting the increase in blood glucose or muscle blood flow
Using vague phrases like ‘more energy’ without specifying glucose

Mark scheme (4 marks)

Adrenaline is the hormone released / produced by the adrenal glands
Adrenaline increases heart rate / blood pressure
Adrenaline increases blood flow to muscles, so muscles receive more oxygen / glucose for contraction / movement
Adrenaline increases blood glucose levels, providing more energy for the body to respond

Key terms in this question

adrenaline · fight or flight response