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

WJEC GCSE Biology (Wales) — 2.5.2 Hormonal coordination · Explain · 4 marks · View as Markdown

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

Adrenaline is released from the adrenal glands when a person experiences a sudden threat or stress.

Model answer (4 marks)

Adrenaline released from the adrenal glands increases heart rate, which pumps more oxygenated blood and glucose to the muscles.

It also stimulates the liver to convert glycogen into glucose, providing extra fuel for cellular respiration and energy release in the muscles.

These changes raise the supply of oxygen and glucose to working muscles, enabling a rapid, powerful response to threat.

Examiner tips

  • Use the exact terms: 'increase heart rate', 'convert glycogen to glucose', 'more oxygenated blood', 'more glucose available for respiration', 'fight or flight response'. Show the causal chain: adrenaline → heart rate ↑ → blood flow ↑ → oxygen/glucose ↑ → muscles ready. Keep the answer concise and directly linked to the marks. Mention both heart rate and glycogen conversion in separate sentences to hit all points.

Common mistakes

  • Writing 'adrenaline makes the heart beat faster' without linking to oxygenated blood. Forgetting to mention glycogen conversion to glucose. Using vague phrases like 'prepares the body' without specifying the mechanisms.

Mark scheme (4 marks)

  1. Adrenaline increases heart rate
  2. so that more oxygenated blood / glucose is delivered to muscles more quickly
  3. Adrenaline causes glycogen to be converted to glucose (in the liver)
  4. so that more glucose is available for respiration / to release energy for muscles

Key terms in this question

adrenaline · fight or flight

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