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

Eduqas GCSE Biology — 2.5.2 Hormonal coordination · Describe · 4 marks · View as Markdown

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

During a stressful situation, the adrenal glands release adrenaline into the bloodstream.

Model answer (4 marks)

Adrenaline released from the adrenal glands increases heart rate, which raises cardiac output.
Adrenaline stimulates the liver to convert glycogen into glucose.
The rise in blood glucose supplies more fuel for cellular respiration.
Higher glucose and oxygen delivery to muscles supports the increased activity of the fight‑or‑flight response.

Examiner tips

  • Use the exact terms ‘heart rate’, ‘glycogen’, ‘glucose’, ‘blood glucose concentration’, ‘oxygen’, ‘muscles’. Show the causal chain: adrenaline → heart rate ↑ → cardiac output ↑ → oxygen delivery ↑. Include the liver as the site of glycogenolysis. Mention that glucose fuels respiration in muscles.
  • common_mistakes
  • :
  • Confusing adrenaline with cortisol or omitting the liver as the site of glycogen conversion. Using vague phrases like ‘more energy’ instead of specifying glucose and oxygen. Leaving out the effect on heart rate or cardiac output.

Mark scheme (4 marks)

  1. Adrenaline increases heart rate
  2. Adrenaline causes glycogen to be converted to glucose (in the liver)
  3. This increases blood glucose concentration / provides more glucose for respiration
  4. More oxygen / glucose is delivered to muscles (for increased respiration / activity)

Key terms in this question

adrenaline · fight or flight

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