Adrenaline is a hormone released during the 'fight-or-flight' response. Explain how adrenaline is produced and released, and describe the effects it has on the body to prepare a person for action.

WJEC A-Level Biology (Wales) — 4.2 Inheritance · Explain · 5 marks · View as Markdown

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

A student hears a loud unexpected noise and immediately feels their heart pounding and their body tensing up.

Model answer (5 marks)

Adrenaline is produced and secreted by the adrenal medulla of the adrenal gland.

When the sympathetic nervous system is activated, adrenaline is released into the bloodstream and carried to target organs.

In the heart, adrenaline binds to β1‑adrenergic receptors, increasing heart rate and contractility.

In the liver and muscle, adrenaline stimulates glycogenolysis, converting glycogen into glucose.

The extra glucose supplies energy for respiration and muscle activity, allowing the body to react quickly.

Examiner tips

  • Use the term "adrenal medulla" for production site. Mention the sympathetic nervous system as trigger. Show the chain: release → bloodstream → target organs. Include both heart rate and glycogenolysis effects.
  • common_mistakes
  • :
  • Saying adrenaline is produced in the pancreas. Forgetting to mention the bloodstream as the transport medium. Describing only heart rate increase without glycogen conversion.

Mark scheme (5 marks)

  1. Adrenaline is produced / secreted by the adrenal gland
  2. Adrenaline is released into the bloodstream and travels to target organs
  3. Adrenaline increases heart rate / pulse rate
  4. Adrenaline causes glycogen to be converted into glucose
  5. This provides more glucose / energy for respiration so muscles can work harder / react quickly

Key terms in this question

adrenaline

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