Adrenaline is a hormone released during the 'fight-or-flight' response. Explain how adrenaline reaches its target organs from the adrenal gland, and describe two ways in which adrenaline prepares the body for action.

Eduqas A-Level Biology — 4.2 Inheritance · Explain · 5 marks · View as Markdown

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

Model answer (5 marks)

Adrenaline is released by the adrenal gland into the bloodstream.
Adrenaline travels in the blood to target organs.
Adrenaline binds to receptors on the surface of target organ cells.
Adrenaline increases heart rate and pulse rate, delivering more oxygen to muscles.
Adrenaline causes glycogen to be converted to glucose, raising blood glucose levels for energy.

Examiner tips

  • Use the exact sequence of release → transport → receptor binding → physiological effect.
  • Include both cardiovascular and metabolic actions to hit all 5 marks.
  • Mention the bloodstream as the transport medium.
  • Show the link between increased heart rate and oxygen delivery.

Common mistakes

  • Confusing adrenaline with cortisol or other hormones.
  • Omitting the bloodstream as the transport route.
  • Failing to specify the target organ cells’ receptors.

Mark scheme (5 marks)

  1. Adrenaline is released / secreted by the adrenal gland into the bloodstream
  2. Adrenaline travels in the blood to target organs
  3. Adrenaline binds to receptors on the surface of target organ cells
  4. Adrenaline increases heart rate / pulse rate (to deliver more oxygen to muscles)
  5. Adrenaline causes glycogen to be converted to glucose / increases blood glucose levels (to provide energy for respiration)

Key terms in this question

adrenaline · adrenal gland · target organs · hormone

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