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

Pearson Edexcel A-Level Biology A (9BI0) — 4.5 Hormonal coordination · Explain · 5 marks · View as Markdown

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

When a person encounters a frightening situation, such as being chased by a dog, the body responds rapidly by releasing a hormone that causes a number of physiological changes.

Model answer (5 marks)

Adrenaline is released from the adrenal glands into the bloodstream.
Adrenaline travels in the blood to target organs.
It increases heart rate, which delivers more oxygen and glucose to the muscles.
It stimulates glycogenolysis, converting glycogen to glucose and raising blood glucose concentration.
These changes provide more energy for the muscles, enabling the person to fight or run away.

Examiner tips

Use the exact sequence of events: release, transport, target organ action, metabolic effect, functional outcome.
Show the link between adrenaline and increased heart rate and glycogenolysis.
Mention the physiological purpose (fight or flight).

Common mistakes

Confusing adrenaline with cortisol or other hormones.
Omitting the step that adrenaline increases heart rate before mentioning glycogenolysis.
Using vague terms like ‘energy’ without specifying glucose or oxygen supply.

Mark scheme (5 marks)

Adrenaline is released from the adrenal glands
Adrenaline travels in the blood to target organs
Heart rate increases, delivering more oxygen and glucose to muscles
Glycogen is converted to glucose, increasing blood glucose concentration
These changes provide more energy for muscles so the person can fight or run away

Key terms in this question

adrenaline · fight or flight