During a 400-metre race, a runner's muscles require a rapid increase in glucose and oxygen. Describe how the body responds to meet these increased demands during intense exercise.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
When a runner begins an intense race, the cardiovascular and endocrine systems must respond rapidly to supply working muscles with the resources they need.
Model answer (5 marks)
Adrenaline is released by the adrenal glands, signalling the heart to beat faster.
Heart rate rises, pumping more blood per minute.
Blood flow is redirected from non‑essential tissues to working muscles.
Blood glucose rises as glycogen is broken down in the liver.
Blood pressure increases, ensuring adequate delivery of oxygen and glucose to the muscles.
Heart rate rises, pumping more blood per minute.
Blood flow is redirected from non‑essential tissues to working muscles.
Blood glucose rises as glycogen is broken down in the liver.
Blood pressure increases, ensuring adequate delivery of oxygen and glucose to the muscles.
Examiner tips
- Use the exact terms from the mark scheme (adrenaline, heart rate, blood flow, blood glucose, blood pressure).
- Show the cause–effect chain: adrenaline → heart rate ↑ → blood flow ↑ → glucose ↑ → pressure ↑.
- Keep each point short and to the point – one sentence per point.
- Mention the organs involved (adrenal glands, heart, liver).
Common mistakes
- Confusing adrenaline with noradrenaline or omitting the adrenal gland source.
- Writing the heart rate increase as a general statement without linking it to adrenaline.
- Failing to mention the liver’s role in glycogenolysis or the rise in blood pressure.
Mark scheme (5 marks)
- Adrenaline is released / secreted by the adrenal glands
- Heart rate increases to deliver more blood / oxygen / glucose to muscles
- Blood flow to muscles increases / blood is redirected to muscles
- Blood glucose concentration increases / glycogen is broken down to glucose in the liver
- Blood pressure increases to ensure sufficient delivery of oxygen and glucose to muscles
Related
- All Edexcel A-Level Biology A: Salters-Nuffield (9BN0) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
More Run for your Life questions
- A student regularly trains by cycling long distances. During a training session,…
- A student takes part in a sprint race. During the race, the student's muscles re…
- A long-distance runner finishes a race and continues to breathe heavily for seve…
- Explain how adrenaline prepares the body for the 'fight or flight' response duri…