# 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.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 7 Run for your Life · Describe · 5 marks

> When a runner begins an intense race, the cardiovascular and endocrine systems must respond rapidly to supply working muscles with the resources they need.

## Mark scheme (5 marks)

1. Adrenaline is released / secreted by the adrenal glands
2. Heart rate increases to deliver more blood / oxygen / glucose to muscles
3. Blood flow to muscles increases / blood is redirected to muscles
4. Blood glucose concentration increases / glycogen is broken down to glucose in the liver
5. Blood pressure increases to ensure sufficient delivery of oxygen and glucose to muscles

## Related

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