# A person drinks a large amount of water on a cold day. Explain how the kidneys respond to maintain water balance in the body.

> WJEC A-Level Biology (Wales) — 4.5 Homeostasis and the kidney · Explain · 5 marks

> After drinking a large volume of water, the water content of the blood rises above the optimum level. The body must respond to restore the correct water balance.

## Mark scheme (5 marks)

1. The hypothalamus detects the rise in water content of the blood (or detects that the blood is too dilute)
2. Less ADH is released / secreted by the pituitary gland
3. The kidney tubules / collecting duct become less permeable to water
4. Less water is reabsorbed back into the blood / more water remains in the tubules
5. A larger volume of dilute urine is produced, reducing the water content of the blood back to the optimum level

## Key terms

- [kidney](https://www.gradenine.co.uk/glossary/kidney)

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-person-drinks-a-large-amount-e1687839) · Published by Druglandscape Ltd.