# A person drinks a large amount of water on a hot day. Describe the changes that occur in the body to return blood water potential to normal.

> WJEC A-Level Biology (Wales) — 3.7 Homeostasis and the kidney · Describe · 5 marks

> After drinking a large volume of water, the water potential of the blood rises above normal. The body must respond to restore the correct water potential.

## Mark scheme (5 marks)

1. The change in blood water potential is detected by the hypothalamus (or osmoreceptors in the hypothalamus)
2. Less ADH (anti-diuretic hormone) is released / secreted from the pituitary gland
3. The kidneys / collecting duct / tubules become less permeable to water
4. More water is excreted / lost in the urine
5. Blood water potential returns to / is restored to normal (negative feedback)

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-12ce5ce3) · Published by Druglandscape Ltd.