# A person eats a large meal containing very little water on a hot day and sweats heavily. Explain how the kidneys respond to maintain water balance in the body.

> Eduqas A-Level Biology — 4.5 Homeostasis and the kidney · Explain · 5 marks

> Sweating causes a significant loss of water from the body. The kidneys play a central role in homeostasis by adjusting the volume and concentration of urine produced.

## Mark scheme (5 marks)

1. Sweating causes blood water concentration to fall / blood becomes more concentrated
2. The hypothalamus detects the decrease in blood water concentration
3. The pituitary gland releases / secretes more ADH into the bloodstream
4. ADH makes the kidney tubules / collecting duct more permeable to water
5. More water is reabsorbed back into the blood / a smaller volume of more concentrated urine is produced

## Related

- [Revision notes for Eduqas A-Level Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-person-eats-a-large-meal-6ad80b0f) · Published by Druglandscape Ltd.