# Describe the role of the kidneys and the hormone ADH in maintaining water balance in the body when a person has been exercising on a hot day and has not drunk enough water.

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

> A person has been exercising on a hot day and has not drunk enough water. As a result, they lose water through sweating and their blood water concentration falls below the normal level.

## Mark scheme (5 marks)

1. The hypothalamus detects the fall in blood water concentration (acts as a receptor / monitors blood water concentration)
2. The pituitary gland releases / secretes more ADH into the bloodstream
3. ADH travels in the blood to the kidneys (as target organ)
4. ADH makes the kidney tubules / collecting duct more permeable to water
5. More water is reabsorbed back into the blood, so a small volume of concentrated urine is produced

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-role-of-the-kidneys-e589afa2) · Published by Druglandscape Ltd.