# Explain how the kidneys help to maintain water balance in the human body when a person becomes dehydrated.

> Eduqas GCSE Biology — 2.5.3 Homeostasis · Explain · 4 marks

> A person spends a long time exercising on a hot day and loses a large amount of water through sweating. They do not drink any water during this time.

## Mark scheme (4 marks)

1. The blood water potential/concentration is detected as having fallen (becomes too low / too concentrated)
2. The hypothalamus / brain detects the change and more ADH is released from the pituitary gland
3. The kidneys reabsorb more water back into the blood
4. Less urine is produced / urine is more concentrated

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