Urine
Biology: AQA GCSE Higher, topic 5.3.14
Water in the Blood
The volume of urine produced depends on the internal conditions. The volume of water in the blood is monitored by the hypothalamus in the brain. This is how the body responds to having too much or too little water in the blood:
Too little water
- The hypothalamus triggers the pituitary gland to release anti-diuretic hormone (ADH).
- This increases the permeability (ability of things to pass through) of the kidney tubules. This means that more water is reabsorbed back into the bloodstream.
- This results in a small volume of concentrated urine.
Too much water
- The hypothalamus triggers the pituitary gland to stop the release of anti-diuretic hormone (ADH).
- This reduces the permeability of the kidney tubules. This means that less water is reabsorbed back into the bloodstream.
- This results in a large volume of dilute urine.
Test yourself on Urine
Which part of the brain monitors the volume of water in the blood?
What happens when there is too little water in our body?
What happens to the kidney tubules when the pituitary gland stops releasing ADH?
Why does more ADH result in a small volume of concentrated urine?
What is the name of the hormone released by the pituitary gland to control water balance?