Water in Urine
Biology: Edexcel IGCSE, topic 3.4.6
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 brain. This is how the body responds to having too much or too little water in the blood:
Too little water
- The brain triggers the release of anti-diuretic hormone (ADH).
- This increases the permeability (ability of things to pass through) of the collecting duct. This means that more water is reabsorbed back into the bloodstream.
- This results in a small volume of concentrated urine.
Too much water
- The brain signals to stop the release of anti-diuretic hormone (ADH).
- This reduces the permeability of the collecting duct. This means that less water is reabsorbed back into the bloodstream.
- This results in a large volume of dilute urine.
Test yourself on Water in Urine
Which hormone helps to control the volume of water in urine?
What happens when there is too little water in our body?