How and why does the volume and composition of urine changes?

Describe how and why the volume and composition of urine changes, after drinking large amounts of water.

1 Answer
Jun 9, 2017

(How) : The volume and content of urine is controlled by the kidney (why) responding to the body's changing water content, to maintain a steady concentration.


The cells of our body require stable surroundings to perform correctly. So body temperature is kept steady, and so are many other qualities such as the glucose and oxygen levels in our blood. Together, all the mechanisms that keep conditions steady are known as homeostasis.

The kidneys control the amount of water being excreted by firstly expelling water at the Bowman's capsules, and then reabsorbing some of this water.

The amount of water reabsorbed is controlled by the hormone ADH (antidiuretic hormone) produced in the hypothalamus. The hypothalamus 'measures' the concentration of the blood and produces the appropriate level of hormone.