1. 2.75 Describe the role of ADH in regulating the water content of the blood (not in book) Name the different sections of the nephron in order.

2.  One of the main functions of the kidney is to regulate the water content of the blood.  The changes in the blood water content are controlled by a hormone produced by the pituitary gland.  This gland is at the base of the brain.  The hormone is called anti-diuretic hormone (ADH).

3.  Diuresis is the flow of urine from the body.  Anti-diuresis means to produce less urine.  So ADH starts to work when your body loses too much water.  Either when you are sweating too much and not replacing lost water by drinking.

4. You lose too much water:  The concentration of the blood starts to increase.  This is then detected by special cells in the brain called the hypothalamus.  The hypothalamus then tells the pituitary gland to release more ADH.  The ADH travels in the blood to the kidney.  ADH causes the collecting duct to become more permeable to water and so water is reabsorbed back into the blood. urine = more concentrated

6.  When the water content of the blood returns to normal, this tells the brain to stop releasing ADH.  Then the kidney tubules reabsorb less water.  This process can work in the reverse when we have to much water in our blood. Explain how this would work when the water content of the blood is too high.