1. ADH and Osmoregulation

2. Anti-diuretic hormone
Secreted by the pituitary gland in the brain

3. Filtrate reaching collecting duct is hypotonic (high water content) in comparison to the surrounding tissue of the medulla – water diffuses into blood

4. Collecting ducts permeability to water is dependent upon the presence/absence of ADH
*Absent - impermeable  water stays in urine
*Present - permeable  water moves into blood

5. Diuretics
Caffeine and other drugs can inhibit Na+ reabsorption, causing less water to return to the blood by osmosis (increases urine output)

6. Diuretics
Alcohol consumption messes with your brain – stops the production of ADH – increases urine output and causes dehydration