ADH

• ADH = a hormone that regulates water levels in the blood
• where is ADH produced?

  in the pituitary gland
• where does ADH travel?

  in the blood to the kidney
• what does ADH cause?

  the collecting duct walls to become more permeable to water
• hormone = a chemical messenger that travels through the blood
• more water reabsorbed = less urine produced
• water levels in blood too low -> more ADH into blood
• water levels in blood too high -> less ADH into blood
• too LOW:

  receptor in brain detects too little water in blood -> pituitary gland releases more ADH into blood -> ADH enters kidneys + makes collecting duct walls more permeable to water -> more water is reabsorbed into blood -> blood water levels return to normal through negative feedback -> smaller volume, higher concentration urine produced
• too high:

  receptor in brain detects too much water in blood -> pituitary gland releases less ADH into blood -> less ADH enters kidneys so collecting duct walls are less permeable to water -> less water reabsorbed by blood -> blood water levels return to normal through negative feedback -> larger volume, dilute urine produced