maintaining water balance

Question 1

what happens if the blood becomes too concentrated (level of water in the blood decreases)

Answer 1

• pituitary gland releases the hormone ADH (Anti Diuretic Hormone) into the bloodstream
• this travels to the kidneys and causes the kidney tubules to become more permeable to water (so more water can now pass out of the kidney tubules)
• more water is reabsorbed from the tubules back into the blood
• less urine is produced so the amount of water in the blood rises back to it’s normal level
  (when it returns to normal the pituitary gland stops releasing ADH)

Question 2

what happens if the blood becomes too dilute (level of water in the blood increases due to person drinking a lot of water)

Answer 2

• concentration of water in the blood rises
• pituitary gland stops releasing ADH
• the kidneys reabsorb less water into the blood
• more urine is produced and the concentration of water in the blood returns back to normal