osmoreg

• if the level of water in the blood falls, aka the blood becomes too concentrated, the pituitary gland releases the hormone ADH into the bloodstream, which travels to kidneys = more water reabsorbed back into blood from the kidney tubules
• effect of ADH on kidneys;

  kidney tubules to become more permeable to water = more water can be reabsorbed from tubules, back into blood = less urine, amount of water in blood rises to normal level
• summary:

  The water level in the body is controlled by the hormone ADH which acts on the kidney tubules. ADH is released by the pituitary gland when the blood is too concentrated and it causes more water to be reabsorbed back into the blood from the kidney tubules. This is controlled by negative feedback.
• as the level of water in the blood returns to normal, from previously being low, the pituitary gland stops releasing ADH
• if the blood is too dilute, high conc of water, pituitary glands stop releasing ADH, so the kidneys reabsorb less water into the blood

  = more urine,

  = conc returns to normal
• on a hot day, more water is reabsorbed due to more water loss via sweat