Water and ions are regulated by antidiuretic hormone (ADH), which is released by lower blood pressure and stretch receptor sensation by heart and large arteries. ADH is released by the hypothalamus and leads to control of the osmolarity of the blood. This release restores the ions and water level, and blood pressure is increased to the required level.
Aldosterone is released by the adrenal cortex and leads to retention of water by regulating sodium and potassium in the blood.
During low blood pressure, enzymes renin is released and causes the formation of angiotensin II, which signals the adrenal cortex to release aldosterone.
