Kidneys are a part of this system as well… • If your blood pressure is too low… • Blood pressure receptors in the juxtaglomerular apparatus detect low blood pressure (due to dehydration or massive blood loss). • This is the monitor and the co-ordinating center
And then… 2) Special cells in the juxtaglomerular apparatus release renin • So the apparatus is also the effector/regulator
And then… 3) Renin, an enzyme, travels in the bloodstream and converts the blood plasma protein angiotensinogen into another protein, angiotensin.
And then… 4) Angiotensin causes the blood vessels to constrict (decreases volume and thereby increases pressure). • This causes the adrenal glands (located on top of the kidneys) to release aldosterone.
And then… 5) Aldosterone causes the distal tubule and collecting ducts to increase water and salt reabsorption which raises blood pressure and blood volume back to normal levels.