So, basically, when our blood volume drops inside our vessels, when our blood pressure drops, and when the profusion rate inside our kidneys drops that simply means when the rate at which our fluid is passing through the kidneys drops, this causes our maculodenta cells to basically release a prostaglandin that travels to our juxtaglomero cells. And this causes those cells to release an enzyme called rena. Now, note that juxtaplinaril cells don't have to be activated, they don't have to be stimulated by the macula density to actually release Rena. And that is they can release Renan independently without being stimulated by the maculodeensa cells. So basically, this apparatus, the juxtaglomero apparatus, contains special types of cells that can sense a drop in blood volume, a drop in blood pressure, and these cells release Renan into our blood system. So if we take a look at the following diagram, a low blood volume, a low blood pressure, and a low kidney perfusion rate basically positively stimulates the kidneys to produce and release our renal enzyme into our bloodstream.