Hormonal Regulation

Within the kidney are specific receptors that respond to chemical messengers. Hormones that control osmoregulatory functions, such as blood pressure.

As blood is being filtered by the nephrons in the kidneys, specialized cells called juxtaglomerular cells, near the renal capsule, can detect a loss of renal blood flow. The drop in pressure induces the release of one hormone, renin, by these cells into the bloodstream.

Renin then interacts with angiotensinogen, a precursor molecule released by the liver, and cleaves it into the hormone, angiotensin one, meanwhile an enzyme released in the lungs, called angiotensin converting enzyme or ACE, converts angiotensin one into angiotensin two.

Angiotensin two has two functions. One as as a vasoconstrictor, constricting small blood vessels and temporarily increasing blood pressure. And the other, to induce the release of the hormone aldosterone from the adrenal cortex.

When aldosterone reaches the brain, it stimulates the release of antidiuretic hormone or ADH from the hypothalamus. Together ADH and aldosterone then stimulate the kidneys to increase the reabsorption of water and sodium from the nephrons, which increases renal blood volume and overall blood pressure.