Question

Describe the hormonal feedback circuits involed in controlling renal functions.

Answer 1

Regulation of kidney function involves feedback circuits.

There are 3 main feedback systems that regulate the kidney functions.

1. Control by JGA:

JGA operates multihormonal Renin-angiotensin-aldosterone system (RAAS). The JGA responds to a decrease in blood pressure or blood volume in the afferent arteriole of the glomerulus and releases an enzyme, renin, into the bloodstream. In the blood, renin initiates chemical reactions that convert a plasma protein called angiotensinogen to a peptide called angiotensin $I$. This is converted to angiotensin $II$ in lungs by angiotensin converting enzyme. Angiotensin $II$ acts on adrenal gland and results in the release of aldosterone from the adrenal gland. Aldosterone increases blood pressure and increases blood flow to the glomerulus. It acts on DCT and collecting duct and increases reabsorption of Na+.

2. Control by ADH:

ADH is released from pituitary gland when osmolarity of blood is increased. It acts on DCT and collecting duct and helps in reabsorption of water.

3. Control by ANF

Atrial Natriuretic Peptides (ANF) opposes the regulation by RAAS. ANF inhibits the release of renin from the JGA and thereby inhibits NaCl reabsorption by collecting duct and reduces aldosterone release from the adrenal gland.