CBSE Class 10 Answered

Depending upon the needs of the body, the amount of urine is regulated by hormones Antidiuretic hormone(secreted by posterior lobe of pituitary), Aldosterone ( secreted by adrenal cortex) and Angiotensin (secreted in juxta-glomerular apparatus, JGA, of kidney).

The JGA plays a complex regulatory role. A flow in glomerular blood flow can activate the JG cells to release renin, which converts angiotensinogen in blood to angiotensin I and further to angiotensin II. Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the adrenal cortex to release aldosterone , which causes reabsorption of water and Na+ from the distal parts of the tubule.

Antidiuretic hormone facilitates water absorption from the latter parts of the tubule, thereby preventing diuresis. An increase in body fluid volume suppresses the ADH release. ADH can also affect the kidney function by its constrictory effects on blood vessels.