REGULATION OF THE KIDNEY FUNCTION
– It is done by hormonal feedback mechanisms involving the hypothalamus, JGA and the heart.
– Changes in blood volume, body fluid volume and ionic concentration activate Osmoreceptors in the body.
1. Regulation by ADH (vasopressin)
– When body fluid level decreases, the osmoreceptors stimulate hypothalamus to release antidiuretic hormone (ADH).
It stimulates water reabsorption from DCT & collecting duct.
Thus, ADH prevents diuresis and increases body fluid volume. – Increase in fluid volume switches off the osmoreceptors and suppresses ADH release to complete the feedback.
– ADH constricts blood vessels resulting in an increase in BP. This increases the glomerular blood flow and GFR.
2. Regulation by JGA (Renin-Angiotensin mechanism)
– JGA (Juxta glomerular apparatus) is a sensitive region formed by cellular modification of DCT and the afferent arteriole at the location of their contact.
– JGA regulates the GFR. – A fall in glomerular blood flow/glomerular blood pressure/GFR activates the JG cells to release renin.
– Renin converts angiotensinogen in blood to angiotensin I and further to angiotensin II (a vasoconstrictor).
– Angiotensin II performs the following functions:
❖ Increases glomerular blood pressure and thereby GFR.
❖ Activates adrenal cortex to release Aldosterone. – Aldosterone causes reabsorption of Na+ and water from the distal parts of the tubule.
This also leads to an increase in blood pressure and GFR.
3. Regulation by ANF
– ANF check on the renin- angiotensin mechanism.
– An increase in blood flow to the atria of the heart causes the release of Atrial Natriuretic Factor (ANF).
– ANF causes vasodilation (dilation of blood vessels) and thereby decreases the blood pressure.