comment on the hormonal regulation on selective reabsorption

Regulation of Kidney Function

• The functioning of kidney is efficiently regulated by hormonal feedback mechanism. It involves − Hypothalamus, Juxtaglomerular apparatus (JGA), and heart.

• Hypothalamus

  • Antidiuretic hormone or ADH plays an important role in regulation.

  • Excessive loss of fluids from the body activates the osmoreceptors and stimulates hypothalamus to release hormone ADH, which helps in water re-absorption and prevents diuresis.

  • A further increase in body fluid volume can turn off the osmoreceptors. This inhibits the ADH release, which in turn completes the feedback.

  • ADH constricts the blood vessels and causes blood pressure to increase, which in turn increases glomerular blood flow and therefore GFR.

• Juxtaglomerular Apparatus (Renin-Angiotensin Mechanism)

  • When GFR falls, JG cells release renin.
    Renin plays an important role in the production of angiotensin II.
    

  • Angiotensin II − Constricts blood vessels to increase blood pressure and hence GFR
    It also activates adrenal cortex to release aldosterone that causes re-absorption of Na⁺ and water from tubule. This also results in an increase in blood pressure and hence GFR.