Question

Assertion : ADH and RAAS work in response to low blood volume and blood pressure.
Reason : ANF works in response to high blood volume and blood pressure.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

ADH (Antidiuretic hormone) and RAAS (Renin Angiotensin Aldosterone System) work in response to low blood volume and low blood pressure. ADH increases the reabsorption of water in the distal convoluted tubule and collecting duct, and thus results in an increase in blood volume and blood pressure.
RAAS is operated by JGA (Juxtaglomerular apparatus). It increases blood volume and blood pressure by two ways: Firstly, it induces the proximal convoluted tubules to reabsorb more NaCl and water and secondly, it stimulates the adrenal gland to release a hormone, called aldosterone that induces the distal convoluted tubule to absorb more Na⁺ and water.
ANF (Atrial Natriuretic Factor) works in response to high blood volume and high blood pressure. It opposes the regulation by RAAS. The walls of the atria of the heart release ANF in response to an increase in blood volume and blood pressure. ANF inhibits release of renin from the JGA and thereby inhibits NaCl reabsorption by the collecting duct and reduces aldosterone release from the adrenal gland. Thus ADH, RAAS and ANF regulate the functions of kidneys and control body fluid osmolarity, salt concentration, blood pressure and blood volume.