Severe decrease in plasma concentration of sodium Figure . Schematic representations of the various hormones in the regulation of body fluid concentration Angiotensin Converting Enzyme inhibitors (ACE inhibitors) are used to treat high blood pressure. Using a flow chart, explain why these drugs are helpful in treating hypertension. XI Std Biology-Zoology Chapter- (synthesized in the liver) to angiotensin I.
Angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II. Angiotensin II stimulates Na reabsorption in the proximal convoluted tubule by vasoconstriction of the blood vessels and increases the glomerular blood pressure. Angiotensin II acts at different sites such as heart, kidney, brain, adrenal cortex and blood vessels. It stimulates adrenal cortex to secrete aldosterone that causes reabsorption of Na , K excretion and absorption of water from the distal convoluted tubule and collecting duct.
This increases the glomerular blood pressure and glomerular filtration rate. This complex mechanism is generally known as Renin- Angiotensin- Aldosterone System (RAAS). Figure . shows the schematic representation of the various hormones in the regulation of body fluid concentration.
Atrial Natriuretic Factor Excessive stretch of cardiac atrial cells cause an increase in blood flow to the atria of the heart and release Atrial Natriuretic Peptide or factor (ANF) travels to the kidney where it increases Na excretion and increases the blood flow to the glomerulus, acting on the afferent glomerular arterioles as a vasodilator or on efferent arterioles as a vasoconstrictor. It decreases aldosterone release from the adrenal cortex and also decreases release of renin, thereby decreasing angiotensin II. ANF acts antagonistically to the renin- angiotensin system, aldosterone and vasopressin.