Question

1. State the functions and physiologic mechanisms controlling body water levels and sodium concentration, including the effective circulating volume, sympathetic nervous system, renin–angiotensin–aldosterone system, and antidiuretic hormone.

Answer 1

If the effective circulatory volume is low, then Renal blood flow- decreases. This activates renin- angiotensin-aldosterone system( RAAS). The activation of RAAS leads release of renin, and finally angiotensin II is formed. Angiotensin II is powerful vasoconstrictor( increases pre- load and after- load that cause increase in cardiac output and stroke volume), increase aldosterone( helps in salt and water retention from the distal tubule of nephron and maintain blood volume), increases sympathetic outflow( it also causes vasoconstriction to increase stroke volume and cardiac output, it also increase contractility of the heart),etc