Q.Explain briefly the renin-angiotensin-aldosterone system (RAAS) and its overall effect on blood pressure and kidney function.

[!TLDR]

RAAS: falling BP -> renin -> angiotensin II (vasoconstriction) -> aldosterone (Na+/water reabsorption) -> BP restored. …

The renin-angiotensin-aldosterone system (RAAS) is a hormonal cascade that restores blood pressure and blood volume whenever they fall too low. It begins when the juxtaglomerular apparatus, sensing a fall in glomerular blood flow or blood pressure, releases the enzyme renin into the blood. Renin converts angiotensinogen, an inactive plasma protein continuously produced by the liver, into angiotensin I; angiotensin I is then converted, chiefly in the capillaries of the lungs, into angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II acts in two ways: it is itself a powerful vasoconstrictor, directly narrowing blood vessels and raising blood pressure, and it also stimulates the adrenal cortex to secrete the hormone aldosterone. Aldosterone acts on the distal convoluted tubule, promoting active reabsorption of Na+ and, following it osmotically, water, which raises blood volume and further raises blood pressure. The overall effect of RAAS, therefore, is to restore both blood pressure and glo …

Trace the cascade step by step in strict order: renin -> angiotensin I -> angiotensin II (ACE) -> aldostero …

Omitting the intermediate angiotensin I to angiotensin II conversion step (via ACE, in the lungs), or confusing angiotensin II's direct vasoconstrictor action with aldosterone's separate action of pr …