Tracing the renin to aldosterone chain
The renin-angiotensin-aldosterone system links a drop in blood pressure or sodium to a hormonal correction. Juxtaglomerular cells in the kidney release renin when they sense low perfusion pressure, low filtered sodium at the macula densa, or sympathetic stimulation. Renin cleaves liver-made angiotensinogen into angiotensin I.
Angiotensin-converting enzyme, found mainly on the lung vasculature, then converts angiotensin I into angiotensin II, the active vasoconstrictor. Angiotensin II tightens blood vessels and prompts the adrenal cortex to secrete aldosterone, completing the cascade named in the diagram.
What aldosterone does to sodium and potassium
Aldosterone acts on the distal tubule and collecting duct of the nephron, increasing reabsorption of sodium and water while promoting potassium and hydrogen ion excretion. Holding onto sodium and water expands blood volume, which raises blood pressure back toward set point. This is why the system is described as a feedback loop rather than a one-way switch.
Because this pathway sets blood pressure and electrolyte balance, several common medications target it, including ACE inhibitors and aldosterone-receptor blockers. The interactions here are genuinely clinical. This is general educational information, not medical advice; medication and electrolyte decisions should be made with a qualified professional.