- RAA system
Hormone | Description |
Renin | Secreted by JG cells in response to ↓ renal perfusion pressure (detected in afferent arteriole), ↑ renal sympathetic discharge (β₁ effect), and ↓ NaCl delivery to macula densa cells. |
ACE | Catalyzes conversion of angiotensin I to angiotensin II. Located in many tissues but conversion occurs most extensively in the lung. Produced by vascular endothelial cells in the lung. |
AT II | Helps maintain blood volume and blood pressure. Affects baroreceptor function; limits reflex bradycardia, which would normally accompany its pressor effects. |
ANP, BNP | Released from atria (ANP) and ventricles (BNP) in response to ↑ volume; inhibits renin-angiotensin-aldosterone system; relaxes vascular smooth muscle via cGMP → ↑ GFR, ↓ renin. Dilates afferent arteriole, promotes natriuresis. |
ADH (vasopressin) | Primarily regulates serum osmolality; also responds to low blood volume states. Stimulates reabsorption of water in collecting ducts. Also stimulates reabsorption of urea in collecting ducts to maximize corticopapillary osmotic gradient. |
Aldosterone | Primarily regulates ECF volume and Na⁺ content; ↑ release in hypovolemic states. Responds to hyperkalemia by ↑ K⁺ excretion. |
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