Regulation of Kidney Function

Your kidneys are super smart! 🧠 They use hormones and feedback loops (with help from your brain, heart, and kidneys themselves) to keep everything balanced. Here’s how:

  • 💧 Osmoreceptors & ADH (Anti-Diuretic Hormone):
    • Special sensors (osmoreceptors) detect changes in blood volume, body fluid levels, or salt concentration.
    • If you lose too much fluid (e.g., sweating), these sensors tell your brain (hypothalamus) to release ADH.
    • ADH makes the kidneys reabsorb more water from urine (in the collecting tubules), so you produce less urine (prevents dehydration!).
    • Extra fluid? Sensors turn off → ADH stops → kidneys release more water 💦.
    • Bonus: ADH also tightens blood vessels → raises blood pressure → boosts kidney filtration (GFR).
  • ⚖️ JGA & Renin-Angiotensin System:
    • If blood pressure or filtration (GFR) drops, kidney cells (JGA) release renin.
    • Renin sets off a chain reaction:
      • Angiotensinogen → Angiotensin I → Angiotensin II (a powerful vessel-squeezer!).
    • Angiotensin II:
      • Raises blood pressure & GFR by narrowing blood vessels.
      • Tells adrenal glands to release aldosterone.
    • Aldosterone makes kidneys reabsorb Na⁺ and water (in distal tubules) → blood pressure & GFR go up 📈.
  • ❤️ Heart’s Safety Check (ANF):
    • Too much blood flowing to the heart? The atria release ANF (Atrial Natriuretic Factor).
    • ANF widens blood vessels → lowers blood pressure → counters the Renin-Angiotensin system.

Micturition (Peeing!)

  • 🫙 Urine made by nephrons collects in the bladder.
  • When full, the bladder stretches → activates stretch receptors.
  • Receptors signal the brain (CNS) → brain sends “go!” message 💌 → you feel the urge to pee!

NEET Must-Knows ⭐

  1. ADH (Vasopressin): Released when body fluids are low → increases water reabsorption → reduces urine output.
  2. Renin-Angiotensin-Aldosterone System (RAAS): Activated by low BP/GFR → raises BP via vasoconstriction & Na⁺/water reabsorption.
  3. ANF vs. RAAS: ANF opposes RAAS → causes vasodilation & lowers BP.
  4. Micturition Reflex: Bladder stretch → CNS signal → voluntary urination.