Renin-Angiotensin-Aldosterone System (RAAS): MCAT Mastery

Blood pressure regulation is critical for survivalβ€”and for MCAT success. One of the most testable mechanisms is the Renin-Angiotensin-Aldosterone System (RAAS). Whether it's passage-based physiology or hormone signaling logic, you’ll need to know this cold. Let’s simplify it with a clear diagram, high-yield notes, and MCAT-ready associations.

πŸ”„ Step-by-Step RAAS Cascade

Step Molecule/Action
1. Renin release From JG cells in kidney
2. Angiotensinogen cleaved Liver β†’ Angiotensin I
3. ACE converts it Lungs: Angiotensin I β†’ Angiotensin II
4. Angiotensin II effects ↑ Vasoconstriction, ↑ ADH, ↑ Aldosterone
5. Aldosterone released Adrenal cortex β†’ ↑ Na⁺ reabsorption
6. Blood pressure increases Water follows Na⁺ β†’ ↑ Volume & Pressure

πŸ’‘ Effects of RAAS on the Body

Target Organ Action
Blood vessels Vasoconstriction via angiotensin II
Kidneys Aldosterone ↑ Na⁺/Hβ‚‚O reabsorption
Brain Stimulates ADH release and thirst
Adrenal glands Produce aldosterone

πŸ§ͺ MCAT Experimental Example

βœ… Question Example:

"A patient taking ACE inhibitors has reduced BP and increased plasma renin..."

Answer: ACE is blocked β†’ less angiotensin II β†’ no aldosterone β†’ Na⁺ not reabsorbed β†’ BP stays low
🧠 ACE inhibitors are a favorite pharmacology angle for test passages!

πŸ” RAAS vs ADH

Hormone Source Trigger Action
Aldosterone Adrenal cortex Angiotensin II Na⁺/Hβ‚‚O reabsorption in distal nephron
ADH (Vasopressin) Posterior pituitary High blood osmolality Water retention in collecting duct

🧠 MCAT Tip: Aldosterone regulates volume, ADH regulates osmolality.

🧠 Final MCAT Tips

  • Know the sequence: Renin β†’ Ang I β†’ Ang II β†’ Aldosterone

  • Understand where each hormone comes from and what it acts on

  • Be ready to analyze medications (like ACE inhibitors or angiotensin blockers)

  • Associate low BP or dehydration with RAAS activation

βœ… Call-to-Action (CTA)

RAAS doesn’t have to be confusing. Use King of the Curve’s visual tools, adaptive questions, and daily concept drills to lock it in.

πŸ‘‰ Start your free KOTC trial now


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Frequently Asked Questions (FAQs)

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  • Regular exercise improves focus, reduces stress, and enhances overall mental clarity.

  • KOTC offers personalized learning tools, gamification features, and adaptive question banks to help students stay on track without burnout.

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