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[HAP-01] Cellular Physiology, Membrane Potentials, Ion Channels & Homeostasis
HAP-01 • 1. Anatomy & PhysiologyLearning Objectives
Compare passive diffusion, facilitated diffusion, primary active transport (Na+/K+-ATPase, H+/K+-ATPase), and secondary active symport/antiport.; Calculate resting membrane potential (-70 to -90 mV) via the Nernst equation and trace action potential phases (depolarization, overshoot, repolarization, hyperpolarization).; Link cellular ion channels directly to canonical pharmacotherapy targets.
Chapter Overview & Core Explanation
Every human cell maintains an electrical voltage across its outer membrane by pumping sodium out and potassium in. Nerve impulses, muscle contractions, and heartbeats happen when specialized ion channels open for a fraction of a second to let ions rush across.
Key Exam & Clinical Takeaways
- The Na+/K+-ATPase pump extrudes 3 Na+ ions for every 2 K+ ions imported per ATP hydrolysed, making the cell interior electronegative.
- IV [10.10] Calcium Gluconate does NOT lower serum potassium concentration—it raises the cardiac threshold potential to prevent ventricular fibrillation while potassium-shifting drugs take effect.