Action Potentials on the MCAT: Phases, Ion Channels, and High-Yield Triggers
Action potentials are electrical impulses that allow nerve cells to communicate and muscles to contract. On the MCAT, you’ll need to know the phases, which ions move, how channels operate, and how experimental drugs affect these processes. Let’s walk through everything you need—with KOTC visuals, tables, and real exam strategies.
⚡ What Is an Action Potential?
An action potential is a brief reversal of membrane potential that travels along the length of a neuron, allowing it to transmit a signal.
🧠 MCAT Tip: Focus on which ion (Na⁺ or K⁺) is moving at each stage!
🔬 Phases of an Action Potential
| Phase | What Happens | Key Ion Movement |
|---|---|---|
| Resting Potential | Membrane at ~ -70 mV, ready to fire | Na⁺ outside, K⁺ inside |
| Depolarization | Membrane becomes positive | Na⁺ rushes in |
| Peak | ~+30 mV achieved | Na⁺ channels inactivate |
| Repolarization | Membrane returns to negative | K⁺ exits cell |
| Hyperpolarization | Membrane dips below -70 mV temporarily | K⁺ channels slow to close |
🧠 Trick Question Alert: MCAT often hides hyperpolarization-related questions in experiments!
🧪 MCAT-Style Passage Examples
✅ Example 1:
"A drug selectively blocks voltage-gated Na⁺ channels..."
✅ Stops depolarization → Action potential fails to start
✅ Example 2:
"Mutation in voltage-gated K⁺ channels slows closing..."
✅ Leads to prolonged hyperpolarization → Neuron less excitable
🔋 Resting Membrane Potential: Quick Reminder
| Feature | Details |
|---|---|
| Maintained by | Na⁺/K⁺ ATPase pump (3 Na⁺ out, 2 K⁺ in) |
| Leak channels | K⁺ leak channels allow slow K⁺ efflux |
| Typical membrane potential | Approximately -70 mV |
🧠 Final MCAT Tips for Action Potentials
Depolarization = Na⁺ influx
Repolarization = K⁺ efflux
Understand voltage-gated vs ligand-gated channel differences
Review experimental drug effects carefully—which ion is disrupted matters!
✅ Call-to-Action (CTA)
Don’t let action potentials trip you up! Visualize every phase and ion movement with King of the Curve’s interactive science maps, MCAT drills, and visual Q-banks designed for faster, deeper learning.
Frequently Asked Questions (FAQs)
-
Aim for 4-6 focused hours, ensuring you incorporate breaks to avoid burnout.
-
Practice mindfulness techniques, take practice exams under realistic conditions, and maintain a balanced lifestyle.
-
Set short-term goals, seek support from mentors, and reward yourself for small achievements.
-
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.
