Neuron Action Potential – AP Biology

Key Phases

Resting (-70mV): Maintained by Na+/K+ Pump (ATP).

Depolarization (+30mV): Sodium (Na+) channels snap open. Na+ rushes IN.

Repolarization: Potassium (K+) channels open. K+ rushes OUT.

Hyperpolarization: Overshoot to -80mV before returning to rest.

All-or-None Principle

Stimulus must cross the Threshold (-55mV) to trigger a full action potential. Weaker stimuli generate graded potentials that die out.