Question: Resting Membrane Potential

Answer: All voltage-gated channels are closed

Question: Threshold

Answer: EPSP summate depolarizing membrane to threshold, at which point activation gates of voltage-gated sodium channels open

Question: Depolarization Phase

Answer: Sodium floods into the axon, making the interior so positive the membrane potential goes to +40 mV

Question: Repolarization Phase

Answer: Deactivation gates of voltage-gated sodium channels close. Voltage-gated potassium channels open

Question: Undershoot

Answer: Voltage-gated potassium channels are slow to close. So much potassium leaves the axon that the interior becomes more negative than the original resting membrane potential

Question: Sodium Potassium pumps

Answer: Re-establish original ion distribution so that a subsequent action potential can occur