Is hyperpolarization and repolarization the same thing?

Hello, I'm an expert in the field of neuroscience with a focus on cellular electrophysiology. Let's dive into the concepts of hyperpolarization and repolarization. Repolarization and hyperpolarization are related but distinct processes that occur during the action potential of a neuron. Repolarization is the phase of the action potential where the neuron's membrane potential returns to its resting state after a depolarization event. This is primarily driven by the efflux of potassium ions (K+) out of the cell, which helps to restore the resting membrane potential. Hyperpolarization, on the other hand, is a condition where the membrane potential becomes more negative than the resting potential. It can occur during the repolarization phase of an action potential, particularly at the end of the repolarization when the membrane potential overshoots the resting potential, resulting in an afterhyperpolarization (AHP). So, while repolarization is the process of returning to the resting membrane potential, hyperpolarization is a state that can occur during the repolarization phase but is characterized by a membrane potential that is more negative than the resting state.

Repolarization typically results from the movement of positively charged K+ ions out of the cell. The repolarization phase of an action potential initially results in hyperpolarization, attainment of a membrane potential, termed the afterhyperpolarization, that is more negative than the resting potential.