Hyperpolarization occurs following repolarization. Voltage-gated potassium channels stay open past the end of repolarization to a final membrane potential between -80 mV and -90 mV. This occurs in order to interrupt the positive feedback loop of the action potential. By overshooting the resting potential, it becomes tougher to quickly re-fire an action potential. Thanks to this, action potentials can’t reverb back down an axon in the opposite direction. The axon is hyperpolarized during the relative refractory period.