Slow afterhyperpolarization
Slow afterhyperpolarisation (sAHP) refers to prolonged periods of hyperpolarisation in a neuron or cardiomyocyte following an action potential or other depolarising event. In neurons, trains of action potentials may be required to induce sAHPs; this is unlike fast AHPs that require no more than a single action potential.
Source: Wikipedia — Slow afterhyperpolarization (CC BY-SA 4.0)