What is after hyperpolarization?

As a neuroscientist with a focus on cellular and molecular neuroscience, I can explain the concept of afterhyperpolarization (AHP) and its sequence in the neuronal firing process. After an action potential, neurons experience a brief period of hyperpolarization known as the afterhyperpolarization (AHP). This phase is characterized by the membrane potential of the neuron becoming more negative than the resting potential. The AHP serves to prevent the neuron from immediately firing another action potential, thus acting as a protective mechanism against excessive neuronal activity. Following the AHP, the neuron's membrane potential will gradually return towards its resting state, a process known as repolarization. During repolarization, ion channels in the neuron's membrane work to restore the resting potential, typically by allowing potassium ions (K⁺) to exit the cell and sodium ions (Na⁺) to enter. Once the neuron reaches its resting potential, it is once again ready to respond to stimuli and potentially generate another action potential. So, to summarize, the sequence after an action potential is as follows: 1. Action Potential: The neuron fires, with a rapid change in membrane potential. 2. Afterhyperpolarization (AHP): The membrane potential becomes more negative than the resting potential. 3. Repolarization: The membrane potential returns to the resting potential, preparing the neuron for subsequent activity.

Afterhyperpolarization, or AHP, describes the hyperpolarizing phase of a neuron's action potential where the cell's membrane potential falls below the normal resting potential. This is also commonly referred to as an action potential's undershoot phase.