A graph of an action potential demonstrates the specific millivolt (mV) changes across a neuron's membrane during different signaling phases. The process begins at a resting potential of roughly -70mV. Upon reaching the threshold of excitation at approximately -55mV, the neuron fires, causing a spike to a peak action potential of 30mV. As the cell recovers, it undergoes repolarization (dropping to around 5mV) and then hyperpolarization, where the charge dips to roughly -80mV before eventually returning to its baseline resting state.