Final answer:
An action potential is often referred to as a "spike" because of its spike-like pattern on a voltage graph, which occurs due to depolarization and repolarization events as Na+ and K+ ions move across a neuron's membrane.
Step-by-step explanation:
Due to its appearance, an action potential is often referred to as a "spike" or "impulse" because of the characteristic spike-like upward and downward shifts in voltage observed in a graph when it is plotted overtime. An action potential is a momentary but significant reversal of the electrical charge across the membrane of a resting neuron that travels rapidly along the axon as a nerve impulse. This electrical event occurs when a neuron receives a chemical stimulus that leads to the sudden influx of sodium ions (Na+) as the membrane becomes permeable, causing depolarization. This is followed by the efflux of potassium ions (K+), leading to repolarization. During an action potential, these events produce a characteristic pattern on voltage graphs that resemble spikes, hence the common reference to spike.