What term describes the ability of the pacemaker cells of the heart to create an electrical impulse without external stimulation?

The ability of pacemaker cells in the heart to generate electrical impulses spontaneously without any external stimulation is known as automaticity. This characteristic is crucial for maintaining the heart's rhythm and ensuring that it beats at a consistent pace. The pacemaker cells, primarily found in the sinoatrial (SA) node, exhibit this property, allowing them to initiate action potentials that subsequently lead to heart contractions.

Automaticity enables the heart to function autonomously, setting the basic heart rate that can be modulated by the autonomic nervous system and various hormonal factors. This intrinsic capacity to initiate impulse formation is fundamental for the normal functioning of the cardiac cycle and is what enables the heart to maintain its rhythm even in the absence of external signals.