Final answer:
The automaticity of cardiac cells refers to their ability to self-initiate electrical impulses at a fixed rate, due to a property known as autorhythmicity, which is essential for the heart's regular rhythm and coordinated contractions.
Step-by-step explanation:
Automaticity of cardiac cells refers to the inherent ability of certain cardiac cells, known as pacemaker cells, to spontaneously depolarize and generate an action potential. These cells possess a unique property called autorhythmicity, which means they can initiate their own electrical impulses at set intervals, thereby determining the heart rate. This is a critical function, as it allows the heart to maintain its regular rhythm without direct control from the nervous or endocrine systems.
The prepotential depolarization is the mechanism behind the autorhythmic property of cardiac muscle, in which the membrane potential slowly rises due to the constant influx of sodium ions through special channels, eventually leading to an action potential that triggers muscular contraction. The pacemaker cells then transfer the depolarization to the rest of the cardiac muscle fibers through gap junctions, coordinating the heart's contractions and enabling it to pump blood efficiently.