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The Cells of the Heart
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The Cells of the Heart
From the standpoint of the electrocardiographer, the heart consists of
three types of cells:
•
Pacemaker cells
—under normal circumstances, the electrical
power source of the heart
•
Electrical conducting cells
—the hard wiring of the heart
•
Myocardial cells
—the contractile machinery of the heart
Myocardial cells
Conduction pathway
Pacemaker
Pacemaker Cells
Pacemaker cells
are small cells approximately 5 to 10 μm long, about
the same as the width of a single strand of a spider’s web. These cells
are able to depolarize spontaneously over and over again. The rate of
depolarization is determined by the innate electrical characteristics
of the cell and by external neurohormonal input. Each spontaneous
depolarization serves as the source of a wave of depolarization that
initiates one complete cycle of cardiac contraction and relaxation.