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Figure 1: Human Heart
Basic Electrophysiology
Properties of cardiac cells
The primary characteristics of the cardiac cells are:
1. Automaticity – This is the ability of the cardiac pacemaker cells to spontaneously initiate
their own electrical impulse without being stimulated from another source. Sites that possess
this characteristic are the SA node, AV junction, and the Purkinje fibers.
2. Excitability – Also referred to as irritability. This characteristic is shared by all cardiac cells
and it is the ability to respond to external stimulus: electrical, chemical, and mechanical.
3. Conductivity – This is the ability of all cardiac cells to receive an electrical stimulus and
transmit the stimulus to the other cardiac cells.
4. Contractility -- This is the ability of the cardiac cells to shorten and cause cardiac muscle
contraction in response to an electrical stimulus. This characteristic can be enhanced through
administration of certain medications, such as digitalis, dopamine and epinephrine.
National Healthcareer Association EKG Study Guide (Ea) 7
