The Heart’s Electrical System
The heart muscle is directed by an electrical system. An impulse is sent through the
heart’s conduction system, causing the heart to beat. As the heart beats, blood is pumped
to the body.
Normal heart rate — 60 to 100 beats per minute.
Tachycardia — heart is beating more than 100 beats per minute.
Bradycardia — heart is beating less than 60 beats per minute.
Keep in mind that certain medications can lower a person’s normal resting heart rate.
An EKG shows the electrical activity of the heart on a tracing. Electrical energy of the
heart follows a specific path.
Pacemakers of the Heart
SA (sino-atrial) node: 60 to 100
beats per minute. The SA node is
in the right atrium and acts as the
heart’s natural pacemaker. It sends
an impulse that travels a path
through the atria.
AV (atrio-ventricular) node:
delays or blocks impulses that are
coming too fast. This
allows time for the blood to
SA node
fill the ventricles.
AV junction: 40 to 60 beats
per minute.
Purkinje fibers
AV node
Purkinje fibers: 20 to 40 beats
per minute.
AV junction
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