Ganong's Review of Medical Physiology, 23rd Edition

CHAPTER 30

Origin of the Heartbeat & the Electrical Activity of the Heart 493

FIGURE 30–4
Normal spread of electrical activity in the heart. A)
Conducting system of the heart.
B)
Sequence of cardiac excitation.
Top:
Anatomical position of electrical activity.
Bottom:
corresponding electrocardiogram. The yellow color denotes areas that are depolarized.
(Reproduced with permission from Goldman MJ:
Principles of Clinical Electrocardiography,
12th ed. Originally published by Appleton & Lange. Copyright © 1986 by McGraw-Hill.)

Electrocardiogram

Time Time Time Time Time

Superior

vena cava

Sinoatrial

node

Right

bundle

branch

Purkinje

fibers

Right

ventricle

Right

atrium

Left

ventricle

Interventricular

septum

Left

atrium

Inferior

vena cava

Atrioventricular node

Bundle of His

Left bundle branch

Atrial excitation

Begins

SA node AV node Atrial

relaxation

Complete Begins Complete

Ventricular excitation Ventricular relaxation

A

B