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P Waves, QRS Complexes, T Waves, and Some Straight Lines
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branch. The right and left ventricles then depolarize at about the
same time, but most of what we see on the EKG represents left
ventricular activation because the muscle mass of the left ventricle is
about three times that of the right ventricle.
Repolarization
After myocardial cells depolarize, they pass through a brief refractory
period during which they are resistant to further stimulation. They
then
repolarize
; that is, they restore the electronegativity of their
interiors so that they can be restimulated.
Just as there is a wave of depolarization, there is also a wave of
repolarization. This, too, can be seen on the EKG. Ventricular
repolarization inscribes a third wave on the EKG, the
T wave
.
Depolarization of the septum
The initial part of the QRS complex represents septal depolarization.
Sometimes, this septal depolarization may appear as a small, discrete,
negative deflection, a Q wave.
Note:
There is a wave of atrial repolarization as well, but it coincides
with ventricular depolarization and is hidden by the much more
prominent QRS complex.