Anatomy & Physiology第 68 / 100 题
Why does the impulse pause briefly at the AV node, and how does that pause appear on the EKG?
a.To let the ventricles repolarize; it appears as the T wave
b.To let the coronary arteries fill; it appears as the QT interval
c.To let the atria finish contracting and fill the ventricles; it appears as the flat segment of the PR interval
d.To slow the SA node; it appears as the ST segment
解析
The AV node delays the impulse about a tenth of a second so the atria can complete their contraction and top off ventricular filling before the ventricles fire, and that delay is the flat portion of the PR interval between the end of the P wave and the start of the QRS. The T wave represents ventricular repolarization. The ST segment is the interval between depolarization and repolarization of the ventricles, and the AV node does not regulate the SA node.
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