Passage of the electrical signal from the structure of the heart labeled "1" to the structure labeled "2" corresponds to what part of the electrocardiogram (EKG)?
Biochemistry / Physiology
Th electrical activity of the heart begins with spontaneous depolarization of the sinoatrial (SA) node ("1")which is the natural "pacemaker" of the heart. This wave of depolarization then spreads to the atria causing their contraction. The depolarization wave enters the atrioventricular (AV) node ("2")where there is a slight delay in conduction of the electrical signal to the ventricles. This delay is necessary so that the ventricles adequately fill up with blood from the atria. The electrical signal then travels along the bundle of His ("3")and multiple terminal Purkinje fibers to reach the ventricular epicardium, causing ventricular contraction.
The PR interval of the EKG represents the electrical activity between the SA and through the AV nodes.