Sinus node is situated at – Correct Answer: a) Junction of the superior vena cava and right atrium
Sinus node is situated subepicardially, in the upper part of the right atrium, at its junction with the superior vena cava. Subepicardial location explains the common occurrence of sinus tachycardia in pericarditis – due to irritation of the sinus node by the inflamed pericardium.
Atrioventricular node is a subendocardial structure situated near the lower part of right side of the interatrial septum and penetrates the annulus fibrosus. Annulus fibrosus electrically isolates the atria from the ventricles.