Zoology - Body Fluids and Circulation Question with Solution | TestHub

Sinu-auricular node or S-A node is located in the wall of the right auricle below the opening of the superior vena cava. The S-A node has unique property of self excitation, which enables it to act the "pacemaker" of the heart. It spontaneously initiates a wave of contraction which spreads over both the auricles more or less simultaneously along the muscle fibres that fan out from the pacemaker.