Class 11 NEET Biology Body Fluids and Circulation

(b) : AV (atrioventricular) node is a mass of modified heart muscle situated in the lower middle part of the right atrium. It receives the impulse to contract from the SA node via the atria and transmits it through the atrioventricular bundles to the ventricles. AV node is called the pacesetter. Here, the impulses are delayed for 0.1 second to ensure that the auricles will contract first and empty fully before the ventricles contract.