ventricular contraction in command of:-

Ans - Purkinji fibers SA node(located in right atrium) sends stimulus to contract atria and after that stimulus travel to the AV node, which is located in the internal septum. After little while stimulus travels to bundle of His and then to purkinje fibers for each side of the heart,then purkinje fiber helps to contract.

Signals arising in the SA node (located in the right atrium) stimulate the atria to contract and travel to the AV node, which is located in the interatrial septum. After a delay, the stimulus diverges and is conducted through the left and right bundle of His to the respective Purkinje fibers for each side of the heart, as well as to the endocardium at the apex of the heart, and then finally to the ventricular epicardium. Purkinje fibers allow the heart's conduction system to create synchronized contractions of the ventricles.