<prompt> Gatekeeper of the heart isSA nodeAV nodePurkinje fibersBundle of His  <response>: Ans. b AV nodeRef: Ganong, 25th edp.521AV node conduction is slow. There is a delay of about 0.1 s in spread of impulseThis delay is mainly responsible for the sequential contraction of atrium followed by ventricles. It is for this reason, AV node is also called Gatekeeper to the ventricles 