Gatekeeper of the heart is

Ans. (b) AV node(Ref: Ganong, 25th ed/p.521)AV 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