Which structure is formed from the bundle of His?

$SAN$ generates an action potential which stimulates both the $A$ to undergo a simultaneous contraction called $B$. This increases the flow of the blood into the ventricles by about $C$ percentage. Choose the correct option for $A, B$ and $C$.

In cardiac muscles,the number of mitochondria is:

The walls of the ventricles are much thicker than those of the atria because

Which is an incorrect statement?

The cardiac pacemaker in a patient fails to function normally. The doctors find that an artificial pacemaker is to be grafted in him. It is likely that it will be grafted at the site of