Blood to the heart is brought by the venous system by:

Identify the correct statement.
$I$. The impulse of the heart beat originates from $SAN$.
$II$. Rate of the heart is determined by $SAN$.
$III$. Bundle of His/$AV$ bundle is present in the interventricular septum.
$IV$. Atrio Ventricular Node $(AVN)$ is situated in the lower left corner of the right auricle.
Choose the correct option.

Which arteries supply blood to the pericardium?

Select the mismatched pair from the following.

Which one of the following is a matching pair?

What is the maximum efficiency of the heart?