Cardiac output is defined as the volume of blood:

Explain heart sounds.

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.

The cardiac impulse,which causes the heartbeat,is delayed in which of the following?

The blood pumped by the $A$ ventricle enters the $B$ artery,whereas the $C$ ventricle pumps blood into the $D$. Choose the correct option for $A, B, C$ and $D$.

What causes the first heart sound?