The nerve-like modified muscle in the right auricle is known as:

Purkinje fibers are found in:

State the location of the $SA$ node and the $AV$ node.

What is the heart rate in children compared to adults?

The circulation of blood was discovered by .....

Select the correct option:
$(1)$ The pericardium is a double-layered membrane surrounding the heart.
$(2)$ The $SA$ node has a higher rate of impulse generation compared to the $AV$ node.