In humans,the heart rate of $72$ beats/minute is regulated by which of the following?

The tricuspid valve is present at the origin of

In the heart of a mammal,the bicuspid valve is situated between:

Autorhythmicity is a special property of the muscles of the

Where is the Eustachian valve found?

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.