Muscles of the heart are

............ can generate the maximum number of action potentials and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore,it is called the pacemaker.

The opening between the right atrium and the right ventricle is guarded by . . . . . . .

Which of the following has the ability to generate an action potential without any external stimulus?

Which structure generates an action potential without any external stimulus?

Cardiac muscles are .....