The P Wave in Sinus Rhythm

The sinus node, since it lives in the high right atrium, and that means that the electrical signal is going to originate there. So when we talk about sinus rhythm, you should have a P wave associated with every QRS. If you have extra P waves, then maybe it's not sinus rhythm. Maybe you got some premature atrial contraction into something like that. And that rate will depend on things like aginergic tone and direct innovation through synthetics, for example, in parasympathetic.