Which statements accurately describe characteristics of normal sinus rhythm (NSR)? (Select all that apply)

Normal sinus rhythm represents the standard physiological cardiac cycle initiated by the sinoatrial node, which serves as the primary cardiac pacemaker located in the right atrium. It is characterized by hemodynamic stability and a highly predictable, rhythmic electrical conduction pattern through the myocardium. A. The adult human heart under normal physiological conditions maintains a resting rate between 60 and 100 beats per minute. Rates below 60 signify sinus bradycardia, while rates exceeding 100 indicate sinus tachycardia. This range ensures optimal cardiac output and adequate diastolic filling time for the coronary arteries. B. In a healthy cardiac cycle, each P wave signifies atrial depolarization, which is the electrical trigger for atrial contraction. In normal sinus rhythm, there must be exactly one P wave preceding every QRS complex, indicating that the electrical impulse originated correctly within the sinoatrial node. C. This statement is physiologically incorrect. In normal sinus rhythm, the P wave must precede the QRS complex, not follow it. A P wave occurring after the QRS complex suggests a junctional rhythm or a retrograde conduction issue, which deviates from the standard electrical pathway of a normal rhythm. D. The T wave represents ventricular repolarization, a critical phase where the ventricles recover electrically and prepare for the next contraction. Normal sinus rhythm requires a single, identifiable T wave following the QRS complex to signify that the ventricular recovery process is occurring in a timely and uniform manner. E. The QRS complex represents the electrical depolarization of the ventricles, which triggers ventricular systole. In normal sinus rhythm, every P wave is followed by exactly one QRS complex at a consistent interval, ensuring that the ventricles contract efficiently to pump oxygenated blood to the systemic circulation.