What does a normal sinus rhythm resemble?

A normal sinus rhythm is characterized by its regularity and consistency, typically reflecting a heart rate between 60 and 100 beats per minute. This rhythm shows slight variations with respiration, a phenomenon known as respiratory sinus arrhythmia. During inhalation, the heart rate may slightly increase, while during exhalation, it may decrease, reflecting the influence of the autonomic nervous system on heart rate. This modulation is considered a normal physiological response and indicates a healthy interaction between the heart and respiratory system.

The other choices do not accurately describe the characteristics of a normal sinus rhythm. Randomized and chaotic patterns are indicative of arrhythmias, a consistent heart rate below 60 bpm represents bradycardia, and a heart rate exceeding 250 bpm indicates tachycardia, neither of which align with the normal sinus rhythm parameters.