|Sinus rhythms originate in the SA Node. The Heart Rates (HR) are particularly important: Please study/learn/know.
Normal sinus rhythm HR: 60-100 b/min
Sinus bradycardia HR: <60 b/min
Sinus tachycardia HR: >100 b/min to ~150 b/min (it is sometimes a little faster that 150 b/min)
Sinus arrhythmia: ~60 to ~100 b/min (yes, it sometimes is slower than 60 bpm and sometimes a little faster than 100 b/min)