Final answer:
In sinus bradycardia, the QRS complex is normal in shape and duration, but the heart rate is slower than usual.
Step-by-step explanation:
In sinus bradycardia, the QRS complex is normal in shape and duration. The QRS complex represents the electrical activation and contraction of the ventricles.
However, in sinus bradycardia, the heart rate (pulse) is slower than normal, typically less than 60 beats per minute.
Therefore, in sinus bradycardia, while the QRS complex may appear normal on an electrocardiogram (ECG), the heart rate is slower than usual.