What prevents the atria and the ventricles from contracting at the same time?

A. Pacemaker cells located in the atria fire before the pacemaker cells in the ventricles. B. It takes time for hormones to diffuse from the atria to the ventricles to trigger contraction. C.The electrical signal generated in the right atrium is delayed at the AV node before passing to the ventricles. D.The ventricular muscle cells contract more slowly than the atrial muscle cells.

The average resting heart rate (hrrest) for a 34 year old is 73 beats per minute2. 34 year old males average heart rates of 71 bpm while females average slightly higher at 76 bpm2. the normal resting heart rate range for all adults and children 10 and over is between 60 and 100 beats per minute3. 90% of 34 year olds resting pulses fall within the range of 54 to 92 bpm. in general, an adult's resting heart rate will be lower for those in better athletic condition.