Bio22 Human Physiology - Cardiovascular: Heart and Blood Vessels Homework Cardiovascular: Ch18 Heart 1. Why is it important for pacemaker cells to have an unstable resting membrane potential? 2. Conduction system of the heart: What does it mean to have an artificial pacemaker and why would you need one? 3. Label the P wave, QRS complex, and T wave for each ECG below. Which one is normal? What is abnormal about the other two? luadral.