Problem: Freddy McFreddy, a 64-year-old male presents to the emergency room with light- headedness, dizziness and profuse sweating. He mentions he had suffered a myocardial infraction six months ago. Immediate ECG evaluation shows an arrhythmia. Further investigation reveals that a pacemaker is needed to ensure normal heart rhythm. Of the following, which describes the ability of the heart to spontaneously contract without external stimuli? Looking for Assignment Help? Macula Densa Automaticity Zona Occludens Axons Gap Junctions