This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
[{'content': 'Heart muscles act as a functional syncitium because: \nSelect and explain. \nA. Striations, B. Gap junctions, C. Long action potential, D. It is voluntary', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans: b (Gap junctions) Ref: Ganong, 22nd ed, p. 78; Guyton, 11th ed, p. 103,104The gap junctions between adjacent cells provide low resistance bridges for the spread of excitation and function it as a functional syncitium even though no protoplasmic bridges are present between the cells.Histological features of cardiac muscle* Striated muscle with actin and myosin filaments.* The fibers branch and interdigitate.* Single nucleus present.* Intercalated disc present at the Z lines.* Gap junctions are present helping it to act as a functional syncytium.* Neural control depends on the pace maker.', 'role': 'assistant'}]