This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Physiology
[{'content': 'The latch-bridge mechanism in smooth muscle is responsible for: \nSelect and explain. \nA. Fast muscle twitch, B. Sustained muscle contraction, C. Excitation-contraction coupling, D. Unstable membrane potential', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Sustained muscle contractionThe twitch duration in sphincters and smooth muscle is particularly longer. Latch bridges are actomyosin complexes that detach slowly; this is made possible by a slow myosin ATPase. In turn, this enables maintenance of tension for longer periods without consumption of more ATP.', 'role': 'assistant'}]