<prompt> The latch-bridge mechanism in smooth muscle is responsible for:Fast muscle twitchSustained muscle contractionExcitation-contraction couplingUnstable membrane potential  <response>: 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. 