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You inhale about 25,000 times a day, and you swallow dozens of times in a single meal.
Your heart beats between 60 and 100 times a minute, even when you aren’t doing much. Suppose you had to actually tell each and every muscle how and when to contract and relax. You wouldn’t have much time to do anything else! Luckily, you don’t have to do that, thanks to involuntary muscles, which operate without you thinking about them at all. They do their work while you go on about your life.
There are two types of involuntary muscles—smooth muscles and cardiac muscles.