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What makes the cells of the muscles contract? – Samarth, age 13, India

What makes the cells of the muscles contract? – Samarth, age 13, India

Muscles are amazing. They’re what let you strum a guitar, kick a soccer ball and high-five your friends. When you decide to move, your brain tells your muscles what to do, and they spring into action. But what is actually happening inside your muscles to make that happen?

To answer that question, you first need to understand how your muscles are put together.

What muscles are made of

Every muscle in your body is an organ, and just like every other organ, muscles are made of cells. Muscle cells, called muscle fibers, are shaped a little differently than most other cells. Muscle fibers are long and ropelike. They can stretch and shorten, kind of like a bungee cord.

Each muscle contains a bunch of these fibers all lined up together, side by side, like a bag of dry spaghetti noodles. Some muscles are made of hundreds of thousands of fibers.

The muscles........

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