Muscle contraction

When we want our muscles to move, our brain tells them what to do. But how do the muscles actually move? Well, inside our muscles, there are tiny little fibers called muscle fibers.

When our brain tells our muscles to move, it sends a message down to the muscle fibers. The message tells the muscle fibers to grab onto each other and pull.

But how do the muscle fibers grab onto each other and pull? That's where a special chemical called "ATP" comes in. ATP is like a battery for our muscles. It gives them the energy they need to move.

When our brain sends a message down to the muscle fibers, it also tells the muscle fibers to use some of their ATP to grab onto each other and pull. When the muscle fibers use their ATP, they create a little spark of electricity.

This spark of electricity makes the muscle fibers change shape, kind of like when you twist a rubber band. When the muscle fibers change shape, they grab onto each other and pull, like a tug-of-war.

This pulling makes our muscles move! And when we're done moving, our muscles use more ATP to let go of each other and go back to their original shape.

So that's how our muscles move. Our brain sends a message down to the muscle fibers, the muscle fibers use ATP to pull on each other, and this pulling makes our muscles move.