There are more than 600 muscles in your body. They pump your blood all through your body, help you move and help you lift things.

Muscles are an elastic tissue, a bit like a rubber band. There are thousands of fibres that make up each muscle. Many muscles are attached to bones, and are called skeletal muscles. Some are attached to organs.

Most muscles work together in pairs. One muscle pulls while the other relaxes. For example, when you bend your arm the biceps muscle pulls and the triceps muscle relaxes. When you make your arm straight, the biceps relaxes and the triceps pulls. 

Voluntary muscles work when you think about wanting to do something. As one muscle contracts the other relaxes and this moves the bones.

Voluntary muscles work when you think about wanting to do something. As one muscle contracts the other relaxes and this moves the bones.

Voluntary muscles

Skeletal muscles, such as those in your arms and legs, only work when you think about making them work. For example, when you want to lift something or go for a run your brain sends and receives signals through your nervous system to make the muscles work. These are the voluntary muscles. So the amount of work they do will depend on how active you are.

Involuntary muscles

Other muscles, such as the those in the diaphragm, the heart and the intestines work without you having to think about them. These are called smooth muscles. You breathe, your heart pumps and your food is digested automatically, your eyes focus, all controlled by the brain and the nerves. These are called involuntary muscles. The one that work your heart is an involuntary one too, but it is called the cardiac muscle. It works harder than any of the others!

Do you know?

  • You use 17 muscles when you smile.

  • You use 43 muscles when you frown. 

 

Read more facts about muscles:

http://www.sciencekids.co.nz/sciencefacts/humanbody/muscles.html

Watch an interactive animation:

http://www.kidsknowit.com/interactive-educational-movies/free-online-movies.php?movie=Skeletomuscular

Watch a video about the kinds of muscles and how they work