Underneath our skin there are muscles.
They are joined onto our bones.
They pull the bones to make my body move.
Some of them work all day and all night.
Humans have more than 600 muscles in their body.
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
Skeletal muscles 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 involuntary muscles. You breathe, your heart pumps and your food is digested automatically, your eyes focus, all controlled by the brain and the nerves. The one that works 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.
The heart is the hardest working muscle.
The smallest muscles are in the ears.
It’s a good idea to get information from more than one source!
Read more facts about muscles:
http://www.sciencekids.co.nz/sciencefacts/humanbody/muscles.html
Watch a video about the kinds of muscles and how they work
https://study.com/academy/lesson/major-muscle-groups-of-the-human-body.html
