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Muscles
Your body has more than 700
muscles. Without these muscles, you’d
be going nowhere! Every move you
make is powered by muscles. Muscles
help you walk, run, and hit a baseball.
When you blink, chew, or talk, you are
using your muscles. Muscles also help
keep your body upright and make your
movements steady.
Muscles are made up of small, thick
bundles of fibers. These fibers are
designed for movement. When muscles
contract, they pull the bones, causing
movement.
About 650 of your muscles are skeletal muscles. Skeletal muscles move
the arms, legs, and other parts of the body. Skeletal muscles are also
called voluntary muscles. That’s because you can control these muscles.
There are two other types of muscles. They are smooth muscles and
cardiac muscles. Smooth muscles are found in the walls of blood vessels
and some organs. Cardiac muscles are found in the walls of the heart.
Muscle Pairs
Skeletal muscles nearly always work in pairs
or groups. While one muscle contracts, the
other relaxes. Look at your upper arm as
you bend your arm at the elbow. The biceps
and triceps muscles in your upper arm are
working together. The biceps contracts and
becomes shorter, while the triceps
relaxes and becomes longer.
It’s important to take care of
your muscles. This means getting
plenty of exercise and eating well.
The more your muscles are used, the
stronger they will become and the better they
will work.
Muscles help you run
and kick soccer balls.
biceps
triceps
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