Download Many Muscles

FROM HEAD TO TOE
173
12
© 2010 AIMS Education Foundation
1
he next time you lift a book or
take a walk or eat an apple, think
about all the muscles you have working
together to make
it possible.
link you eyes. Wiggle your
fingers. Nod your head.
All of these motions were made
possible by muscles. Without
muscles you would be a pile of
skin and bones. You
wouldn’t be able
to stand,
talk, shrug,
or even
smile.
ou can also do this with the
muscles in your eyelids. Your eyes
are constantly blinking to keep your
eyes moist and to keep
out dust and other
particles. But
you have the
ability to
blink or
wink on
command,
to hold
your eyes
closed, or
to hold one
eye open at
a time.
11
2
4
9
ou have about 600 skeletal
muscles in your body. The largest
is the gluteus maximus. This is the
muscle on your bottom. The smallest
muscle is inside your ear. It is called
the stapedius. It is just a little over one
millimeter long.
ardiac muscle is a special kind
of involuntary muscle. It’s only
found in the heart. Your heart muscle
pumps about 100,000 times each day
to move blood through your body.
ome of your muscles are
normally controlled by
your brain but can also
be controlled by you
if you think about
it. You breathe all
day and all night
without giving it
much thought,
but if you want,
you can hold your
breath, take a deep
breath, or breathe in
and out very quickly.
ou have three kinds of muscles
in your body—skeletal, smooth,
and cardiac. Skeletal muscles are what
you usually think of when you think of
muscles. These are the muscles that are
attached to your bones. They help you
walk, talk, lift, carry,
squat, bend, smile,
and more.
10
FROM HEAD TO TOE
3
174
© 2010 AIMS Education Foundation
6
7
our other muscles are
involuntary. That means
that you can’t control
them. Your brain
keeps them
doing what they
should be doing
automatically.
You have
two kinds of
involuntary
muscles—smooth
and cardiac.
uscles can only pull; they cannot
push. That means that many
skeletal muscles need to work in pairs to
help your body parts move. Your arms are
a good example. You have one muscle—
the biceps—that pulls on your forearm,
allowing you to bring your hand to your
shoulder. Its pair—the triceps—pulls on the
back of your elbow, making your
arm straight again.
keletal muscles are also called
voluntary muscles because these
are the muscles that you can control.
You can lift your
arms, kick your
legs, smile,
frown, and
pick up a
pencil just
by thinking
about
it and
doing it.
mooth muscles are found in your
digestive system. They contract
and relax to move food through your
body. The iris in your eye is also a
smooth muscle. It controls the amount
of light that comes into your eyes
through the pupils. Your bladder is
another place where smooth muscles
are at work.
8
FROM HEAD TO TOE
5
175
© 2010 AIMS Education Foundation