Download What Makes Your Body Move?

Body Works
What Makes Your Body Move?
Exploration Connection:
Your muscles
Your skeleton allows your body to move, but what makes
it move? Your muscles. Some muscles are “voluntary.” They
are the ones you control, the ones that let you exercise—or
relax. Some muscles are “involuntary.” They just do their
job with no effort on your part—like your heart muscles.
How do you think muscles make your body move?
What muscles immediately come to mind
when you think of your own body? Your body
has muscles wherever your bones can move.
Some muscles are near the surface, like
those that move your arms and legs. You can
feel them tense and bulge as you move. Some
are deep inside you, like the diaphragm and rib
muscles that help you breathe, or the stomach
and intestinal muscles that push food along as
it is digested.
Muscles are unusual tissues that can change
the energy in their cells to pulling power. Most
muscles are attached to bones by strong white
cords called tendons. One end of the tendon is
attached to the muscle, the other end to
the bone. Muscles move bones by
pulling on tendons.
Muscle movement is controlled
by nerves which, in turn, are
controlled by signals from the brain.
At the right signal, the long, thin cells inside
the muscle become shorter and thicker. As the
muscle shortens, it pulls the bone it is attached
to forward.
Exploration:
Make a muscle model.
Cut the index card in half. Draw
arm bones and label them. Punch
three holes in each half, as shown.
Fasten the cards together with
the paper fastener. Tie a ribbon to
each hole on the lower arm bone,
and then thread them through the
holes on the upper arm bone.
Pull on the loose end of one
ribbon at a time. Observe what happens.
Now design your own model of an arm muscle. For
example, how could you use empty paper towel tubes?
What else would you need?
Biceps
Try your model out and make any alterations you
think might improve it.
Interpret your results.
Triceps
▲ Biceps muscle
contracted
Biceps muscle
relaxed
Biceps
Triceps
You have no muscles
in your fingers and
toes. Look at this
picture and see if
you can tell what
moves your toes.
Tendons
• What happened to the “bones” when you pulled the
“muscles” in your model?
• Do arm muscles push or pull? Do they both work at the
same time?
• How would your arm work if it had only one muscle?
• Did your model teach you anything else about
your muscles?
Communicate your results.
• Write up your exploration and invite a family
member to try it.
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Muscles
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