Download THE MUSCULAR SYSTEM

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THE MUSCULAR SYSTEM
The muscular system produces movement. There are over 600 different muscles in
your body. Muscles cover the skeleton. They also line the walls of some organs, such as
the heart and stomach. Tendons attach muscles to bone.
Muscles can be voluntary and involuntary. Voluntary muscles are the ones that you
can control. You can tell them when to move. Most voluntary muscles are attached to
bones. Involuntary muscles, like those of the heart, move without your having to think
about them. The muscles that control your eyelids may seem like voluntary muscles. You
can blink your eyes when you want to. However, you cannot keep your eyes from
blinking when they need to! You do not have complete control over them.
Muscles cause movement by contracting or getting shorter and firmer. This action
pulls on the bones or other body structures. Muscles move the blood through your body.
They also move food and wastes through your body.
Muscle tone is achieved through exercise. If a person has good muscle tone, the
muscles do not completely relax. They are always slightly contracted. For you to have
good muscle tone, plenty of blood needs to reach the muscle cells. This requires exercise.
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There are three types of muscles in the body. Each type of muscle cell looks
different. The smooth muscles are long and thin and pointed at each end. The stomach
has smooth muscle cells. Cardiac muscles make up the heart. They
branch out and weave together. Skeletal muscles are long and shaped
like cylinders (similar to straws). Unlike the other muscle cells, the
skeletal muscle cells have many nuclei. The tongue and lips are skeletal
muscles, as are the biceps and triceps in your arms.
Match each description with the correct word.
______ 1. muscles that make up the heart
a. tendons
______ 2. muscles over which you have complete control
b. involuntary
______ 3. what muscles do to cause movement
c. contract
______ 4. necessary for muscle tone
d. cardiac
______ 5. muscle cells with many nuclei
e. exercise
______ 6. attach muscles to bone
f. skeletal
______ 7. muscles that move without conscious effort
g. voluntary
The Muscular System
Answer Key
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1.
2.
3.
4.
5.
6.
7.
d
g
c
e
f
a
b
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