2. Two main types of Muscles:
1.) Skeletal Muscles
2.) Smooth Muscles.
There is a third kind of muscle which has
characteristics of both skeletal and smooth
muscles. It is called the cardiac muscle. It is
found only in the heart.
3. Moving the Different Muscles
The skeletal muscles move through the conscious effort
of the person. You can start anytime you want to. The
muscles of your arms and legs are skeletal muscles. They
are classified as voluntary muscles.
The smooth muscle and cardiac muscle move even
without you thinking about it. They do not start and stop
according to your will.
The muscles in your blood vessels are involuntary
muscles. Even if you try hard, you cannot stop your pulse.
The blood vessels continue to pulsate at regular intervals.
However, the pulse rate increases when you move briskly
as when you did the "Jumping Jack."
The cardiac muscle behaves like the involuntary
muscles. You cannot stop or start it at your own will. It
beats faster when you do brisk movements like exercise.
4. Skeletal Muscles
Skeletal muscles are attached to the
bones. They move the bones of the arms,
legs, fingers and other parts of the skeleton.
The fibers of skeletal muscles are marked
by light and dark bands or are striated and
bigger than smooth muscle fibers. The
skeletal muscles usually move voluntarily
and so, they are called voluntary muscles.
But there are also times when the skeletal
muscle also may move without conscious
control.
5. Smooth Muscle
Smooth muscles are found in various organs
of the body. They are found in the walls of the
stomach, intestines, blood vessels, and
bladder.
The fibers of smooth muscles are not
striated and are smaller than skeletal muscle
fibers. A smooth muscle fiber has only one
nucleus.
Smooth muscle move slowly and
automatically as they contract and relax. The
processes inside the body continue even if we
are not aware of it because of the work of the
6. Cardiac Muscle
Cardiac Muscle makes up the walls of the
heart. When cardiac muscle cells contract,
they push blood out of the heart and into the
arteries. The blood then circulate throughout
the body.
Cardiac Muscles have characteristics of
both the skeletal and smooth muscles. Like
skeletal muscle fibers, cardiac muscle cells
have striations. Like smooth muscle fibers,
each cardiac muscle cell has only one
nucleus and contracts automatically.
