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Muscle
types. Striated muscle. Whole muscle
Striated,
or striped, muscle constitutes a large fraction of the total
body weight in humans. Striated muscle contracts to move
limbs and maintain posture. Both ends of most striated muscles
articulate the skeleton and thus are often called skeletal
muscles. They are attachedto the bones by tendons, which
have some elasticity provided by the proteins collagen and
elastin, the major chemical components of tendons.
Each
striated muscle has blood vessels and nerves associated
with it. The vessels transport blood to and from the muscle,
supplying oxygen and nutrients and removing carbon dioxide
and other wastes. The signals that initiate contraction
are sent from the central nervous systemto the muscle via
the motor nerves. Muscles also respond to hormones produced
by various endocrine glands; hormones interact with complementary
receptors on the surfaces of cells to initiate specific
reactions. Each muscle also has important sensory structures
called stretch receptors, which monitor the state of the
muscle and return the information to the central nervous
system. Stretch receptors are sensitive to the velocity
of the movement of the muscle and the change in length of
the muscle. They complete a feedback system that allows
the central nervous system to assess muscular movement and
to adjust motor signals in light of themovement.
