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 The
muscular system = machines of the body
 The essential function of a muscle is to contract
(shorten).
 Muscles are therefore responsible for all body
movement.

Produce movement

Maintain posture

Stabilize joints

Generate heat
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.8
Three basic muscle types
• Skeletal muscle
• Cardiac muscle
• Smooth muscle
They differ in cell
structure, body location,
and how they are
stimulated to contract.
Skeletal and smooth
muscle cells are
elongated into muscle
fibers.

Most are attached by
tendons to bones

Cells are multinucleate

Striated –visible banding

Voluntary –conscious
control

Cells are surrounded and
bundled by connective
tissue = great force, but
tires easily
Smooth Muscle Characteristics
• Has no striations
• Spindle-shaped cells
• Single nucleus
• Involuntary – no
conscious control
• Found mainly in the
walls of hollow
organs
• Slow, sustained and
tireless
Figure 6.2a
http://linkstudio.info/images/portfolio/medani/Swallow.swf

Has striations

Usually has a single
nucleus

Joined to another
muscle cell at an
intercalated disc

Involuntary

Found only in the heart
Skeletal muscle cells are surrounded and bundled by connective
tissue.
• Endomysium—a delicate connective tissue sheath that encloses a single
muscle fiber.
• Perimysium—a coarser connective tissue that wraps around a fascicle
(bundle) of muscle fibers
• Epimysium—an even thicker
connective tissue that covers
the entire skeletal muscle.
The epimysia blend together to
form tendons (cord-like) and
aponeuroses (sheet-like),
which connect muscle to bone.
Interactions of Skeletal Muscle
• Prime mover (agonists) – muscle with the
major responsibility for a certain movement
• Antagonist – muscle that opposes or
reverses a prime mover. When prime mover
is active its antagonist is stretched and
relaxed.
• Synergist – muscle that aids a prime mover
in a movement and helps prevent rotation

Sites of muscle attachment
• Bones
• Cartilages
• Connective tissue coverings