Health Science Education 1
Angie Pruitt, MSN, RN, CNS
Involuntary Movement
and
Lack Striations
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Involuntary or unconscious control
Contraction essentially the same as skeletal
The cells have important differences.
Elongated with tapering ends. (remember skeletal
muscle was elongated with round ends)
 Contains filaments of Actin and Myosin, organized
differently, more random
 NOT STRIATED because Actin and Myosin are
arranged differently.
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Multiunit smooth muscle:
 In irises of the eyes
 Walls of the blood vessels.
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Visceral smooth muscle:
 more common type of smooth muscle
 in the walls of hollow organs
▪ stomach, intestines, urinary bladder, and uterus.
http://www.youtube.com/watch?v=Ln09qihUi3g&feature=related
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Smooth muscle fibers
 One fiber is stimulated, the impulse moves over its surface
exciting adjacent fibers
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Visceral smooth muscles
 Rhythmicity-a pattern of repeated
contractions. Remember Peristalsis??
http://www.youtube.com/watch?v=o18UycWRsaA&feature=related
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Smooth muscle like skeletal muscle contracts
by reactions of Actin and Myosin.
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2 neurotransmitters in smooth muscle:
 Acetylcholine
 Norepinephrine.
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Stimulates contractions in some smooth
muscles and inhibits contractions in others.
Hormones also affect smooth muscle.
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Slower to contract and relax
Maintains a forceful contraction longer.
Change length without changing tautness
 The stomach and intestinal walls stretch as the
organs fill.
Moving on to Cardiac
Muscle 
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This is called progress!
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Only in the heart
Striated cells joined end to end, forming
fibers.
Intercalated disks allow muscle impulses to
pass freely so they travel rapidly from cell to
cell.
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Cardiac muscle is self exciting and rhythmic.
A pattern of contraction and relaxation
repeats again and again and causes the
rhythmic contractions of the heart.
Cardiac muscle is involuntary.
As stated previously, skeletal muscles provide a
variety of body movements.
 Each muscles movement depends on the kind of
joint it is associated with and the way the muscle
attaches on either side of that joint.
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Bones form moveable joints and function as levers.
End of a skeletal muscle fastens to a relatively
immovable or fixed part at such a joint,
 Other end connects to a moveable part of the other
side of the joint.
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The immoveable part is the origin
The movable end is its insertion
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When a muscle contracts, its insertion is
pulled toward its origin
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Some muscles have more than one origin or
insertion.
 Example: the biceps has 2 origins. The word biceps means
2 heads. The head of a muscle is the part nearest its
origin.
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Attaches at 2 spots on the scapula
Individual muscles
Muscles are named according to any of the
following criteria: size,shape, location, action,
number of attachments, or direction of its fibers.