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CHAPTER 14
MUSCULAR SYSTEM
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Structure and Function
• The human body has more than 600 muscles
• The functions of the muscular system
–
–
–
–
Aid in movement
Provide and maintain posture
Protect internal organs
Provide movement of blood, food, and waste
products through the body
– Open and close body openings
– Produce heat
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Table 14-1 Types of Muscle
Tissue
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Skeletal Muscle
• Makes up more than 40% of a person’s body
weight
• Looks striated, or banded, under the
microscope
• Skeletal muscles have three parts
– Origin is one end of the muscle, attached to the
less movable part of the bone
– Insertion is the other end of the muscle, attached
to the more movable part of the bone
– The action, or body, is the thick middle part of the
muscle
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Figure 14-5 Basic Types of
Muscle Movement
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Visceral Muscle
• Lines various hollow organs
• Makes up the walls of blood vessels
• Found in the tubes of the digestive
system
• Smooth and has no striations
• Controlled by the autonomic nervous
system
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Cardiac Muscle
•
•
•
•
Found only in the heart
Striated muscle
Under involuntary control
Has specialized cells that provide a
stimulus for contraction
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Muscle Contraction
• Isotonic contraction is muscle shortening that
produces movement
• Muscle tone or tonus is a state of partial
contraction that maintains a person’s posture
• Isometric contraction does not cause muscle
shortening or movement
• A twitch is a quick, jerky contraction of a
whole muscle from one stimulus
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Muscle Contraction (continued)
• Tetanic contraction is more sustained than a
twitch and is caused by many stimuli in rapid
succession
• Fibrillation is uncoordinated contraction of
muscle fibers
• Convulsions are contractions of groups of
muscles in an abnormal manner
• Spasms are involuntary, sudden, and
prolonged contractions
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Figure 14-8 Sliding Filament Theory
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Assessment Techniques
• Reflex tests
• Joint motion measured using a
protractor
• Blood tests
• Electromyography tests
• Muscle biopsy
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Disorders of the Muscular
System
• Back pain
– From weakened muscles around the spine in the
lower back
• Contracture
– A condition in which muscles remain contracted as
a joint loses flexibility and ligaments and tendons
shorten
• Muscle cramp
– A sudden involuntary contraction of a muscle
producing pain
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Disorders of the Muscular
System (continued)
• Muscular dystrophy
– A group of genetic diseases involving painless,
gradual atrophy of muscle tissue
• Fibromyalgia
– A group of muscle disorders affecting the tendons,
ligaments, and other fibrous tissues
• Gangrene
– Caused by Clostridium bacteria that kill muscle
tissue
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Disorders of the Muscular
System (continued)
• Hernia
– The abnormal protrusion of a body part into
another body area
• Myasthenia gravis
– A condition in which nerve impulses are not
transmitted normally from the brain to the muscles
• Poliomyelitis
– A viral infection that results in paralysis of muscles
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Disorders of the Muscular
System (continued)
• Muscle sprain
– A traumatic injury to the tendons, muscles, or
ligaments of a joint
• Muscle strain
– Torn or stretched tendons and muscles, causing
pain
• Pes planus
– Called “flatfoot” or “fallen arches,” may be
congenital or result from weakened foot muscles
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Disorders of the Muscular
System (continued)
• Tetanus
– Commonly called “lockjaw,” is caused by a
bacterial infection
• Trichinosis
– A parasitic infection caused by eating undercooked
pork
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Issues and Innovations
• Sports medicine
– Treating sports injuries
– Directing healthful development and training of
athletes
– Biomechanics
• Fitness fad
– Importance of regular exercise for good health
– Exercise obsession
Copyright 2003 by Mosby, Inc. All
rights reserved.