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Chapter 28
The Muscular System
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Major Skeletal Muscles
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Skeletal Muscle Tissue
• Attaches to bone to permit movement
• Skeletal muscle movement is voluntary
• Skeletal muscle cells are long and strong and
are arranged in bundles enclosed in tough
connective tissue sheaths
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Smooth Muscle Tissue
• Small, delicate muscle cells found throughout
the internal organs of the body
• Smooth muscle activity is involuntary and
occurs constantly in functions such as
breathing, peristalsis, blood vessel
contraction, and pupil dilation.
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Cardiac Muscle Tissue
• Muscle tissue found only in the heart
• Arranged in a continuous network without
sheath separation
• When one cell receives the signal to contract,
all neighboring cells are stimulated and they
contract together
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Six Functions of Skeletal Muscles
• Contractions provide heat.
• Contractions permit movement.
• Hold the trunk and head erect
• Protect blood vessels and nerves
• Help blood flow return to the heart
• Provide protective padding for internal organs
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Muscle Activity and Heat Production
• Muscles use stored glycogen as an energy
source
– As muscles function they change glycogen to
glucose
• As this fuel is used, heat is produced and
warms the body
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Muscle Teams
• When muscles contract they become shorter
and thicker.
• Skeletal muscles that bend joints are called
flexors.
• Skeletal muscles that straighten out a joint are
called extensors.
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Muscle Teams
• When a flexor muscle is partnered with an
extensor muscle they work as a team to bend
and straighten joints.
• The biceps and triceps of the upper arm are
an example of a muscle team.
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Action of the Biceps/Triceps
Muscle Team
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Muscle Tone
• Most skeletal muscles are partially contracted
at all times so that the body remains erect.
• This constant state of contraction is known as
muscle tone.
• As people age, the amount of connective
tissue and elastic fibers increase
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Muscle Sheaths and Bursae
• Muscle sheaths
– Membranes that separate muscle groups to
prevent friction from movement
• Bursae
– A sheath that is shaped like a sac and has a
slippery fluid lining that acts as a cushion to
minimize pressure and friction
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Peristalsis
• Involuntary contraction of smooth muscle that results from
alternate contraction and relaxation of the layers of the
smooth muscle
• This is what works food through our body.
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Sphincter Muscles
• Smooth, donut-shaped muscles that pinch
shut intermittently to control the flow of
blood, food, or liquid
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Tendons and Ligaments
• Tendons
– Strong, fibrous connective tissue sheaths that do
not bend or stretch
– Tendons attach muscle to bone.
– The longest and thickest tendon in the body is the
Achilles tendon
• Ligaments
– Flexible, fibrous tissue that supports organs
– Ligaments connect bones to bones at the joints.
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Bursitis and Tendonitis
• Bursitis
– Painful inflammation of the bursae that cover and lubricate
muscles and tendons
• Tendonitis
– Painful inflammation of the tendons and muscle
attachments to the bone
– Most often caused by a sports-related injury
Epicondylitis is treated by local anesthetic, injection of
corticosteroids, immobilization and manipulation of the
tendon attachment
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Fibromyalgia Syndrome
• Chronic musculoskeletal
condition that causes
widespread pain and
the presence of tender
points or trigger points
throughout the body
• Positive diagnosis when
11 of the 18 trigger
points are painful
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Muscular Dystrophy
• Group of congenital disorders that result in
progressive wasting away of skeletal muscle
and eventually death
– Duchenne’s
• Diagnosed usually by age 1; death occurs by age 10 to
15
• Makes up about half of all cases
– Erb’s
• Slow progression of atrophy that occurs later in
childhood or adolescence
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Mixed Dystrophy
• Does not appear to be inherited
• Can affect both sexes
• Usually begins between ages 30 and 50; death
usually occurs within 5 years after onset
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Torticollis
• Congenital or acquired neck deformity that
bends the head toward the affected side
• Caused by shortening or spasms of the
sternocleidomastoid muscle
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Other important info
• The muscle that lies beneath the pectoralis major and is
between the ribs is intercostal.
• Your shoulders are protected by your deltoid
• The quadriceps femoris is made up of vvastus lateralis, rectus
femoris and the vastus intermedius
• The hamstring group is made up of the semimembranosus, a
portion of the adductor magnus and the biceps femoris
• The main muscle in the calf of the leg is gastrocenemius
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Definitions to know
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Adduction
Abduction
Skeletal muscle tissue
Extensor
Cardiac muscle tissue
Flexor
Tetanus
contracture
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Smooth muscle tissue
Tendon
Origin
Insertion
Strain
Sphincter
Obicularis oculi
Diaphragm
Obicularis oris
fibromyalgia
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