The Muscular System

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The Body Systems: Clinical and Applied Topics

62

The Muscular System

muscular paralysis are usually caused by ner-

vous system disorders. These movements will

The muscular system includes over 700 skeletal

be described further in sections dealing with

muscles that are directly or indirectly attached to

abnormal nervous system function.

the skeleton by tendons or aponeuroses. The mus-

SIGNS AND SYMPTOMS

cular system produces movement, as the contrac-

tions of skeletal muscles pull on the attached

OF MUSCULAR SYSTEM

bones. Muscular activity does not always result in

movement, however; it can also be important in

DISORDERS

stabilizing skeletal elements and preventing move-

ment. Skeletal muscles are also important in

Two common symptoms of muscular disorders are

guarding entrances or exits of internal passage-

pain

and

weakness

in the affected skeletal mus-

ways, such as those of the digestive, respiratory,

cles. The potential causes of muscle pain include:

urinary, or reproductive systems, and in generating

1.

Muscle trauma:

Examples of traumatic injuries

heat to maintain our stable body temperatures.

7

to a skeletal muscle would include a laceration,

Skeletal muscles contract only under the com-

a deep bruise or crushing injury, a muscle tear,

mand of the nervous system. For this reason, clini-

or a damaged tendon.

cal observation of muscular activity may provide

direct information about the muscular system, and

2.

Muscle infection:

Skeletal muscles may be

indirect information about the nervous system. The

infected by viruses, as in some forms of myosi-

assessment of facial expressions, posture, speech,

tis, or colonized by parasitic worms, such as

and gait can be an important part of the physical

those responsible for

trichinosis

(p. 64). These

examination. Classical signs of muscle disorders

infections usually produce pain that is restrict-

include the following:

ed to the involved muscles. Diffuse muscle pain

may develop in the course of other infectious

•

Gower’s sign

is a distinctive method of stand-

diseases, such as influenza or measles.

ing from a sitting or lying position on the floor.

This method is used by children with

muscular

3.

Related problems with the skeletal system:

dystrophy

(p. 65). They move from a sitting

Muscle pain may result from skeletal problems,

position to a standing position by pushing the

such as arthritis (p. 59) or a sprained ligament

trunk off the floor with the hands and then

near the point of muscle origin or insertion.

moving the hands to the knees. The hands are

4.

Problems with the nervous system:

Muscle pain

then used as braces to force the body into the

may be experienced due to inflammation of

standing position. This extra support is neces-

sensory neurons or stimulation of pain path-

sary because the pelvic muscles are too weak

ways in the CNS.

to swing the weight of the trunk over the legs.

Muscle strength can be evaluated by applying

•

Ptosis

is a drooping of the upper eyelid. It may

an opposite force against a specific action. For

be seen in

myasthenia gravis

(p. 66),

botulism

example, the examiner might exert a gentle extend-

(p. 65),

myotonic dystrophy

(p. 65), or following

ing force while asking the patient to flex the arm.

damage to the cranial nerve (N III) innervating

Because the muscular and nervous systems are so

the

levator palpabrae superioris muscle

of the

closely interrelated, a single symptom, such as

eyelid.

muscle weakness, can have a variety of different

•A

muscle mass

, an abnormal dense region with-

causes (Figure A-22). Muscle weakness may also

in a muscle, is sometimes seen or felt in a skele-

develop as a consequence of a condition that affects

tal muscle. A muscle mass may result from torn

the entire body, such as anemia or acute starvation.

muscle or tendon tissue, a hematoma, or the

Figure A-23 (p. 64) provides an overview of

deposition of bone around a skeletal muscle, as

muscular system disorders.

in

myositis ossificans

.

Necrotizing Fasciitis

• Abnormal contractions may indicate problems

EAP

p. 178

with the muscle tissue or its innervation.

Muscle

spasticity

exists when a muscle has excessive

Several bacteria produce enzymes such as

muscle tone. A

muscle spasm

is a sudden,

hyaluronidase

or

cysteine protease.

Hyaluronidase

strong, and painful involuntary contraction.

breaks down hyaluronic acid and the proteoglycans

(large polysaccharide molecules linked by polypep-

•

Muscle flaccidity

exists when the relaxed skele-

tide chains) that make up the intercellular cement

tal muscle appears soft and relaxed and its

between adjacent cells. Cysteine protease breaks

contractions are very weak or absent.

down conective tissue proteins. These bacteria are

•

Muscle atrophy

is skeletal muscle deterioration,

dangerous because they can spread rapidly by

or

wasting,

due to disuse, immobility, or inter-

liquifying the matrix and dissolving the intercellu-

ference with the normal muscle innervation.

lar cement that holds epithelial cells together. The

• Abnormal patterns of muscle movement, such

streptococci

are one group of bacteria that secrete

as

tics, choreiform movements,

or

tremors,

and

both of these enzymes.

Streptococcus A

bacteria are

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The Muscular System

63

Infection

Myositis

Trichinosis

Trauma

Inherited disorders

Muscular bruise

Muscular dystrophies

or tear

Myotonic dystrophy

Primary

Muscular System

Disorders

7

Probable immune

disorders

Myasthenia

gravis

Guillain–Barré

syndrome

Cardiovascular

problems

SYMPTOM:

MUSCLE WEAKNESS

Anemia

Heart failure

Vascular blockage

Metabolic or

nutritional problems

Electrolyte disturbances

(ex.: hypercalcemia,

Problems with

hypocalcemia)

peripheral nerves

Starvation

Nervous System

Trauma

Disorders

Demyelination

disorders

Diphtheria

Destruction of

Problems at

Problems with

motor pathways

motor neurons

synaptic knobs

in neuromuscular

Spinal cord

Stroke

junctions

Polio

injuries

Multiple

Rabies

Botulism

Huntington’s

Other neurotoxins

sclerosis

Demyelination

disease

disorders

Figure A-22 Potential Causes of Muscle Weakness

involved in many human diseases, most notably

minor cuts become major open wounds, with interi-

“strep throat,” a pharyngeal infection. In most

or connective tissues dissolving. There were only 7

cases the immune response is sufficient to contain

reported cases, but 5 of the victims died. The

and ultimately defeat these bacteria before exten-

pathogen responsible was a strain of

Streptococcus A

sive tissue damage has occurred.

that overpowered immune defenses and swiftly

However, in 1994 tabloid newspapers had a field

invaded and destroyed soft tissues. More over, the

day recounting stories of “killer bugs” and “flesh-eat-

pathogens eroded their way along the fascial wrap-

ing bacteria” that terrorized residents of the city of

ping that covers skeletal muscles and other organs.

Gloucester, England. The details were horrific—

The term for this condition is

necrotizing fasciitis.

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The Body Systems: Clinical and Applied Topics

64

Infection

Trauma

Myositis

Necrotizing fasciitis

Hernias

Tetanus

Compartment syndrome

Trichinosis

Bruises and tears

Fibromyalgia

Carpal tunnel syndrome

MUSCLE

DISORDERS

Inherited disorders

Tumors

Myomas

Muscular dystrophy

Sarcomas

Duchenne’s muscular dystrophy

7

Secondary disorders

Nervous system:

Immune problems:

Botulism

Myasthenia gravis

Poliomyelitis

Metabolic problems:

Cardiovascular system:

Anemia

Hypercalcemia

Heart failure

Hypocalcemia

Figure A-23 Disorders of the Muscular System

In some cases the muscle tissue was also destroyed,

larvae then migrates through the body tissues to

a condition called

myositis.

reach the muscles, where they complete their early

The problem is not restricted to the United

development. The migration and subsequent set-

Kingdom. Some form of very aggressive infectious

tling produce a generalized achiness, muscle and

soft tissue invasion occurs roughly 75–150 times

joint pain, and swelling in infected tissues. An esti-

annually in the U.S. At present it is uncertain

mated 1.5 million Americans carry

Trichinella

whether the recent surge in myositis and necrotizing

around in their muscles, and up to 300,000 new

faciitis reflects increased awareness of the condition

infections occur each year. The mortality rate for

or the appearance of a new strain of strep bacteria.

people who have symptoms severe enough to

require treatment is approximately 1 percent.

Trichinosis

EAP

p. 178

Fibromyalgia and Chronic

Trichinosis

(trik-i-N«-sis;

trichos,

hair +

nosos,

Fatigue Syndrome

EAP

p. 178

disease) results from infection by a parasitic nema-

tode worm,

Trichinella spiralis.

Symptoms include

Fibromyalgia

(

-algia,

pain) is a disorder that has

diarrhea, weakness, and muscle pain. The muscu-

formally been recognized only since the mid-1980s.

lar symptoms are caused by the invasion of skele-

Although first described in the early 1800s, the

tal muscle tissue by larval worms, which create

condition is still somewhat controversial because

small pockets within the perimysium and endomy-

the reported symptoms cannot be linked to any

sium. Muscles of the tongue, eyes, diaphragm,

anatomical or physiological abnormalities.

chest, and leg are most often affected.

However, physicians now recognize a distinctive

Larvae are common in the flesh of pigs, horses,

pattern of symptoms that warrant consideration as

dogs, and other mammals. The larvae are killed

a clinical entity.

when the meat is cooked; people are most often

Fibromyalgia may be the most common muscu-

exposed by eating undercooked pork. Once eaten,

loskeletal disorder affecting women under 40 years

the larvae mature within the intestinal tract, where

of age. There may be as many as 6 million cases in

they mate and produce eggs. The new generation of

the United States today. Symptoms include chronic

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The Muscular System

65

aches, pain, and stiffness and multiple tender

and calcium levels rise to the point that key pro-

points at specific, characteristic locations. The four

teins denature. The muscle fiber then degenerates.

most common tender points are (1) just below the

Researchers have recently identified and cloned the

kneecap, (2, 3) distal to the medial and lateral epi-

gene for dystrophin; that gene is located on the X

condyles of the humerus, and (4) the junction

chromosome. Rats with DMD have been cured by

between the second rib and the cartilage attaching

insertion of this gene into their muscle fibers, a

it to the sternum. An additional clinical criterion is

technique that may eventually be used to treat

that the pains and stiffness cannot be explained by

human patients.

other mechanisms. Individuals with this condition

The inheritance of DMD is sex-linked: Women

frequently  report chronic fatigue; they feel tired on

carrying the defective genes are unaffected, but each

awakening and often complain of awakening

of their male children will have a 50 percent chance

repeatedly during the night.

of developing DMD. Now that the specific location of

Most of these symptoms could be attributed to

the gene has been identified, it is possible to deter-

other problems. For example, chronic depression can

mine whether or not a woman is carrying the defec-

lead to fatigue and poor-quality sleep. As a result, the

tive gene. It is also possible to use an innovative

7

pattern of tender points is really the diagnostic key to

prenatal test to determine if a fetus has this condi-

fibromyalgia. This symptom distinguishes fibromyal-

tion. In this procedure, a small sample of fluid is col-

gia from

chronic fatigue syndrome

(CFS). The cur-

lected from the membranous sac that surrounds the

rent symptoms accepted as a definition of CFS

fetus. This fluid contains fetal cells, called

amnio-

include (1) sudden onset, usually following a viral

cytes,

that are collected and cultivated in the labora-

infection, (2) disabling fatigue, (3) muscle weakness

tory. Researchers then insert a gene, called

MyoD,

and pain, (4) sleep disturbance, (5) fever, and (6)

that triggers their differentiation into skeletal muscle

enlargement of cervical lymph nodes.

fibers. These cells can then be tested not only for the

Attempts to link either fibromyalgia or CFS to a

signs of muscular dystrophy but for indications of

viral infection or to some physical or psychological

other inherited muscular disorders.

trauma have not been successful, and the cause

MYOTONIC DYSTROPHY

.

Myotonic dystrophy

is

remains unknown. Treatment is limited to relieving

a form of muscular dystrophy that occurs in the

symptoms when possible. For example, anti-inflam-

united states at an incidence of 13.5 per 100,000

matory medications may help relieve pain, drugs

population. Symptoms may develop in infancy, but

can be used to promote sleep, and exercise pro-

more often develop after puberty. As with other

grams may help maintain normal range of motion.

forms of muscular dystrophy, adults developing

myotonic dystrophy experience a gradual reduction

The Muscular Dystrophies

in muscle strength and control. Problems with other

EAP

p. 185

systems, especially cardiovascular and digestive sys-

The

muscular dystrophies

(DIS-tr|-fƒz) are inher-

tems, often develop. There is no effective treatment.

ited diseases that produce progressive muscle

The inheritance of myotonic dystrophy is

weakness and deterioration. One of the most com-

unusual because children of an individual with

mon and best understood conditions is

myotonic dystrophy commonly develop more severe

Duchenne’s muscular dystrophy (DMD).

This

symptoms than those of the parent. The increased

form of muscular dystrophy appears in childhood,

severity of the condition appears to be related to

often between the ages of 3 and 7. The condition

the presence of multiple copies of a specific gene on

generally affects only males. A progressive muscu-

chromosome 19. For some reason, the nucleotide

lar weakness develops, and the individual usually

sequence of that gene gets repeated several times,

dies before age 20 because of respiratory paralysis.

and the number can increase from generation to

Skeletal muscles are primarily affected, although

generation. This has been called a “genetic stutter.”

for some reason the facial muscles continue to

The greater the number of copies, the more severe

function normally. In later stages of the disease,

the symptoms. It is not known why the stutter

the facial muscles and cardiac muscle tissue may

develops, nor how the genetic duplication affects

also become involved.

the severity of the condition.

The skeletal muscle fibers in a person with

Botulism

DMD patient are structurally different from those

EAP

p. 184

of other individuals. Abnormal membrane perme-

¯-nus)

Botulinus

(bot- -LI

toxin

prevents the release

ability, cholesterol content, rates of protein synthe-

of ACh at the synaptic terminal. It thus produces a

sis, and enzyme composition have been reported.

severe and potentially fatal paralysis of skeletal

DMD sufferers also lack a protein, called

dys-

muscles. A case of botulinus poisoning is called

trophin,

found in normal muscle fibers. It is

1 The toxin is produced by a bacterium,

botulism.

attached to the inner surface of the sarcolemma

Clostridium botulinum,

that does not need oxygen to

near the triads. Although the functions of this pro-

grow and reproduce. Because the organism can live

tein remain uncertain, dystrophin is suspected to

play a role in the regulation of calcium ion chan-

This disorder was described 200 years ago by German

1

nels in the sarcolemma. In children with DMD, cal-

physicians treating patients poisoned by dining on contami-

cium channels remain open for an extended period,

nated sausages.

Botulus

is the Latin word for sausage.

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The Body Systems: Clinical and Applied Topics

66

quite well in a sealed can or jar, most cases of botu-

unknown reasons, women are affected twice as

lism are linked to improper canning or storing pro-

often as men. Estimates of the incidence of this

cedures, followed by failure to cook the food

disease in the United States range from 2 to 10

adequately before eating. Canned tuna or beets,

cases per 100,000 population.

smoked fish, and cold soups have most often been

One approach to therapy involves the adminis-

involved with cases of botulism. Boiling for a half

tration of drugs, such as

neostigmine,

that are

hour destroys both the toxin and the bacteria.

termed

cholinesterase inhibitors.

As their name

Symptoms usually begin 12–36 hours after eat-

implies, these compounds are enzyme inhibitors;

ing a contaminated meal. The initial symptoms are

they tie up the active sites at which cholinesterase

often disturbances in vision, such as seeing double

normally binds ACh. With cholinesterase activity

or a painful sensitivity to bright lights. These

reduced, the concentration of ACh at the synapse

symptoms are followed by other sensory and motor

can rise enough to stimulate the surviving receptors

problems, including blurred speech and an inabili-

and produce muscle contraction.

ty to stand or walk. Roughly half of botulism

Polio

EAP

p. 184

patients experience intense nausea and vomiting.

7

These symptoms persist for a variable period (days

Because skeletal muscles depend on their motor

to weeks), followed by a gradual recovery; some

neurons for stimulation, disorders that affect the

patients are still recovering after a year.

nervous system can have an indirect affect on the

The major risk of botulinus poisoning is respi-

muscular system. The

poliovirus

is a virus that

ratory paralysis and death by suffocation.

does not produce clinical symptoms in roughly 95

Treatment is supportive: bed rest, observation,

percent of infected individuals. The virus produces

and, if necessary, use of a mechanical respirator.

variable symptoms in the remaining 5 percent.

In severe cases drugs that promote the release of

Some individuals develop a nonspecific illness

ACh, such as

guanidine hydrochloride,

may be

resembling the flu. A second group of individuals

administered. The overall mortality rate in the

develop a brief

meningitis

(p. 74), an inflammation

United States is about 10 percent.

of the protective membranes surrounding the CNS.

In the third group of people, the virus attacks

Myasthenia Gravis

EAP

p. 184

somatic motor neurons in the CNS.

Myasthenia gravis

(m -as-TH¬-nƒ-uh GRA-vis) is

In this third form of the disease, the individual

characterized by a general muscular weakness that

develops a fever 7–14 days after infection. The fever

is often most pronounced in the muscles of the

subsides, but recurs roughly a week later, accom-

arms, head, and chest. The first symptom is usual-

panied by muscle pain, cramping, and paralysis of

ly a weakness of the eye muscles and drooping eye-

one or more limbs. Respiratory paralysis may also

lids. Facial muscles are often weak as well, and the

occur, and the mortality rate for this form of polio

individual develops a peculiar smile known as the

is 2–5 percent for children and 15–30 percent of

“myasthenic snarl.” As the disease progresses,

adults. If the individual survives, some degree of

pharyngeal weakness leads to problems with chew-

recovery usually occurs over a period of up to 6

ing and swallowing, and it becomes difficult to hold

months.

the head upright.

For unknown reasons, the survivors of paralyt-

The muscles of the upper chest and upper

ic polio may develop progressive muscular weak-

extremities are next to be affected. All the volun-

ness 20–30 years after the initial infection. This

tary muscles of the body may ultimately be

postpolio syndrome

is characterized by fatigue,

involved. Severe myasthenia gravis produces respi-

muscle pain, and weakness, and, in some cases,

ratory paralysis, with a mortality rate of 5–10 per-

muscular atrophy. There is no treatment for this

cent. However, the disease does not always

condition, although rest seems to help.

progress to such a life-threatening stage. For

Polio has been almost completely eliminated

example, roughly 20 percent of patients experience

from the U.S. population due to a successful

eye problems with no other symptoms.

immunization program. In 1954 there were 18,000

The condition results from a decrease in the

new cases in the United States; there were 8 in

number of ACh receptors on the motor end plate.

1976, and none since 1994. The World Health

Before the remaining receptors can be stimulated

Organization now reports that polio has been erad-

enough to trigger a strong contraction, the ACh

icated from the entire Western Hemisphere.

molecules are destroyed by cholinesterase. As a

Unfortunately, many parents refuse to immunize

result, muscular weakness develops.

their children against the poliovirus, because they

The primary cause of myasthenia gravis

assume that the disease has been “conquered.”

appears to be a malfunction of the immune system.

Failure to immunize is a mistake because (1) there

Roughly 70 percent of the individuals with myas-

is still

no cure

for polio, (2) the virus remains in the

thenia gravis have an abnormal thymus, an organ

environment in many areas of the world, and (3) up

involved with the maintenance of normal immune

to 38 percent of children ages 1–4 have not been

function. In myasthenia gravis, the immune

immunized. A major epidemic could therefore

response attacks the ACh receptors of the motor

develop very quickly if the virus were brought into

end plate as if they were foreign proteins. For

the United States from another part of the world.

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The Muscular System

67

abdominal organs slide into the thoracic cavity,

Hernias

EAP

p. 204

most often through the

esophageal hiatus,

the

When the abdominal muscles contract forcefully,

opening used by the esophagus. The severity of the

pressure in the abdominopelvic cavity can increase

condition will depend on the location and size of

dramatically, and those pressures are applied to

the herniated organ(s). Hiatal hernias are actually

internal organs. If the individual exhales at the same

very common, and most go unnoticed. Radiologists

time, the pressure is relieved, because the

see them in about 30 percent of individuals whose

diaphragm can move upward as the lungs collapse.

upper gastrointestinal tracts are examined with

But during vigorous isometric exercises or when lift-

barium contrast techniques. When clinical compli-

ing a weight while holding one’s breath, pressure in

cations develop, they usually occur because

the abdominopelvic cavity can rise to 106 kg/cm2

abdominal organs that have pushed into the tho-

(1500 lb/in.2), roughly 100 times normal pressures.

racic cavity are exerting pressure on structures or

Pressures this high can cause a variety of problems,

organs there. As is the case with inguinal hernias,

among them the development of a

hernia.

a diaphragmatic hernia may result from congenital

A

hernia

develops when a visceral organ pro-

factors or from an injury that weakens or tears the

7

trudes abnormally through an opening in a muscu-

diaphragmatic muscle.

lar wall or partition. There are many types of

Sports Injuries

hernias; we will consider only

inguinal

(groin)

her-

EAP

p. 208

nias

and

diaphragmatic hernias

here.

Sports injuries affect amateurs and professionals

Late in the development of the male, the testes

alike. A 5-year study of college football players

descend into the scrotum by passing through the

indicated that 73.5 percent experienced mild

abdominal wall at the

inguinal canals.

In the adult

injuries, 21.5 percent moderate injuries, and 11.6

male, the spermatic ducts and associated blood

percent severe injuries during their playing

vessels penetrate the abdominal musculature at

careers. Contact sports are not the only activities

the

inguinal canals

on their way to the abdominal

that show a significant injury rate; a study of 1650

reproductive organs. In an inguinal hernia, the

joggers running at least 27 miles per week reported

inguinal canal enlarges, and the abdominal con-

1819 injuries in a single year.

tents such as a portion of the intestine (or more

Muscles and bones respond to increased use

rarely the bladder) are forced into the inguinal

by enlarging and strengthening. Poorly conditioned

canal (Figure A-24). If the herniated structures

individuals are therefore more likely to subject

become trapped or twisted within the inguinal sac,

their bones and muscles to intolerable stresses

surgery may be required to prevent serious compli-

than are people in good condition. Training is also

cations. Inguinal hernias are not always caused by

important in minimizing the use of antagonistic

unusually high abdominal pressures. Injuries to

muscle groups and keeping joint movements within

the abdomen, or inherited weakness or distensibili-

the intended ranges of motion. Planned warm-up

ty of the canal, may have the same effect.

exercises before athletic events stimulate circula-

The esophagus and major blood vessels pass

tion, improve muscular performance and control,

through an opening in the diaphragm, the muscle

and help prevent injuries to muscles, joints, and

that separates the thoracic and abdominopelvic

ligaments. Stretching exercises stimulate muscle

cavities. In a

diaphragmatic hernia,

also called a

circulation and help keep ligaments and joint cap-

hiatal hernia

(h -£-tal;

hiatus,

a gap or opening),

sules supple. Such conditioning extends the range

of motion and prevents sprains and strains when

sudden loads are applied.

Dietary planning can also be important in pre-

venting injuries to muscles during endurance

events, such as marathon running. Emphasis has

often been placed on the importance of carbohy-

Inguinal

drates, leading to the practice of “carbohydrate

External

canal

loading” before a marathon. But while operating

abdominal

within aerobic limits, muscles also utilize amino

oblique

Inguinal

acids extensively, so an adequate diet must include

hernia

External

both carbohydrates and proteins.

inguinal

Improved playing conditions, equipment, and

Herniated

ring

regulations also play a role in reducing the inci-

intestine

Spermatic

dence of sports injuries. Jogging shoes, ankle or

cord

knee braces, helmets, and body padding are exam-

ples of equipment that can be effective. The sub-

stantial penalties now earned for personal fouls in

contact sports have reduced the numbers of neck

and knee injuries.

Several injuries common to those engaged in

Figure A-24 An Inguinal Hernia

active sports may also affect nonathletes, although

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The Body Systems: Clinical and Applied Topics

68

the primary causes may differ. A partial listing of

Carpal Tunnel Syndrome

EAP

p. 211

activity-related conditions includes the following:

Tenosynovitis

is the inflammation of a tendon

•

Bone bruise:

Bleeding within the periosteum of

sheath. Carpal tunnel syndrome results from

a bone

tenosynovitis of the tendon sheath surrounding the

•

Bursitis:

Inflammation of the bursae around

flexor tendons of the palm. The inflammation leads

one or more joints

to compression of the

median nerve,

a mixed (sen-

sory and motor) nerve that innervates the palm.

•

Muscle cramps:

Prolonged, involuntary, and

Symptoms include pain, especially on palmar flex-

painful muscular contractions

ion, a tingling sensation or numbness on the palm,

•

Sprains:

Tears or breaks in ligaments or tendons

and weakness in the abductor pollicis. This condi-

•

Strains:

Tears in muscles

tion is fairly common and often strikes those

engaged in repetitive hand movements, such as

•

Stress fractures:

Cracks or breaks in bones

typing, working at a computer keyboard, or playing

subjected to repeated stresses or trauma

the piano. Treatment involves administration of

•

Tendinitis:

Inflammation of the connective tis-

anti-inflammatory drugs such as aspirin, injection

sue surrounding a tendon

of anti-inflammatory agents, such as

glucocorti-

Many of these conditions have been discussed in

coids

(steroid hormones produced by the adrenal

previous chapters.

cortex), and use of splints to prevent wrist flexion

Finally, many sports injuries would be prevent-

and stabilize the region.

ed if people who engage in regular exercise used

Carpal tunnel syndrome is an example of a

common sense and recognized their personal limi-

cumulative trauma disorder,

or

overuse syndrome.

tations. It can be argued that some athletic events,

These disorders are caused by repetitive move-

such as the ultramarathon, place such excessive

ments of the arms, hands, and fingers. These mus-

stresses on the cardiovascular, muscular, respira-

culoskeletal problems now account for over 50

tory, and urinary systems that they cannot be rec-

percent of all work-related injuries in the United

ommended, even for athletes in peak condition.

States.

CRITICAL-THINKING QUESTIONS

c. increase the force and strength of muscle

contractions

3-1.

A patient experiencing a severe hyper-

CeCe answers this question correctly but becomes

kalemia could have the following related problems:

immediately concerned about this effect on a select

a. a below-normal potassium ion concentration

group of skeletal muscles. What is CeCe concerned

of the interstitial fluid

about?

b. a more-negative membrane potential of

3-3.

Tom broke his right leg in a football game.

nerves and muscles

After six weeks in a cast, the cast is finally

c. unresponsive skeletal muscles and cardiac

removed, and when he takes his first few steps, he

arrest

loses his balance and falls. What is the most likely

explanation?

d. muscle weakness and increased strength of

twitch contractions

a. the bone fracture is not completely healed

e. all of the above

b. the right leg muscles have atrophied due to

disuse

3-2.

Making hospital rounds, Dr. R., an anes-

c. Tom has an undiagnosed neuromuscular

thesiologist, meets with a first-semester anatomy

disorder

and physiology student named CeCe who is sched-

uled for surgery the next day. Having just finished

3-4.

Samples of muscle tissue are taken from a

the unit on skeletal muscles and the nervous sys-

champion tennis player and a nonathlete of the

tem, CeCe is eager to learn about the anesthesia

same age and gender. Both samples are subjected

that will be used during the surgery. Dr. R.

to enzyme analysis. How would you expect the two

explains he will be using a drug,

succinyl choline,

samples to differ?

that competes with acetylcholine and blocks the

3-5.

Calvin steps into a pothole and twists his

action of this neurotransmitter at the neuromuscu-

ankle. He is in a great deal of pain and cannot stand.

lar junction. What effect will this have on CeCe’s

In the hospital, the examining physician notes that

skeletal muscles?

Calvin can plantar flex and dorsiflex the foot, but he

a. produce paralysis of all the skeletal muscles

cannot perform inversion without extreme pain.

Which muscle has probably been injured?

b. cause tetany of the skeletal muscles

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The Muscular System

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NOTES

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