Download LEARNING OBJECTIVE 1: Describe how connective tissue is part of

CHAPTER 9
MUSCULAR SYSTEM
LEARNING OBJECTIVE 1: Describe how connective tissue is part of the structure of a skeletal
muscle.
Lecture Suggestions and Guidelines
1. Introduce the terms fascia, tendon, aponeuroses, and compartments.
2. Describe how skeletal muscles are covered by fascia.
3. Describe aponeuroses as broad, fibrous sheets of connective tissues, which may surround groups of cells within
the muscle’s structure.
4. Distinguish among the epimysium, perimysium, fascicles, and endomysium.
Application Question(s)
1. Ask students to sketch a typical muscle fiber depicting the various kinds of tissue that compose skeletal muscle.
What kinds of tissue should be included?
Answer: The sketch should include layers of connective tissue, fascia, epimysium, perimysium, fascicles, and
endomysium.
Critical Thinking Issue(s)
1. A musician complains of a crackling feeling in her wrist every time she plays the piano. What might be the
cause?
Answer: Traumatic tenosynovitis is a common disorder seen in piano players, typists, and computer
programmers resulting from excessive use of certain tendons. The crackling of the wrist, which the piano player
felt, is primarily due to the formation of fibrin on the tendon surface and wall of the tendon sheath.
LEARNING OBJECTIVE 2: Name the major parts of a skeletal muscle fiber and describe the function
of each part.
Lecture Suggestions and Guidelines
1. Describe the anatomy and physiology of a single muscle fiber (a single cell of a muscle) by including the terms
sarcolemma, sarcoplasm, myofibrils, myosin, actin, titin, sarcomere, sarcoplasmic reticulum, and transverse
tubules.
2. Describe the arrangement of I bands and A bands which account for the striation pattern of skeletal muscle
fibers.
3. Discuss the events, which occur during a muscle strain.
4. Discuss a motor unit and the neuromuscular junction.
Application Question(s)
1. Prior to the big track meet on Saturday morning, would it be better to “warm-up” or “save your strength?”
Answer: Responses will vary, but the students should keep in mind that appropriate warm-up exercises are
essential to good performance and will decrease the likelihood of strains, sprains, and other injuries. On the
other hand, it is literally impossible to hoard strength, in fact, unused muscles over an extended period of time
will actually atrophy.
Critical Thinking Issue(s)
1. Ask students to debate the issue “Marathon runners are born, not made.”
Answer: Recent research has refuted previous belief that muscle fiber types are genetically determined.
Actually, experimentation has shown that muscle fiber types can be converted from white muscle fibers (fasttwitch) to red muscle fibers (slow-twitch), which can contract for prolonged periods of time, through
appropriate physical training and conditioning.
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LEARNING OBJECTIVE 3: Explain the major events that occur during muscle fiber contraction.
Lecture Suggestions and Guidelines
1. Introduce the role of actin and myosin reactions to generate the force of muscle fiber contraction.
2. Describe how troponin and tropomyosin molecules block the binding sites on actin molecules when a muscle
fiber is at rest.
3. Discuss the role of calcium ions in exposing the binding sites on the actin filaments.
4. Introduce the sliding filament theory of muscle contraction.
5. Discuss Duchenne’s muscular dystrophy.
6. Introduce the neurotransmitter acetylcholine and the enzyme acetylcholine-esterase.
Application Question(s)
1. Apply the concepts of muscle contraction and relaxation by having the students develop two sets of index
cards. The first set is composed of eight cards, each of which describes one major step in the muscle
contraction process. Scatter the eight cards and ask students to rearrange them in the correct sequence. The
second set is composed of six cards, each of which describes one major step in the muscle relaxation process.
Repeat the procedure used for the first set of cards.
Once the students have mastered each process, mix the two sets of cards together and ask students to separate
them once again by process in the correct sequence.
Answer: N/A
Critical Thinking Issue(s)
1. Ask students to prepare a short report on Myasthenia gravis. The report should include causes, signs and
symptoms, and treatment modalities.
Answer: The precise cause of Myasthenia gravis is unknown. It appears to be an autoimmune disease,
characterized by extreme muscle fatigue. Autoantibodies destroy acetylcholine receptors on the sarcolemma,
resulting in the failure of nerve impulse transmission to muscles at the myoneural junction. If left untreated, the
diaphragm may become paralyzed, causing respiratory failure. Treatment usually involves administration of
anticholinesterases.
LEARNING OBJECTIVE 4: Explain how energy is supplied to the muscle fiber contraction
mechanism, how oxygen debt develops, and how a muscle may become fatigued.
Lecture Suggestions and Guidelines
1.
2.
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4.
5.
6.
7.
Discuss ATP molecules as the energy sources used during muscle fiber contraction.
Introduce creatine phosphate as an initial source of energy used to regenerate ATP from ADP and phosphate.
Describe glucose, stored in the muscles in the form of glycogen, as an energy source for synthesizing ATP.
Briefly compare anaerobic and aerobic respiration.
Introduce the terms hemoglobin and myoglobin.
Describe oxygen debt and the accumulation of lactic acid.
Introduce the term fatigue and its effect upon muscle contraction.
Application Question(s)
1. How does the accumulation of lactic acid in muscle tissue cause muscle fatigue? Are athletes more tolerant of
lactic acid accumulation than non-athletes?
Answer: Lactic acid accumulation causes muscle fatigue by preventing muscle fibers from responding to
stimulation via a lowered pH. In general, athletes produce less lactic acid than non-athletes by stimulating new
capillary growth within muscles and by producing more mitochondria within muscle cells.
Critical Thinking Issue(s)
1. What are “shin splints?”
Answer: “Shin splints” is a milder form of a disease called anterior tibial syndrome. The patient experiences
swelling, pain, and paralysis of muscles near the tibia. The cause is primarily the result of inadequate physical
training, resulting in a strain of the long flexor muscle of the toes.
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LEARNING OBJECTIVE 5: Distinguish between fast and slow muscle fibers.
Lecture Suggestions and Guidelines
1. Introduce slow-contracting (slow-twitch) postural muscles. Discuss their red color in the presence of
myoglobin, the number of mitochondria, and their high respiratory capacity.
2. Introduce fast-contracting (fast-twitch) muscles. Discuss their white color (poorer blood supply), fewer
mitochondria, and reduced respiratory capacity.
Application Question(s)
1. Compare the mechanism by which a weight lifter’s muscles adapt to increasing demand compared to a longdistance runner’s ability to adapt.
Answer: A weight lifter will increase the number of myofibrils in the muscle tissue, whereas a long distance
runner will increase the number and size of mitochondria within the muscle cells.
Critical Thinking Issue(s)
1. How does potassium affect muscle tissue metabolism?
Answer: Both hypokalemia and hyperkalemia have adverse effects upon muscle metabolism, causing paralysis
in either case.
LEARNING OBJECTIVE 6: Distinguish between a twitch and a sustained contraction.
and
LEARNING OBJECTIVE 7: Describe how exercise affects skeletal muscles.
and
LEARNING OBJECTIVE 8: Explain how various types of muscular contractions produce body
movements and help maintain posture.
Lecture Suggestions and Guidelines
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6.
Introduce the terms myogram and threshold stimulus.
Define twitch, latent period, period of contraction, period of relaxation, and refractory period.
Discuss multiple motor unit summation.
Compare an eyelid twitch to the act of lifting a weight.
Discuss the role of muscle tone in maintaining posture.
Give examples of isometric and isotonic exercises.
Application Question(s)
1. Distribute copies of real-life myograms to the students. Assist them in the interpretation of the myogram by
identifying a single muscle twitch, the staircase effect, summation, and a tetanic contraction.
Answer: N/A
Critical Thinking Issue(s)
1. How does the body maintain homeostasis by responding to exercise? Ask students to develop a schematic
diagram depicting the relationship between exercise and cell respiration.
Answer: Exercise leads to increased cell respiration which in turn triggers increased ATP production,
increased need for oxygen, increased heat production, increased perspiration, increased carbon dioxide
production, and increased heart rate and respiration.
LEARNING OBJECTIVE 9: Distinguish between the structures and functions of a multiunit smooth
muscle and a visceral smooth muscle.
Lecture Suggestions and Guidelines
1. Compare and contrast the anatomy of the two major types of smooth muscles; multiunit smooth muscle and
visceral smooth muscle.
2. Give examples of the location of multiunit and visceral muscle found in the human body, e.g., multiunit smooth
muscle in the walls of blood vessels vs. visceral smooth muscle found in the stomach and urinary bladder.
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3. Discuss rythmicity as it applies to visceral smooth muscles.
4. Emphasize two major features of visceral smooth muscle: a) transmission of impulses from cell to cell; and b)
rythmicity as it pertains to peristalsis.
Application Question(s)
1. Compare and contrast the structure and function of multiunit and visceral smooth muscle. Ask students to give
examples of each.
Answer: Multiunit smooth muscle-fibers are well organized, single fibers. Contracts after motor nerve impulse
or hormonal stimulation. For example: walls of blood vessels. Visceral smooth muscle-sheets of spindle-shaped
cells. Longitudinal outer coat with a circular inner coat. Fibers can stimulate each other through rythmicity.
Example: urinary bladder.
Critical Thinking Issue(s)
1. Peristalsis is the rythmic contraction of smooth muscle that occurs in certain tubular organs. Ask students to
give examples of cases in which reverse peristalsis may occur.
Answer: Stimulation of the emetic center which induces vomiting, a back flow of urine through the ureters to
the kidney due to a calculus, a back flow of blood due to an insufficient valve, etc.
LEARNING OBJECTIVE 10: Compare the contraction mechanisms of skeletal, smooth, and cardiac
muscle fibers.
Lecture Suggestions and Guidelines
1. Describe the fiber contraction mechanism of skeletal muscles, including the reactions of actin and myosin,
triggering by membrane impulses and release of calcium ions, ATP usage, and the presence of acetylcholine
and norepinephrine.
2. Introduce the fiber contraction mechanism of smooth muscles, which is similar to skeletal muscle, but include
differences such as the lack of troponin, the presence of calmodulin, etc.
3. Describe cardiac muscle contractions in terms of length of contraction, the presence of intercalated disks and
the all-or-none response.
Application Question(s)
1. Does aerobic exercise cause a significant increase in skeletal muscle size?
Answer: Aerobic exercise benefits primarily the cardiovascular system. Skeletal muscle size is enhanced by
resistance in the form of isometric exercises.
Critical Thinking Issue(s)
1. Ask students to compare and contrast the three major types of muscle (skeletal, smooth, and cardiac) in terms
of major location, major function, cellular characteristics, mode of control, and contraction characteristics.
Answer: See Table 9.2 in the textbook.
LEARNING OBJECTIVE 11: Explain how the locations of skeletal muscles help produce movements
and how muscles interact.
Lecture Suggestions and Guidelines
1. Introduce the terms origin and insertion and give examples of each.
2. Define prime movers and give an example. Discuss the concept that observation of body movements makes a
determination of the roles of particular muscles possible.
3. Compare/contrast synergists and antagonists and give examples of each.
Application Question(s)
1. Ask each student to choose ten muscles and deduce the origin of the name for each one. For example, the
biceps brachii is named based upon the fact that it has two origins (biceps) and is found in the brachial (brachii)
region. Gluteus maximus is named based upon its location (gluteal region) and its size (maximus).
Answer: Responses will vary, but students should be aware that muscles are named based upon several criteria,
such as location, size, number of origins, shape, action, etc.
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Critical Thinking Issue(s)
1. Ask students to draw an analogy between the major interactions of skeletal muscles, i.e., prime movers,
synergists, and antagonists and a group of students or co-workers with whom they had to work to complete a
project. Who were the prime movers, the synergists, and the antagonists, and what were their actions and roles?
Answer: The analogies should be interesting. Every group has at least one leader or person who does the
majority of the work, a number of assistants who are willing to help, and one or more antagonists who attempt
to resist the efforts of others.
LEARNING OBJECTIVE 12: Identify and locate the major skeletal muscles of each body region and
describe the action of each muscle.
Lecture Suggestions and Guidelines
1. Introduce the naming of skeletal muscles, in terms of direction of muscle fibers, muscle size, location of the
muscle and its origin/insertion points, the number of origins, the muscle shape and its action.
2. Summarize major skeletal muscles by name, location, origin, insertion, and action. Include a short description
of major muscles in each of the following categories: facial expression, mastication, head movement, pectoral
girdle, upper arm, forearm, wrist and hand, abdominal wall, pelvic outlet, thigh, lower leg, ankle, foot, and toes.
3. Repetition is the key. Use wall charts, models, overheads, and student volunteers to reiterate the location and
action of each muscle.
Application Question(s)
1. Repetition is the key to identifying the major muscles by name, location, and action. Use models, wall charts,
and overheads repetitively. Dissection will reinforce learning as well. Ask students to develop tables, by major
region of the anterior and posterior muscles to include the name, origin, insertion, and action.
Answer: N/A
Critical Thinking Issue(s)
1. Based on the students’ knowledge of the muscular system, ask each to develop a simple exercise regimen
designed to strengthen the lower back. Which muscle groups would the student include?
Answer: Responses will vary but, would most likely include, at a minimum, the extensor muscles of the lumbar
region, the flexor muscles of the coxal region, and the abdominal muscles.
RELATED DISEASES OF HOMEOSTATIC INSTABILITY
1. Muscular Dystrophy—Genetic in nature, caused by a dominant sex-linked gene that interferes with protein
synthesis. Muscle fibers become necrotic, and are replaced with connective tissue and fat.
2. Myasthenia Gravis—Failure in the transmission of the impulse from the nerves to the muscles at the myoneural
junction. Cause unknown, but appears to be autoimmune in nature.
3. Anterior tibial syndrome—A serious form of “shin splints,” in which the affected muscles may become
necrotic. It is believed that the strenuous exercise of an untrained muscle liberates excess quantities of
metabolites that lead to severe swelling of the muscle causing ischemic necrosis.
SUGGESTIONS FOR ADDITIONAL READING
Alexander, R. McNeill. June 4, 1992. The work that muscles can do. Nature, vol. 357. Principles of physics lie
behind the functioning of the musculoskeletal system.
Huxley, Hugh, and Jean Hanson. October 1991. Changes in the cross-striations of muscle during contraction and
stretch and their structural interpretation. The Journal of NIH Research.
Wright, P.F. and D.T. Karzon. February 23, 1995. Minimizing the risks associated with the prevention of
poliomyelitis. New England Journal of Medicine, vol. 332. Very rarely, polio vaccine can cause symptoms of the
illness it is intended to prevent.
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