Download Lecture Suggestions and Guidelines

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 (fast-twitch) to red muscle fibers
(slow-twitch), which can contract for prolonged periods of time, through
appropriate physical training and conditioning.
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 acetylcholineesterase.
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 muscle fiber
contraction, how oxygen debt develops, and how a muscle may become fatigued.
Lecture Suggestions and Guidelines
1. Discuss ATP molecules as the energy sources used during muscle fiber
contraction.
2. Introduce creatine phosphate as an initial source of energy used to regenerate ATP
from ADP and phosphate.
3. Describe glucose, stored in the muscles in the form of glycogen, as an energy
source for synthesizing ATP.
4. Briefly compare anaerobic and aerobic respiration.
5. Introduce the terms hemoglobin and myoglobin.
6. Describe oxygen debt and the accumulation of lactic acid.
7. 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.
LEARNING OBJECTIVE 5: Distinguish between fast- and slow-twitch 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 long-distance 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
1. Introduce the terms myogram and threshold stimulus.
2. Define twitch, latent period, period of contraction, period of relaxation, and
refractory period.
3. Discuss multiple motor unit summation.
4. Compare an eyelid twitch to the act of lifting a weight.
5. Discuss the role of muscle tone in maintaining posture.
6. 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.
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.
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.
McDonagh, Sorcha. August 2, 2003. Turbo gene: getting a speed boost from DNA.
Science News, vol. 164, no. 5, pg. 70.
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.