Learning Outcome 1: List Various Outcomes of Muscular Actions
Chapter 8:
MUSCULAR SYSTEM
8.1 Introduction
Learning Outcome 1: List various outcomes of muscular actions.
- Lecture Suggestions and Guidelines
a. Describe why all movements require muscles.
b. Discuss muscles as organs composed of specialized cells.
c. Identify the three basic types of muscles.
- Application Question(s)
a. Ask students to develop a chart that compares and contrasts the structure and function of various muscles.
Answer: Responses will vary, but should include a discussion of examples of skeletal, smooth, and cardiac muscle.
- Critical Thinking Issue(s)
a. Compare and contrast various muscle actions.
Answer: Responses may include a discussion of muscle tone, the movement of nutrients and fluids, the role of a heartbeat, and the production of heat through shivering.
8.2 Structure of a Skeletal Muscle
Learning Outcome 2: Describe how connective tissue is part of a skeletal muscle.
- Lecture Suggestions and Guidelines
a.Introduce the muscular system and describe its interactions with other major systems within the human body.
b.Describe fascia as layers of fibrous connective tissue.
c.Define epimysium, perimysium, and endomysium.
d.Give a brief overview of the general structure of a skeletal muscle.
- Application Question(s)
a.Provide students with an unlabeled diagram that illustrates how layers of fibrous connective tissue called fascia separate an individual skeletal muscle from adjacent muscles and hold it in position. Ask them to label the diagram as completely as possible.
Answer: The labeled diagram may include a bone, tendon, fascia, muscle, epimysium, perimysium, endomysium, fascicle, axon, muscle fibers, blood vessels, sarcolemma, nucleus, sarcoplasmic reticulum, myofibrils, and filaments.
- Critical Thinking Issue(s)
a.A musician complains of a crackling feeling in her wrist every time she plays the piano. What might explain this phenomenon?
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 Outcome 3: Name the major parts of a skeletal muscle fiber, and describe the function of each.
- Lecture Suggestions and Guidelines
a. Describe a skeletal muscle as having numerous myofibrils, each consisting of units called sarcomeres.
b. Describe the roles of actin and myosin.
c. Discuss the appearance of striations.
d. Explain the bands, lines, and zones of a skeletal muscle.
e. Lecture on the connection between the motor neuron and muscle fiber.
f. Describe a motor unit.
- Application Question(s)
a. Provide students with a variety of microscope slides applicable to this chapter objective. Ask them to draw and label what they see.
Answer: The slides may illustrate myofibrils, sarcomeres, Z lines, actin, myosin, M lines, H zones, I bands, A bands, and sarcoplasm.
- Critical Thinking Issue(s)
a. Discuss the meaning of the presence or absence of striations by comparing skeletal muscle, cardiac muscle, and smooth muscle.
Answer: The striated appearance of skeletal and cardiac muscle begins with an alternating configuration of light and dark bands of myofibrils. The myofibrils are actually chains of sarcomeres, which contain even smaller structures called myofilaments. It is the unique banding pattern of the myofilaments that produces a striated appearance. This banding pattern is absent in smooth muscle.
8.3 Skeletal Muscle Contraction
Learning Outcome 4: Describe the major events of skeletal muscle fiber contraction.
and
Learning Outcome 5: Describe how the muscle fiber contraction mechanism obtains energy.
- Lecture Suggestions and Guidelines
a. Discuss the sliding filament theory.
b. Introduce the role of ATPase.
c. Describe the stimulus for contraction, including the role of acetylcholine and acetylcholinesterase.
d. Describe in some detail the major events of muscle fiber contraction and muscle fiber relaxation.
e. Explain how ATP molecules supply the energy for muscle fiber contraction and the role of
creatine phosphate.
f. Distinguish between hemoglobin and myoglobin.
- Application Question(s)
a. Ask students to develop a set of index cards, each of which has one or two key words that represents a major event of muscle contraction. Develop a second set in a similar manner for muscle relaxation. Have each student place the steps in the correct order, and then briefly present the major steps to the class in more detail.
Answer: Suggestions for key words in describing contraction are acetylcholine release, acetylcholine diffuses, membrane stimulated, calcium diffusion, linkages, cross-bridges, and fiber shortens. Suggestions for key words in describing relaxation are acetylcholinesterase, calcium transport, linkages, sliding, and fiber relaxes.
- Critical Thinking Issue(s)
a. Discuss the connection between anaerobic respiration and aerobic respiration when describing how a muscle cell uses energy.
Answer: A muscle cell uses energy released in cellular respiration to synthesize ATP. ATP is then used to power muscle contraction or to synthesize creatine phosphate. Later, creatine phosphate may be used to synthesize ATP. The oxygen required to support aerobic respiration is carried in the blood and stored in myoglobin. In the absence of sufficient oxygen, pyruvic acid is converted to lactic acid. The maximum number of ATPs generated per glucose molecule varies with cell type.
Learning Outcome 6: Describe how oxygen debt develops and how a muscle may become fatigued.
- Lecture Suggestions and Guidelines
a. Describe how muscle fibers depend on the aerobic phase of respiration for energy.
b. Discuss the causes of muscle fatigue and cramping.
c. Lecture on the relationship among lactic acid, oxygen debt, and muscle fatigue.
d. Explain the relationship between cellular respiration and heat production.
- Application Question(s)
a. What causes muscle cramping? What may be done to treat muscle cramps?
Answer: Cramps may occur anywhere in the body. They are a sharp, involuntary muscle contraction that may be caused by fatigue, electrolyte imbalance, or dehydration. Muscle cramps are usually treated with fluid intake and gradual stretching of the muscle.
- Critical Thinking Issue(s)
a. Distinguish between a strain and a sprain.
Answer: A muscle strain is sometimes referred to as a pulled muscle. It is caused by tearing of muscle fibers or a tendon, resulting from an abnormally violent contraction. A sprain is caused by the tearing of a ligament, resulting from a sudden force such as a violent twisting motion of the ankle.
8.4 Muscular Responses
Learning Outcome 7: Distinguish between a twitch and a sustained contraction.
- Lecture Suggestions and Guidelines
a. Give an overview of threshold stimulus.
b. Describe what is meant by an all-or-none response.
c. Ensure a basic understanding of the recording of a muscle contraction, including how to read a myogram.
d. Discuss summation and a tetanic contraction.
e. Describe the recruitment of motor units and how the strength of a contraction may increase due to
this recruitment.
- Application Question(s)
a. Provide students with myogram printouts and ask them to identify peaks and troughs.
Answer: Students should be able to identify the period of contraction and the period of relaxation. A variety of myograms may help the students to differentiate a series of twitches from a summation or tetanic contraction.
- Critical Thinking Issue(s)
a. Discuss hypoparathyroidism as it pertains to this chapter objective.
Answer: Responses should include a discussion of tetany, a sustained muscular contraction. Low levels of calcium in the blood may result in overstimulation of certain skeletal muscles. Muscles of the hands and feet, as well as the laryngeal muscles, are very susceptible to these spasms.
Learning Outcome 8: Explain how muscular contractions produce body movements and help maintain posture.
- Lecture Suggestions and Guidelines
a. Distinguish between isometric and isotonic contraction.
b. Reiterate examples of how one may sustain or increase muscle tone.
c. Explain the connection between muscle tone and the maintenance of posture.
d. Describe a muscle pull.
- Application Question(s)
a. Ask students to develop a list of excuses most commonly cited for not exercising and strategies for dealing with these excuses.
Answer: Responses should address excuses relating to age, time availability, cost, hopelessness, stress, attitude, etc.
- Critical Thinking Issue(s)
a. Discuss the health-related benefits associated with regular aerobic exercise.
Answer: Responses should include a discussion of reduction of the risk of cardiovascular disease, help in controlling diabetes, development of stronger bones, promotion of joint stability, reduction in lower back problems, improvement of self-image, etc.
8.5 Smooth Muscle
Learning Outcome 9: Distinguish between the structures and functions of multiunit smooth muscle and visceral smooth muscle.
- Lecture Suggestions and Guidelines
a. Reiterate the structure of a smooth muscle cell.
b. Give examples of the locations of multiunit and visceral smooth muscles.
c. Describe the process of peristalsis.
- Application Question(s)
a. Ask students to prepare a brief report that compares the structure and function of multiunit and visceral smooth muscle, including examples of each.
Answer: Multiunit smooth muscle exhibits fibers that are well organized. The single fibers contract due to motor nerve impulses or hormonal stimulation. The walls of blood vessels are examples of this phenomenon. Visceral smooth muscles are sheets of spindle-shaped cells composed of a longitudinal outer coat and a circular inner coat. Fibers stimulate each other during rhythmicity. The urinary bladder is an example of visceral smooth muscle.
- Critical Thinking Issue(s)
a. Peristalsis is the rhythmic contraction of smooth muscle that occurs in certain tubular organs. Discuss examples of reverse peristalsis.
Answer: Examples may include the stimulation of the emetic center which induces vomiting, a back flow of urine through the ureters due to blockage, or a back flow of blood resulting from an insufficient heart valve.
Learning Outcome 10: Compare the contraction mechanisms of skeletal and smooth muscle fibers.
and
8.6 Cardiac Muscle
Learning Outcome 11: Compare the contraction mechanisms of skeletal and cardiac muscle fibers.
- Lecture Suggestions and Guidelines
a. Give an overview of three major types of muscle – skeletal, smooth, and cardiac.
b. Compare major characteristics of skeletal, smooth, and cardiac muscle, including major location, major function, cellular characteristics, mode of control, and contraction characteristics.
c. Explain the role of intercalated disks.
- Application Question(s)
a. Ask students to develop a chart that compares various characteristics among skeletal, cardiac, and smooth muscles.
Answer: The chart should include information regarding location, appearance, presence or absence of striations, control mechanisms, contraction speed, and functions.
- Critical Thinking Issue(s)
a. Provide students with a variety of microscope slides of skeletal, cardiac, and smooth muscle. Ask them to draw what they see and to comment on any similarities and differences among the three types.
Answer: Responses should include a discussion of striations, nuclear configurations, transverse tubule systems, and intercalated disks.
8.7 Skeletal Muscle Actions
Learning Outcome 12: Explain how the locations and interactions of skeletal muscles make possible certain movements.
- Lecture Suggestions and Guidelines
a. Reiterate the definitions of the term’s origin and insertion.
b. Explain what is meant by the terms prime mover, synergist, and antagonist.
c. Describe various criteria used to name a muscle. For example, its shape, its number of origins, its size, its function, etc.
- Application Question(s)
a. Ask students to make a list of twenty-five muscles and determine by which criteria each muscle derived
its name.
Answer: Students should categorize the muscles they have chosen by size, location, number of origins, shape, direction of the muscle fibers, action, and origin/insertion points.
- Critical Thinking Issue(s)
a. Have classmates demonstrate various muscle movements to each other. The classmates should identify the skeletal muscles involved, and determine which muscles are contracting or relaxing during each demonstration.
Answer: Demonstrations will vary but should emphasize the concepts of prime movers, antagonists, synergists, and fixators.
8.8 Major Skeletal Muscles
Learning Outcome 13: Describe the locations and actions of the major skeletal muscles of each body region.
- Lecture Suggestions and Guidelines
a. Lecture on the names, locations, and functions of the major skeletal muscles, including
b. the muscles of facial expression, mastication, head movements, muscles that move the pectoral girdle, arm, forearm, wrist, hand, fingers, muscles of the abdominal wall, pelvic outlet, muscles that move the thigh, leg, ankle, foot and toes. Use drawings, wall charts, overhead transparencies, models, and dissected specimens when appropriate. At a minimum, students should learn the muscle name, location, and action. The origin and insertion points may be optional, but would also aid the student in a comprehensive understanding of the muscular system.
- Application Question(s)
a. Ask students to locate on a wall chart or model, as many superficial skeletal muscles of the anterior and posterior aspects as possible. The name, origin, insertion, and major actions should also be noted.
Answer: Repetition is a key element. Students should be able to identify and discuss a minimum of thirty-six skeletal muscles.
- Critical Thinking Issue(s)
a. Discuss the adverse effects of anabolic steroid use to build muscular strength and endurance.
Answer: Responses should include a discussion of the following possible adverse side effects: increase in aggressive behavior, addiction, psychosis, hair growth, sexual dysfunction, high blood pressure, atherosclerosis, liver damage, cancer, etc.
Related Films
The Art of the Physical Exam. 20 min. Wayne State University Cit Productions Center.
How the Body Moves: The Muscles. 20 min. Time Life Multimedia.
Human Body: Muscular System. 22 min. Coronet Film and Video.
Lower Extremity. 20 min. Teaching Films, Inc.
Muscle: A Study of Integration. 25 min. McGraw Hill Training Systems.
Muscle: Chemistry of Contraction. 15 min. Encyclopaedia Britannica Educational Corp.
Muscle Contraction and Oxygen Debt. 16 min. McGraw Hill Training Systems.
Muscle: Dynamics of Contraction. 21 min. Encyclopaedia Britannica Educational Corp.
Muscle: Electrical Activity of Contraction. 9 min. Encyclopaedia Britannica Educational Corp.
The Muscle Spindle. 19 min. University of Illinois Film Center.
Muscles. 28 min. McGraw Hill Training Systems.
Muscles. 28 min. Films for the Humanities & Sciences.
Repetitive Strain Injuries. 27 min. Films for the Humanities and Sciences.
Skeleton and Muscles. 18 min. TV Video Publishing.
UpperExtremity. 36 min. Teaching Films, Inc.
Suggestions for Additional Reading
Anderson, K., and Behm, D. 2005. The impact of Instability Resistance Training on Balance and Stability. Sports Medicine, 35(1), 43-53. Retrieved June 8, 2007, from Academic Search Complete database.
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. A reprint of the 1954 Nature paper reporting the discovery of the sliding filament mechanism of muscle contraction, plus interviews with the researchers.
Johns, Donald R. October 1996. The other human genome. Nature Medicine, vol. 2. Mitochondria contain genes, and when they mutate, diseases result that often affect the muscles.
Kearney, Jay T. June 1996. Training the Olympic athlete. Scientific American. Athletic success depends on an optimally functioning musculoskeletal system.
Kurtzweil, Paula. October 1996. Paget's disease. FDA Consumer. Paget's disease enlarges bones.
Lewis, Ricki. July/August 1991. Arthritis: Modern treatments for that old pain in the joints. FDA Consumer. New Hope for the many people who suffer from inflamed joints.