Psychology Chapter 9 Homework Myoblasts Cardiac And Smooth Muscle Not Fuse

Unlock access to all the studying documents.

View Full Document

CHAPTER

Muscles and Muscle Tissue

Objectives

Overview of Muscle Tissues

2. List four important functions of muscle tissue.

Skeletal Muscle

5. Describe the sliding filament model of muscle contraction.

6. Explain how muscle fibers are stimulated to contract by describing events that occur at

the neuromuscular junction.

8. Follow the events of excitation-contraction coupling that lead to cross bridge activity.

9. Define motor unit and muscle twitch, and describe the events occurring during the three

phases of a muscle twitch.

14. Describe factors that influence the force, velocity, and duration of skeletal muscle

contraction.

15. Describe three types of skeletal muscle fibers and explain the relative value of each type.

Smooth Muscle

17. Compare the gross and microscopic anatomy of smooth muscle cells to that of skeletal

muscle cells.

19. Distinguish between unitary and multi unit smooth muscle structurally and functionally.

Developmental Aspects of Muscles

20. Describe embryonic development of muscle tissues and the changes that occur in skeletal

muscles with age.

Suggested Lecture Outline

I. Overview of Muscle Tissues (pp. 276–278; Table 9.1)

A. Types of Muscle Tissue (p. 277; Table 9.1)

1. Skeletal muscle is associated with the bony skeleton and consists of large cells that

bear striations and are under voluntary control.

B. Special Characteristics of Muscle Tissue (p. 277)

1. Excitability, or responsiveness, is the ability to receive and respond to a stimulus.

C. Muscle Functions (pp. 277–278; Table 9.1)

1. Muscles produce movement by acting on the bones of the skeleton, pumping blood, or

propelling substances throughout hollow organ systems.

2. Muscles aid in maintaining posture by adjusting the position of the body with respect

to gravity.

II. Skeletal Muscle (pp. 278–305; Figs. 9.1–9.24; Tables 9.1–9.3)

A. Gross Anatomy of Skeletal Muscle (pp. 278–279; Fig. 9.1; Tables 9.1, 9.3)

1. Each muscle has a nerve and blood supply that allows neural control and ensures

adequate nutrient delivery and waste removal.

2. Connective tissue sheaths are found at various structural levels of each muscle:

endomysium surrounds each muscle fiber, perimysium surrounds groups of muscle

fibers, and epimysium surrounds whole muscles.

B. Microscopic Anatomy of a Skeletal Muscle Fiber (pp. 279–285; Figs. 9.2–9.5; Tables

9.1, 9.3)

1. Skeletal muscle fibers are large, cylindrical cells with multiple nuclei beneath the

sarcolemma, or plasma membrane.

4. Striations are due to a repeating series of dark A bands and light I bands.

5. Myofilaments make up the myofibrils and consist of thick and thin filaments.

6. Striations, alternating dark A bands and light I bands, extend the length of each

myofibril.

a. Each A band has a lighter central region, the H zone, which is bisected vertically by

an M line.

7. There are two types of myofilaments in muscle cells: thick filaments composed of

bundles of myosin, and thin filaments composed of strands of actin.

8. Thin filaments also have a set of regulatory proteins: tropomyosin, that wrap around

actin filaments, stabilizing it and blocking myosin binding sites; and troponin, which

binds to both actin and tropomyosin, and binds calcium ions.

9. The sarcoplasmic reticulum, a smooth endoplasmic reticulum that regulates the avail-

ability of calcium ions, surrounds each myofibril, and forms terminal cisterns at the

C. The sliding filament model of muscle contraction states that during contraction, the thin

filaments slide past the thick filaments. Overlap between the myofilaments increases and

the sarcomere shortens (p. 285; Fig. 9.6).

D. Physiology of Skeletal Muscle Fibers (pp. 285–293; Figs. 9.7–9.12; Table 9.1)

1. The neuromuscular junction is a connection between an axon terminal of a somatic

5. Repolarization restores the resting polarity to the sarcolemma and is accomplished by

diffusion of potassium ions out of the cell.

a. During repolarization, the muscle cell is in a refractory period and may not be

depolarized until repolarization is complete.

6. Excitation-contraction coupling is the sequence of events by which an action potential

on the sarcolemma results in the sliding of the myofilaments.

a. A nerve impulse reaches the axon terminal, causing the release of ACh to the

synaptic cleft.

b. ACh binds to ACh receptors in the sarcolemma, and a net influx of sodium ions

causes the generation of an end plate potential.

E. Contraction of a Skeletal Muscle (pp. 293–298; Figs. 9.13–9.18)

1. A motor unit consists of a motor neuron and all the muscle fibers it innervates. It is

smaller in muscles that exhibit fine control.

2. The muscle twitch is the response of a muscle to a single action potential on its motor

neuron, and has three phases: the latent period, corresponding to the lag between

contraction to become sustained, a condition called tetanus.

b. Multiple motor unit summation (recruitment) involves the response of a muscle to

increasing stimulus voltage: smaller stimuli result in contraction of the smallest

motor units, and as voltage increases, larger, more forceful motor units respond,

leading to progressively greater contractile force.

6. Isometric contractions result in increases in muscle tension, but no lengthening or

shortening of the muscle occurs, and often are used to maintain posture or joint

stability while movement occurs at other joints.

F. Muscle Metabolism (pp. 298–301; Figs. 9.19–9.20)

1. Muscles contain very little stored ATP, and consumed ATP is replenished rapidly

through phosphorylation by creatine phosphate, anaerobic glycolysis, and aerobic

respiration.

2. As muscle metabolism transitions to meet higher demand during vigorous exercise,

3. As stored ATP and creatine phosphate are consumed, ATP is produced by breaking

down blood glucose or stored glycogen in glycolysis, an anaerobic pathway that pre-

cedes both aerobic and anaerobic respiration. If adequate oxygen is not available to

4. Aerobic respiration provides most of the ATP during light to moderate activity,

includes glycolysis, along with reactions that occur within the mitochondria, and

produces 32 ATP per glucose, as well as water, and CO2, which will be lost from the

body in the lungs.

6. Muscle fatigue is the physiological inability to contract, and results from ionic

imbalances that interfere with normal excitation-contraction coupling.

7. Excess postexercise oxygen consumption (EPOC) is the extra oxygen the body

8. Muscle activity produces excess energy that is lost from the body as heat: excess

body heat can be lost through sweating and radiant heat loss from skin, while heat

production through shivering can be used to warm the body when it is too cold.

G. Force of Muscle Contraction (pp. 301–302; Figs. 9.21–9.22)

1. As the number of muscle fibers stimulated increases, force of contraction increases.

4. The length-tension relationship optimizes the overlap between the thick and thin

filaments that produces optimal contraction.

H. Velocity and Duration of Contraction (pp. 302–304; Figs. 9.23–9.24; Tables

9.2–9.3)

1. There are three muscle fiber types: slow oxidative fibers, fast glycolytic fibers, and

fast oxidative fibers.

a. Slow oxidative fibers contract slowly, rely mostly on aerobic respiration, and are

highly fatigue resistant.

2. All muscles have varying amounts of all fiber types and, while the proportion of each

type is a genetically influenced trait, that proportion can be modified by specific types

of exercise.

3. As the load on a muscle increases, velocity and duration of contraction decreases.

4. Recruitment of additional motor units increases velocity and duration of contraction.

I. Adaptations to Exercise (pp. 304–305)

1. Aerobic exercise promotes an increase in capillary penetration, the number of mito-

chondria, and synthesis of myoglobin, leading to higher efficiency and endurance,

III. Smooth Muscle (pp. 305–311; Figs. 9.25–9.28; Table 9.3)

A. Microscopic Structure of Smooth Muscle Fibers (pp. 305–307; Figs. 9.25–9.27;

Table 9.3)

3. Contraction of the opposing layers of muscle leads to a rhythmic form of contraction,

called peristalsis, which propels substances through the organs.

4. Smooth muscle lacks neuromuscular junctions, but has varicosities: numerous

bulbous swellings that release neurotransmitters to a wide synaptic cleft.

5. Smooth muscle cells have a less developed sarcoplasmic reticulum, sequestering large

amounts of calcium in extracellular fluid within caveolae in the cell membrane.

B. Contraction of Smooth Muscle (pp. 307–309; Fig. 9.28; Table 9.3)

1. Mechanism of Contraction

a. Smooth muscle fibers exhibit slow, synchronized contractions due to electrical

coupling by gap junctions.

2. Regulation of Contraction

a. Autonomic nerve endings release either acetylcholine or norepinephrine, which

may result in excitation of certain groups of smooth muscle cells, and inhibition of

others.

3. Special Features of Smooth Muscle Contraction

a. Smooth muscle initially contracts when stretched, but contraction is brief, and then

the cells relax to accommodate the stretch.

b. Because the muscle filaments have an irregular overlapping pattern, smooth muscle

C. Types of Smooth Muscle (p. 309)

1. Unitary smooth muscle, called visceral muscle, is the most common type of smooth

muscle. It contracts rhythmically as a unit, is electrically coupled by gap junctions,

and exhibits spontaneous action potentials.

contractions.

IV. Developmental Aspects of Muscles (pp. 312–313, 315; Fig. 9.29)

A. Nearly all muscle tissue develops from specialized mesodermal cells called myoblasts

(p. 312).

B. Skeletal muscle fibers form through the fusion of several myoblasts, and are actively

contracting by week 7 of fetal development (p. 312; Fig. 9.29).

F. Muscular dystrophy is characterized by atrophy and degeneration of muscle tissue.

Enlargement of muscles is due to fat and connective tissue deposit (pp. 312, 315).

Cross References

Additional information on topics covered in Chapter 9 can be found in the chapters listed below.

1. Chapter 2: ATP; ions

2. Chapter 3: General cellular structural components; membrane transport; microfilaments;

gap junctions; membrane potentials

6. Chapter 10: Skeletal muscles of the body; interaction between muscle and bones

7. Chapter 11: General structure and function of synapses and neurotransmitters

8. Chapter 13: Sensory receptors located in skeletal muscle; motor neurons of the peripheral

nervous system and the neuromuscular junction

Lecture Hints

1. Point out that extend is a root of the word extensibility, indicating lengthening, or stretch-

2. Because the prefixes endo-, epi-, and peri- are often used in anatomical terminology,

emphasize the meanings and indicate that students will see these again.

3. Clearly describe the stepwise progression through related terms myofilament, myofibril,

4. In the description of the sliding filament mechanism, present an animation showing

6. Emphasize that graded muscle contraction is achieved by increasing the frequency of

stimulation of motor units or increasing the number of motor units activated.

7. As a way of introducing isometric and isotonic contractions, ask the class if muscle

contraction always results in movement. Whatever their answer, illustrate the point by

8. To illustrate length-tension relationships, ask the class to comment on the amount of

9. When explaining the differences between slow and fast (oxidative) fibers, it is helpful

10. Explain that all muscle types contain actin and myosin myofilaments, but that the

arrangement (in part) accounts for the structural and functional differences.

11. Be sure to inform students that the terms striated and skeletal muscle are interchangeable,

and that although cardiac muscle is striated, the term striated should not be used as a

name for cardiac muscle.

Activities/Demonstrations

1. Audiovisual materials are listed in the Multimedia in the Classroom and Lab section of

this Instructor Guide (p. 387).

2. Demonstrate muscle contraction using a simple myograph or kymograph apparatus and

3. Ask students to demonstrate examples of isometric and isotonic contractions and to

4. Set up a microscope with a slide of a motor unit for class viewing.

6. Use an articulated skeleton to point out various origins and insertions; then ask students

to specify the resulting movement.

7. Pick apart a piece of cooked chicken breast to demonstrate individual fascicles.

8. Obtain a 3-D model of a sarcomere to exhibit tubules and myofibrils.

10. Stress the importance of extracellular calcium ions to smooth muscle contraction, and

distinguish this from skeletal muscle, which is more reliant on stored intracellular

calcium ions.

Critical Thinking/Discussion Topics

1. Why is it more beneficial for a person stranded in the cold to keep moving and exercising

rather than remaining inactive?

2. Muscles that are immobilized for long periods of time, as with a cast, frequently get

smaller. Why? What is necessary to revitalize them?

6. Why do athletes “warm up” before a competitive event? Would you expect the warm-up

period to make contraction more or less efficient? Why?

7. Visit a local gym frequented by body builders. Obtain information on the procedures

used to build muscle mass and an explanation of how those procedures accomplish that

goal.

8. If the number of myosin heads were doubled, what would be the effect on force

production? ATP consumption?

Library Research Topics

1. Why have muscle cells “lost” their ability to regenerate? What current research is being

done in this area?

5. Explore the current theories for the etiology of muscular dystrophy.

6. What is the current status of the sliding filament model of muscle contraction? Do we

know all there is to know?

8. Describe several metabolic diseases of muscle (usually due to an enzyme or enzyme

group deficiency).

10. Define the term myositis. What causative agents could result in this form of muscle

disease?

List of Figures and Tables

All of the figures in the main text are available in JPEG format, PPT, and labeled & unlabeled

format on the Instructor Resource DVD. All of the figures and tables will also be available in

Transparency Acetate format. For more information, go to www.pearsonhighered.com/educator.

Figure 9.1 Connective tissue sheaths of skeletal muscle: epimysium,

perimysium, and endomysium.

Figure 9.2 Microscopic anatomy of a skeletal muscle fiber.

Figure 9.5 Relationship of the sarcoplasmic reticulum and T tubules to

myofibrils of skeletal muscle.

Figure 9.6 Sliding filament model of contraction.

Figure 9.7 The phases leading to muscle fiber contraction.

Figure 9.8 Events at the Neuromuscular Junction.

Figure 9.9 Summary of events in the generation and propagation of an action

potential in a skeletal muscle fiber.

Figure 9.16 Relationship between stimulus intensity (graph at top) and muscle

tension (tracing below).

Figure 9.21 Factors that increase the force of skeletal muscle contraction.

Figure 9.22 Length-tension relationships of sarcomeres in skeletal muscles.

Figure 9.23 Factors influencing velocity and duration of skeletal muscle

contraction.

Figure 9.24 Influence of load on duration and velocity of muscle contraction.

Figure 9.25 Arrangement of smooth muscle in the walls of hollow organs.

Figure 9.26 Innervation of smooth muscle.

Figure 9.27 Intermediate filaments and dense bodies of smooth muscle fibers

harness the pull generated by myosin cross bridges.

Answers to End-of-Chapter Questions

Multiple-Choice and Matching Question answers appear in Appendix H of the main text.

Short Answer Essay Questions

15. The functions are: excitability—the ability to receive and respond to a stimulus;

16. a. In direct attachment, the epimysium of the muscle is fused to the periosteum of a bone,

and in indirect attachment, the muscle connective tissue sheaths extend beyond the

17. a. A sarcomere is the region of a myofibril between two successive Z-lines and is the

smallest contractile unit of a muscle cell. The myofilaments are within the sarcomere.

18. AChE destroys the ACh after it is released. This prevents continued muscle fiber contrac-

tion in the absence of additional stimulation. (p. 286)

19. A slight (but smooth) contraction involves rapid stimulation of a few motor units and

20. Excitation-contraction coupling is the sequence of events by which an action potential trav-

eling along the sarcolemma leads to the contraction of a muscle fiber. (p. 290; Fig. 9.11)

21. A motor unit is the motor neuron and all the muscle fibers it controls. (p. 293; Fig. 9.13)

23. False, most body muscles contain a mixture of fiber types. This allows muscles to exhibit

24. Muscle fatigue is the physiological inability to contract. It occurs due to ATP deficit,

lactic acid buildup, and ionic imbalance. (p. 300)

25. EPOC is excess postexercise oxygen consumption, and is defined as the additional

26. Smooth muscle is located within the walls of hollow organs, including blood vessels. It is

highly fatigue resistant, and tolerates stretch. These characteristics are essential because

Critical Thinking and Clinical Application Questions

1. Regular resistance exercise leads to increased muscle strength by causing muscle cells to

hypertrophy, or increase in size. The number of myofilaments increases in these muscles.

(p. 305)

2. The reason for the tightness is rigor mortis. The myosin cross bridges are “locked on” to

the actin because of the lack of ATP necessary for release. Peak rigidity occurs at 12

3. Chemical A would be a better muscle relaxant. By blocking binding of ACh to the motor

end plate, neural stimulation of the cell is blocked, and the muscle cell cannot depolarize.

4. The calcium actually binds to troponin, which changes shape and moves the tropomyosin

to expose the myosin head binding sites. (p. 289)