Muscles and Muscle Tissue Student Objectives When you have completed the exercises in this chapter, you will have accomplished the following objectives: Overview of Muscle Tissues 1. Compare and contrast the basic types of muscle tissue. 2. List four important functions of muscle tissue. Skeletal Muscle Anatomy 3. Describe the gross structure of a skeletal muscle. 4. Describe the microscopic structure and func tional roles of the myofibrils, sarcoplasmic reticulum} and T tubules of skeletal mucle fibers. 5. Describe the sliding filament model of muscle contraction. Physiology of Skeletal Muscle Fibers and Skeletal Muscles 6. Explain how muscle fibers are stimulated to contract by describing events that occur at the neuromuscular junction. 7. Describe how an action potential is generated. 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. 10. Explain huw smooth} graded contractions of a skeletal muscle are produced. 11. Differentiate between isometric and isotonic contractions. 12. Describe three ways in which ATP is regenerated during skeletal muscle contraction. 13. Define oxygen deficit and muscle fatigue. List possible causes of muscle fatigue. 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. 16. Compare and contrast the effects of aerobic and resistance exercise on skeletal muscles and on other body systems. Smooth Muscle 17. Compare the gross and microscopic anatomy of smooth muscle cells to that of skeletal muscle cells. 18. Compare and contrast the contractile mechanisms and the means of activation of skeletal and smooth muscles. 19. Distinguish between single-unit and multiunit 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. 188
Chapter 9 Muscles and Muscle Tissue 189 The specialized muscle tissues are responsible for virtually all body movements, both internal and external. Most of the body's muscle is of the voluntary type and is called skeletal muscle because it is attached to the skeleton. Voluntary muscles allow us to manipulate the external environment, move our bodies, and express emotions on our faces. The balance of the body's muscle is smooth muscle and cardiac muscle, which form the bulk of the walls of hollow organs and the heart, respectively. Smooth and cardiac muscles are involved in the transport of materials within the body. Study activities in Chapter 9 deal with the microscopic and gross structures of skeletal and smooth muscle. (Cardiac muscle is discussed more thoroughly in Chapter 18.) Important concepts of muscle physiology are also examined in this chapter. THE FRAMEWORK Overview of Muscle Tissues 1. Nine characteristics of muscle tissue are listed below. Identify each muscle type by choosing the correct key choices and writing the letters in the answer blanks. Key Choices A. Cardiac B. Smooth C. Skeletal 1. Involuntary 2. Banded appearance 3. Longitudinally and circularly arranged layers 4. Dense connective tissue packaging 5. Gap junctions 6. Coordinated activity allows it to act as a pump 7. Moves bones and the facial skin 8. Referred to as the muscular system 9. Voluntary 10. Best at regenerating when injured
Chapter 9 Muscles and Muscle Tissue 191 Skeletal Muscle Anatomy 1. Identify the structures described in Column A by matching them with the terms in Column B. Enter the correct letters (and terms if desired) in the answer blanks. Then, select a different color for each of the terms in Column B that has a color-coding circle and color the structures in Figure 9.2. Column A 1. Connective tissue surrounding a fascicle 2. Just deep to the deep fascia 3. Contractile unit of muscle 4. A muscle cell 5. Thin connective tissue investing each muscle cell 6. Plasma membrane of the muscle cell 7. A long filamentous organelle found within muscle cells that has a banded appearance 8. Actin, myosin-, or titin-containing structure 9. Cordlike extension of connective tissue beyond the muscle, serving to attach it to the bone Column B A. Endomysium 0 B. Epimysium 0 C. Fascicle 0 D. Fiber 0 E. Myofilament F. Myofibril 0 G. Perimysium 0 H. Sarcolemma I. Sarcomere J. Sarcoplasm K. Tendon 0 10. A discrete bundle of muscle cells ----- Figure 9.2
192 Study Guide for Human Anatomy & Physiology 2. Figure 9.3 is a diagrammatic representation of a small portion of a relaxed muscle cell (the bracket indicates the portion that has been enlarged). First, select a different color for each of the structures with a coding circle. Color the coding circles and the corresponding structures on Figure 9.3. When you have finished, bracket and label an A band, an I band, and a sarcomere. Then, match the numbered lines (1, 2, and 31 in part B to the cross sections in part C. o Thin myofilaments o Thick myofilaments o Z discs A."'~}.~?: (0'.. ':':'!:;'~: I'",~ '.:.:.:::'..f? B c 1 2 3.. 0 0 0 0 0 0 0 o 0 0 0 0 0 0...... 000 o 0 0:0:0:0:0 0 000 0 0 0 0... 0 o 0 0 0 0. 1 2 3 Figure 9.3
210 Study Guide for Human Anatomy & Physiology INO Multiple Choice Select the best answer or answers from the choices given. 1. Select the typels) of muscle tissue that fit the following description: self-excitable, pacemaker cells, gap junctions, extremelyextensible, limited SRI calmodulin activated. A. Skeletal muscle C. Smooth muscle B. Cardiac muscle D. Involuntary muscle 2. Which of the following would be associated with a skeletal muscle fascicle? A. Perimysium B. Nerve C. Artery and at least one vein D. Epimysium 3. Skeletal muscle is not involved in: A. movement of skin B. propulsion of a substance through a body tube C. heat production D. inhibition of body movement 4. Which of the following are part of a thin myofilament? A. ATP-binding site C. Globular actin B. TnI D. Calcium 5. Factors involved in calcium release and uptake during contraction and relaxation include: A. calsequestrin D. terminal cisternae B. T tubules E. sarcolemma C. SR 6. In comparing electron micrographs of a relaxed skeletal muscle fiber and a fully contracted muscle fiber, whieh would be seen only in the relaxed fiber? A. Z discs D. A bands B. Triads E. H zones C. I bands 7. After ACh attaches to its receptors at the neuromuscular junction, the next step is: A. potassium-gated channels open B. calcium binds to troponin C. the T tubuics depolarize D. cross bridges attach E. ATP is hydrolyzed 8. Detachment of the cross bridges is directly triggered by: A. hydrolysis of ATP B. repolarization of the T tubules C. the power stroke D. attachment of ATP to myosin heads 9. Transmission of the stimulus at the neuromuscular junction involves: A. synaptic vesicles C. ACh B. TnT D. junctional folds 10. Which of the following locations are important sites for calcium activity? A. SR B. T tubules C. Axonal ending D. Junctional folds of sarcolemma
Chapter 9 Muscles and Muscle Tissue 211 11. Acetylcholinesterase hydrolyzes ACh during which phaseis) of a muscle twitch? A. Latent period B. Period of contraction C. Period of relaxation D. Refractory period 12-13. Use the following graph to answer Questions 12 and 13: o 5 10 15 20 25 30 35 40 45 50 55 Voltage (The muscle is stimulated once at each voltage indicated) 12. What is the threshold stimulus for this muscle? A. 5 volts D. 40 volts B. 10 volts E. 45 volts C. 15 volts I I 13. What is the maximal stimulus for this muscle? A. 15 volts C. 45 volts B. 40 volts D. 55 volts 14. Small motor units are associated with: A. precision C. fine control B. power D. weak contraction 15. Holding up the corner of a heavy couch to vacuum under it involves which type(s) of contraction? A. Tetanic C. Isometric B. Isotonic D. Tone 16. Your ability to lift that heavy couch would be increased by which type of exercise? A. Aerobic C. Resistance B. Endurance D. Swimming 17. Which of the following activities depends most on anaerobic metabolism? A. Jogging B. Swimming a race C. Sprinting D. Running a marathon 18. The first energy source used to regenerate ATP when muscles are extremely active is: A. fatty acids C. creatine phosphate B. glucose D. pyruvic acid 19. ATP directly powers: A. exocytosis of synaptic vesicles B. sodium influx at the sarcolemma C. calcium release into the sarcoplasm D. recocking of the myosin head 20. Which statement is true about contractures? A. Depletion of ATP is absolute. B. Contraction is weak. C. Muscle cramping is due to depletion of electrolytes. D. The neuromuscular junction has been affected. 21. When paying back the oxygen deficit: A. lactic acid is formed B. lactic acid is reconverted to pyruvic acid C. ATP formation requires creatine phosphate D. muscle cells utilize glycogen reserves 22. Factors affecting force of contraction include: A. number of motor units stimulated B. cross-sectional area of the muscle/muscle fibers C. load D. degree of muscle stretch prior to the contraction
212 Study Guide for Human Anatomy & Physiology 23. The ideal length-tension relationship is: A. maximal overlap of thin and thick myofilaments B. minimal overlap of thin and thick myofilaments C. no overlap of thin and thick myofilaments D. intermediate degree of overlap of thin and thick myofilaments 24. When the velocity of contraction is zero, the contraction is: A. strongest B. equal to the load C. greater than the load D. isometric 25. Which of these bands or lines does not narrow when a skeletal muscle fiber contracts? A. H zone B. A band C. I band D. M line 26. Characteristics of red, but not white, muscle are: A. abundant mitochondria B. richly vascularized C. fast contraction D. slow to fatigue 27. Which of the following is (arei unique to smooth muscle cells, compared with the other types of muscle cells? A. Produce endomysium B. Utilize calmodulin C. Can contract even when maximally stretched D. Self-excitable 28. Smooth muscle contraction is stimulated by: A. hormones B. inhibition of calmodulin C. neurotransmitters D. stretching 29. Which of the following is (are) true of singleunit but not multiunit smooth muscle? A. Presence of gap junctions B. Each muscle fiber has its own nerve ending C. Sheetlike arrangement in hollow organs D. Contracts in a corkscrewlike manner 30. The ancestry of muscle cells comprises: A. myoblasts B. satellite cells C. mesenchyme D. mesoderm 31. What fiber types would be most useful in the leg muscles of a long-distance runner? A. White fast-twitch B. White slow-twitch C. Intermediate fast-twitch D. Red slow-twitch 32. Relative to differences between eccentric and concentric contractions, eccentric contractions: A. put the body in a position to contract concentrically B. occur as the muscle is actually increasing in length C. are more likely to cause muscle soreness the day after a strenuous activity D. involve unchanging muscle length and tension
Chapter 9 Muscles and Muscle Tissue 213 Word Dissection For each of the following word roots, fill in the literal meaning and give an example, using a word found in this chapter. Word root Translation Example 1. fasci 2. lemma 3. metric 4. mya 5. penna 6. raph 7. sarco 8. stalsis 9. stria 10. synap 11. tetan
Chapter 10 The Muscular System 235 1-----..;;e 2 ---------:~ 3 --------:~ 4 ---------;;::; ~7-------14 Te:;.:...----- 15 11-=::------- 16 5 ------.,~~~~ 6 ------:,,~ 7--..;~ :~.;;:;;...:~~--17 18 11 -----'-:-~,...;.:;~~~. 12 ------;;..:.:~~.'f//// 11f~::..:...,.;.:-----19..e;;-;----- 20 1IfI'~~~---- 21 13---~~ 11/1Ie:----- 22 Figure 10.11
Chapter 10 The Muscular System 237 ~,...----7 ;I;'ljIl~~!(!1.:;:...;.;.;:... 8 --10 3---~~ 4 ---~~~.'I'j 5 --------;.~, I.. I ~, \ I \ ' Figure 10.12