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C H A P T E R ^ - Muscles and Muscle Tissue Overview o f 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 ind'Muscle Tissue 191 Skeletal Muscle 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 Column B 1. Connective tissue surrounding a fascicle 2. Just deep to the deep fascia 3. Contractile unit of muscle 4. A muscle cell H". Epimysium / Fascicle J^. Fiber . _ 5. Thin connective tissue investing each muscle cell Vf. Myofilament 6. Plasma-membrane of the muscle cell . Myofibril 7. A long filamentous organelle found within muscle cells that has a banded appearance 8. Actin-, myosin-, or titin-containing structure C Endomysi Slum 9- Cordlike extension of connective tissue beyond the muscle, serving to attach it to the bone - . @ j?. Perimysium (~) j ^ . • Sarcolemma Sarcomere yt. Tendon Q 10. A discrete bundle of muscle cells Figure 9.2 Q 92 Chapter 9 Muscles and Muscle Tissue 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 0 9 Figure 9.3- When you have finished, bracket and label an A band/ an I banci, and a sarcomere/" Then, match the numbered lines (1, 2, and 3) in part B to the cross sections in part C. ^ Thin myofilaments Q Thick myofilaments ^ Z discs B 0.0.0 •o*o*o • • • 0 0 0 0 0 0 0 0 0 0 0 0 2 Figure 9.3 0:6:6:6:0 0:0:0:0 o'o'o Chapter 9 Muscles and Muscle Tissue 193 3. After referring to Figure 9-3 showing the configuration of a relaxed sarcomere, at the right, draw a contracted sarcomere. Label the thin myofilaments,"the thick myofilaments, and the Z lines. Draw an arrow beside one myosin head on each end of the A band to indicate the direction of the working stroke. 4. Fill in the blanks at the right below, giving the location of calcium during the stated phases of muscle contraction. Use the key choices provided at the left. Key Choices A. Becoming bound to calsequestrin 1. Unstimulated fiber B. Attached to troponin 2. Contracting fiber C. In terminal cisternae 3- Recovering fiber 5. Figure 9-4 shows the intimate relationship between the sarcolemma and two important muscle cell organelles—the sarcoplasmic reticulum (SR) and the myofibrils—in a small segment of a muscle cell. Identify each structure below by coloring the coding circles and the corresponding structures on the diagram. Then bracket and label the composite structure called the triad. Myofibrils Mitochondrion SR Q T tubule i -..yV; t.- Figure 9.4 Sarcolernma 1 94 Chapter 9 Muscles and Muscle Tissue : 6. Correctly relate the story of contraction events in a muscle fiber by numbering each event below. The first step is indicated (number 1). 1. Myosin heads bind to active sites on actin molecules. t 2. ATP is hydrolyzed. 3. Myosin heads return to their high-energy shape (cocked), ready for the next working stroke. 4. Calcium ions bind to troponin. 5. Cycling continues until calcium ions are sequestered by the SR. 6. Myosin cross bridges detach from actin. 7. Troponin changes shape. 8. ADP and Pj (inorganic phosphate) are released from the thick filament. 9. Myosin heads pull on the thin filaments (working stroke) and slide them toward the center of the sarcomere. 10. ATP binds to the thick filament. 11. Tropomyosin is moved into the groove between the F-actin strands exposing active sites on actin. 10. Which of these bands or lines narrows when a skeletal muscle contracts? Check ( / ) the appropriate answer. J 1. H band 2. A band 3. I band 4. M line Chapter 9 Muscles:an'd Muscle Tissue 8. 195 Figure 9-6 shows the components of a neuromuscular junction. Identify the parts by coloring the coding circles and the corresponding structures in the diagram. Add small arrows to indicate the location of the ACh receptors and label appropriately. Mitochondrion Q) Synaptic vesicles (7) T tubule of Junctional folds Synaptic cleft (3^ Sarcomere h Figure 9.6 12. Number the following statements in their proper sequence to describe excitation-contraction coupling in a skeletal muscle cell. The first step has already been identified as number 1. 1. Acetylcholine is released by the axonal ending, diffuses to the muscle cell, and attaches to ACh receptors on the sarcolemma. 2. The action potential, carried deep into the cell via the T tubules, causes the SR to release calcium ions. 3. AChE breaks down ACh, which separates from its receptors. 4. The muscle cell relaxes and lengthens. 5. The calcium ion concentration at the myofilaments increases; the myofilaments slide past one another, and the cell shortens. 6. Depolarization'occurs, and the action potential is generated along the sarcolemma. G? 7. Within 30 ms after the action potential ends, Ca2+ concentration at the myofilaments decreases. 1 96 Chapter 9 Muscles and Muscle Tissue 1 1 . Figure 9.7 diagrams the elements involved in excitation-contraction coupling. Color the coding circles and the corresponding structures. Axonal ending Q Tropomyosin Q ^ Actin (3 Myosin ^ Sarcolemma @ Troponin © SR Q Mitochondria (3 Synaptic vesicles containing acetylcholine Figure 9.7 T tubule Calcium ions 1 98 Chapter 9 Muscles and Muscle Tissue •; 15. In the appropriate graph spaces below, draw the indicated myograrrts. Be sure to include arrows at the bottom to indicate each stimulus. For the twitch myogram, label the latent, contraction, and relaxation periods. Figure 9.8 ' Chapter 9 Muscles'ran'cl Muscle Tissue 201 19. Check the appropriate column in the chart to characterize each type of skeletal muscle fiber. Fast g l y c o l y t i c fibers Slow o x i d a t i v e fibers Characteristics Rapid twitch rate Fast o x i d a t i v e fibers J / Fast myosin ATPases Use mostly aerobic metabolism •J Large myoglobin stores Large glycogen stores Fatigue slowly / - J Fibers are white Fibers are small J Fibers contain many capillaries and mitochondria 21. Which of the following occur within a muscle cell during oxygen debt? Place a check mark ( / ) by the correct choices. y Decreased AllATP 1. i^ecreasea 5. Increased oxygen 2. Increased ATP 6. Decreased carbon dioxide y 3. Increased lactic acid 4. Decreased oxygen C H A L L E N G I N G At t h e Clinic Y 7. Increased carbon dioxide 8. Increased glucose R S E L F / 2. Gregor, who works at a pesticide factory, comes to the clinic complaining of muscle spasms that interfere with his movement and breathing. A blood test shows that he has become contaminated with organophosphate pesticide. The doctor states that this type of pesticide is an acetylcholinesterase inhibitor. H o w would you explain to Gregor what this means? - , (j L , AA^^-, \ \ .A h nAAjMjh Stop a n d T h i n k 5. Which is a cross bridge attachment more similar to: a precision rowing team or a person pulling a rope and bucket out of a well? 3. chickens are capable of only brief bursts of flight, and their flying muscles consist of white fibers, The breast muscles of ducks, by contrast, consist of red and intermediate fibers. What can you deduce about the flying abilities of ducks?