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Chapter 10 1. Which types of muscle tissue can be consciously controlled and which cannot be consciously controlled? Ans: pg. 300 – a) skeletal; b) cardiac and smooth 2. How does the appearance of smooth muscle differ from that of cardiac or skeletal muscle? Ans: pg. 300 – smooth muscle is spindle shaped and does not have striations 3. What are the general functions of muscle tissue? Ans: pg. 301 – producing body movements, stabilizing body positions, storing and moving substances within the body, generating heat 4. What properties do all muscle tissues have in common? And: pg. 301 – electrical excitability, contractility, extensibility, elasticity 5. Which property do muscle tissue and neurons share? Ans: pg. 301 – electrical excitability 6. What are the types of fascia that are associated with skeletal muscles? Ans: pg. 302 – superficial and deep fascia 7. Which connective tissue coat surrounds groups of muscle fibers, separating them into bundles? What are these bundles called? Ans: pg. 302 – a) perimysium; b) fasicles 8. What the structural and functional differences among tendons, aponeuroses, and tendon sheaths? Ans: pg. 302, 304 – structural: tendons are a cord of dense regular connective tissue composed of parallel bundles of collagen fibers, aponeuroses are a broad, flat layer of dense regular connective tissue, tendon sheaths are tubes of fibrous connective tissue; functional: tendons connect muscles to bones, aponeuroses connect muscles to muscles, tendon sheaths enclose tendons 9. How do skeletal muscle fibers become multinucleated? Ans: pg. 305 – during embryonic development, a hundred or more small mesodermal cells called myoblasts fuse forming the muscle fibers with multiple nuclei 10. How does muscle hypertrophy occur? Ans: pg. 305 – by enlargement of existing muscle fibers 11. T tubules, myoglobin, and sarcoplasmic reticulum are unique to muscle fibers. What are their functions? Ans: pg. 306 – T tubules: propagate action potential into the muscle fiber; myoglobin: binds oxygen molecules that diffuse into muscle fibers from 1 interstitial fluid and releases oxygen when mitochondria need it for ATP production; sarcoplasmic reticulum: stores calcium ions 12. Among the following, which is smallest: muscle fiber, thick filament, myofibril? Ans: pg. 307 – thick filament 13. Which components of a myofibril are found within the I band? The A band: The H zone? Ans: pg. 307 – a) I band: thin filaments (actin); b) A band: thick and thin filaments; c) H zone: thick filaments 14. Which components of a myofibril attach to the M line? Which attach to the Z disc? Ans: pg. 307 – a) thick filament; b) thin filaments and titin 15. Which proteins of a myofibril compose thick filaments? Which proteins compose thin filaments? Ans: pg. 308 – a) myosin; b) actin 16. What is the function of titin? Ans: pg. 309 – anchors a thick filament to both a Z disc and the M line, helping stabilize the position of the thick filament 17. Which portion of the sarcolemma contains acetylcholine receptors? Ans: pg. 310 – motor end plate 18. What prevents an action potential arriving at the synaptic end bulbs of a motor neuron from being transferred directly to a muscle fiber? Ans: pg. 310 - the synaptic cleft 19. Describe the steps that occur for an action potential arriving at a synaptic end bulb to result in an action potential in a muscle fiber. Ans: pg. 310, 311 – release of acetylcholine, activation of ACh receptors, generation of muscle action potential, termination of ACh activity 20. What happens to acetylcholine once it has bound to its receptor? Ans: pg. 312 – it is broken down by acetylcholinesterase 21. What happens to the distance between neighboring Z discs when thin filaments in a sarcomere slide toward the M line? When thin filaments slide away from the M line? Ans: pg. 313 – a) it decreases; b) it increases 22. If the lengths of the thick and thin filaments do not change during contraction, how does the muscle fiber shorten? 2 Ans: pg. 313 – individual sarcomeres shorten resulting in the shortening of the whole muscle fiber 23. What is the source and function of calcium ions in sarcomere contraction? Ans: pg. 313, 314 – source is sarcoplasmic reticulum and function is to bind to troponin, moving the troponin-tropomyosin complex away from the myosinbinding sites in actin 24. As each myosin head detaches from a thin filament, what stops the thin filament from sliding back to its original, relaxed position? Ans: pg. 315 – some of the myosin heads are attached to actin and others are detached and preparing to bind again 25. How does sarcomere shortening result in shortening of an entire muscle and movement of a bone? Ans: pg. 315 – Z discs pull on neighboring sarcomeres, which shortens the whole muscle fiber and ultimately leads to shortening of the entire muscle 26. How does a skeletal muscle fiber relax? Ans: pg. 315, 316 – calcium ion release channels in the SR close and calcium ion active transport pumps use ATP to restore low levels of calcium ions in the sarcoplasm, the troponin-tropomyosin complex slides back into position where it blocks the myosin binding sites on the actin molecules, then the muscle relaxes 27. Which numbered steps in Figure 10.12 are part of excitation-contraction coupling? Ans: pg. 316 – 4, 5, 6 28. What are three functions of ATP in muscle contraction and relaxation? Ans: pg. 316 – provide energy for cross bridge movement and detachment and for operation of the calcium pump 29. What is a motor unit? Ans: pg. 318 – one motor neuron and all the skeletal muscle fibers it stimulates 30. Would muscles of the fingers likely contain many small or a few large motor units? Would lower back muscles likely contain many small or a few large motor units? Ans: pg. 318 – a) many small motor units; b) a few large motor units 31. Which events occur during the latent period of a twitch contraction? During the relaxation period? Ans: pg. 31, 319 – a) the muscle action potential sweeps over the sarcolemma, calcium ions are released from the sarcoplasmic reticulum and bind to troponin which allows the myosin heads to start binding to actin; b) calcium ions are transported back into the sarcoplasmic reticulum, the level of calcium ions 3 decreases in the sarcoplasm, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, power strokes cease, the muscle fiber relaxes 32. During which period of a twitch contraction do sarcomeres shorten? Ans: pg. 318 – contraction period 33. What are unfused tetanus and fused tetanus? Which type of stimulation can allow you to life a heavier object? Ans: pg. 319 – a) unfused tetanus: a sustained but wavering contraction; fused tetanus: a sustained contraction in which individual twitches cannot be detected; b) fused tetanus 34. How are calcium ions related to tetanus? Ans: pg. 320 – both kinds of tetanus result from the release of additional calcium ions from the sarcoplasmic reticulum; due to the calcium ion increase in the sarcoplasm, fused tetanus contractions are more forceful 35. In what ways does motor unit recruitment assist muscle function? Ans: pg. 320 – produces smooth movements rather than a series of jerky movements 36. What do we mean when we say a muscle is flaccid? Ans: pg. 320 – it becomes limp and loses muscle tone 37. Which type of contraction can allow you to: a. Make a sudden small jerk of your arm when startled? b. Maintain your neck’s position while you are walking? c. Drag a chair to a table? d. Slowly sit down in the chair? Ans: pg. 320, 321 – a) concentric isotonic; b) isometric; c) eccentric isotonic; d) eccentric isotonic 38. Which molecule is the only direct source of contraction energy for a muscle fiber? Ans: pg. 323 – ATP 39. Which ATP-producing reactions provide ATP during a 1000-meter run? Which occur within mitochondria? Ans: pg. 324 – a) energy transfer from creatine phosphate, anaerobic cellular respiration, and aerobic cellular respiration; b) aerobic cellular respiration 40. Which ATP-producing reactions occur when contractions occur faster than oxygen can be supplied to the muscle fiber? Which occur when adequate oxygen is present? Besides ATP, what other end products result from each reaction series? 4 Ans: pg. 324 – a) anaerobic cellular respiration; b) aerobic cellular respiration; c) anaerobic cellular respiration: lactic acid; aerobic cellular respiration: carbon dioxide and water 41. What is muscle fatigue? Ans: pg. 324 – the inability of a muscle to contract forcefully after prolonged activity 42. Why is the term recovery oxygen uptake more accurate than oxygen debt? Ans: pg. 325 – because oxygen is required to provide the ATP needed for increased metabolic activity, increased cardiac and respiratory activity, and increased tissue repair 43. Why are some skeletal muscle fibers classified as “fast” and others are said to be “slow”? Ans: pg. 326 – because of the rate of ATP hydrolysis by myosin ATPase 44. In what order are the various types of skeletal muscle fibers recruited when you sprint to make it to the bus stop? Ans: pg. 326 – SO fibers, FOG fibers, FG fibers 45. Of the three types of muscle tissue, which: a. Have contractile proteins organized into sarcomeres? b. Contain transverse tubules? c. Contain intermediate filaments? d. Contain dense bodies? Ans: pg. 330, 331 – a) skeletal and cardiac; b) skeletal and cardiac; c) smooth; d) smooth 46. What are the functions of intercalated discs? In which muscle tissue type are they found? Ans: pg. 328 – a) connect cardiac muscle fibers through desmosomes and gap junctions; b) cardiac muscle 47. What is the source of calcium ions for each of the three types of muscle tissue? Ans: pg. 331 – skeletal: sarcoplasmic reticulum; cardiac and smooth: sarcoplasmic reticulum and interstitial fluid 48. What are the major functional differences between cardiac and skeletal muscle tissue? Between smooth and skeletal muscle tissue? Ans: pg. 331 – a) cardiac muscle is autorhythmic, skeletal requires innervation by a motor neuron; cardiac muscle contracts in a continuous, rhythmic manner, skeletal muscle can contract quickly or slowly; cardiac muscle moves blood through the body, skeletal moves bones; b) smooth muscle contraction starts more slowly than skeletal and lasts much longer, smooth muscle can stretch to a greater 5 extent before contraction that other muscle types, smooth muscle regulatory protein is calmodulin rather than the troponin found in skeletal muscle 49. Which type of smooth muscle is found in the walls of hollow organs? Which is found in large blood vessels? Ans: pg. 328 – a) visceral (single-unit), b) multiunit 50. How does the speed of onset and duration of contraction in a smooth muscle fiber compare with that in a skeletal muscle fiber? Ans: pg. 331 – speed of onset is slower and duration of contraction is longer in smooth muscle compared to skeletal muscle 6