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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
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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?
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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
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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?
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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
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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
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