Chapter 09 Muscle
Student: ___________________________________________________________________________
1. A myofibril is
A. A skeletal-muscle cell
B. Composed of filaments
C. Composed of proteins
D. Both a skeletal-muscle cell and composed of filaments
E. Both composed of filaments and composed of proteins
2. Thick filaments in skeletal muscle are composed of
A. Actin
B. Myosin
C. Troponin
D. Calmodulin
E. Tropomyosin
3. During isotonic contraction of a skeletal-muscle fiber the
A. Sarcomeres shorten
B. A bands shorten
C. I bands shorten
D. Both sarcomeres shorten and I bands shorten are correct
E. Both A bands shorten and I bands shorten are correct
4. Which of the following statements regarding the shortening of a skeletal-muscle fiber is not true? When a
skeletal-muscle fiber shortens, the
A. Sarcomeres shorten
B. Distance between Z lines decreases
C. Myofilaments shorten
D. Myofilaments slide past each other
E. Length of the A bands remains the same
5. In skeletal muscle, calcium facilitates contraction by binding to
A. Tropomyosin
B. Actin
C. Troponin
D. Myosin
E. The thick filament
6. Binding of ________ to myosin permits cross-bridge _____________ between actin and myosin.
A. ATP; attachment
B. ATP; detachment
C. Calcium; attachment
D. Calcium; detachment
E. Actin; detachment
7. ATP is necessary for each of the following mechanisms or functions in skeletal muscle except
A. Sequestration of Ca2+ into the sarcoplasmic reticulum
B. Dissociation of actin from myosin
C. Release of Ca2+ from the sarcoplasmic reticulum
D. Movement of myosin cross bridges
E. Maintenance of the polarized state of the skeletal-muscle membrane
8. Rigor mortis occurs in a dead person because
A. ATP, which is necessary for the detachment of cross bridges, is not being formed
B. ATP, which is necessary for the formation of cross bridges, is not being formed
C. ATP, which is necessary for the formation of cross bridges, continues to be formed for several hours after
death
D. Deterioration of muscle proteins prevents detachment of cross bridges
E. None of the choices are correct
9. Rigor mortis is caused by
A. Buildup of lactic acid
B. Lack of Ca2+
C. Depletion of glycogen
D. Lack of ATP
E. Deficient acetylcholine receptors
10. The removal of calcium ions from the cytosol of skeletal muscle causes
A. The myosin binding sites on actin to be uncovered by tropomyosin
B. Tropomyosin to change conformation and thereby move troponin molecules over cross-bridge binding sites
C. Troponin to change conformation and thereby expose cross-bridge binding sites
D. The myosin binding sites on actin to be covered by tropomyosin
E. None of the choices are correct
11. Which of the following statements is true regarding skeletal-muscle contraction?
A. The cross-bridge cycle refers to the sequence of events between the time an individual cross bridge binds to a
thin filament at the start of a muscle contraction and the time the cross bridge releases the filament at the end of
the contraction
B. Excitation-contraction coupling refers to the binding of energized myosin to actin
C. Binding of myosin to actin cannot take place in the absence of calcium ion
D. A single twitch in skeletal muscle lasts about as long as the action potential that caused it
E. All of the choices are true
12. "Motor unit" refers to
A. A single motor neuron plus all the muscle fibers it innervates
B. A single muscle fiber plus all of the motor neurons that innervate it
C. All of the motor neurons supplying a single muscle
D. A pair of antagonistic muscles
E. All of the muscles that affect the movement of any given joint
13. The transverse tubules in a skeletal-muscle fiber
A. Store calcium ions
B. Form the Z lines
C. Provide a means of transmitting an action potential in the muscle plasma membrane to central portions of the
fiber
D. Store ATP
E. Run in parallel with the myofibrils
14. An action potential in the motor end plate rapidly spreads to the central portions of a muscle cell by means
of the
A. Z lines
B. Sarcoplasmic reticulum
C. H zone
D. Transverse tubules
E. Pores in the plasma membrane
15. Which of the following statements regarding the motor end plate of a skeletal-muscle fiber is true?
A. Muscarinic receptors in the end plate are activated by binding to acetylcholine
B. Temporal summation of end plate potentials is required in order to trigger an action potential in the
muscle-fiber membrane
C. Acetylcholinesterase in the end plate membrane catalyzes the breakdown of acetylcholine
D. Sympathetic nerve fibers innervate skeletal muscle
E. All of the choices are true
16. Curare
A. Is an autoimmune disease
B. Blocks acetylcholinesterase
C. Is a muscarinic acetylcholine antagonist
D. Is a nicotinic acetylcholine antagonist
E. Both blocks acetylcholinesterase and is a muscarinic acetylcholine antagonist are correct
17. Myasthenia gravis is an autoimmune disease - that is, a disease in which one's immune system gradually
attacks a part of one's own body, in this case the receptors for acetylcholine at the neuromuscular junction.
Which of the following drugs might be useful in treating this disease?
A. A drug that inhibits acetylcholinesterase
B. A drug that inhibits release of acetylcholine
C. Curare
D. Atropine (a muscarinic antagonist)
E. All of the choices are correct
18. During an isometric contraction of a skeletal muscle,
A. The I bands shorten and the A bands stay the same length
B. The thick and thin filaments slide past each other
C. Sarcomere length does not change
D. Both the I bands shorten and the A bands stay the same length and the thick and thin filaments slide past
each other take place
E. None of the choices happen
19. During any isometric twitch in a skeletal muscle,
A. Tension exceeds load
B. Tetanus occurs
C. Load exceeds tension
D. The whole muscle shortens
20. Which of the following statements regarding skeletal-muscle contraction is true?
A. During a lengthening contraction, the tension exerted by the muscle exceeds the load on the muscle
B. Every isometric contraction begins and ends as an isotonic contraction
C. During every muscle contraction, muscle fibers change length
D. During every muscle contraction, tension is developed in the muscle
E. None of the choices are true
21. Which of the following statements best explains how tetanus can be generated in a skeletal muscle, given
the all-or-none nature of action potentials?
A. During a single action potential in a skeletal muscle, there is not enough time for all of the calcium in the
sarcoplasmic reticulum to diffuse into the cytosol and bind to troponin
B. Skeletal muscle has no absolute refractory period
C. Skeletal muscle has a much longer absolute refractory period than does a motor neuron
D. During a single action potential in a skeletal muscle, there is not enough time for maximal tension to develop
before the Ca-ATPase begins sequestering calcium ions
E. Both during a single action potential in a skeletal muscle, there is not enough time for all of the calcium in
the sarcoplasmic reticulum to diffuse into the cytosol and bind to troponin and skeletal muscle has a much
longer absolute refractory period than does a motor neuron are correct
22. Which of the following statements regarding skeletal-muscle contraction is true?
A. The tension developed during the contraction of a muscle fiber is dependent upon the initial length of the
fiber
B. There is a positive correlation between muscle-fiber length at the beginning of a contraction and the tension
that can be developed by the fiber: the longer the fiber, the greater the tension
C. There is a positive correlation between the frequency of action potentials in a single muscle fiber and the
tension it can develop: the greater the frequency, the greater the tension, up to a plateau
D. Both the tension developed during the contraction of a muscle fiber is dependent upon the initial length of
the fiber and there is a positive correlation between muscle-fiber length at the beginning of a contraction and the
tension that can be developed by the fiber: the longer the fiber, the greater the tension are true
E. Both the tension developed during the contraction of a muscle fiber is dependent upon the initial length of the
fiber and there is a positive correlation between the frequency of action potentials in a single muscle fiber and
the tension it can develop: the greater the frequency, the greater the tension, up to a plateau are true
23. The optimal length of a skeletal muscle is
A. The length at which the muscle can generate its maximal tetanic tension
B. The shortest length the muscle can achieve while attached to bone, because the amount of overlap between
thick and thin filaments is maximal then
C. Approximately the same as its resting length
D. Both the length at which the muscle can generate its maximal tetanic tension and the shortest length the
muscle can achieve while attached to bone, because the amount of overlap between thick and thin filaments is
maximal then are correct
E. Both the length at which the muscle can generate its maximal tetanic tension and approximately the same as
its resting length are correct
24. The first means by which ATP is produced at the onset of contractile activity in a skeletal muscle is
A. Transfer of energy and phosphate from creatine phosphate to ADP
B. Oxidative phosphorylation
C. Glycolysis
D. Oxidation of fatty acids
E. Catabolism of myoglobin
25. When a muscle has been contracting for an extended period of time (more than a few minutes), the primary
source of ATP is
A. Transfer of energy and phosphate from creatine phosphate to ADP
B. Glycolysis
C. Oxidative phosphorylation
D. Breakdown of myosin
E. None of the choices are correct
26. After heavy exercise, breathing remains labored for some time, indicating a continuing need for increased
oxygen. In muscle cells recovering from exercise,
A. Oxygen is used for oxidation of lactic acid metabolites to generate ATP
B. ATP is used to synthesize glycogen from glucose
C. ATP is used to phosphorylate creatine
D. Both oxygen is used for oxidation of lactic acid metabolites to generate ATP and ATP is used to synthesize
glycogen from glucose are correct
E. All of the choices are correct
27. Muscle fatigue
A. Is caused by depletion of ATP stores
B. After short-duration, high-intensity exercise is caused by depletion of muscle glycogen stores
C. After long-duration, low-intensity exercise is caused by excessive hydrogen ion concentrations that interfere
with contractile protein activity
D. After long-duration, low-intensity exercise is caused by build up of potassium ion in the lumen of T tubules
E. Is caused by none of these choices
28. Which of the following statements regarding myosin in skeletal muscle is/are true?
A. Myosin heads contain two functional sites, one for actin and one for tropomyosin
B. Myosin is an ATPase
C. The rate of ATP hydrolysis by myosin is the same in all types of skeletal muscle
D. Both myosin heads contain two functional sites, one for actin and one for tropomyosin and myosin is an
ATPase are true
E. All of the choices are true
29. Which of the following is not true regarding the comparison of type I (slow oxidative) and type II b
(fast-glycolytic) skeletal-muscle fibers?
A. Type I fibers have more abundant mitochondria
B. Type I fibers fatigue more readily
C. Type I fibers have more abundant myoglobin
D. Type I fibers have more abundant capillaries
E. Type I motor units contain fewer fibers than type II b motor units
30. Which of the following statements about different kinds of skeletal-muscle fibers is true?
A. Slow-oxidative fibers have a greater abundance of glycogen than do fast-glycolytic fibers
B. Fast-glycolytic fibers have a greater abundance of myoglobin than do slow-oxidative fibers
C. Fast-glycolytic fibers can generate greater tension than can slow-oxidative fibers
D. Both slow-oxidative fibers have a greater abundance of glycogen than do fast-glycolytic fibers and
fast-glycolytic fibers have a greater abundance of myoglobin than do slow-oxidative fibers are true
E. All of the choices are true
31. One cause of fatigue in fast-glycolytic muscle fibers is
A. Depletion of ATP in the fiber
B. Depletion of creatine phosphate in the fiber
C. Depletion of oxygen in the fiber
D. Accumulation of potassium ion in the lumen of T tubules
E. All of the choices are correct
32. Fast-glycolytic muscle fibers differ from slow-oxidative fibers in that
A. The former rely on creatine phosphate as an ATP source for the first few seconds of contraction whereas the
latter do not
B. The former have a smaller diameter than the latter
C. The former can generate greater maximal tension than the latter
D. The former generate less lactic acid than do the latter
E. All of the choices are true
33. Which of the following is not a determinant of whole-muscle tension?
A. Number of muscle fibers contracting
B. Tension produced by each contracting fiber
C. Extent of motor unit recruitment
D. Frequency of motor neuron stimulation
E. Proportion of the muscle fibers in each motor unit that are contracting at any given time
34. Which of the following statements regarding skeletal muscle is true?
A. Some skeletal-muscle fibers have pacemaker activity
B. Skeletal-muscle fibers are joined together by gap junctions
C. A given skeletal-muscle fiber will contract when excitatory nervous stimuli sufficiently exceed inhibitory
nervous stimuli at the motor end plate
D. A given skeletal-muscle fiber will contract when excitatory nervous stimuli sufficiently exceed inhibitory
nervous stimuli at the cell body of the motor neuron that innervates that fiber
E. None of the choices are true
35. The tension in a skeletal muscle can be increased by increasing
A. The number of motor units stimulated
B. The rate of stimulation to each motor unit
C. The number of fibers in the muscle through exercise
D. The number of motor units stimulated and the rate of stimulation to each motor unit
E. All of the choices are correct
36. Which of the following statements regarding whole-muscle contraction is true?
A. The order of recruitment of motor units in a muscle is such that the last units recruited are the first to
experience fatigue
B. The order of recruitment of motor units in a muscle is such that the first units recruited generate the most
tension
C. Motor units whose motor neurons have small-diameter cell bodies contract first, followed by motor units
with larger-diameter motor neurons
D. Both the order of recruitment of motor units in a muscle is such that the last units recruited are the first to
experience fatigue and the order of recruitment of motor units in a muscle is such that the first units recruited
generate the most tension are true
E. Both the order of recruitment of motor units in a muscle is such that the last units recruited are the first to
experience fatigue and motor units whose motor neurons have small-diameter cell bodies contract first,
followed by motor units with larger-diameter motor neurons are true
37. John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Jim is a
marathon runner who specializes in long, steady runs. Compared to Jim, John is likely to have
A. Legs with a larger diameter
B. Legs with a smaller diameter
C. Hypertrophy of type I muscle fibers
D. Legs with a larger diameter and hypertrophy of type I muscle fibers
E. Legs with a smaller diameter and hypertrophy of type I muscle fibers
38. John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Jim is a
marathon runner who specializes in long, steady runs. Compared to John, Jim is likely to have
A. More glycogen stored in his type II b muscle fibers
B. More mitochondria in his type I and II a muscle fibers
C. More myoglobin in his type II b muscle fibers
D. Both more glycogen stored in his type II b muscle fibers and more myoglobin in his type II b muscle fibers
E. Both more mitochondria in his type I and II a muscle fibers and more myoglobin in his type II b muscle
fibers
39. Olympic speed (ice) skaters have large, muscular legs that are unusual in that the left leg is generally even
larger in diameter than the right. This is an example of
A. Disuse atrophy of the right leg
B. Hypertrophy of fast-glycolytic muscle fibers as a result of exercise
C. An increase in the number of fast muscle fibers as a result of exercise
D. Both disuse atrophy of the right leg and hypertrophy of fast-glycolytic muscle fibers as a result of exercise
E. Both hypertrophy of fast-glycolytic muscle fibers as a result of exercise and an increase in the number of fast
muscle fibers as a result of exercise
40. Which of the following statements is not true?
A. Nervous stimulation of skeletal muscle is always excitatory, whereas nervous stimulation of smooth muscle
may be excitatory or inhibitory
B. A single smooth-muscle cell may be innervated by both a sympathetic neuron and a parasympathetic neuron
C. The contractile activity of smooth-muscle cells may be affected by hormones
D. In the absence of neural input, skeletal muscle cannot generate tension
E. None of the choices are true
41. A major difference between smooth muscle and skeletal muscle is that
A. Myosin is the regulatory protein in smooth muscle
B. Myosin is the regulatory protein in skeletal muscle
C. Skeletal muscle may exhibit spontaneous activity
D. Only skeletal muscle requires increased calcium ion concentration in the cytosol for contraction
E. None of the choices are correct
42. Unlike skeletal muscle,
A. Smooth muscle is striated
B. Smooth muscle does not have thick and thin filaments
C. Smooth muscle does not use troponin-tropomyosin to regulate cross-bridge activity
D. Smooth muscle does not use changes in cytosolic calcium to regulate cross-bridge activity
E. The myosin in smooth muscle requires phosphorylation before it can bind to ATP
43. Excitation-contraction coupling
A. In skeletal-muscle cells requires the influx of extracellular calcium ion
B. In smooth-muscle cells requires the influx of extracellular calcium ion
C. In all kinds of muscle requires the release of calcium ion from the sarcoplasmic reticulum
D. Both in skeletal-muscle cells requires the influx of extracellular calcium ion and in smooth-muscle cells
requires the influx of extracellular calcium ion are correct
E. Both in smooth-muscle cells requires the influx of extracellular calcium ion and in all kinds of muscle
requires the release of calcium ion from the sarcoplasmic reticulum are correct
44. Which of the following statements regarding contraction in skeletal and smooth muscle is true?
A. In skeletal muscle, calcium ion mediates changes in thin filaments that lead to cross-bridge activity; in
smooth muscle, calcium ion mediates changes in thick filaments that lead to cross-bridge activity
B. In skeletal muscle, calcium ion binds to a regulatory protein on thin filaments; in smooth muscle, calcium ion
binds to a regulatory protein on thick filaments
C. In skeletal muscle, calcium ion binds to troponin; in smooth muscle, calcium ion binds to calmodulin
D. Both in skeletal muscle, calcium ion mediates changes in thin filaments that lead to cross-bridge activity; in
smooth muscle, calcium ion mediates changes in thick filaments that lead to cross-bridge activity and in skeletal
muscle, calcium ion binds to troponin; in smooth muscle, calcium ion binds to calmodulin are true
E. All of the choices are true
45. Which of the following is not true regarding single-unit smooth-muscle cells? They
A. Have individual innervation of each cell
B. Have many gap junctions between cells
C. May have pacemaker activity
D. Respond to stretch by contracting
E. Have tone
46. Multiunit smooth-muscle cells
A. Have individual innervation of each cell
B. Have many gap junctions between cells
C. Respond to stretch by contracting
D. Both have individual innervation of each cell and have many gap junctions between cells are correct
E. Both have individual innervation of each cell and respond to stretch by contracting are correct
47. Although both skeletal and cardiac muscle exhibit striated appearance and the property of contractility there
are functional differences between them. Which of the following is not a difference between cardiac and
skeletal muscle?
A. Cardiac muscle cells are arranged in layers surrounding hollow cavities in the heart
B. Skeletal muscle cells are long and multinucleate, depending on neuronal stimuli
C. Cardiac muscle cells are depolarized initially by the influx of calcium ions
D. Skeletal muscle cells depolarize prior to contraction
E. In cardiac muscle cells a resting membrane potential must be present to provide for excitation and
contraction
48. Which of the following choices gives the correct sequence of events following the depolarization of
transverse tubules in excitation-contraction coupling in cardiac muscle?
A. Calcium release into sarcoplasm, calcium ion influx through sarcolemma, actin and myosin attach, thin
myofilaments slide toward the middle of sarcomeres
B. Actin and myosin attach, thin myofilaments slide toward the middle of sarcomeres, calcium release into
sarcoplasm
C. Calcium release into sarcoplasm, actin and myosin attach, calcium ion influx through sarcolemma, thin
myofilaments slide toward the middle of sarcomeres
D. Calcium release into sarcoplasm, actin and myosin attach, thin myofilaments slide toward the middle of
sarcomeres, calcium ion influx through sarcolemma
E. Calcium ion influx through sarcolemma, calcium release into sarcoplasm, actin and myosin attach, thin
myofilaments slide toward the middle of sarcomeres
49. The electrical depolarization which spreads through the heart musculature and precedes contraction of atria
and ventricles is dependent upon the rapid inward diffusion of which of the following ions?
A. Sodium
B. Calcium
C. Nitrate
D. Chloride
E. Potassium
F. events?
50. The conclusion of cardiac muscle contraction is marked by which of the following
A. Concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca 2+-ATPase pumps
B. Concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca 2+/Na+ cotransporters
in sarcoplasmic reticulum and sarcolemma
C. The release of actin protein degrading enzymes
D. The release of myosin degrading enzymes
E. Both concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca 2+-ATPase
pumps and concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca 2+/Na+
cotransporters in sarcoplasmic reticulum and sarcolemma are correct
51. L-type calcium channels in cardiac muscle cells
A. Are essentially present and the same in both skeletal and cardiac muscle
B. Are directly related to making them fatigue resistant
C. Are responsible for preventing titanic contractions in them
D. Cause the absolute refractory period to be very short lived
E. Provide the mechanism necessary for producing contractions of varying intensity or force
52. Some athletes in activities requiring ATP for more than a few seconds may turn to dietary supplements
containing ____ to increase the amount of _____ immediately available within the muscles.
A. Fatty acids, calcium ions
B. Sports drinks (Gatorade, Powerade, etc.) , electrolytes and mineral spirits
C. Sugars, glucose
D. Proteins, amino acids
E. Creatine, ATP
53. Myasthenia gravis
A. Is an autoimmune disease
B. Occurs when the motor neuron terminals cannot secrete enough acetylcholine to stimulate the motor end
plate adequately
C. Can be treated with a drug that temporarily inhibits acetylcholinesterase
D. Both is an autoimmune disease and occurs when the motor neuron terminals cannot secrete enough
acetylcholine to stimulate the motor end plate adequately are correct
E. Both is an autoimmune disease and can be treated with a drug that temporarily inhibits acetylcholinesterase
are correct
54. Skeletal muscles are made up of bundles of muscle fibers held together by sheaths called tendons.
True False
55. The name given to the unit of repeating pattern in a myofibril is "sarcomere."
True False
56. The force-generating sites in a myofibril are the Z lines.
True False
57. During skeletal-muscle contraction, the distance between the Z lines of a sarcomere decreases because of
shortening of the filaments.
True False
58. During skeletal-muscle contraction, the I band and H zone shorten but the A band stays the same.
True False
59. The cross-bridge cycle refers to the sequence of events between the time an individual cross bridge binds to
a thin filament at the start of a muscle contraction and the time the cross bridge releases the filament at the end
of the contraction.
True False
60. The energy for muscle contraction is provided by the hydrolysis of ATP.
True False
61. Actin is an ATPase.
True False
62. The binding of ATP to myosin causes an allosteric change in myosin's actin-binding site such that the
affinity of myosin for actin is decreased.
True False
63. The phenomenon of rigor mortis demonstrates that myosin can bind to actin in the absence of ATP, but the
bond cannot then be broken.
True False
64. Binding of myosin to actin cannot take place in the absence of calcium ion.
True False
65. Excitation-contraction coupling refers to the binding of energized myosin to actin.
True False
66. The site of calcium-ion storage in muscle cells is the lateral sacs of the transverse tubules.
True False
67. Curare blocks neuromuscular transmission by preventing the release of neurotransmitter from the motor
neuron.
True False
68. Organophosphate "nerve gases" induce paralysis by blocking neural stimulation of the neuromuscular
junctions, while botulinum toxin produces the same effect by inhibiting acetylcholinesterase.
True False
69. The term "twitch" refers to the mechanical response of a muscle fiber during one cross-bridge cycle.
True False
70. All isotonic contractions begin and end as isometric contractions.
True False
71. During isometric contraction of a skeletal-muscle fiber, tension increases but the fiber length stays the
same.
True False
72. The latent period of an isotonic twitch is shorter than the latent period of an isometric twitch.
True False
73. Sustained contraction and tension in a skeletal muscle is called tetanus.
True False
74. A skeletal muscle generates its greatest twitch tension when it is stretched to twice its resting length.
True False
75. Fast fibers can be distinguished from slow fibers by the rate at which their myosin-ATPases split ATP.
True False
76. Characteristics of oxidative fibers include numerous mitochondria, abundant myoglobin and large stores of
glycogen.
True False
77. The difference in color between white muscle and red muscle is accounted for by the greater abundance of
glycogen in white muscle.
True False
78. The fiber type intermediate between the two extremes of fast glycolytic and slow oxidative is slow
glycolytic.
True False
79. Muscles used for delicate, finely controlled movements have smaller motor units than more coarsely
controlled muscles.
True False
80. In general, activating a slow-oxidative motor unit in a muscle will generate more tension than activating a
fast-glycolytic motor unit.
True False
81. Endurance exercise, such as long-distance swimming, causes a preferential increase in glycolytic enzymes
and increased mass of the exercising muscles.
True False
82. The larger the diameter of a skeletal-muscle fiber, the greater the tension it can generate.
True False
83. Recruitment of different types of motor units in a muscle is the primary means of varying the amount of
tension generated in that muscle.
True False
84. The shortening velocity of a skeletal muscle fiber increases with decreasing load because the rate at which
the cross-bridge cycle can occur increases with decreasing load.
True False
85. A flexor muscle pulls on bone to decrease the angle at a joint, whereas an extensor pushes the bone to
increase the angle.
True False
86. The decrease in mass and strength of muscle as a result of damage to the nerves innervating the muscle is
called disuse atrophy.
True False
87. The calcium-binding protein in smooth muscle is calmodulin.
True False
88. The myosin in smooth-muscle cells differs from that in skeletal muscle in that smooth-muscle myosin
requires phosphorylation before it can bind to actin.
True False
89. In smooth-muscle cells that can produce action potentials, cell membrane depolarization opens
voltage-sensitive sodium channels.
True False
90. Nervous stimulation of skeletal muscle is always excitatory, whereas nervous stimulation of smooth muscle
may be excitatory or inhibitory.
True False
91. Smooth-muscle cells may contract in the absence of nervous stimulation.
True False
92. Multiunit smooth muscle is characterized by many gap junctions between cells.
True False
93. In cardiac muscle contractile cells the release of calcium through L-type calcium channels depolarizes the
sarcoplasmic reticulum and inhibits the release of any additional calcium necessary for excitation-contraction
coupling.
True False
94. Abundant mitochondria is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
95. Abundant myoglobin is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
96. A large diameter is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
97. Fast myosin ATPase activity is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
98. Recruited first is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
99. Fatigued first is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
100. Few mitochondria is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
101. Little myoglobin is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
102. Small diameter is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
Chapter 09 Muscle Key
1. A myofibril is
A. A skeletal-muscle cell
B. Composed of filaments
C. Composed of proteins
D. Both a skeletal-muscle cell and composed of filaments
E. Both composed of filaments and composed of proteins
2. Thick filaments in skeletal muscle are composed of
A. Actin
B. Myosin
C. Troponin
D. Calmodulin
E. Tropomyosin
3. During isotonic contraction of a skeletal-muscle fiber the
A. Sarcomeres shorten
B. A bands shorten
C. I bands shorten
D. Both sarcomeres shorten and I bands shorten are correct
E. Both A bands shorten and I bands shorten are correct
4. Which of the following statements regarding the shortening of a skeletal-muscle fiber is not true? When a
skeletal-muscle fiber shortens, the
A. Sarcomeres shorten
B. Distance between Z lines decreases
C. Myofilaments shorten
D. Myofilaments slide past each other
E. Length of the A bands remains the same
5. In skeletal muscle, calcium facilitates contraction by binding to
A. Tropomyosin
B. Actin
C. Troponin
D. Myosin
E. The thick filament
6. Binding of ________ to myosin permits cross-bridge _____________ between actin and myosin.
A. ATP; attachment
B. ATP; detachment
C. Calcium; attachment
D. Calcium; detachment
E. Actin; detachment
7. ATP is necessary for each of the following mechanisms or functions in skeletal muscle except
A. Sequestration of Ca2+ into the sarcoplasmic reticulum
B. Dissociation of actin from myosin
C. Release of Ca2+ from the sarcoplasmic reticulum
D. Movement of myosin cross bridges
E. Maintenance of the polarized state of the skeletal-muscle membrane
8. Rigor mortis occurs in a dead person because
A. ATP, which is necessary for the detachment of cross bridges, is not being formed
B. ATP, which is necessary for the formation of cross bridges, is not being formed
C. ATP, which is necessary for the formation of cross bridges, continues to be formed for several hours after
death
D. Deterioration of muscle proteins prevents detachment of cross bridges
E. None of the choices are correct
9. Rigor mortis is caused by
A. Buildup of lactic acid
B. Lack of Ca2+
C. Depletion of glycogen
D. Lack of ATP
E. Deficient acetylcholine receptors
10. The removal of calcium ions from the cytosol of skeletal muscle causes
A. The myosin binding sites on actin to be uncovered by tropomyosin
B. Tropomyosin to change conformation and thereby move troponin molecules over cross-bridge binding sites
C. Troponin to change conformation and thereby expose cross-bridge binding sites
D. The myosin binding sites on actin to be covered by tropomyosin
E. None of the choices are correct
11. Which of the following statements is true regarding skeletal-muscle contraction?
A. The cross-bridge cycle refers to the sequence of events between the time an individual cross bridge binds to a
thin filament at the start of a muscle contraction and the time the cross bridge releases the filament at the end of
the contraction
B. Excitation-contraction coupling refers to the binding of energized myosin to actin
C. Binding of myosin to actin cannot take place in the absence of calcium ion
D. A single twitch in skeletal muscle lasts about as long as the action potential that caused it
E. All of the choices are true
12. "Motor unit" refers to
A. A single motor neuron plus all the muscle fibers it innervates
B. A single muscle fiber plus all of the motor neurons that innervate it
C. All of the motor neurons supplying a single muscle
D. A pair of antagonistic muscles
E. All of the muscles that affect the movement of any given joint
13. The transverse tubules in a skeletal-muscle fiber
A. Store calcium ions
B. Form the Z lines
C. Provide a means of transmitting an action potential in the muscle plasma membrane to central portions of the
fiber
D. Store ATP
E. Run in parallel with the myofibrils
14. An action potential in the motor end plate rapidly spreads to the central portions of a muscle cell by means
of the
A. Z lines
B. Sarcoplasmic reticulum
C. H zone
D. Transverse tubules
E. Pores in the plasma membrane
15. Which of the following statements regarding the motor end plate of a skeletal-muscle fiber is true?
A. Muscarinic receptors in the end plate are activated by binding to acetylcholine
B. Temporal summation of end plate potentials is required in order to trigger an action potential in the
muscle-fiber membrane
C. Acetylcholinesterase in the end plate membrane catalyzes the breakdown of acetylcholine
D. Sympathetic nerve fibers innervate skeletal muscle
E. All of the choices are true
16. Curare
A. Is an autoimmune disease
B. Blocks acetylcholinesterase
C. Is a muscarinic acetylcholine antagonist
D. Is a nicotinic acetylcholine antagonist
E. Both blocks acetylcholinesterase and is a muscarinic acetylcholine antagonist are correct
17. Myasthenia gravis is an autoimmune disease - that is, a disease in which one's immune system gradually
attacks a part of one's own body, in this case the receptors for acetylcholine at the neuromuscular junction.
Which of the following drugs might be useful in treating this disease?
A. A drug that inhibits acetylcholinesterase
B. A drug that inhibits release of acetylcholine
C. Curare
D. Atropine (a muscarinic antagonist)
E. All of the choices are correct
18. During an isometric contraction of a skeletal muscle,
A. The I bands shorten and the A bands stay the same length
B. The thick and thin filaments slide past each other
C. Sarcomere length does not change
D. Both the I bands shorten and the A bands stay the same length and the thick and thin filaments slide past
each other take place
E. None of the choices happen
19. During any isometric twitch in a skeletal muscle,
A. Tension exceeds load
B. Tetanus occurs
C. Load exceeds tension
D. The whole muscle shortens
20. Which of the following statements regarding skeletal-muscle contraction is true?
A. During a lengthening contraction, the tension exerted by the muscle exceeds the load on the muscle
B. Every isometric contraction begins and ends as an isotonic contraction
C. During every muscle contraction, muscle fibers change length
D. During every muscle contraction, tension is developed in the muscle
E. None of the choices are true
21. Which of the following statements best explains how tetanus can be generated in a skeletal muscle, given
the all-or-none nature of action potentials?
A. During a single action potential in a skeletal muscle, there is not enough time for all of the calcium in the
sarcoplasmic reticulum to diffuse into the cytosol and bind to troponin
B. Skeletal muscle has no absolute refractory period
C. Skeletal muscle has a much longer absolute refractory period than does a motor neuron
D. During a single action potential in a skeletal muscle, there is not enough time for maximal tension to develop
before the Ca-ATPase begins sequestering calcium ions
E. Both during a single action potential in a skeletal muscle, there is not enough time for all of the calcium in
the sarcoplasmic reticulum to diffuse into the cytosol and bind to troponin and skeletal muscle has a much
longer absolute refractory period than does a motor neuron are correct
22. Which of the following statements regarding skeletal-muscle contraction is true?
A. The tension developed during the contraction of a muscle fiber is dependent upon the initial length of the
fiber
B. There is a positive correlation between muscle-fiber length at the beginning of a contraction and the tension
that can be developed by the fiber: the longer the fiber, the greater the tension
C. There is a positive correlation between the frequency of action potentials in a single muscle fiber and the
tension it can develop: the greater the frequency, the greater the tension, up to a plateau
D. Both the tension developed during the contraction of a muscle fiber is dependent upon the initial length of
the fiber and there is a positive correlation between muscle-fiber length at the beginning of a contraction and the
tension that can be developed by the fiber: the longer the fiber, the greater the tension are true
E. Both the tension developed during the contraction of a muscle fiber is dependent upon the initial length of
the fiber and there is a positive correlation between the frequency of action potentials in a single muscle fiber
and the tension it can develop: the greater the frequency, the greater the tension, up to a plateau are true
23. The optimal length of a skeletal muscle is
A. The length at which the muscle can generate its maximal tetanic tension
B. The shortest length the muscle can achieve while attached to bone, because the amount of overlap between
thick and thin filaments is maximal then
C. Approximately the same as its resting length
D. Both the length at which the muscle can generate its maximal tetanic tension and the shortest length the
muscle can achieve while attached to bone, because the amount of overlap between thick and thin filaments is
maximal then are correct
E. Both the length at which the muscle can generate its maximal tetanic tension and approximately the same as
its resting length are correct
24. The first means by which ATP is produced at the onset of contractile activity in a skeletal muscle is
A. Transfer of energy and phosphate from creatine phosphate to ADP
B. Oxidative phosphorylation
C. Glycolysis
D. Oxidation of fatty acids
E. Catabolism of myoglobin
25. When a muscle has been contracting for an extended period of time (more than a few minutes), the primary
source of ATP is
A. Transfer of energy and phosphate from creatine phosphate to ADP
B. Glycolysis
C. Oxidative phosphorylation
D. Breakdown of myosin
E. None of the choices are correct
26. After heavy exercise, breathing remains labored for some time, indicating a continuing need for increased
oxygen. In muscle cells recovering from exercise,
A. Oxygen is used for oxidation of lactic acid metabolites to generate ATP
B. ATP is used to synthesize glycogen from glucose
C. ATP is used to phosphorylate creatine
D. Both oxygen is used for oxidation of lactic acid metabolites to generate ATP and ATP is used to synthesize
glycogen from glucose are correct
E. All of the choices are correct
27. Muscle fatigue
A. Is caused by depletion of ATP stores
B. After short-duration, high-intensity exercise is caused by depletion of muscle glycogen stores
C. After long-duration, low-intensity exercise is caused by excessive hydrogen ion concentrations that interfere
with contractile protein activity
D. After long-duration, low-intensity exercise is caused by build up of potassium ion in the lumen of T tubules
E. Is caused by none of these choices
28. Which of the following statements regarding myosin in skeletal muscle is/are true?
A. Myosin heads contain two functional sites, one for actin and one for tropomyosin
B. Myosin is an ATPase
C. The rate of ATP hydrolysis by myosin is the same in all types of skeletal muscle
D. Both myosin heads contain two functional sites, one for actin and one for tropomyosin and myosin is an
ATPase are true
E. All of the choices are true
29. Which of the following is not true regarding the comparison of type I (slow oxidative) and type II b
(fast-glycolytic) skeletal-muscle fibers?
A. Type I fibers have more abundant mitochondria
B. Type I fibers fatigue more readily
C. Type I fibers have more abundant myoglobin
D. Type I fibers have more abundant capillaries
E. Type I motor units contain fewer fibers than type II b motor units
30. Which of the following statements about different kinds of skeletal-muscle fibers is true?
A. Slow-oxidative fibers have a greater abundance of glycogen than do fast-glycolytic fibers
B. Fast-glycolytic fibers have a greater abundance of myoglobin than do slow-oxidative fibers
C. Fast-glycolytic fibers can generate greater tension than can slow-oxidative fibers
D. Both slow-oxidative fibers have a greater abundance of glycogen than do fast-glycolytic fibers and
fast-glycolytic fibers have a greater abundance of myoglobin than do slow-oxidative fibers are true
E. All of the choices are true
31. One cause of fatigue in fast-glycolytic muscle fibers is
A. Depletion of ATP in the fiber
B. Depletion of creatine phosphate in the fiber
C. Depletion of oxygen in the fiber
D. Accumulation of potassium ion in the lumen of T tubules
E. All of the choices are correct
32. Fast-glycolytic muscle fibers differ from slow-oxidative fibers in that
A. The former rely on creatine phosphate as an ATP source for the first few seconds of contraction whereas the
latter do not
B. The former have a smaller diameter than the latter
C. The former can generate greater maximal tension than the latter
D. The former generate less lactic acid than do the latter
E. All of the choices are true
33. Which of the following is not a determinant of whole-muscle tension?
A. Number of muscle fibers contracting
B. Tension produced by each contracting fiber
C. Extent of motor unit recruitment
D. Frequency of motor neuron stimulation
E. Proportion of the muscle fibers in each motor unit that are contracting at any given time
34. Which of the following statements regarding skeletal muscle is true?
A. Some skeletal-muscle fibers have pacemaker activity
B. Skeletal-muscle fibers are joined together by gap junctions
C. A given skeletal-muscle fiber will contract when excitatory nervous stimuli sufficiently exceed inhibitory
nervous stimuli at the motor end plate
D. A given skeletal-muscle fiber will contract when excitatory nervous stimuli sufficiently exceed inhibitory
nervous stimuli at the cell body of the motor neuron that innervates that fiber
E. None of the choices are true
35. The tension in a skeletal muscle can be increased by increasing
A. The number of motor units stimulated
B. The rate of stimulation to each motor unit
C. The number of fibers in the muscle through exercise
D. The number of motor units stimulated and the rate of stimulation to each motor unit
E. All of the choices are correct
36. Which of the following statements regarding whole-muscle contraction is true?
A. The order of recruitment of motor units in a muscle is such that the last units recruited are the first to
experience fatigue
B. The order of recruitment of motor units in a muscle is such that the first units recruited generate the most
tension
C. Motor units whose motor neurons have small-diameter cell bodies contract first, followed by motor units
with larger-diameter motor neurons
D. Both the order of recruitment of motor units in a muscle is such that the last units recruited are the first to
experience fatigue and the order of recruitment of motor units in a muscle is such that the first units recruited
generate the most tension are true
E. Both the order of recruitment of motor units in a muscle is such that the last units recruited are the first to
experience fatigue and motor units whose motor neurons have small-diameter cell bodies contract first,
followed by motor units with larger-diameter motor neurons are true
37. John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Jim is a
marathon runner who specializes in long, steady runs. Compared to Jim, John is likely to have
A. Legs with a larger diameter
B. Legs with a smaller diameter
C. Hypertrophy of type I muscle fibers
D. Legs with a larger diameter and hypertrophy of type I muscle fibers
E. Legs with a smaller diameter and hypertrophy of type I muscle fibers
38. John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest. Jim is a
marathon runner who specializes in long, steady runs. Compared to John, Jim is likely to have
A. More glycogen stored in his type II b muscle fibers
B. More mitochondria in his type I and II a muscle fibers
C. More myoglobin in his type II b muscle fibers
D. Both more glycogen stored in his type II b muscle fibers and more myoglobin in his type II b muscle fibers
E. Both more mitochondria in his type I and II a muscle fibers and more myoglobin in his type II b muscle
fibers
39. Olympic speed (ice) skaters have large, muscular legs that are unusual in that the left leg is generally even
larger in diameter than the right. This is an example of
A. Disuse atrophy of the right leg
B. Hypertrophy of fast-glycolytic muscle fibers as a result of exercise
C. An increase in the number of fast muscle fibers as a result of exercise
D. Both disuse atrophy of the right leg and hypertrophy of fast-glycolytic muscle fibers as a result of exercise
E. Both hypertrophy of fast-glycolytic muscle fibers as a result of exercise and an increase in the number of fast
muscle fibers as a result of exercise
40. Which of the following statements is not true?
A. Nervous stimulation of skeletal muscle is always excitatory, whereas nervous stimulation of smooth muscle
may be excitatory or inhibitory
B. A single smooth-muscle cell may be innervated by both a sympathetic neuron and a parasympathetic neuron
C. The contractile activity of smooth-muscle cells may be affected by hormones
D. In the absence of neural input, skeletal muscle cannot generate tension
E. None of the choices are true
41. A major difference between smooth muscle and skeletal muscle is that
A. Myosin is the regulatory protein in smooth muscle
B. Myosin is the regulatory protein in skeletal muscle
C. Skeletal muscle may exhibit spontaneous activity
D. Only skeletal muscle requires increased calcium ion concentration in the cytosol for contraction
E. None of the choices are correct
42. Unlike skeletal muscle,
A. Smooth muscle is striated
B. Smooth muscle does not have thick and thin filaments
C. Smooth muscle does not use troponin-tropomyosin to regulate cross-bridge activity
D. Smooth muscle does not use changes in cytosolic calcium to regulate cross-bridge activity
E. The myosin in smooth muscle requires phosphorylation before it can bind to ATP
43. Excitation-contraction coupling
A. In skeletal-muscle cells requires the influx of extracellular calcium ion
B. In smooth-muscle cells requires the influx of extracellular calcium ion
C. In all kinds of muscle requires the release of calcium ion from the sarcoplasmic reticulum
D. Both in skeletal-muscle cells requires the influx of extracellular calcium ion and in smooth-muscle cells
requires the influx of extracellular calcium ion are correct
E. Both in smooth-muscle cells requires the influx of extracellular calcium ion and in all kinds of muscle
requires the release of calcium ion from the sarcoplasmic reticulum are correct
44. Which of the following statements regarding contraction in skeletal and smooth muscle is true?
A. In skeletal muscle, calcium ion mediates changes in thin filaments that lead to cross-bridge activity; in
smooth muscle, calcium ion mediates changes in thick filaments that lead to cross-bridge activity
B. In skeletal muscle, calcium ion binds to a regulatory protein on thin filaments; in smooth muscle, calcium ion
binds to a regulatory protein on thick filaments
C. In skeletal muscle, calcium ion binds to troponin; in smooth muscle, calcium ion binds to calmodulin
D. Both in skeletal muscle, calcium ion mediates changes in thin filaments that lead to cross-bridge activity; in
smooth muscle, calcium ion mediates changes in thick filaments that lead to cross-bridge activity and in skeletal
muscle, calcium ion binds to troponin; in smooth muscle, calcium ion binds to calmodulin are true
E. All of the choices are true
45. Which of the following is not true regarding single-unit smooth-muscle cells? They
A. Have individual innervation of each cell
B. Have many gap junctions between cells
C. May have pacemaker activity
D. Respond to stretch by contracting
E. Have tone
46. Multiunit smooth-muscle cells
A. Have individual innervation of each cell
B. Have many gap junctions between cells
C. Respond to stretch by contracting
D. Both have individual innervation of each cell and have many gap junctions between cells are correct
E. Both have individual innervation of each cell and respond to stretch by contracting are correct
47. Although both skeletal and cardiac muscle exhibit striated appearance and the property of contractility there
are functional differences between them. Which of the following is not a difference between cardiac and
skeletal muscle?
A. Cardiac muscle cells are arranged in layers surrounding hollow cavities in the heart
B. Skeletal muscle cells are long and multinucleate, depending on neuronal stimuli
C. Cardiac muscle cells are depolarized initially by the influx of calcium ions
D. Skeletal muscle cells depolarize prior to contraction
E. In cardiac muscle cells a resting membrane potential must be present to provide for excitation and
contraction
48. Which of the following choices gives the correct sequence of events following the depolarization of
transverse tubules in excitation-contraction coupling in cardiac muscle?
A. Calcium release into sarcoplasm, calcium ion influx through sarcolemma, actin and myosin attach, thin
myofilaments slide toward the middle of sarcomeres
B. Actin and myosin attach, thin myofilaments slide toward the middle of sarcomeres, calcium release into
sarcoplasm
C. Calcium release into sarcoplasm, actin and myosin attach, calcium ion influx through sarcolemma, thin
myofilaments slide toward the middle of sarcomeres
D. Calcium release into sarcoplasm, actin and myosin attach, thin myofilaments slide toward the middle of
sarcomeres, calcium ion influx through sarcolemma
E. Calcium ion influx through sarcolemma, calcium release into sarcoplasm, actin and myosin attach, thin
myofilaments slide toward the middle of sarcomeres
49. The electrical depolarization which spreads through the heart musculature and precedes contraction of atria
and ventricles is dependent upon the rapid inward diffusion of which of the following ions?
A. Sodium
B. Calcium
C. Nitrate
D. Chloride
E. Potassium
F. events?
50. The conclusion of cardiac muscle contraction is marked by which of the following
A. Concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca 2+-ATPase pumps
B. Concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca 2+/Na+ cotransporters
in sarcoplasmic reticulum and sarcolemma
C. The release of actin protein degrading enzymes
D. The release of myosin degrading enzymes
E. Both concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca 2+-ATPase
pumps and concentration of calcium ions in the cytosol is greatly reduced by active transport; Ca 2+/Na+
cotransporters in sarcoplasmic reticulum and sarcolemma are correct
51. L-type calcium channels in cardiac muscle cells
A. Are essentially present and the same in both skeletal and cardiac muscle
B. Are directly related to making them fatigue resistant
C. Are responsible for preventing titanic contractions in them
D. Cause the absolute refractory period to be very short lived
E. Provide the mechanism necessary for producing contractions of varying intensity or force
52. Some athletes in activities requiring ATP for more than a few seconds may turn to dietary supplements
containing ____ to increase the amount of _____ immediately available within the muscles.
A. Fatty acids, calcium ions
B. Sports drinks (Gatorade, Powerade, etc.) , electrolytes and mineral spirits
C. Sugars, glucose
D. Proteins, amino acids
E. Creatine, ATP
53. Myasthenia gravis
A. Is an autoimmune disease
B. Occurs when the motor neuron terminals cannot secrete enough acetylcholine to stimulate the motor end
plate adequately
C. Can be treated with a drug that temporarily inhibits acetylcholinesterase
D. Both is an autoimmune disease and occurs when the motor neuron terminals cannot secrete enough
acetylcholine to stimulate the motor end plate adequately are correct
E. Both is an autoimmune disease and can be treated with a drug that temporarily inhibits acetylcholinesterase
are correct
54. Skeletal muscles are made up of bundles of muscle fibers held together by sheaths called tendons.
FALSE
55. The name given to the unit of repeating pattern in a myofibril is "sarcomere."
TRUE
56. The force-generating sites in a myofibril are the Z lines.
FALSE
57. During skeletal-muscle contraction, the distance between the Z lines of a sarcomere decreases because of
shortening of the filaments.
FALSE
58. During skeletal-muscle contraction, the I band and H zone shorten but the A band stays the same.
TRUE
59. The cross-bridge cycle refers to the sequence of events between the time an individual cross bridge binds to
a thin filament at the start of a muscle contraction and the time the cross bridge releases the filament at the end
of the contraction.
FALSE
60. The energy for muscle contraction is provided by the hydrolysis of ATP.
TRUE
61. Actin is an ATPase.
FALSE
62. The binding of ATP to myosin causes an allosteric change in myosin's actin-binding site such that the
affinity of myosin for actin is decreased.
TRUE
63. The phenomenon of rigor mortis demonstrates that myosin can bind to actin in the absence of ATP, but the
bond cannot then be broken.
TRUE
64. Binding of myosin to actin cannot take place in the absence of calcium ion.
TRUE
65. Excitation-contraction coupling refers to the binding of energized myosin to actin.
FALSE
66. The site of calcium-ion storage in muscle cells is the lateral sacs of the transverse tubules.
FALSE
67. Curare blocks neuromuscular transmission by preventing the release of neurotransmitter from the motor
neuron.
FALSE
68. Organophosphate "nerve gases" induce paralysis by blocking neural stimulation of the neuromuscular
junctions, while botulinum toxin produces the same effect by inhibiting acetylcholinesterase.
FALSE
69. The term "twitch" refers to the mechanical response of a muscle fiber during one cross-bridge cycle.
FALSE
70. All isotonic contractions begin and end as isometric contractions.
TRUE
71. During isometric contraction of a skeletal-muscle fiber, tension increases but the fiber length stays the
same.
TRUE
72. The latent period of an isotonic twitch is shorter than the latent period of an isometric twitch.
FALSE
73. Sustained contraction and tension in a skeletal muscle is called tetanus.
TRUE
74. A skeletal muscle generates its greatest twitch tension when it is stretched to twice its resting length.
FALSE
75. Fast fibers can be distinguished from slow fibers by the rate at which their myosin-ATPases split ATP.
TRUE
76. Characteristics of oxidative fibers include numerous mitochondria, abundant myoglobin and large stores of
glycogen.
FALSE
77. The difference in color between white muscle and red muscle is accounted for by the greater abundance of
glycogen in white muscle.
FALSE
78. The fiber type intermediate between the two extremes of fast glycolytic and slow oxidative is slow
glycolytic.
FALSE
79. Muscles used for delicate, finely controlled movements have smaller motor units than more coarsely
controlled muscles.
TRUE
80. In general, activating a slow-oxidative motor unit in a muscle will generate more tension than activating a
fast-glycolytic motor unit.
FALSE
81. Endurance exercise, such as long-distance swimming, causes a preferential increase in glycolytic enzymes
and increased mass of the exercising muscles.
FALSE
82. The larger the diameter of a skeletal-muscle fiber, the greater the tension it can generate.
TRUE
83. Recruitment of different types of motor units in a muscle is the primary means of varying the amount of
tension generated in that muscle.
TRUE
84. The shortening velocity of a skeletal muscle fiber increases with decreasing load because the rate at which
the cross-bridge cycle can occur increases with decreasing load.
TRUE
85. A flexor muscle pulls on bone to decrease the angle at a joint, whereas an extensor pushes the bone to
increase the angle.
FALSE
86. The decrease in mass and strength of muscle as a result of damage to the nerves innervating the muscle is
called disuse atrophy.
FALSE
87. The calcium-binding protein in smooth muscle is calmodulin.
TRUE
88. The myosin in smooth-muscle cells differs from that in skeletal muscle in that smooth-muscle myosin
requires phosphorylation before it can bind to actin.
TRUE
89. In smooth-muscle cells that can produce action potentials, cell membrane depolarization opens
voltage-sensitive sodium channels.
FALSE
90. Nervous stimulation of skeletal muscle is always excitatory, whereas nervous stimulation of smooth muscle
may be excitatory or inhibitory.
TRUE
91. Smooth-muscle cells may contract in the absence of nervous stimulation.
TRUE
92. Multiunit smooth muscle is characterized by many gap junctions between cells.
FALSE
93. In cardiac muscle contractile cells the release of calcium through L-type calcium channels depolarizes the
sarcoplasmic reticulum and inhibits the release of any additional calcium necessary for excitation-contraction
coupling.
FALSE
94. Abundant mitochondria is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
95. Abundant myoglobin is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
96. A large diameter is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
97. Fast myosin ATPase activity is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
98. Recruited first is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
99. Fatigued first is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
100. Few mitochondria is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
101. Little myoglobin is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II
102. Small diameter is typical of which type of skeletal-muscle fibers?
A. Type I
B. Type II