Florida International University

BIO PCB 4023

Chapter 12

1)A skeletal muscle is composed of a bundle of        , each composed of many muscle fibers wrapped by connective tissue.

1. 1. myofilaments
   2. myofibrils
   3. fascicles
   4. sarcomeres
   5. muscle cells
2. What structure, composed of connective tissue, transmits force from contracting skeletal muscle to bone?
   1. fascicle
   2. myofibril
   3. tendon
   4. aponeurosis
   5. ligament
3. The fundamental repeating unit of the myofibril, called a          , gives skeletal muscle its striated appearance and is bordered by                              .
   1. sarcomere : M lines
   2. sarcomere : I bands
   3. crossbridge : Z lines
   4. crossbridge : A bands
   5. sarcomere : Z lines
4. What is the region of the striated muscle's banding patterns that contains only the connections between the tails of myosin molecules and is the mid-point of the sarcomere?
   1. M line B) H zone C) A band D) Z line E) I band
5. The contractile portion of the thin filament is composed of what protein?
   1. actin
   2. titin
   3. myosin
   4. tropomyosin
   5. troponin
6. What is the regulatory protein component of the thin filament that binds to calcium, thereby initiating skeletal muscle contraction?
   1. actin
   2. myosin
   3. tropomyosin
   4. troponin
   5. titin  1
7. Which of the following is a structural protein that extends along each thick filament from M line to Z line?
   1. tropomyosin
   2. titin
   3. myosin
   4. troponin
   5. actin
8. The shortening of a skeletal muscle fiber during contraction involves which of the following?
   1. the Z lines not changing their position
   2. the A bands shortening
   3. the thick filaments shortening

8. 4. the sarcomeres shortening
   5. the thin filaments shortening
9. During skeletal muscle contraction, as the muscle shortens, the thick and thin filaments
   1. condense.
   2. do not interact.
   3. lengthen.
   4. slide past one another.
   5. shorten.
10. When a skeletal muscle is passively stretched, that cell has a tendency to spring back once the force that was stretching the muscle is removed due to
    1. actin and myosin acting as a spring using the energy stored by the stretching.
    2. the active interaction between actin and myosin (energy required).
    3. titin acting as a spring using the energy stored by the stretching.
    4. the passive interaction between actin and myosin (no energy required).
    5. the elastic connective tissue that surrounds the muscle cells and fascicles.
11. The repeated, oscillating interaction between actin and myosin which results in the generation of force by a skeletal muscle cell is called what?
    1. Z line interaction
    2. crossbridge cycling
    3. sarcomeric facilitation
    4. titin cycling
    5. the sliding-filament model
12. What converts the myosin head into the high-energy state?
    1. binding to ATP only
    2. the condensation of ATP
    3. the hydrolysis of ATP
    4. binding to actin
    5. binding to titin

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13. The release of an inorganic phosphate from the myosin molecule directly results in which of the following?
    1. cocking of the myosin head
    2. binding of actin to myosin
    3. breaking of the actin myosin complex
    4. development of rigor
    5. power stroke
14. In order for crossbridge cycling to occur, the actin-myosin complex must be broken by which of the following?
    1. conformational change that occurs as the myosin head changes from the high to low energy state
    2. binding of ATP to myosin
    3. binding of tropomyosin to myosin
    4. binding of ATP to actin
    5. binding of the troponin complex to actin
15. The sequence of events that links the muscle's action potential to changes in skeletal muscle force development is called what?
    1. crossbridge cycling
    2. excitation-contraction coupling
    3. oxidative phosphorylation
    4. the sliding-filament model
    5. myoaction coupling

16. During skeletal muscle contraction, multiple crossbridge cycles are occurring between the same thick and thin filament. Which of the following best describes this process?
    1. Crossbridge cycling is asynchronous between a certain thick and thin filament.
    2. No more than one myosin head detaches from the thin filament at the same time.
    3. Crossbridge cycling is highly synchronized between a certain thick and thin filament.
    4. No more than one myosin head links to the thin filament at the same time.
    5. Tropomyosin only exposes one binding site on actin at a time allowing only one crossbridge to form with actin at a given time.

17. Contraction of skeletal muscle fibers is stimulated by what type of neuron?
    1. afferent
    2. parasympathetic
    3. sympathetic
    4. motor
    5. autonomic

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18. Which of the following is NOT a specialization observed at the neuromuscular junction?
    1. The terminal bouton fans out over a wide area of the sarcolemma.
    2. The motor end plate is relatively large compared with other synapses.
    3. There is a high density of acetylcholine receptors in the motor end plate.
    4. Every action potential that reaches the axon terminal of the motor neuron will generate an action potential in the healthy muscle fiber.
    5. Each muscle fiber is innervated by multiple motor neurons.
19. Increases in the amount of cytoplasmic calcium required to initiate a muscle contraction are mediated by the coupling between a                          on the T tubule and a            on the membrane of the sarcoplasmic

reticulum.

19. 1. ryanodine receptor : calcium pump
    2. calcium-induced calcium release channel : dihydropyridine receptor
    3. dihydropyridine receptor : ryanodine receptor
    4. calcium pump : ryanodine receptor
    5. dihydropyridine receptor : calcium pump
20. Which of the following is the voltage sensor that initiates an increase in cytoplasmic calcium in response to an action potential?
    1. sodium channel
    2. dihydropyridine receptor
    3. ryanodine receptor
    4. calcium pump
    5. calcium-induced calcium release channel
21. The binding of calcium to troponin will directly allow which of the following?
    1. the binding of ATP to myosin
    2. the movement of tropomyosin, thereby exposing the actin-binding site on the myosin molecule
    3. the hydrolysis of ATP
    4. the movement of tropomyosin, thereby exposing the myosin-binding site on the actin molecule
    5. the further release of calcium into the cytoplasm
22. What area of a sarcomere shows up as light striations when viewed under a microscope?
    1. Z line B) H zone C) I band D) A band E) M line

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23. Which of the following best describes the interaction between transverse (T) tubules and the sarcoplasmic reticulum in skeletal muscle contraction?

1. 1. Action potentials in T tubules are detected by DHP receptors, which are coupled to ryanodine receptors in the sarcoplasmic reticulum and open channels for calcium.
   2. Action potentials in T tubules cause a depolarization of the sarcoplasmic reticulum membrane, thereby opening calcium channels to trigger calcium release.
   3. Action potentials in T tubules trigger the release of norepinephrine, which binds to receptors on the sarcoplasmic reticulum and triggers calcium release.
   4. Action potentials in T tubules trigger the release of acetylcholine, which binds to receptors on the sarcoplasmic reticulum and triggers calcium release.
   5. Action potentials in T tubules are detected by ryanodine receptors, which are coupled to DHP receptors in the sarcoplasmic reticulum and open channels for calcium.

24. During the cross-bridge cycle, ATP binding to myosin causes which of the following?
    1. the myosin head to attach to actin
    2. the myosin head to be in its high-energy form
    3. the myosin head to detach from actin
    4. the myosin head to interact with calcium channels, triggering calcium release from the sarcoplasmic reticulum
    5. the myosin head to swing forward pulling actin toward the M line
25. What is the function of T tubules?
    1. They conduct action potentials from the sarcolemma to the interior of the muscle cell.
    2. Actin and myosin are synthesized here.
    3. They store calcium.
    4. They hold the thick filaments to the Z line.
    5. They provide elasticity to the muscle.
26. What is a motor unit?
    1. all the muscle fibers in a fascicle
    2. a muscle fiber and all the motor neurons that innervate it
    3. a spinal nerve and all the muscle fibers it innervates
    4. a motor neuron and all the muscle fibers it innervates
    5. all the myofibrils in a muscle fiber
27. In order to allow discrete contractile events to occur, calcium is rapidly removed from the cytoplasm via
    1. calcium pumps (active transport of calcium).
    2. ryanodine channels.
    3. calcium-binding proteins on the sarcoplasmic reticulum.
    4. dihydropyridine receptors.
    5. calcium-sequestering proteins in the cytoplasm.

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28. Which of the following is not part of the process whereby skeletal muscles relax?
    1. Sarcolemmal calcium channels open to allow the efflux of calcium.
    2. The amount of calcium bound to troponin decreases.
    3. The binding of calcium to a low-affinity site closes sarcoplasmic reticulum calcium channels.
    4. A calcium pump actively removes calcium.
    5. A myosin-binding site on the actin molecule is blocked by tropomyosin.
29. What enzyme catalyzes the reaction that creates creatine phosphate?
    1. creatine kinase
    2. ATP hydrolase
    3. creatine hydrogenase
    4. creatine phosphatase
    5. creatine hydrolase
30. Since the creatine phosphorylation reaction is substrate driven, an increase in the concentration of creatine

within a skeletal muscle fiber will directly have what effect?

30. 1. decrease creatine kinase activity
    2. increase glucose metabolism
    3. increase ATP generation
    4. increase creatine phosphate concentration
    5. decrease creatine phosphate concentration
31. During intense (heavy) exercise, the initial ability of oxidative phosphorylation to provide enough ATP for the sudden demand of increased force generation by the skeletal muscle is                     , thereby causing the muscle fiber to quickly and massively boost its energy production from        until oxygen delivery and other mechanisms come up to speed.
    1. enhanced : fatty acids
    2. inadequate : fatty acids
    3. inadequate : substrate-level phosphorylation
    4. enhanced : glucose
    5. enhanced : substrate-level phosphorylation
32. As the intensity of exercise increases (and the potential gap between energy demand and creation threatens to widen), the muscles quickly underwrite their escalating energy demands by augmenting oxidative with substrate-level phosphorylation, resulting in the increased generation of which of the following?
    1. water from the electron transport chain
    2. lactic acid
    3. glucose
    4. fatty acid
    5. ATP  6
33. When an action potential is generated within a motor neuron,
    1. the muscle cells of the motor unit will occasionally contract.
    2. only select muscle cells within the motor unit are stimulated to contract.
    3. all of the muscle cells within the motor unit are stimulated to relax.
    4. the muscle cells from a neighboring motor unit will contract.
    5. every muscle cell of the motor unit is stimulated to contract.
34. Which is the longest phase of a twitch?
    1. contraction B) plateau C) initial D) relaxation E) latent
35. Which of the following is NOT part of the explanation for the all-or-nothing property of an isometric twitch contraction of skeletal muscle?
    1. equal numbers of crossbridges activated by the calcium released
    2. all-or-nothing property of the action potential generated by a skeletal muscle
    3. equivalent calcium reuptake by the sarcoplasmic reticulum
    4. equivalent activation of calmodulin stimulating myosin light-chain kinase activity
    5. equivalent calcium released by each action potential
36. Which of the following is a property of isometric skeletal muscle contraction?
    1. rapid lengthening of the muscle
    2. Load is greater than the force generated by the muscle.
    3. rapid shortening of the muscle
    4. Load is less than the force generated by the muscle.
    5. Load is equal to the force generated by the muscle.
37. Which of the following is a property of isotonic skeletal muscle contraction?
    1. Muscle length will be increased by contraction.
    2. There is a rapid increase in force with no change in muscle length.
    3. Load is greater than the force generated by the muscle.

37. 4. There is a slow increase in force with no change in muscle length.
    5. Load is less than the force generated by the muscle.
38. Which of the following statements about excitation-contraction coupling in skeletal muscle is FALSE?
    1. An action potential in the sarcolemma stimulates the opening of voltage-gated calcium channels in the plasma membrane and the sarcoplasmic reticulum.
    2. Calcium binds to troponin, causing a shift in tropomyosin, thereby exposing the binding sites on actin for myosin.
    3. An end-plate potential triggers an action potential on the sarcolemma.
    4. Calcium ATPases in the sarcoplasmic reticulum are necessary for relaxation of the muscle.
    5. DHP receptors on the T tubules detect changes in voltage and communicate to ryanodine receptors on the sarcoplasmic reticulum to open calcium channels.

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39. Which of the following statements about end-plate potentials is FALSE?
    1. They are almost always of sufficient magnitude to generate an action potential in the sarcolemma.
    2. They are graded potentials.
    3. They are always depolarizations.
    4. They are a result of acetylcholine binding to muscarinic cholinergic receptors.
    5. They are terminated by removal of acetylcholine from the synaptic cleft.
40. Which of the following best describes an isotonic contraction?
    1. When the contractile elements lengthen, they shorten the elastic elements and move the load.
    2. When the contractile elements shorten, they lengthen the elastic elements but do not move the load.
    3. When the contractile elements lengthen, they lengthen the elastic elements but do not move the load.
    4. The contractile elements stay the same length as the elastic elements shorten and move the load.
    5. When the contractile elements shorten, they create enough force to move the load.
41. The speed with which the skeletal muscle generates force is determined primarily by
    1. tropomyosin.
    2. troponin.
    3. the type of myosin and its ATPase present.
    4. actin.
    5. the amount of energy available.
42. Which of the following is the property of skeletal muscle whereby an increase in the frequency of action potentials enhances the force developed by the muscle cell?
    1. force-velocity relationship
    2. external tension
    3. length-tension relationship
    4. summation
    5. internal tension
43. The tension produced during skeletal muscle contraction can be increased by all of the following EXCEPT
    1. increasing the load on the muscle.
    2. recruiting motor units.
    3. increasing the frequency of action potentials in the motor neuron innervating the muscle.
    4. increasing the frequency of action potentials in the muscle fiber.
    5. initiating the contraction when the muscle is at its optimum length.
44. Which of the following statements about summation and tetanus is FALSE?
    1. Summation and tetanus result in greater tension in the muscle.
    2. The maximum tension developed during summation and tetanus is treppe.
    3. Summation and tetanus result from increases in cytosolic calcium levels.
    4. Summation and tetanus occur at high frequencies of skeletal muscle stimulation.
    5. Summation and tetanus do not occur in cardiac muscle.

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45. Once a skeletal muscle cell begins to shorten during an isotonic twitch contraction,
    1. the amount of force generated by the muscle will continue to increase.
    2. the amount of force generated by the muscle will remain constant.
    3. the muscle will continue to shorten until the force generated by the muscle stops increasing.
    4. the muscle will stop shortening once the force is greater than the load.
    5. the amount of force generated by the muscle will start to decrease.
46. Which of the following conditions will result in a skeletal muscle that produces a greater amount of force?
    1. fewer sarcomeres in parallel
    2. more sarcomeres in series
    3. fewer myofibrils per muscle cell
    4. more sarcomeres in parallel
    5. fewer sarcomeres in series
47. Which of the following is NOT an accurate description of specific muscle fiber types?
    1. Fast glycolytic fibers produce their ATP by glycolysis.
    2. Slow oxidative fibers are quick to fatigue.
    3. Slow oxidative fibers are the smallest diameter fibers.
    4. Fast oxidative fibers have a high mitochondrial density.
    5. Fast glycolytic fibers are the largest diameter fibers.
48. As skeletal muscle is further stretched beyond the length where optimum force is developed,
    1. the thick filaments overlap one another, thereby reducing their ability to interact with actin.
    2. the amount of calcium released by the sarcoplasmic reticulum is reduced as length increases.
    3. the thin filaments are pulled away from the thick filaments, thereby reducing actin's ability to interact with myosin.
    4. the thin filaments overlap one another, thereby reducing their ability to interact with myosin.
    5. the thick filaments are pulled away from one another, thereby reducing their ability to interact with actin.

49. As the sarcomere length of skeletal muscle is reduced beyond the length where optimum force is developed,
    1. the thick filaments overlap one another, thereby reducing their ability to interact with actin.
    2. the thick filaments are pulled away from one another, thereby reducing their ability to interact with actin.
    3. the thin filaments overlap one another with myosin bumping into the Z-line, thereby causing the force generated by crossbridges to be exerted on the sarcomere itself rather than transmitted to the ends of

the muscle fiber.

1. 4. the thin filaments are pulled away from one another, thereby reducing their ability to interact with myosin.
   5. the amount of calcium released by the sarcoplasmic reticulum is reduced as length increases.

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50. In the body, the sarcomere length of skeletal muscle cells is usually
    1. 3 microns.
    2. quite variable from one muscle to the next.
    3. much greater than optimum length.
    4. near optimal.
    5. much less than optimum length.
51. Which of the following does NOT influence the force generated by an individual muscle fiber?
    1. fiber diameter
    2. summation
    3. recruitment
    4. frequency of stimulation

51. 5. length at onset of contraction
52. What is an increase in the number of active motor units that would increase the force developed by a skeletal muscle called?
    1. treppe
    2. length-tension relationship
    3. summation
    4. recruitment
    5. tetanus
53. Contraction of motor units in a(n)      manner allows a muscle to maintain a smooth level of force for a duration of time without fatiguing.
    1. asymmetrical
    2. synchronous
    3. random
    4. symmetrical
    5. asynchronous
54. Which of the following BEST describes the relationship between motor neuron size, motor unit size, and order of recruitment?
    1. large motor neurons : small motor unit : last to be recruited
    2. large motor neurons : large motor unit : last to be recruited
    3. large motor neurons : large motor unit : first to be recruited
    4. large motor neurons : small motor unit : first to be recruited
    5. There is no relationship.

55. A muscle is stimulated at a frequency that allows the muscle to relax completely between contractions. However, the amount of tension increases with each contraction. What is this called?
    1. treppe B) tetanus C) twitch D) summation E) recruitment

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56. The mechanism responsible for the size principle involves
    1. larger sympathetic neurons that contain the greatest number of muscle cells and reach threshold easier than smaller neurons.
    2. smaller motor units that contain the greatest number of muscle cells and reach threshold easier than larger neurons.
    3. larger motor neurons that innervate the greatest number of muscle cells and reach threshold easier than smaller neurons.
    4. smaller sympathetic neurons that contain the least number of muscle cells and reach threshold easier than larger neurons.
    5. smaller motor neurons that innervate the least number of muscle cells and reach threshold easier than larger neurons.

57. Which of the following is NOT a property of glycolytic fibers as compared to oxidative fibers?
    1. high capacity for lactic acid production
    2. poor ability to produce ATP in the absence of oxygen
    3. absence of myoglobin
    4. fewer capillaries
    5. readily fatigable
58. What molecule, present primarily within oxidative skeletal muscle cells, acts as an oxygen buffer due to its ability to bind oxygen?
    1. myosin
    2. myoglobin
    3. hemoglobin
    4. myosin light chain

58. 5. lactic acid
59. What causes some muscle fibers to appear red and dark?
    1. presence of lots of mitochondria
    2. presence of myoglobin
    3. presence of myoglobin and lots of mitochondria
    4. high concentration of actin and myosin
    5. greater blood supply
60. What is the site where a muscle attaches to a stationary bone called?
    1. insertion B) adductor C) abductor D) origin E) flexor
61. What connects muscles to bone?
    1. ligaments B) cartilage C) capillaries D) tendons E) T tubules
62. Relative to the triceps muscle, the biceps is its
    1. insertion. B) agonist. C) abductor. D) antagonist. E) origin.

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63. What type of receptor detects muscle length?
    1. Golgi tendon organ
    2. ryanodine
    3. DHP
    4. nociceptor
    5. muscle spindle
64. What is an annulospiral ending?
    1. a structure in the cochlea that contains hair cells
    2. sensory endings in the Golgi tendon organ that detect muscle tension
    3. a structure in the semicircular canals that contains hair cells
    4. sensory endings in the muscle spindle that detect muscle length
    5. a structure in the utricle that contains hair cells
65. What type of efferent neuron innervates intrafusal muscle fibers?
    1. type Ia
    2. type Ib
    3. type II
    4. alpha motor neurons
    5. gamma motor neurons
66. Which of the following statements is TRUE regarding activation of alpha and gamma motor neurons?
    1. Gamma motor neurons are activated before alpha motor neurons.
    2. During light activity, gamma motor neurons are activated first; during heavy activity, alpha motor neurons are activated first.
    3. Alpha and gamma motor neurons are activated at the same time.
    4. During light activity, alpha motor neurons are activated first; during heavy activity, gamma motor neurons are activated first.
    5. Alpha motor neurons are activated before gamma motor neurons.
67. Which of the following is the correct order of muscle fiber recruitment, from first to last?
    1. slow oxidative : fast oxidative : fast glycolytic
    2. fast glycolytic : slow oxidative : fast oxidative
    3. slow oxidative : fast glycolytic : fast oxidative
    4. fast glycolytic : fast oxidative : slow oxidative
    5. fast oxidative : fast glycolytic : slow oxidative

68. Which of the following muscle types has the slowest contraction time?
    1. smooth muscle
    2. slow oxidative skeletal muscle
    3. fast glycolytic skeletal muscle
    4. fast oxidative skeletal muscle
    5. cardiac muscle

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69. Which of the following mechanisms does NOT account for the decrease in force development by muscle cells during sustained force development?
    1. Compression of muscle during contraction can reduce blood flow to the muscle.
    2. Glycolytic fibers produce lactic acid and inhibit enzyme activity with their hydrogen ion.
    3. Oxidative fibers can be depleted of glycogen, their primary energy source.
    4. The crossbridges can become resistant to ATP.
    5. Repeated action potentials along the same neuron can lead to neuromuscular fatigue.
70. Which of the following is NOT an adaptation of skeletal muscle that would be observed in response to aerobic training?
    1. an increase in capillary density
    2. an increase in the number of oxidative fibers
    3. an increase in the concentration of oxidative enzymes
    4. an increase in the diameter of the skeletal muscle fibers
    5. an increase in mitochondrial density
71. Where are gap junctions commonly found?
    1. single-unit smooth muscle only
    2. multi-unit smooth muscle only
    3. cardiac muscle only
    4. both single-unit smooth muscle and cardiac muscle
    5. both single-unit and multi-unit smooth muscle
72. Which of the following is true of ALL muscle types?
    1. They contract by using the sliding filament mechanism and crossbridge cycling.
    2. Recruitment increases the strength of contraction.
    3. They contain T tubules.
    4. They are striated.
    5. They contain calmodulin.
73. In smooth muscle, calcium triggers contraction by binding to what protein?
    1. myosin light chain kinase
    2. calmodulin
    3. DHP receptors
    4. myosin light chain
    5. troponin
74. Calcium binding to calmodulin causes phosphorylation by myosin light chain kinase of what protein in what type of muscle?
    1. troponin in skeletal and cardiac muscle only
    2. troponin in smooth muscle only
    3. actin in cardiac and smooth muscle
    4. actin in smooth muscle only
    5. myosin in smooth muscle only

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75. Which of the following adaptations does NOT generally occur with aerobic exercise?
    1. an increase in the number of myofibrils per muscle fiber

75. 2. an increase in the number of mitochondria per muscle fiber
    3. an increase in the blood supply to the muscles
    4. an increase in the aerobic capacity of muscle
    5. a conversion of fast glycolytic fibers to fast oxidative fibers
76. The interaction between actin and myosin in smooth muscle requires
    1. that the calcium-calmodulin complex directly phosphorylates myosin light chain, allowing myosin to bind to actin.
    2. the interaction between calcium and troponin to expose the myosin binding site on the actin molecule.
    3. the activation of troponin, which stimulates myosin light-chain kinase to phosphorylate myosin light chain, allowing myosin to bind with actin.
    4. the tropomyosin must be moved out of the way by troponin before myosin can bind to actin.
    5. that the calcium-calmodulin complex activates myosin light-chain kinase, which phosphorylates myosin thereby allowing it to bind with actin.

77. What is the source of variability in the response of smooth muscle cells from different organs to autonomic nervous activity (some relax to sympathetic nervous output while others contract)?
    1. the duration of neurotransmitter release from the autonomic neurons
    2. the amount of neurotransmitter released into the synaptic cleft
    3. the presynaptic modulation of the autonomic neurons
    4. the type of receptor present on the effector organ
    5. the neurotransmitter released by the autonomic nervous system
78. Which of the following could cause a pacemaker potential?
    1. spontaneous opening of chloride channels
    2. spontaneous closing of calcium channels
    3. spontaneous opening of sodium channels
    4. spontaneous opening of potassium channels
    5. All of the answers are correct.
79. Which of the following stores calcium to be released for muscle contraction?
    1. sarcoplasmic reticulum
    2. tendons
    3. motor end plate
    4. sarcomeres
    5. actin and myosin

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80. Which of the following transmits action potentials to the interior of the muscle cell to trigger calcium release?
    1. sarcomeres
    2. motor end plate
    3. sarcoplasmic reticulum
    4. actin and myosin
    5. tendons
81. Which of the following generates the mechanical force of a muscle through crossbridge cycling?
    1. sarcomeres
    2. actin and myosin
    3. tendons
    4. sarcoplasmic reticulum
    5. motor end plate
82. Which of the following attaches muscle to bone?
    1. actin and myosin
    2. tendons
    3. sarcomeres

82. 4. motor end plate
    5. sarcoplasmic reticulum
83. What is the functional unit of skeletal muscle?
    1. motor end plate
    2. sarcoplasmic reticulum
    3. sarcomeres
    4. actin and myosin
    5. tendons
84. Which of the following contains ryanodine receptors?
    1. tendons
    2. actin and myosin
    3. motor end plate
    4. sarcoplasmic reticulum
    5. sarcomeres
85. Which of the following contains DHP receptors?
    1. motor end plate
    2. transverse tubules
    3. sarcomeres
    4. sarcoplasmic reticulum
    5. tendons  15
86. Which of the following contains nicotinic cholinergic receptors?
    1. motor end plate
    2. actin and myosin
    3. sarcomeres
    4. tendons
    5. sarcoplasmic reticulum
87. Which of the following extends the length of the thick filaments?
    1. Z line B) I band C) H zone D) M line E) A band
88. What region of thick filaments has no overlap with thin filaments?
    1. M line B) Z line C) H zone D) A band E) I band
89. What is the region of thin filaments that has no overlap with thick filaments called?
    1. M line B) A band C) H zone D) Z line E) I band
90. What anchors thin filaments together?
    1. I band B) A band C) H zone D) Z line E) M line
91. What anchors thick filaments together?
    1. A band B) Z line C) I band D) M line E) H zone
92. Which of the following appears as light bands under the microscope?
    1. H zone B) Z line C) A band D) I band E) M line
93. Which of the following appears as dark bands under the microscope?
    1. A band B) I band C) Z line D) H zone E) M line
94. Which protein binds calcium in smooth muscle cells?
    1. troponin
    2. myosin light-chain kinase

1. 3. tropomyosin
   4. titin
   5. calmodulin

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95. What binds calcium in skeletal muscle cells?
    1. titin
    2. calmodulin
    3. myosin light-chain kinase
    4. troponin
    5. tropomyosin
96. What binds calcium in cardiac muscle cells?
    1. calmodulin
    2. myosin light-chain kinase
    3. titin
    4. troponin
    5. tropomyosin
97. What are the elastic fibers that anchor thick filaments in place?
    1. tropomyosin
    2. myosin light-chain kinase
    3. calmodulin
    4. troponin
    5. titin
98. What is the enzyme that modulates the ability of myosin to bind actin in smooth muscle?
    1. tropomyosin
    2. calmodulin
    3. myosin light-chain kinase
    4. titin
    5. troponin
99. Which type of skeletal muscle fiber contains a high concentration of mitochondria?
    1. fermentative
    2. oxidative
    3. glycolytic
    4. fast
    5. slow
100. Which type of skeletal muscle fiber contains high shortening velocities?

1. glycolytic
2. oxidative
3. fermentative
4. slow
5. fast  17

101. Which type of skeletal muscle fiber catalyzes hydrolysis of ATP slowly?

1. oxidative
2. fast
3. fermentative
4. slow
5. glycolytic

102. Which type of skeletal muscle fiber fatigues rapidly?

A) oxidative B) fast C) slow D) isotonic E) glycolytic

103. Which type of skeletal muscle fiber contains myoglobin?

1. slow
2. fast
3. glycolytic
4. oxidative
5. fermentative

104. Which type of skeletal muscle fiber has most of its energy come from substrate-level phosphorylation?

1. fast
2. fermentative
3. slow
4. oxidative
5. glycolytic

105. Which type of skeletal muscle fiber is white muscle?

1. fast
2. glycolytic
3. fermentative
4. oxidative
5. slow

106. Which muscle type contains actin and myosin?

1. smooth muscle only (single-unit or multi-unit)
2. smooth and cardiac muscle only
3. skeletal and smooth muscle only
4. skeletal, smooth, and cardiac muscle
5. skeletal muscle only

18

107. Which muscle type contracts by the sliding-filament mechanism?

1. skeletal, smooth, and cardiac muscle
2. smooth muscle only (single-unit or multi-unit)
3. skeletal and smooth muscle only
4. skeletal muscle only
5. smooth and cardiac muscle only

108. Where does calcium bind to troponin?

1. skeletal and smooth muscle only
2. smooth muscle only (single-unit or multi-unit)
3. skeletal muscle only
4. smooth and cardiac muscle only
5. skeletal and cardiac muscle only

109. Calcium binds to calmodulin where?

1. skeletal, smooth, and cardiac muscle
2. smooth muscle only (single-unit or multi-unit)
3. smooth and cardiac muscle only
4. skeletal muscle only
5. skeletal and smooth muscle only

110. Some muscle cells have pacemaker activity. These include

1. skeletal muscle only.
2. smooth muscle only (single-unit or multi-unit).
3. skeletal, smooth, and cardiac muscle.

4. skeletal and smooth muscle only.
5. smooth and cardiac muscle only.

111. Which muscles are innervated by autonomic nervous system?

1. smooth and cardiac muscle only
2. skeletal, smooth, and cardiac muscle
3. smooth muscle only (single-unit or multi-unit)
4. skeletal and smooth muscle only
5. skeletal muscle only

112. Gap junctions are present between which cells?

1. smooth and cardiac muscle only
2. skeletal and smooth muscle only
3. skeletal muscle only
4. smooth muscle only (single-unit or multi-unit)
5. skeletal, smooth, and cardiac muscle

19

113. Calcium for contraction comes entirely from the sarcoplasmic reticulum in which of the following?

1. skeletal muscle only
2. skeletal and smooth muscle only
3. skeletal, smooth, and cardiac muscle
4. smooth and cardiac muscle only
5. smooth muscle only (single-unit or multi-unit)

114. In which muscle type do thick and thin filaments organize into sarcomeres?

1. smooth and cardiac muscle only
2. skeletal and cardiac muscle only
3. skeletal muscle only
4. skeletal and smooth muscle only
5. smooth muscle only (single-unit or multi-unit)

Figure 12.1

115. What is the structure indicated by the number 1 in Figure 12.1 and what is its functional significance

1. M line : where the tails of the myosin molecules are bound to one another
2. H zone : area of myosin not overlapped by actin
3. sarcomere : the functional unit of muscle contraction whose length is changed as a muscle shortens and lengthens
4. A band : length of myosin attached to an M line
5. Z line : anchors the thin filaments together

116. What is the structure indicated by the number 2 in Figure 12.1 and what is its functional significance?

1. M line : where the tails of the myosin molecules are bound to one another
2. Z line : anchors the thin filaments together
3. H zone : area of myosin not overlapped by actin
4. sarcomere : the functional unit of muscle contraction whose length is changed as a muscle shortens and lengthens
5. A band : length of myosin attached to an M line

20

117. What is the structure indicated by the number 3 in Figure 12.1 and what is its functional significance?

1. A band : length of myosin attached to an M line
2. H zone : area of myosin not overlapped by actin
3. Z line : anchors the thin filaments together
4. sarcomere : the functional unit of muscle contraction whose length is changed as a muscle shortens and lengthens

5. M line : where the tails of the myosin molecules are bound to one another

118. What is the structure indicated by the number 4 in Figure 12.1 and what is its functional significance?

1. A band : length of myosin attached to an M line
2. H zone : area of myosin not overlapped by actin
3. M line : where the tails of the myosin molecules are bound to one another
4. sarcomere : the functional unit of muscle contraction whose length is changed as a muscle shortens and lengthens
5. Z line : anchors the thin filaments together

119. What is the structure indicated by the number 5 in Figure 12.1 and what its functional significance?

1. H zone : area of myosin not overlapped by actin
2. M line : where the tails of the myosin molecules are bound to one another
3. A band : length of myosin attached to an M line
4. Z line : anchors the thin filaments together
5. sarcomere : the functional unit of muscle contraction whose length is changed as a muscle shortens and lengthens

120. What is the structure indicated by the number 6 in Figure 12.1 and what is its functional significance?

1. I band : area of actin not having a crossbridge
2. sarcomere : the functional unit of muscle contraction whose length is changed as a muscle shortens and lengthens
3. Z line : anchors the thin filaments together
4. A band : length of myosin attached to an M line
5. H zone : area of myosin not overlapped by actin

121. Which structure(s) in Figure 12.1 would be altered by muscle shortening? A) 1, 2, and 4 B) 2, 3, and 6 C) 3, 5, and 6 D) 1, 3, and 5 E) 4, 5, and 6
122. The continuation of the sarcolemma that penetrates the interior of the muscle fiber and thereby facilitates the release of calcium from the sarcoplasmic reticulum is called what?

1. transverse tubule
2. actin
3. tropomyosin
4. sarcoplasmic reticulum
5. troponin  21

123. What is the protein component of the thin filament that blocks the myosin-binding site on the actin monomer?

1. tropomyosin
2. troponin
3. sarcoplasmic reticulum
4. actin
5. transverse tubule

124. Troponin is a complex of three proteins that bind to tropomyosin, calcium, and

1. tropomyosin.
2. troponin.
3. sarcoplasmic reticulum.
4. actin.
5. transverse tubule.

125. Calcium is stored in what region of skeletal muscle cells?

1. troponin
2. transverse tubule

3. actin
4. tropomyosin
5. sarcoplasmic reticulum

126. The three proteins found to make up the thin filaments are actin, tropomyosin, and

1. actin.
2. transverse tubule.
3. tropomyosin.
4. troponin.
5. sarcoplasmic reticulum.

127. Heavy intensity exercise generates what byproduct that contributes to fatigue?

1. pyruvic acid
2. lactic acid
3. glycogen
4. CO2
5. fatty acids

128. The time between the occurrence of an action potential in skeletal muscle and the onset of tension is called what?

1. latent period
2. synaptic delay
3. relative refractory period
4. absolute refractory period
5. reticence  22

129. Mechanisms whereby force of skeletal muscle fibers can be altered include all of the following EXCEPT

1. fiber length.
2. conversion of myosin ATPase type.
3. recruitment.
4. fiber diameter (sarcomeres in parallel).
5. frequency of stimulation (summation).

130. The two types of sensory endings found in muscle spindles are the annulospiral endings and

1. Ruffini's corpuscle.
2. Pacinian corpuscle.
3. Merkel's disks.
4. flower-spray endings.
5. free endings.

131. What type of motor neuron innervates intrafusal muscle fibers?

A) epsilon B) delta C) alpha D) gamma E) beta

132. What is the antagonistic muscle to the triceps?

1. brachialis
2. biceps
3. quadriceps
4. coracobrachialis
5. posterior deltoid

133. What are the three types of muscle fibers that are found in all skeletal muscles?

1. slow oxidative, fast oxidative, and slow glycolytic
2. fast oxidative, slow glycolytic, and fast glycolytic
3. fast oxidative, fast oxidative, and fast glycolytic
4. slow oxidative, fast oxidative, and fast glycolytic

5. slow oxidative, slow glycolytic, and fast glycolytic

134. Postural muscles of the legs and back tend to have a high proportion of what fiber type?

1. slow glycolytic
2. fast glycolytic
3. fast oxidative
4. slow oxidative
5. fast and slow glycolytic

23

135. In smooth muscle, calcium binds to calmodulin and then activates the enzyme

1. adenylate cyclase.
2. calmodulin ATPase.
3. tyrosine kinase.
4. myosin light-chain phosphatase.
5. myosin light-chain kinase.

136. The decreased ability of a muscle to maintain a constant force of contraction during repetitive stimulation is called what?

1. tetanus
2. treppe
3. fatigue
4. O2 depletion
5. wasting

137. In smooth muscle, the structures analogous to Z lines in skeletal muscle are called

1. MLCK.
2. dense bodies.
3. intercalated disks.
4. S lines.
5. gap junctions.

138. Intercalated disks contain what type of special junctions?

1. tight junctions only
2. desmosomes
3. gap junctions only
4. both gap junctions and tight junctions
5. hemidesmosomes

139. Force development by muscle cells requires an interaction between actin and myosin. Describe the proteins

involved in the development of force through the process of the sliding-filament theory, including crossbridge cycling.

140. In order for skeletal muscle to develop force, a muscle cell must be able to convert the action potential generated at a neuromuscular junction into crossbridge cycling. Describe the process of

excitation-contraction coupling in skeletal muscle, including all of the important ion channels and the structures involved in this process.

141. Energy in the form of ATP is essential to the contractile process. Describe the cellular sources of energy for skeletal muscle fibers and how those energy sources play a role maintaining muscle activity at low- and

high-intensities of activity.

142. While muscle cells respond in an all-or-nothing manner to a single action potential, the extent of force that they generate can be modified by a number of factors. Describe the mechanisms whereby individual skeletal muscle cells can modify force development.

143. Irrespective of an individual muscle cell's ability to regulate the amount of force developed by that cell, the force generated by a skeletal muscle is also controlled at the whole muscle level. Describe the mechanism whereby force of a whole muscle can be modified, including a discussion on motor units.