ZOOL. 251 EXAM QUESTIONS - MUSCULAR

[1-9] [10-19] [20-29] [30-39] [40-49] [50-59] [60-69] [70-79] [80-89] [90-99] [100-109] [110-119] [120-129] [130-139]

[BATCH 961]

[BATCH 981]

[BATCH 971]

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BATCH 961

[1-9] [10-19] [20-29] [30-39] [40-49] [50-59] [60-69] [70-79]

1-9

1. The "knee jerk" monosynaptic reflex is an example of a:
   1. extensor thrust reflex.
   2. stress reflex.
   3. cross extensor reflex.
   4. stretch reflex. [top]

2. What type of neuron innervates the intrafusal fibers?
   1. interneurons
   2. alpha motor neurons
   3. delta motor neurons
   4. gamma motor neurons [top]

3. Which of the following is a type of striated muscle?

   1. skeletal muscle 2. cardiac muscle 3. smooth muscle

   1. 1 only
   2. 2 only
   3. 1 and 2
   4. 3 only
   5. all of the above are striated muscle [top]

4. Which of the following is capable of rapid contractions yet is fatigue-resistant?
   1. smooth muscle
   2. skeletal muscle
   3. cardiac muscle
   4. both c and d [top]

5. Which of the following has myofibrils containing sarcomeres?
   1. smooth muscle
   2. skeletal muscle
   3. cardiac muscle
   4. both c and d [top]

6. Acetylcholine the only neurotransmitter that regulates:
   1. smooth muscle
   2. skeletal muscle
   3. cardiac muscle
   4. both c and d [top]

7. Alpha motor neurons control the contraction of:
   1. smooth muscle
   2. skeletal muscle
   3. cardiac muscle
   4. both c and d [top]

8. Which of the following has a slow, sustained contraction?
   1. smooth muscle
   2. skeletal muscle
   3. cardiac muscle
   4. both c and d [top]

9. This type of muscle is found in the walls of the digestive tract:
   1. smooth muscle
   2. skeletal muscle
   3. cardiac muscle
   4. both c and d [top]

10-19

10. Which of the following has intercalated discs?
    1. smooth muscle
    2. skeletal muscle
    3. cardiac muscle
    4. both a and c
    5. both b and c [top]

11. Which of the following is not a function of muscle?
    1. producing movement
    2. stabilizing joints
    3. dissipate heat
    4. guard entrances and exits [top]

12. Which of the following is composed of loose connective tissue?
    1. epimysium
    2. perimysium
    3. endomysium [top]

13. A flat, ribbon-like, attachment of muscle to bone is termed a...
    1. tendon
    2. aponeurosis
    3. fleshy attachment
    4. direct attachment [top]

14. Muscle cells contain a glucose-storage molecule termed....
    1. myoglobin
    2. glycogen
    3. sarcolemma
    4. myoblast [top]

15. Which of the following should not affect the strength or force of skeletal muscle contraction?
    1. the number of muscle fibers contracting
    2. the degree of muscle stretch
    3. the stretch on the series-elastic elements
    4. a and c are correct
    5. All of these affect the strength of contraction [top]

16. Muscle tissue has all the following properties except:
    1. excitability.
    2. contractility.
    3. extensibility.
    4. rigidity. [top]

17. Which of the following is a result of anaerobic or strength exercise?
    1. increase in number of muscle cells
    2. increase in the size of muscle cells
    3. decrease in the number of mitochondria
    4. decrease in the number of myofibrils within the muscle cells [top]

18. Calcium can be said to be the "trigger" for skeletal muscle contraction because it causes:

1. a conformational change in troponin. 2. an action potential on the sarcolemma. 3. myosin conformational changes.

1. 1 only
2. 1 and 3
3. 3 only
4. 1 and 2 [top]

19. Myoglobin:
    1. breaks down glycogen.
    2. is a protein involved in the direct phosphorylation of ADP.
    3. holds a reserve supply of oxygen in muscle cells.
    4. produces the end-plate potential. [top] [10]

20-29

20. An elaborate network of membranes in skeletal muscle cells that functions in calcium storage and release is the:
    1. sarcoplasmic reticulum.
    2. endoplasmic reticulum.
    3. intermediate filament network.
    4. myofibrilar network. [top]

21. A sarcomere is:

1. the simplest functional unit of skeletal muscle. 2. the area between two Z lines. 3. the H zone.

1. 1
2. 2
3. 3
4. 1 and 2 are both correct. [top]

22. Immediately following the arrival of the stimulus at a skeletal muscle cell, there is a short period before the contraction starts, during which calcium levels rise to a critical level to trigger contraction. This period is called the:

1. contraction period
2. relaxation period
3. latent period
4. refractory period [top]

23. Creatine phosphate functions in the muscle cell by:
    1. forming a temporary chemical compound with myosin.
    2. forming a chemical compound with actin.
    3. storing energy which will be transferred to ADP to re-synthesize ATP as needed.
    4. inducing a conformational change in the myofilaments. [top]

24. Which of the following is composed of myosin?
    1. thick filaments
    2. thin filaments
    3. all myofilaments
    4. Z line
    5. a and d are correct [top]

25. Where are the active sites found to which myosin cross bridges (myosin heads) attach during muscle contraction?
    1. myosin filaments
    2. actin filaments
    3. Z line
    4. thick filaments [top]

26. Which of these surrounds a fascicle of muscle cells?
    1. perimysium
    2. endomysium
    3. epimysium [top]

27. The sliding filament model of contraction involves:
    1. the Z lines sliding over the myofilaments.
    2. the shortening of thick filaments so that thin filaments slide past.
    3. actin and myosin proteins shortening.
    4. actin and myosin sliding past each other but they themselves do not shorten. [top]

28. Theoretically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped:
    1. maximum force production would result since the muscle has a maximum range of travel.
    2. no muscle tension could be generated.
    3. cross bridge attachment would be optimum because of all the free binding sites on actin.
    4. ATP consumption would increase since the sarcomere is "trying" to contract. [top]

29. In this type of muscle contraction, the muscle increases length:
    1. concentric contraction
    2. eccentric contraction
    3. isometric contraction [top] [20]

30-39

30. In this type of muscle contraction, tension or force is generated but the sarcomeres do not change length:
    1. concentric contraction
    2. eccentric contraction
    3. isometric contraction

Match the following:

38. Which of the following is the most important way to increase the strength of contraction by a muscle like a biceps?
    1. load up the series elastic elements
    2. temporal summation
    3. motor unit recruitment
    4. optimize the degree of muscle stretch [top]

39. In addition to pulling on bones to cause movement, muscles also:
    1. maintain posture.
    2. stabilize joints.
    3. generate heat activity.
    4. b and c.
    5. All of these. [top] [30]

40-49

40. Which of the following acts as an ATPase during the contraction cycle of muscle?
    1. actin molecules
    2. troponin molecules
    3. tropomyosin
    4. myosin head (cross-bridge)
    5. myosin tail [top]

41. Which of the following binds calcium during the contraction cycle of muscle?
    1. actin molecules
    2. troponin molecules
    3. tropomyosin
    4. myosin head (cross-bridge)
    5. myosin tail [top]

42. Calcium ions are pumped into the sarcoplasmic reticulum during the _________ phase of muscle contraction.
    1. latent
    2. contraction
    3. recovery
    4. relaxation [top]

43. During anaerobic glycolysis:
    1. ATP is produced
    2. pyruvic acid is produced
    3. lactic acid is produced
    4. a and b are correct
    5. all are correct [top]

44. A muscle that is stimulated so frequently that the relaxation phase is completely eliminated is said to exhibit:
    1. complete tetanus
    2. treppe
    3. wave summation
    4. recruitment [top]

45. When lactic acid levels increase, a muscle will display:
    1. increased strength of contraction
    2. fatigue
    3. treppe
    4. tetanus
    5. atrophy [top]

46. When myosin binds to actin,
    1. ATP is hydrolyzed
    2. ATP binds
    3. ATP is released
    4. the myosin head goes from high energy state to low energy state (power stroke)
    5. actin goes from high energy state to low energy state (power stroke) [top]

47. Which of the following would have the smallest motor units?
    1. large muscles of the upper arm
    2. postural muscles of the back
    3. muscles that control the fingers
    4. muscles of the calf
    5. a and b are correct [top]

48. At the neuromuscular junction, which of the following is the site where the neurotransmitter is stored?
    1. synaptic cleft
    2. synaptic vesicles
    3. motor end plate [top]

49. Which of the following statements is true concerning motor neurons?
    1. There are several motor neurons for each muscle fiber.
    2. The number of motor neurons associated with each muscle fiber depends on the location of the muscle.
    3. The smaller the motor unit the more precise the muscle movement can be.
    4. Muscle contraction is not absolutely dependent on its nerve supply.
    5. a and d are correct [top] [40]

50-59

50. The functional role of the T tubules is to:
    1. stabilize the G and F actin.
    2. quickly spread action potentials throughout the muscle cell.
    3. hold cross bridges in place in a resting muscle.
    4. synthesize ATP to provide energy for muscle contraction.
    5. release calcium stored in the T tubules into the cell’s cytoplasm [top]

51. Athletes sometimes complain of "oxygen debt," a condition that results when insufficient oxygen is available to completely break down pyruvic acid. As a result the pyruvic acid is converted to:
    1. acetic acid.
    2. stearic acid.
    3. hydrochloric acid.
    4. lactic acid. [top]

52. The mechanism of contraction in smooth muscle parallels that of skeletal muscle in the following ways:
    1. Actin and myosin interact by the sliding filament mechanism.
    2. One of the triggers for contraction is a rise in intracellular calcium.
    3. ATP provides the energy for the sliding process.
    4. All of these are correct. [top]

53. At the neuromuscular junction, which of the following breaks down the neurotransmitter?
    1. acetylcholine
    2. synaptic vesicles
    3. motor end plate
    4. acetylcholinesterase [top]

Match the following:

According to the sliding filament model of muscle contraction, during a muscle contraction the:

61. Explain rigor mortis at the molecular level. Be as complete as possible. [top]

62. Which of the following should not affect the strength or force of skeletal muscle contraction?
    1. the number of muscle fibers contracting
    2. the degree of muscle stretch
    3. the stretch on the series-elastic elements
    4. All of these affect the strength of contraction. [top]

64. Which of the following is not a usual result of exercise?
    1. increase in efficiency of the respiratory system
    2. increase in the number of muscle cells
    3. increase in the efficiency of the circulatory system
    4. increase in the number of myofibrils within the muscle cells [top]

65. In muscle contraction, calcium apparently acts to:
    1. increase the action potential transmitted along the sarcolemma.
    2. release the inhibition on Z lines.
    3. remove the blocking action of tropomyosin.
    4. cause ATP binding to actin. [top]

66. Which of these surrounds the individual muscle cell?
    1. perimysium
    2. endomysium
    3. epimysium
    4. fascicle [top]

67. Which of the following is most correct?

1. Muscle length and tension remain constant during isotonic contraction.

2. Myofilaments are sliding during isotonic contraction.

3. The A band does not shorten during isotonic contraction.

1. 1
2. 2
3. 3
4. Both 2 and 3 are correct. [top]

68. Which of the following would act as a stimulus to initiate a smooth muscle contraction?
    1. hormonal activity
    2. neurotransmitters
    3. a change in the pH of a muscle
    4. All of these.
    5. none to the above [top]

69. Which of the following statements is true concerning motor neurons?
    1. There are several motor neurons for each muscle fiber.
    2. The number of motor neurons associated with each muscle fiber depends on the location of the muscle.
    3. The smaller the motor unit the more precise the muscle movement can be.
    4. Muscle contraction is not absolutely dependent on its nerve supply. [top] [50] [60]

70-79

70. Three discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. Which of the following athletic endeavors best represents the use of red fibers?
    1. a sprint by an Olympic runner
    2. the Boston marathon
    3. a game of singles in tennis
    4. All of these. [top]

80-89

71. Which of the following has a fast-acting myosin ATPase and high levels of glycogen?
    1. red fibers
    2. intermediate fibers
    3. white fibers [top]

72. Of the following muscle types, which has only one nucleus, no sarcomeres, and no gap junctions?
    1. visceral smooth muscle
    2. cardiac muscle
    3. multiunit smooth muscle
    4. skeletal muscle [top]

73. The cells of single-unit visceral muscle:
    1. contract as a unit rhythmically.
    2. are electrically coupled to one another by gap junctions.
    3. exhibit spontaneous action potentials.
    4. all of the above [top]

74. An excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle is:
    1. cholinesterase.
    2. norepinephrine.
    3. acetylcholine.
    4. gamma aminobutyric acid (GABA). [top]

75. Smooth muscle is characterized by all the following except:
    1. it stimulated to contract several ways.
    2. there are no thick filaments than thin filaments.
    3. there are no sarcomeres.
    4. there are noncontractile intermediate filaments that attach to dense bodies within the cell. [top]

76. Calcium is required for acetylcholine release from the axon because it:
    1. causes electrical activity to travel down the axon.
    2. binds to the acetylcholine receptor on the surface of the muscle.
    3. causes electrical activity to travel across the surface of the muscle cell.
    4. signals the release of acetylcholine from synaptic vesicles.
    5. calcium is not required [top]

77. How is the contraction of smooth muscle terminated? [top]

78. Which of the following should not affect the strength or force of skeletal muscle contraction?
    1. the number of muscle fibers contracting
    2. the degree of muscle stretch
    3. the stretch on the series-elastic elements
    4. All of these affect the strength of contraction. [top]

79. The contraction of which of the following types of muscle would be unaffected by a drug that blocked the movement of calcium into the muscle cell?
    1. skeletal
    2. cardiac
    3. smooth
    4. a and b
    5. b and c [top] [50] [70]

80-89

80. In muscle contraction, calcium apparently acts to:
    1. increase the action potential transmitted along the sarcolemma.
    2. release the inhibition on Z lines.
    3. remove the blocking action of tropomyosin.
    4. cause ATP binding to actin. [top]

BATCH 981

[80-89]

81. Explain the role of troponin, tropomyosin, and calcium in muscle contraction [top]

82. All of the following are functions of muscle EXCEPT:

1. generate heat
2. stabilize joints
3. maintain posture
4. produce movement by shortening
5. all the above are functions [top]

83. The dense layer of collagen fibers that surrounds an entire skeletal muscle is the
    1. tendon
    2. epimysium
    3. endomysium
    4. perimysium
    5. fascicle [top]

84. Muscle fibers differ from "typical cells" in that muscle fibers
    1. have many nuclei
    2. lack a cell membrane
    3. are very small
    4. lack mitochondria
    5. (b and c) [top]

85. The ___________________ is an elaborate system of membranous tubes that wraps around each myofibril and functions to store calcium
    1. T-tubule system
    2. sarcoplasmic reticulum
    3. sarcomere
    4. sarcolemma
    5. sarcoplasm [top]

86. In order to get a long-lasting contraction
    1. the frequency of action potentials should be low
    2. calcium levels must remain elevated in the sarcoplasm
    3. the sarcoplasmic reticulum must quickly restore calcium
    4. acetylcholine must be quickly removed from the NMJ
    5. elastic fibers must be inactivated [top]

87. The following events occur during a muscle contraction. The correct sequence of these events is:

1-myosin heads bind to actin 2-myosin heads split a phosphate group off ATP

3-calcium concentrations rise dramatically in the cytoplasm 4-myosin heads pivot and pull on actin

5-myosin head binds ATP and detaches from actin 6-T-tubules depolarize and change permeability of sarcoplasmic reticulum

1. 4,5,6,1,2,3
2. 5,4,1,2,6,3
3. 6,1,2,5,4,3
4. 6,3,1,4,2,5
5. 5,2,6,3,1,4 [top]

88. A muscle that is stimulated so frequently that the relaxation phase is completely eliminated is said to exhibit
    1. incomplete tetanus
    2. complete tetanus
    3. treppe
    4. wave summation
    5. recruitment [top]

89. The nervous system can precisely control the amount of tension our muscles generate by
    1. activating motor units of different sizes
    2. activating different numbers of motor units
    3. altering the frequency of action potentials down the motor neurons
    4. (a and c)
    5. (a,b, and c) [top] [50] [80]

90-99

90. During relaxation, muscles return to their original length because of all of the following EXCEPT
    1. actin and myosin actively pushing away from one another
    2. antagonistic muscle contraction
    3. gravity
    4. elastic forces
    5. recoil of the epi-, peri-, and endomysium [top]

91. Choose the fuel that combines with adenosine diphosphate (ADP) to regenerate ATP. There’s only enough of this fuel within muscles to support about 15 seconds:
    1. of intense contraction
    2. AMP
    3. creatine phosphate
    4. glucose
    5. lactic acid
    6. glycogen [top]

92. This disease is caused by a defective protein that causes calcium channels in the sarcoplasmic reticulum to remain open too long
    1. amyasthenia gravis
    2. botulism
    3. Duchenne’s muscular dystrophy
    4. trichinosis
    5. multiple sclerosis [top]

BATCH 971

[100-109] [110-119] [120-129] [130-139]

93. The contractile elements of skeletal muscle fibers are actually just a modified form of a basic cell component. What is the name applied to this component?
    1. microtubules
    2. microfilaments
    3. centrioles
    4. intermediate filaments
    5. none of the above [top]

94. The primary role of the sarcoplasmic reticulum is:
    1. calcium regulation
    2. impulse conduction
    3. glycogen storage
    4. protein synthesis
    5. none of the above [top]

95. Arrange the following in order of increasing size:

1-myofibril; 2-fiber; 3-myofilament; 4-fascicle; 5-muscle.

1. c, b, a, d, e
2. c, a, d, b, e
3. c, d, b, a, e
4. c, a, b, d, e
5. none of the above [top]

96. Visceral smooth muscle is similar to skeletal muscle in which of the following aspects?
    1. multiple nuclei/cell
    2. rapid contraction
    3. nerve input required for contraction
    4. myofilament sliding produces contraction
    5. none of the above [top]

97. The unique skeletal muscle adaptation that allows almost instantaneous activation of all the myofibrils within an individual muscle fiber is:
    1. sarcoplasmic reticulum
    2. sarcolemma
    3. t-tubule system
    4. sarcoplasm
    5. none of the above [top]

98. The primary result of ACh binding to nicotinic cholinergic receptors at the neuromuscular junction is to:
    1. open gap junctions
    2. open chemically-gated Na channels
    3. open voltage-gated Na channels
    4. open voltage gated Ca channels
    5. none of the above [top]

99. Once an action potential reaches the axon terminus at a neuromuscular junction, the event that is essential for neurotransmitter release is:
    1. Na channels close
    2. Ca channels open
    3. K channels close
    4. ATP is liberated
    5. none of the above [top] [50] [90]

100-109

100. The primary mechanism of action for which of the following includes binding or blockade of nicotinic ACh receptors in the neuromuscular junction?
     1. tetanus
     2. rigor mortis
     3. myasthenia gravis
     4. curare
     5. none of the above [top]

101. The presence of striated fibers, many mitochondria, multiple nuclei, and T-tubules would best characterize which type of muscle?
     1. cardiac
     2. smooth
     3. skeletal
     4. all of the above
     5. none of the above [top]

102. According to the sliding filament theory, skeletal muscle contraction depends upon sarcoplasmic reticulum Ca release and Ca binding by which molecule?
     1. actin
     2. tropomyosin
     3. troponin
     4. myosin
     5. none of the above [top]

103. In a muscle at rest, a section through which portion of a sarcomere would provide a cross-section of both actin and myosin?
     1. I band
     2. H band
     3. Z band
     4. A band
     5. none of the above [top]

104. The thin filament binding sites for myosin are located on which of the following types of molecules?
     1. troponin
     2. tropomyosin
     3. titin
     4. G-actin
     5. none of the above [top]

105. In regard to muscle contraction and sarcomere shortening, which of the following is correct?
     1. A and I bands decrease
     2. A band decreases and I band stays the same
     3. I band decreases and A band stays the same
     4. A band increases and I band decreases
     5. none of the above [top]

106. Which of the following is a function of ATP in the process of skeletal muscle contraction?
     1. resetting of the myosin heads
     2. calcium uptake in the sarcoplasmic reticulum
     3. actin-myosin bridge detachment
     4. all of the above
     5. none of the above [top]

107. The state of sustained muscle contraction or rigor mortis that occurs after death is due to?
     1. absence of Ca
     2. absence of ATP
     3. absence of oxygen
     4. absence of neuromuscular junction activity
     5. none of the above [top]

108. Curare competitively blocks the acetylcholine (ACh) receptor and is occasionally used to relax muscles during surgery. Which of the following treatments might aid in the postoperative recovery from the effects of curare?
     1. botulinus toxin which would block ACh release
     2. neostigmine, an acetylcholine esterase inhibitor
     3. nifedipine, to block Ca channels
     4. tetrodotoxin, to block Na channels
     5. none of the above [top]

109. Which of the following events will not lead to muscle contraction?
     1. depolarization of T-tubules
     2. Ca release from troponin
     3. Ca release by the sarcoplasmic reticulum
     4. depolarization of the sarcolemma
     5. none of the above [top] [50] [100]

110-119

110. Cholinergic receptors found at motor end plates and postganglionic neurons of the autonomic nervous system would be classified as:
     1. adrenergic
     2. nicotinic
     3. muscarinic
     4. histaminergic
     5. none of the above [top]

111. The soft connective tissue layer most closely associated with skeletal muscle fibers is the?
     1. epimysium
     2. deep fascia
     3. endomysium
     4. perimysium
     5. none of the above [top]

112. Which area of the sarcomere contains only actin filaments and is termed the "light band?"
     1. I band
     2. H band
     3. Z band
     4. A band
     5. M line [top]

113. While nicotinic cholinergic receptors are widely dispersed, muscarinic receptors are restricted to where?
     1. neuromuscular junctions
     2. postganglionic autonomic neurons
     3. parasympathetic postganglionic effector sites
     4. all of the above
     5. none of the above [top]

114. The molecule which calcium binds to initiate smooth muscle contraction is:
     1. troponin
     2. calmodulin
     3. tropomyosin
     4. myosin light chain kinase
     5. none of the above [top]

115. In a neuromuscular junction the space between the axon terminal and the muscle sarcolemma is termed:
     1. gap junction
     2. the great divide
     3. synaptic cleft
     4. caveoli
     5. none of the above [top]

116. A molecule that provides a short-term energy storage source for muscle contraction is:
     1. acetylcholine
     2. glucose
     3. creatine phosphate
     4. glycogen
     5. none of the above [top]

117. The ions that flood across the sarcolemma of a muscle cell to initiate an action potential would be?
     1. calcium
     2. potassium
     3. magnesium
     4. sodium
     5. none of the above [top]

118. Dense bodies are important to which of the following processes?
     1. neuron depolarization
     2. smooth muscle contraction
     3. cardiac muscle contraction
     4. skeletal muscle contraction
     5. none of the above [top]

119. A cell characterized by a single nucleus, few mitochondria, and absence of t-tubules and troponin would be which type of muscle cell?
     1. skeletal
     2. multiunit smooth
     3. visceral smooth
     4. cardiac
     5. none of the above [top] [50] [100] [110]

120-129

120. Which of the following is a function of ATP in the process of skeletal muscle contraction?
     1. resetting of the myosin heads
     2. calcium uptake in the sarcoplasmic reticulum
     3. actin-myosin bridge detachment
     4. all of the above
     5. none of the above [top]

121. Which of the following basic cell structures has been modified and/or augmented for a specific purpose in skeletal muscle?
     1. microfilaments
     2. smooth endoplasmic reticulum
     3. plasma membrane
     4. all of the above
     5. none of the above [top]

122. What is a motor unit?
     1. a unipolar neuron and its interneurons
     2. a multipolar neuron and its muscle fibers
     3. a bipolar neuron and its muscle fibers
     4. a multipolar neuron and its interneurons
     5. none of the above [top]

123. The plasma membrane of muscle cells is referred to as the:
     1. neurilemma
     2. axolemma
     3. sarcolemma
     4. endomysium
     5. deep fascia [top]

124. Which of the following statements best describes the events of the sliding filament model of muscle contraction?
     1. the Z lines slide over the myofilaments
     2. both the actin and myosin filaments shorten
     3. the thick filaments shorten so the thin filaments can slide past
     4. the actin and myosin filaments slide past each other without shortening
     5. none of the above [top]

125. The primary factor that leads to muscle fatigue is:
     1. relative deficit in available ATP
     2. relative deficit in available O₂
     3. relative deficit in available Ca
     4. relative deficit in available lactic acid
     5. none of the above [top]

126. The non-muscle cell equivalent of the sarcoplasmic reticulum is:
     1. smooth endoplasmic reticulum
     2. Golgi apparatus
     3. rough endoplasmic reticulum
     4. microtubules
     5. none of the above [top]

127. In skeletal muscle cells the T-tubules are continuous with:
     1. smooth endoplasmic reticulum
     2. sarcolemma
     3. sarcomere
     4. sarcoplasm
     5. none of the above [top]

128. Among the myofilaments and associated proteins, where is the ATP binding site located?
     1. G-actin
     2. troponin
     3. myosin tail
     4. tropomyosin
     5. myosin heads [top]

129. Over stretching of a skeletal muscle decreases contractile force because?
     1. reduces actin-myosin overlap
     2. increases actin-myosin overlap
     3. has no effect on actin-myosin overlap
     4. disconnects actin from the Z-disk
     5. none of the above [top] [50] [100] [120]

130-139

130. Which of the following is an important determinant of skeletal muscle contractile force?
     1. muscle fiber size
     2. stimulus strength
     3. number of motor units activated
     4. 1 and 3
     5. 1, 2 and 3 [top]

131. Which of the following is a unique characteristic of smooth muscle?
     1. sarcomeres
     2. dense bodies
     3. extensive T-tubule system
     4. multinucleate
     5. none of the above [top]

132. The ability of skeletal muscle fibers to store and release large amounts of intracellular Ca is to due to the:
     1. sarcoplasmic reticulum
     2. sarcolemma
     3. T-tubule system
     4. sarcomere
     5. none of the above [top]

133. The "all or none law" tells us that muscle contractile tension is stimulus independent. However there is a stair-step increase in muscle tension when the frequency of stimulation is increased. What is the phenomenon called?
     1. threshold
     2. rigor
     3. treppe
     4. complete tetanus
     5. none of the above [top]

134. An example of a chemically gated ion channel would be:
     1. sodium channels in the sarcolemma
     2. sodium channels in the axolemma
     3. sodium channels associated with ACh receptors in a neuromuscular junction
     4. sodium channels in the sarcoplasmic reticulum
     5. none of the above [top]

135. Where is Ca involved in the process of excitation-contraction coupling?
     1. axon terminal neurotransmitter release
     2. sarcolemma depolarization and action potential generation
     3. initiation of actin-myosin binding
     4. 1 and 3
     5. none of the above [top]

136. The unique protein that accounts for the ability of the sarcoplasmic reticulum to store large amounts of calcium is?
     1. connectin
     2. desmin
     3. calsequestrin
     4. titin
     5. none of the above [top]

137. Which of the following would contribute to improved performance following a "warm-up" period?
     1. general enhancement of enzyme activity
     2. increased Ca availability
     3. "taking-up-slack" in muscle connective tissues
     4. all of the above
     5. none of the above [top]

138. A new poison has been discovered that prevents muscle fibers from responding despite appropriate motor neuron activation. However, the muscle fiber response is intact when stimulated directly. Which of the following three possible mechanisms would explain this effect?
     1. blocks ACh release
     2. blocks ACh binding to the receptor
     3. augments acetylcholinesterase activity
     4. all of the above
     5. none of the above [top] [50] [100] [130]