Anatomy & Physiology: Muscular System Practice Exam Quiz
What is the basic contractile unit of a muscle?
a) Myofilament
b) Sarcomere
c) Myofibril
d) Muscle fiber
Which of the following is a characteristic of smooth muscle?
a) Striated and voluntary
b) Non-striated and involuntary
c) Striated and involuntary
d) Non-striated and voluntary
Which type of muscle tissue is responsible for voluntary movement?
a) Cardiac muscle
b) Skeletal muscle
c) Smooth muscle
d) All muscle tissues
What is the role of calcium ions in muscle contraction?
a) Block the actin binding sites
b) Stimulate ATP production
c) Bind to troponin and expose actin binding sites
d) Break down acetylcholine
Which of the following is NOT a function of the muscular system?
a) Movement of the body
b) Maintenance of posture
c) Production of heat
d) Secretion of hormones
What is the term for the muscle’s ability to respond to stimuli?
a) Contractility
b) Excitability
c) Extensibility
d) Elasticity
Which protein is primarily responsible for muscle contraction?
a) Actin
b) Myosin
c) Tropomyosin
d) Troponin
What is the primary energy source for muscle contractions during short bursts of activity?
a) ATP
b) Glycogen
c) Oxygen
d) Creatine phosphate
Which part of the nervous system stimulates skeletal muscle contraction?
a) Autonomic nervous system
b) Somatic nervous system
c) Central nervous system
d) Peripheral nervous system
What type of muscle contraction involves the muscle lengthening while generating force?
a) Concentric contraction
b) Eccentric contraction
c) Isometric contraction
d) Isotonic contraction
Which muscle is responsible for the movement of the forearm during a bicep curl?
a) Triceps brachii
b) Biceps brachii
c) Deltoid
d) Latissimus dorsi
What is the main characteristic of cardiac muscle?
a) Voluntary and striated
b) Involuntary and non-striated
c) Involuntary and striated
d) Voluntary and non-striated
What structure connects muscles to bones?
a) Ligaments
b) Tendons
c) Cartilage
d) Fascia
What is the term for a muscle’s ability to return to its original shape after contraction?
a) Elasticity
b) Extensibility
c) Excitability
d) Contractility
The “all-or-nothing” principle applies to which of the following?
a) Muscle fibers
b) Muscle groups
c) Tendons
d) Myofibrils
Which of the following is the function of the sarcoplasmic reticulum in muscle cells?
a) Store calcium ions
b) Produce ATP
c) Transmit nerve impulses
d) Synthesize proteins
Which part of the muscle is the main energy reservoir for muscle contraction?
a) Mitochondria
b) Sarcomere
c) Myofibrils
d) Nucleus
What is the role of troponin in muscle contraction?
a) Bind with calcium to uncover actin binding sites
b) Provide energy for muscle contraction
c) Block myosin binding to actin
d) Store calcium ions
Which muscle type is specialized for maintaining posture?
a) Smooth muscle
b) Skeletal muscle
c) Cardiac muscle
d) All muscle types
Which of the following muscles is responsible for the movement of the jaw during chewing?
a) Masseter
b) Temporalis
c) Buccinator
d) Sternocleidomastoid
The term “muscle tone” refers to:
a) The total strength of a muscle
b) The resting tension in a muscle
c) The degree of muscle contraction
d) The speed of muscle contraction
What is the name of the sheath that surrounds a muscle fiber?
a) Endomysium
b) Perimysium
c) Epimysium
d) Fascia
Which of the following describes the structure of a muscle fascicle?
a) A group of muscle fibers surrounded by the endomysium
b) A group of myofibrils surrounded by the perimysium
c) A group of myofilaments surrounded by the epimysium
d) A group of muscle fibers surrounded by the perimysium
Which of the following statements about slow-twitch muscle fibers is true?
a) They are adapted for endurance activities.
b) They contract rapidly and fatigue quickly.
c) They have fewer mitochondria than fast-twitch fibers.
d) They are white in color.
Which muscle action involves a decrease in the angle between two bones?
a) Extension
b) Flexion
c) Abduction
d) Rotation
What is the energy source for prolonged muscle activity in aerobic conditions?
a) Creatine phosphate
b) Glucose
c) Fatty acids
d) ATP
What is the primary neurotransmitter involved in muscle contraction?
a) Dopamine
b) Serotonin
c) Acetylcholine
d) Norepinephrine
Which of the following best describes an isometric contraction?
a) The muscle shortens during contraction
b) The muscle remains at a constant length during contraction
c) The muscle lengthens during contraction
d) The muscle does not contract at all
Which type of muscle fibers is used primarily during short bursts of intense activity?
a) Slow-twitch fibers
b) Fast-twitch fibers
c) Both types of fibers
d) Intermediate fibers
What is the name of the protein that blocks the active sites on actin molecules when the muscle is at rest?
a) Tropomyosin
b) Troponin
c) Myosin
d) Titin
31. Which of the following is the primary function of the myosin heads during muscle contraction?
a) Store calcium ions
b) Bind to actin filaments
c) Release energy for ATP synthesis
d) Activate troponin
32. Which structure is responsible for transmitting action potentials along muscle fibers?
a) Sarcoplasmic reticulum
b) T-tubules
c) Endoplasmic reticulum
d) Myofibrils
33. Which of the following is a primary characteristic of fast-twitch muscle fibers?
a) They fatigue slowly and are used for endurance activities.
b) They contract slowly but provide sustained power.
c) They generate rapid, forceful contractions but fatigue quickly.
d) They contain more myoglobin than slow-twitch fibers.
34. Which muscle is responsible for extending the forearm at the elbow joint?
a) Triceps brachii
b) Biceps brachii
c) Deltoid
d) Pectoralis major
35. Which of the following muscle fibers are rich in mitochondria and myoglobin?
a) Fast-twitch fibers
b) Slow-twitch fibers
c) Intermediate fibers
d) Both fast- and slow-twitch fibers
36. What is the term for a sustained muscle contraction caused by repeated stimulation?
a) Muscle twitch
b) Tetany
c) Fatigue
d) Concentric contraction
37. What happens during muscle relaxation?
a) Myosin heads continue to bind with actin.
b) Calcium ions are released from the sarcoplasmic reticulum.
c) ATP is no longer required.
d) Calcium ions are pumped back into the sarcoplasmic reticulum.
38. Which of the following describes an isotonic contraction?
a) The muscle lengthens but does not generate force.
b) The muscle remains at a constant length while generating force.
c) The muscle shortens while generating force.
d) The muscle does not change length during contraction.
39. Which of the following muscle groups is involved in the action of a “bicep curl”?
a) Quadriceps
b) Hamstrings
c) Biceps brachii and brachialis
d) Triceps brachii and deltoid
40. Which structure in the muscle fiber stores calcium?
a) Mitochondria
b) Sarcoplasmic reticulum
c) T-tubules
d) Myofibrils
41. Which of the following is a characteristic of cardiac muscle tissue?
a) It is multinucleated.
b) It is under voluntary control.
c) It has intercalated discs.
d) It lacks striations.
42. Which of the following muscles is responsible for plantar flexion of the foot?
a) Tibialis anterior
b) Gastrocnemius
c) Biceps femoris
d) Rectus femoris
43. What is the primary source of energy for muscle contraction during long periods of exercise?
a) Glucose
b) Glycogen
c) Fatty acids
d) Creatine phosphate
44. Which of the following is a component of the sliding filament theory?
a) Myosin heads pull actin filaments toward the center of the sarcomere.
b) Actin filaments move away from the center of the sarcomere.
c) The sarcoplasmic reticulum releases potassium ions.
d) Myosin and actin filaments lengthen.
45. Which part of the muscle cell is responsible for the contraction of the muscle?
a) Sarcoplasm
b) Myofibrils
c) Nucleus
d) Mitochondria
46. Which of the following is a major function of smooth muscle?
a) Pump blood
b) Control voluntary movement
c) Move food through the digestive system
d) Provide support for the skeletal system
47. What is the term for a muscle’s ability to stretch without being damaged?
a) Excitability
b) Elasticity
c) Extensibility
d) Contractility
48. Which of the following muscles is responsible for elevating the scapula?
a) Latissimus dorsi
b) Trapezius
c) Pectoralis major
d) Serratus anterior
49. What is the function of the neurotransmitter acetylcholine in muscle contraction?
a) It triggers the release of calcium ions from the sarcoplasmic reticulum.
b) It breaks down ATP for energy.
c) It transmits the action potential across the neuromuscular junction.
d) It initiates the sliding filament mechanism.
50. Which of the following conditions occurs when muscle fibers are deprived of oxygen for an extended period?
a) Muscle twitch
b) Oxygen debt
c) Muscle hypertrophy
d) Rigor mortis
51. Which of the following muscles is primarily responsible for flexing the forearm?
a) Triceps brachii
b) Deltoid
c) Biceps brachii
d) Gluteus maximus
52. What is the name of the connective tissue that surrounds an entire muscle?
a) Endomysium
b) Perimysium
c) Epimysium
d) Fascia
53. Which of the following is responsible for the “strength” of a muscle contraction?
a) The number of fibers contracting
b) The type of muscle fibers
c) The amount of ATP available
d) The frequency of action potentials
54. Which of the following is a function of the muscle spindle?
a) Detect changes in muscle length
b) Stimulate muscle contraction
c) Inhibit action potentials
d) Regulate blood flow to muscles
55. What is the term for a muscle’s ability to shorten and generate force?
a) Extensibility
b) Elasticity
c) Contractility
d) Excitability
56. Which of the following best describes the role of ATP in muscle contraction?
a) ATP binds to actin, causing the muscle to contract.
b) ATP is required for muscle relaxation and for detaching myosin heads from actin.
c) ATP breaks down to release calcium ions.
d) ATP is stored in the sarcoplasmic reticulum.
57. Which of the following actions would involve concentric contraction of the biceps brachii?
a) Lowering a dumbbell
b) Holding a dumbbell at arm’s length
c) Lifting a dumbbell
d) Stretching the biceps
58. Which part of the muscle fiber is responsible for storing oxygen?
a) Mitochondria
b) Myoglobin
c) Sarcomeres
d) Sarcoplasmic reticulum
59. Which of the following is a characteristic of type IIb muscle fibers (fast-twitch)?
a) High endurance
b) Few mitochondria
c) Rich in myoglobin
d) Slow contraction time
60. What is the role of the muscle antagonist during movement?
a) Initiates the movement
b) Stretches to allow movement
c) Stabilizes the joint
d) Contracts to oppose the primary movement
61. Which of the following is the role of calcium ions in muscle contraction?
a) Calcium ions bind to troponin, moving tropomyosin and allowing myosin to bind to actin.
b) Calcium ions bind to myosin, enabling cross-bridge formation.
c) Calcium ions are pumped into the T-tubules for energy production.
d) Calcium ions break down ATP for energy.
62. Which of the following structures is found in skeletal muscle fibers but not in smooth muscle?
a) Actin and myosin filaments
b) Sarcomeres
c) Nuclei
d) Myofibrils
63. What type of muscle fiber is most useful for endurance activities like long-distance running?
a) Type IIb (fast-twitch) fibers
b) Type IIa (fast-twitch, oxidative) fibers
c) Type I (slow-twitch) fibers
d) None of the above
64. What is the primary energy source for muscle contraction during short bursts of activity (e.g., weight lifting)?
a) Fatty acids
b) ATP stored in muscles
c) Creatine phosphate
d) Glycogen
65. Which of the following is true about smooth muscle?
a) It is multinucleated.
b) It is striated and voluntary.
c) It has intercalated discs.
d) It is non-striated and involuntary.
66. Which of the following structures is responsible for transmitting the electrical signal from the motor neuron to the muscle fiber?
a) Synaptic cleft
b) T-tubules
c) Sarcoplasmic reticulum
d) Myofibrils
67. Which of the following is the primary function of the muscle spindle?
a) To initiate contraction of muscle fibers
b) To detect muscle stretch and provide feedback to the central nervous system
c) To release calcium ions into the sarcoplasmic reticulum
d) To store ATP for energy production
68. Which protein binds to calcium to initiate muscle contraction?
a) Tropomyosin
b) Actin
c) Troponin
d) Myosin
69. What is the functional unit of a muscle fiber called?
a) Myofilament
b) Sarcomere
c) Myofibril
d) Muscle fascicle
70. Which muscle is primarily responsible for the flexion of the knee joint?
a) Rectus femoris
b) Hamstrings
c) Gastrocnemius
d) Quadriceps
71. What is the term for the brief period after a muscle fiber contracts and before it relaxes?
a) Latent period
b) Relaxation phase
c) Contraction phase
d) Refractory period
72. Which muscle is responsible for the adduction of the arm?
a) Pectoralis major
b) Latissimus dorsi
c) Deltoid
d) Trapezius
73. Which of the following describes an eccentric contraction?
a) The muscle lengthens while generating force.
b) The muscle shortens while generating force.
c) The muscle remains at a constant length.
d) The muscle generates no force.
74. Which of the following is true about fast-twitch muscle fibers?
a) They have a high resistance to fatigue.
b) They are primarily used for endurance activities.
c) They contract rapidly but fatigue quickly.
d) They contain a lot of myoglobin and mitochondria.
75. Which of the following structures is responsible for the release of acetylcholine into the synaptic cleft?
a) Motor end plate
b) Synaptic vesicles
c) T-tubules
d) Sarcoplasmic reticulum
76. Which part of the sarcomere contains only thick myosin filaments?
a) A band
b) I band
c) H zone
d) Z disk
77. Which muscle group is responsible for extending the thigh at the hip joint?
a) Hamstrings
b) Quadriceps
c) Gluteal muscles
d) Adductors
78. Which of the following is true about muscle tone?
a) It is the maximum force a muscle can generate.
b) It is the result of constant, low-level contraction of muscles even at rest.
c) It occurs only during intense exercise.
d) It is unrelated to muscle health.
79. What is the role of the transverse tubules (T-tubules) in muscle contraction?
a) They store calcium ions for muscle contraction.
b) They carry action potentials deep into the muscle fiber.
c) They generate ATP for muscle contraction.
d) They produce acetylcholine for muscle stimulation.
80. Which muscle is responsible for the movement of the jaw during chewing?
a) Masseter
b) Temporalis
c) Buccinator
d) Sternocleidomastoid
81. Which of the following muscles is responsible for rotating the head?
a) Trapezius
b) Sternocleidomastoid
c) Deltoid
d) Pectoralis minor
82. Which of the following describes a muscle that is antagonistic to the biceps brachii during elbow flexion?
a) Triceps brachii
b) Brachialis
c) Pectoralis major
d) Latissimus dorsi
83. What type of muscle contraction occurs when the muscle generates force but does not change in length?
a) Concentric
b) Isotonic
c) Isometric
d) Eccentric
84. Which of the following structures is responsible for storing and releasing calcium ions in muscle fibers?
a) Mitochondria
b) Sarcoplasmic reticulum
c) Myofibrils
d) Nucleus
85. Which of the following describes the relationship between the origin and insertion of a muscle?
a) The origin is the point where the muscle moves.
b) The insertion is the point where the muscle is anchored to the bone.
c) The origin is the point where the muscle is fixed, and the insertion is where the muscle attaches to the moving bone.
d) Both the origin and insertion are fixed.
86. Which of the following best describes muscle hypertrophy?
a) Decrease in muscle fiber size due to lack of exercise.
b) Increase in muscle fiber size due to strength training.
c) The formation of new muscle fibers.
d) Decrease in muscle fiber number.
87. What is the role of ATP in muscle relaxation?
a) It causes myosin heads to detach from actin.
b) It initiates the release of calcium ions from the sarcoplasmic reticulum.
c) It binds to troponin to stop contraction.
d) It re-establishes the resting membrane potential.
88. Which muscle is involved in breathing and located between the ribs?
a) Diaphragm
b) Intercostal muscles
c) Sternocleidomastoid
d) Trapezius
89. Which of the following is the primary function of the diaphragm?
a) To raise the ribs during inhalation
b) To assist in vocalization
c) To compress the abdominal cavity
d) To assist with forced exhalation
90. Which of the following terms describes a muscle that stabilizes the origin of a prime mover?
a) Agonist
b) Synergist
c) Antagonist
d) Fixator
91. Which of the following is the main function of the sarcoplasmic reticulum in muscle cells?
a) It stores and releases calcium ions.
b) It produces ATP for muscle contraction.
c) It facilitates the transmission of electrical impulses.
d) It stores glycogen for energy.
92. Which of the following is true about muscle fibers?
a) They are multinucleated.
b) They contain only smooth muscle.
c) They are formed from single cells.
d) They have a central nucleus and lack striations.
93. What type of connective tissue surrounds an individual muscle fiber?
a) Endomysium
b) Perimysium
c) Epimysium
d) Fascia
94. Which of the following muscles is responsible for plantar flexion of the foot?
a) Tibialis anterior
b) Gastrocnemius
c) Quadriceps
d) Hamstrings
95. What type of contraction occurs when a muscle shortens while producing force?
a) Eccentric contraction
b) Isometric contraction
c) Concentric contraction
d) Isotonic contraction
96. Which of the following statements is true about the sliding filament theory?
a) Myosin filaments contract while actin filaments slide.
b) Actin filaments contract while myosin filaments slide.
c) Actin and myosin filaments slide past each other, but neither contracts.
d) The sarcomere shortens as the actin and myosin filaments slide.
97. Which of the following statements describes the role of ATP in muscle contraction?
a) ATP binds to actin to enable cross-bridge formation.
b) ATP is used to pump calcium ions back into the sarcoplasmic reticulum.
c) ATP breaks down myosin heads during muscle relaxation.
d) ATP is not necessary for muscle contraction.
98. Which of the following structures is responsible for the generation of action potentials in muscle cells?
a) Sarcoplasmic reticulum
b) Motor end plate
c) T-tubules
d) Sarcolemma
99. What is the role of the troponin-tropomyosin complex in muscle contraction?
a) It prevents the binding of myosin to actin when the muscle is relaxed.
b) It binds to calcium ions to initiate muscle contraction.
c) It transports ATP to the actin filament.
d) It stores calcium ions for muscle contraction.
100. Which of the following muscles is primarily responsible for shoulder abduction?
a) Pectoralis major
b) Latissimus dorsi
c) Deltoid
d) Infraspinatus
101. Which part of the body is responsible for stabilizing the shoulder joint during upper limb movements?
a) Rotator cuff muscles
b) Latissimus dorsi
c) Pectoralis major
d) Trapezius
102. Which of the following muscles is responsible for the movement of the tongue?
a) Sternocleidomastoid
b) Masseter
c) Mylohyoid
d) Genioglossus
103. Which of the following is true about cardiac muscle?
a) It is striated and involuntary.
b) It is non-striated and voluntary.
c) It is striated and voluntary.
d) It is non-striated and involuntary.
104. Which of the following statements is true about skeletal muscle fibers?
a) They have multiple nuclei located in the center of the fiber.
b) They are connected by intercalated discs.
c) They are composed of multinucleated cells.
d) They have a single nucleus located in the center of the fiber.
105. Which of the following muscles is responsible for flexing the forearm at the elbow joint?
a) Triceps brachii
b) Brachialis
c) Deltoid
d) Infraspinatus
106. What type of muscle contraction occurs when the muscle lengthens while producing force?
a) Eccentric contraction
b) Isometric contraction
c) Concentric contraction
d) Isotonic contraction
107. Which of the following best describes a synergist muscle?
a) A muscle that stabilizes the joint during movement.
b) A muscle that opposes the action of the prime mover.
c) A muscle that assists the prime mover in performing a movement.
d) A muscle that generates the most force during an action.
108. Which muscle is responsible for the extension of the knee joint?
a) Quadriceps femoris
b) Hamstrings
c) Gastrocnemius
d) Gluteus maximus
109. Which part of the nervous system directly controls skeletal muscle contraction?
a) Autonomic nervous system
b) Sympathetic nervous system
c) Somatic nervous system
d) Enteric nervous system
110. Which of the following describes the function of the neuromuscular junction?
a) It is where the action potential is generated.
b) It is where the muscle fibers are stimulated by motor neurons.
c) It is where oxygen is stored in muscle fibers.
d) It is where calcium ions are released.
111. What is the primary function of the muscle fascia?
a) To store calcium ions for contraction.
b) To surround and protect muscle fibers.
c) To generate ATP for muscle contraction.
d) To initiate muscle contraction.
112. Which of the following structures is responsible for transmitting electrical signals from the neuromuscular junction to the interior of the muscle fiber?
a) Sarcoplasmic reticulum
b) T-tubules
c) Myofibrils
d) Sarcolemma
113. Which of the following muscles is responsible for the elevation of the scapula?
a) Rhomboid
b) Trapezius
c) Latissimus dorsi
d) Serratus anterior
114. What is the function of myosin during muscle contraction?
a) Myosin binds to ATP to release energy.
b) Myosin slides past actin to shorten the sarcomere.
c) Myosin is responsible for the release of calcium ions.
d) Myosin stores energy needed for contraction.
115. Which of the following is a characteristic of fast-twitch muscle fibers?
a) High endurance
b) Slow contraction speed
c) Quick fatigue
d) Rich in mitochondria
116. What is the role of acetylcholine in muscle contraction?
a) It binds to troponin, initiating muscle contraction.
b) It binds to the motor end plate and stimulates an action potential.
c) It transports calcium ions to the sarcoplasmic reticulum.
d) It causes myosin heads to detach from actin.
117. What is the term for the point of attachment of a muscle to the more stationary bone?
a) Insertion
b) Origin
c) Tendon
d) Ligament
118. Which of the following muscle groups is responsible for hip extension?
a) Quadriceps
b) Gluteal muscles
c) Adductors
d) Hamstrings
119. What type of muscle fiber has the greatest endurance and is most resistant to fatigue?
a) Type I (slow-twitch) fibers
b) Type IIa fibers
c) Type IIb fibers
d) Type III fibers
120. What is the role of creatine phosphate in muscle contraction?
a) It helps in the breakdown of glucose for energy.
b) It directly supplies ATP to muscle fibers.
c) It stores calcium ions for release during contraction.
d) It initiates action potentials in muscle cells.
121. Which of the following best describes the function of the sarcomere in muscle contraction?
a) It connects muscle fibers to tendons.
b) It is the basic unit of muscle contraction.
c) It stores calcium for muscle relaxation.
d) It regulates ATP production during muscle contraction.
122. Which of the following muscle groups is responsible for knee flexion?
a) Quadriceps
b) Hamstrings
c) Gastrocnemius
d) Gluteal muscles
123. What is the term for the contraction of a muscle that does not result in movement?
a) Isotonic contraction
b) Isometric contraction
c) Eccentric contraction
d) Concentric contraction
124. Which of the following statements is true about smooth muscle?
a) It is striated and under voluntary control.
b) It is non-striated and under involuntary control.
c) It is striated and under involuntary control.
d) It is non-striated and under voluntary control.
125. What is the primary role of calcium ions during muscle contraction?
a) They bind to myosin heads to release energy.
b) They help break down ATP for energy.
c) They bind to troponin to initiate contraction.
d) They transport ATP to the muscle fibers.
126. What is the name of the contractile unit within a muscle fiber?
a) Myosin
b) Actin
c) Sarcomere
d) Myofibril
127. Which of the following is true about Type II muscle fibers?
a) They have high endurance and are resistant to fatigue.
b) They are slow to contract and generate little force.
c) They generate quick bursts of power and fatigue quickly.
d) They are primarily used for endurance activities.
128. Which of the following muscles is responsible for flexion of the neck?
a) Sternocleidomastoid
b) Trapezius
c) Latissimus dorsi
d) Scalenes
129. What is the role of the actin filament in muscle contraction?
a) It binds to ATP to release energy for muscle movement.
b) It forms cross-bridges with myosin to initiate muscle contraction.
c) It stores calcium ions during muscle relaxation.
d) It moves calcium ions into the sarcoplasmic reticulum.
130. Which of the following muscles is responsible for the adduction of the arm?
a) Deltoid
b) Pectoralis major
c) Latissimus dorsi
d) Supraspinatus
131. What is the function of myosin during muscle contraction?
a) It slides past actin, generating force for muscle contraction.
b) It binds to calcium ions to trigger contraction.
c) It stores ATP for muscle contraction.
d) It transports action potentials along muscle fibers.
132. Which of the following muscles is responsible for flexion of the hip?
a) Rectus femoris
b) Iliopsoas
c) Gluteus medius
d) Biceps femoris
133. What is the term for the point where a muscle attaches to a stationary bone?
a) Origin
b) Insertion
c) Tendon
d) Epimysium
134. Which of the following muscle types is responsible for movement of the heart?
a) Smooth muscle
b) Skeletal muscle
c) Cardiac muscle
d) Epithelial muscle
135. Which of the following is a characteristic of slow-twitch muscle fibers?
a) High force generation
b) Quick fatigue
c) High endurance
d) Low resistance to fatigue
136. Which of the following best describes a motor unit?
a) A single motor neuron and all the muscle fibers it innervates.
b) The collection of muscle fibers responsible for contraction.
c) The point of connection between the motor neuron and muscle fibers.
d) The muscle’s ability to produce sustained contractions.
137. Which of the following muscles is involved in the movement of the jaw for chewing?
a) Masseter
b) Orbicularis oris
c) Temporalis
d) Buccinator
138. Which of the following is a function of the muscle tone in skeletal muscles?
a) To create a smooth and continuous contraction.
b) To generate movement during voluntary contraction.
c) To maintain posture and prevent the muscle from relaxing.
d) To reduce energy expenditure during muscle contraction.
139. Which of the following is true regarding muscle fatigue?
a) It is caused by a lack of calcium ions in the muscle fibers.
b) It is caused by the accumulation of lactic acid in muscle cells.
c) It results from a lack of oxygen in the blood.
d) It occurs due to depletion of glycogen reserves.
140. Which of the following muscle types lacks striations?
a) Skeletal muscle
b) Smooth muscle
c) Cardiac muscle
d) None of the above
141. Which muscle is responsible for closing the eyelids?
a) Orbicularis oculi
b) Zygomaticus
c) Masseter
d) Temporalis
142. Which of the following muscles is responsible for extension of the arm?
a) Pectoralis major
b) Deltoid
c) Triceps brachii
d) Latissimus dorsi
143. Which of the following muscles is responsible for dorsiflexion of the foot?
a) Tibialis anterior
b) Gastrocnemius
c) Soleus
d) Flexor digitorum longus
144. Which of the following best describes the role of the mitochondria in muscle cells?
a) They store calcium ions required for muscle contraction.
b) They release neurotransmitters at the neuromuscular junction.
c) They generate ATP for muscle contraction.
d) They store oxygen used by muscle cells during exercise.
145. Which of the following muscle types is under involuntary control?
a) Skeletal muscle
b) Cardiac muscle
c) Smooth muscle
d) Both b and c
146. Which of the following muscles is responsible for the rotation of the head?
a) Sternocleidomastoid
b) Trapezius
c) Scalenes
d) Levator scapulae
147. Which of the following terms describes a muscle that opposes the action of the prime mover?
a) Agonist
b) Antagonist
c) Synergist
d) Fixator
148. Which muscle is involved in the abduction of the arm?
a) Latissimus dorsi
b) Biceps brachii
c) Supraspinatus
d) Pectoralis major
149. Which of the following is an example of an isometric muscle contraction?
a) Biceps curl
b) Holding a plank position
c) Jumping jacks
d) Running
150. What structure connects muscles to bones?
a) Ligament
b) Tendon
c) Cartilage
d) Fascia
151. What is the primary function of the sarcoplasmic reticulum in muscle fibers?
a) To store and release oxygen
b) To store and release calcium ions
c) To synthesize ATP
d) To transmit action potentials
152. Which of the following muscles is responsible for plantarflexion of the foot?
a) Tibialis anterior
b) Gastrocnemius
c) Soleus
d) Flexor digitorum longus
153. What is the role of the neuromuscular junction in muscle contraction?
a) It stores calcium ions for muscle relaxation.
b) It transmits electrical impulses from the motor neuron to the muscle fiber.
c) It releases ATP to fuel muscle movement.
d) It connects the sarcomere to the muscle cell membrane.
154. Which type of muscle fiber is specialized for sustained, endurance activities?
a) Type I fibers
b) Type IIa fibers
c) Type IIb fibers
d) Type III fibers
155. What is the term used to describe the gradual increase in muscle strength and size due to resistance training?
a) Muscular hypertrophy
b) Muscular atrophy
c) Isometric contraction
d) Concentric contraction
156. Which of the following statements is true about cardiac muscle?
a) It is voluntary and striated.
b) It is involuntary and non-striated.
c) It is voluntary and non-striated.
d) It is involuntary and striated.
157. Which muscle is responsible for extension of the leg at the knee joint?
a) Rectus femoris
b) Biceps femoris
c) Gastrocnemius
d) Sartorius
158. Which of the following is a characteristic of fast-twitch muscle fibers?
a) High endurance
b) Slow to fatigue
c) Quick to fatigue
d) Small diameter
159. Which of the following is the primary function of the pectoralis major muscle?
a) Arm adduction
b) Arm flexion
c) Arm extension
d) Arm rotation
160. Which of the following muscles is responsible for the movement of the tongue?
a) Sternocleidomastoid
b) Masseter
c) Styloglossus
d) Genioglossus
161. Which of the following muscles is responsible for the flexion of the elbow?
a) Biceps brachii
b) Triceps brachii
c) Brachialis
d) Both a and c
162. What is the term for a muscle that assists the prime mover in performing an action?
a) Agonist
b) Antagonist
c) Synergist
d) Fixator
163. Which of the following is true about muscle fibers during concentric contraction?
a) They shorten as they contract.
b) They lengthen as they contract.
c) They do not change in length.
d) They generate less force than during eccentric contraction.
164. Which muscle is responsible for elevating the scapula?
a) Trapezius
b) Pectoralis minor
c) Rhomboid major
d) Serratus anterior
165. What is the name of the protein that binds to calcium ions to initiate muscle contraction?
a) Actin
b) Myosin
c) Troponin
d) Tropomyosin
166. Which of the following is responsible for the “all-or-nothing” response in muscle fibers?
a) The size of the motor unit
b) The frequency of stimulation
c) The force of contraction
d) The threshold stimulus
167. Which muscle group is primarily responsible for knee extension?
a) Quadriceps
b) Hamstrings
c) Gastrocnemius
d) Gluteal muscles
168. Which of the following is a characteristic of smooth muscle?
a) It has multiple nuclei per cell.
b) It is striated.
c) It is controlled by the somatic nervous system.
d) It is found in the walls of hollow organs.
169. Which of the following is true about skeletal muscle?
a) It is involuntary and non-striated.
b) It is voluntary and striated.
c) It is voluntary and non-striated.
d) It is involuntary and striated.
170. Which muscle is responsible for flexion of the neck?
a) Sternocleidomastoid
b) Trapezius
c) Scalenes
d) Splenius capitis
171. What is the main function of the deltoid muscle?
a) Flexion of the shoulder
b) Extension of the shoulder
c) Abduction of the shoulder
d) Adduction of the shoulder
172. What structure within the muscle fiber stores and releases calcium ions during muscle contraction?
a) Mitochondrion
b) Sarcoplasmic reticulum
c) Nucleus
d) Golgi apparatus
173. Which of the following best describes the function of the troponin-tropomyosin complex in muscle contraction?
a) It generates ATP for muscle contraction.
b) It blocks the active sites on actin molecules at rest.
c) It transports calcium ions into the muscle fiber.
d) It regulates the movement of myosin heads during contraction.
174. Which of the following muscles is responsible for raising the eyebrows?
a) Orbicularis oculi
b) Frontalis
c) Buccinator
d) Zygomaticus
175. Which of the following best describes an isotonic contraction?
a) The muscle remains the same length as it contracts.
b) The muscle shortens as it contracts.
c) The muscle generates maximum tension but does not shorten.
d) The muscle lengthens as it contracts.
176. What is the role of the myofibrils in muscle contraction?
a) They store glycogen for energy.
b) They contain the contractile proteins actin and myosin.
c) They store calcium ions for contraction.
d) They transmit electrical impulses to the muscle fibers.
177. Which of the following muscles is responsible for the rotation of the shoulder?
a) Latissimus dorsi
b) Supraspinatus
c) Infraspinatus
d) Biceps brachii
178. Which of the following is a function of the diaphragm?
a) Flexes the lumbar spine
b) Aids in respiration
c) Helps in the rotation of the trunk
d) Stabilizes the pelvis
179. Which of the following muscles is responsible for the extension of the back?
a) Erector spinae
b) Latissimus dorsi
c) Rectus abdominis
d) Trapezius
180. What is the role of the T-tubules in muscle contraction?
a) To store calcium ions for muscle relaxation
b) To conduct electrical impulses deep into the muscle fibers
c) To transport oxygen to muscle cells
d) To connect the sarcomeres within the muscle fibers
Questions and Answers for Study guide
Explain the sliding filament theory of muscle contraction.
Answer:
The sliding filament theory describes the process of muscle contraction at the molecular level. It explains how actin and myosin filaments within the sarcomere interact to produce contraction.
- Initiation: Muscle contraction begins with the release of acetylcholine at the neuromuscular junction, triggering an action potential in the muscle fiber. The action potential travels along the sarcolemma and down the T-tubules to the sarcoplasmic reticulum, causing the release of calcium ions (Ca²⁺).
- Calcium Binding: Calcium ions bind to troponin, causing a conformational change that moves tropomyosin away from actin’s active sites.
- Cross-Bridge Formation: Myosin heads, which are energized by ATP hydrolysis, attach to the exposed active sites on actin, forming cross-bridges.
- Power Stroke: The myosin heads pivot, pulling the actin filaments toward the center of the sarcomere. This shortens the sarcomere and generates force.
- Detachment: A new ATP molecule binds to the myosin head, causing it to detach from actin.
- Resetting: ATP is hydrolyzed, re-energizing the myosin head, which returns to its starting position. This cycle repeats as long as calcium ions and ATP are present.
- Relaxation: When the stimulation ceases, calcium ions are actively pumped back into the sarcoplasmic reticulum, tropomyosin re-covers the active sites on actin, and the muscle relaxes.
Compare and contrast the structure and function of skeletal, cardiac, and smooth muscles.
Answer:
Skeletal Muscle:
- Structure: Long, cylindrical, multinucleated fibers; striated.
- Function: Responsible for voluntary movements; attached to bones and controlled by the somatic nervous system.
Cardiac Muscle:
- Structure: Short, branched cells with one or two nuclei; striated; intercalated discs.
- Function: Involuntary control; pumps blood throughout the body; regulated by the autonomic nervous system and hormonal signals.
Smooth Muscle:
- Structure: Spindle-shaped, single-nucleated cells; non-striated.
- Function: Involuntary movements; controls functions in hollow organs such as the digestive tract, blood vessels, and bladder; regulated by the autonomic nervous system and hormones.
Comparison:
- All three muscle types generate force and produce movement.
- Skeletal and cardiac muscles are striated, while smooth muscle is not.
- Skeletal muscles are voluntary, whereas cardiac and smooth muscles are involuntary.
Describe the role of calcium ions (Ca²⁺) in muscle contraction and relaxation.
Answer:
Calcium ions play a pivotal role in both the contraction and relaxation of muscle fibers:
- Contraction:
- When an action potential reaches the muscle fiber, it triggers the release of calcium ions from the sarcoplasmic reticulum into the cytoplasm.
- Calcium binds to troponin, causing a conformational change that moves tropomyosin away from actin’s binding sites.
- This exposes the active sites on actin, allowing myosin heads to form cross-bridges and initiate contraction.
- Relaxation:
- After the contraction stimulus ends, calcium ions are actively pumped back into the sarcoplasmic reticulum using ATP.
- The removal of calcium ions from the cytoplasm allows tropomyosin to re-cover the binding sites on actin, preventing cross-bridge formation.
- This restores the muscle to a relaxed state.
Without calcium, the interaction between actin and myosin cannot occur, highlighting its essential role in muscle physiology.
Explain how muscle fatigue occurs and its physiological causes.
Answer:
Muscle fatigue is the decline in a muscle’s ability to generate force. It can result from prolonged or intense activity and involves multiple physiological factors:
- Depletion of Energy Resources:
- During prolonged activity, ATP, glycogen, and creatine phosphate levels diminish, reducing the energy supply needed for muscle contraction.
- Accumulation of Metabolic Byproducts:
- The build-up of lactic acid during anaerobic respiration lowers pH levels, which can inhibit enzyme activity and interfere with muscle fiber excitation.
- Electrolyte Imbalance:
- Intense exercise can disrupt the balance of sodium, potassium, and calcium ions, affecting the muscle’s ability to respond to stimulation.
- Reduced Neural Input:
- The nervous system may reduce signals to the muscle, a protective mechanism to prevent damage from overexertion.
- Oxygen Debt:
- Insufficient oxygen supply during intense exercise limits aerobic respiration, causing a reliance on less efficient anaerobic processes.
Muscle fatigue is reversible, and recovery involves replenishing energy stores, removing lactic acid, and restoring ionic balance.
Describe the role of ATP in muscle contraction and relaxation.
Answer:
ATP is essential for both the contraction and relaxation of muscles, serving multiple roles:
- Energy for Cross-Bridge Cycling:
- ATP binds to the myosin head, causing it to detach from actin after the power stroke.
- ATP hydrolysis energizes the myosin head, resetting it to its active position for the next contraction cycle.
- Calcium Pumping:
- ATP powers the active transport of calcium ions back into the sarcoplasmic reticulum, which is crucial for muscle relaxation.
- Maintaining Ion Gradients:
- ATP is required to maintain the sodium-potassium ion gradients across the sarcolemma, ensuring the propagation of action potentials.
Without ATP, muscles would remain in a contracted state, known as rigor mortis, which occurs post-mortem when ATP production ceases.
Discuss the structure and function of the sarcomere in muscle contraction.
Answer:
The sarcomere is the structural and functional unit of a muscle fiber responsible for contraction. It is composed of specific regions and proteins that enable its function:
- Structure:
- Z-lines: Boundaries of the sarcomere; anchor thin filaments (actin).
- A-band: Central region containing overlapping thick (myosin) and thin filaments.
- I-band: Region of thin filaments not overlapping with thick filaments; shortens during contraction.
- H-zone: Central part of the A-band containing only thick filaments; disappears during contraction.
- M-line: Center of the sarcomere; stabilizes thick filaments.
- Function:
- Muscle contraction occurs when the actin and myosin filaments slide past each other, shortening the sarcomere.
- ATP and calcium ions drive this process by enabling cross-bridge formation and movement.
Sarcomeres work together in series along the muscle fiber to produce coordinated contractions.
Explain the difference between isometric and isotonic muscle contractions.
Answer:
Muscle contractions can be classified into two main types based on how they generate force and produce movement:
- Isometric Contraction:
- Definition: Muscle tension increases, but the length of the muscle does not change.
- Example: Holding a heavy object in a fixed position or performing a plank exercise.
- Mechanism: The muscle generates force equal to the resistance without movement of the joint.
- Isotonic Contraction:
- Definition: Muscle changes length while producing tension to move a load.
- Types:
- Concentric: Muscle shortens as it contracts (e.g., lifting a dumbbell).
- Eccentric: Muscle lengthens while under tension (e.g., lowering a dumbbell).
Both types are crucial for everyday activities and exercise, with isometric contractions providing stability and isotonic contractions enabling movement.
Describe the role of the neuromuscular junction in muscle contraction.
Answer:
The neuromuscular junction (NMJ) is the synapse between a motor neuron and a muscle fiber, facilitating communication for muscle contraction:
- Structure:
- Motor Neuron Axon: Releases neurotransmitters.
- Synaptic Cleft: Space between the neuron and muscle fiber.
- Motor End Plate: Specialized region of the sarcolemma with receptors for neurotransmitters.
- Function:
- Signal Transmission:
- The action potential travels down the motor neuron, triggering the release of acetylcholine (ACh) into the synaptic cleft.
- ACh binds to receptors on the motor end plate, causing sodium ions to enter the muscle fiber.
- This generates an action potential in the sarcolemma, leading to muscle contraction.
- Signal Transmission:
- Termination:
- Acetylcholinesterase breaks down ACh in the synaptic cleft, stopping the signal and allowing the muscle to relax.
The NMJ ensures precise control of muscle contractions.
Outline the physiological adaptations of muscles to regular exercise.
Answer:
Regular exercise leads to several physiological changes in muscle structure and function, which depend on the type of training:
- Strength Training (Resistance Exercise):
- Hypertrophy: Increase in muscle fiber size due to enhanced synthesis of actin and myosin proteins.
- Increased Strength: Improved ability to recruit motor units and generate force.
- Stronger Tendons and Ligaments: Adaptation to handle increased loads.
- Endurance Training (Aerobic Exercise):
- Increased Mitochondria: Enhances ATP production through oxidative phosphorylation.
- Improved Capillary Density: Enhances oxygen and nutrient delivery to muscle fibers.
- Enhanced Myoglobin Content: Improves oxygen storage and utilization.
- Metabolic Adaptations:
- Increased glycogen storage and efficiency in using fat as a fuel source.
- Improved resistance to fatigue.
These adaptations improve overall muscle performance and resistance to injury.
Discuss the process of muscle repair and regeneration after injury.
Answer:
Muscle repair and regeneration involve a series of steps mediated by specialized cells and signaling molecules:
- Inflammation:
- Injury triggers an inflammatory response, with immune cells releasing cytokines to clear damaged tissue and stimulate repair.
- Activation of Satellite Cells:
- Satellite cells, located between the sarcolemma and basal lamina, become activated by injury.
- These cells proliferate and differentiate into myoblasts, which are essential for muscle regeneration.
- Formation of New Muscle Fibers:
- Myoblasts fuse to form new myofibers or repair damaged ones.
- Growth factors like insulin-like growth factor-1 (IGF-1) play a critical role in this process.
- Remodeling and Maturation:
- The newly formed fibers mature and integrate into existing tissue.
- Collagen deposition by fibroblasts strengthens the repair site.
- Recovery:
- Physical therapy and proper nutrition aid the recovery process, ensuring optimal regeneration.
Muscle regeneration is a dynamic process influenced by the severity of the injury and the individual’s overall health.
Discuss the role of muscle metabolism during exercise.
Answer:
Muscle metabolism provides the energy needed for muscle contraction during exercise. The energy pathways vary based on exercise intensity and duration:
- Immediate Energy (Phosphagen System):
- Creatine phosphate donates a phosphate group to ADP to quickly generate ATP.
- Supplies energy for short, high-intensity activities (e.g., sprinting, weightlifting).
- Short-Term Energy (Anaerobic Glycolysis):
- Glucose is broken down to pyruvate, producing ATP without oxygen.
- Lactic acid is formed when oxygen is insufficient, leading to fatigue.
- Long-Term Energy (Aerobic Respiration):
- Occurs in the mitochondria using oxygen to break down glucose, fatty acids, and amino acids.
- Produces large amounts of ATP, sustaining prolonged, moderate-intensity exercise (e.g., jogging).
- Fatigue and Recovery:
- Prolonged exercise depletes glycogen stores, reduces ATP production, and increases metabolic byproducts.
- Recovery involves replenishing energy stores and clearing lactic acid.
Efficient muscle metabolism ensures sustained performance and minimizes fatigue.
Describe the anatomical and functional differences between skeletal, cardiac, and smooth muscle tissue.
Answer:
Muscle tissues differ in structure, function, and control mechanisms:
- Skeletal Muscle:
- Anatomy: Long, cylindrical, multinucleated cells with striations.
- Function: Voluntary movements, posture, and heat production.
- Control: Somatic nervous system.
- Cardiac Muscle:
- Anatomy: Branched, striated cells with one or two nuclei; connected by intercalated discs.
- Function: Involuntary contraction to pump blood throughout the body.
- Control: Autonomic nervous system and intrinsic pacemaker cells.
- Smooth Muscle:
- Anatomy: Spindle-shaped, non-striated cells with a single nucleus.
- Function: Involuntary control of hollow organs (e.g., blood vessels, digestive tract).
- Control: Autonomic nervous system and hormonal signals.
Each type of muscle tissue is specialized for its role in the body.
Discuss the importance of calcium in muscle contraction and relaxation.
Answer:
Calcium plays a critical role in both initiating and terminating muscle contraction:
- Initiation of Contraction:
- Calcium ions are released from the sarcoplasmic reticulum into the sarcoplasm in response to nerve stimulation.
- Calcium binds to troponin, causing a conformational change that moves tropomyosin away from myosin-binding sites on actin.
- This enables myosin heads to form cross-bridges with actin, leading to contraction.
- Termination of Contraction:
- Calcium ions are actively transported back into the sarcoplasmic reticulum by calcium pumps (requiring ATP).
- Troponin and tropomyosin return to their resting positions, blocking the binding sites on actin.
- This prevents further cross-bridge formation, allowing muscle relaxation.
Calcium’s regulation ensures proper contraction and relaxation cycles, essential for muscle function.
Explain the causes and physiological effects of muscle fatigue.
Answer:
Muscle fatigue occurs when a muscle loses its ability to generate force, often during prolonged or intense activity:
- Causes:
- Metabolic Factors: Depletion of ATP, creatine phosphate, and glycogen stores.
- Ion Imbalances: Accumulation of potassium and hydrogen ions disrupts membrane potential and enzyme activity.
- Lactic Acid Accumulation: Lowers pH, impairing calcium binding and enzymatic function.
- Central Fatigue: Reduced neural stimulation from the brain due to psychological or physical strain.
- Physiological Effects:
- Reduced Contraction Strength: Decreased force production due to inadequate energy supply.
- Slower Recovery: Prolonged fatigue affects subsequent muscle performance.
- Delayed Onset Muscle Soreness (DOMS): Microtears in muscle fibers and inflammation cause pain after strenuous exercise.
Proper training, nutrition, and rest help mitigate muscle fatigue and enhance recovery.