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The functional unit of muscle contraction is


A) the muscle.
B) the muscle fiber.
C) the myosin cross-bridge.
D) the sarcomere.

E) A) and B)
F) None of the above

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Fibers of muscles whose motor neurons are severed


A) hypertrophy.
B) may be replaced by fat or fibrous connective tissue.
C) cannot ever be reinnervated.
D) die as their sarcomeres are progressively eliminateD.

E) A) and B)
F) A) and C)

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The structures that connect cardiac muscle cells are


A) intervertebral discs.
B) neuromuscular junctions.
C) intercalated discs.
D) motor end plates.

E) All of the above
F) A) and B)

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Transverse tubules


A) store sodium ions for the action potential at the cell surface.
B) transmit muscle impulses into the cell interior.
C) store calcium ions.
D) connect actin and myosin.

E) B) and C)
F) None of the above

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In order to stimulate skeletal muscle fibers,motor neurons release the neurotransmitter ______.

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Muscles that assist an agonist are called ______.

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Threshold stimulus is the


A) maximum stimulus required to release acetylcholine.
B) minimum stimulus required to produce ATP.
C) maximum stimulus required to contract a muscle.
D) minimum strength of stimulation required to contract a muscle fiber.

E) A) and B)
F) A) and C)

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Transverse tubules and sarcoplasmic reticulum are well developed in


A) smooth muscle fibers.
B) skeletal muscle fibers.
C) cardiac muscle fibers.
D) skeletal and cardiac muscle fibers.

E) B) and C)
F) All of the above

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Functions of muscles include


A) heartbeat.
B) muscle tone.
C) moving bones.
D) all of the above.

E) None of the above
F) A) and C)

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The linea alba is


A) a muscle extending from the ischial spine to the coccyx and sacrum.
B) a curved,broad muscle on the side of the chest.
C) a muscle beneath the skull.
D) a band of tough connective tissue to which abdominal wall muscles attach.

E) A) and C)
F) A) and B)

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Binding sites on the surface of actin allow the formation of cross-bridges with molecules of


A) ATP.
B) myosin.
C) troponin.
D) tropomyosin.

E) A) and B)
F) All of the above

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Which of the following statements is correct?


A) Tropomyosin molecules move and expose specific sites on myosin filaments.
B) Actin filaments slide along myosin filaments.
C) Cross-bridges form between actin and the sarcolemma.
D) Filaments of troponin and tropomyosin slide past one another.

E) C) and D)
F) None of the above

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The type of muscle cell that lacks transverse tubules,has a single nucleus,and is under involuntary control is


A) skeletal muscle.
B) smooth muscle.
C) cardiac muscle.
D) striated muscle.

E) A) and B)
F) A) and C)

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Oxygen debt in muscles may develop because of


A) the inability of respiratory and circulatory systems to supply enough oxygen to skeletal muscles when used strenuously for a minute or two.
B) the inability of myoglobin molecules to store enough oxygen when skeletal muscles are used strenuously for a minute or two.
C) too much oxygen used in forming pyruvic acid when skeletal muscles are contracted strenuously for a minute or two.
D) too high a concentration of oxygen in the atmosphere.

E) All of the above
F) C) and D)

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Which of the following is not true?


A) Red fibers contract more slowly than white.
B) Red fibers contain more myoglobin than white.
C) Red fibers have fewer mitochondria than white.
D) Red fibers fatigue more slowly than white.

E) A) and C)
F) C) and D)

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A gluteal gait,in which a person walks with a waddling limp,is usually caused by a disorder of the


A) gluteus maximus and gluteus medius.
B) gluteus maximus and gluteus minimus.
C) gluteus medius and gluteus minimus.
D) gluteus maximus and tensor fasciae latae.

E) All of the above
F) None of the above

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A motor unit is


A) many myofibrils in a sarcolemmA.
B) many motor end plates at a neuromuscular junction.
C) a motor neuron and the muscle fibers connected to it.
D) the functional unit of a muscle fiber.

E) A) and D)
F) C) and D)

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Neurotransmitters are stored in vesicles in


A) myofibrils.
B) motor units.
C) motor end plates.
D) motor neuron endings.

E) A) and B)
F) A) and D)

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A myogram is


A) a chart that shows how many muscle cells a neuron synapses with.
B) a recording of the events of a twitch.
C) a measurement of muscle tone.
D) a depiction of the results of a stress test.

E) A) and D)
F) A) and B)

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The amount of oxygen liver cells require to support the conversion of lactic acid to produce glucose or glycogen is the


A) refractory quantity.
B) oxygen debt.
C) anaerobic concentration.
D) aerobic conversion.

E) A) and D)
F) B) and C)

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