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Lifting weights will cause muscles to enlarge. This is primarily due to


A) an increase in the number of muscle cells.
B) an increase in the size of muscle cells.

C) A) and B)
D) undefined

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Which fibers dominate many of the back and calf muscles that contract almost continually to maintain posture?


A) Slow-twitch
B) Fast-twitch
C) Intermediate

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

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The ________ is the connective tissue covering of a fascicle.

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Invaginations of the muscle cell membrane that extend deep into the cell are known as the


A) T-tubules.
B) terminal cisternae.
C) titin complexes.
D) Z-discs.
E) end plates.

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

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Which is not a protein found in thin filaments?


A) Actin
B) Troponin
C) Tropomyosin
D) Myosin
E) No exceptions; all are found in thin filaments

F) C) and D)
G) B) and D)

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When tension output exceeds resistance and the muscle exerts a constant force as it changes length, the contraction is described as ________.

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Energy requirements for smooth muscle contractions are generally higher than those for skeletal muscle contractions.

A) True
B) False

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For relaxation to occur,


A) calcium leaves the sarcoplasmic reticulum, and troponin binds calcium and blocks the binding sites on actin.
B) calcium enters the myofibril, it detaches from myosin, and the binding sites on myosin become inactive.
C) sarcoplasm calcium levels fall, calcium is removed from troponin, and tropomyosin blocks binding sites on actin.
D) extracellular calcium levels fall, calcium is pumped into the myofibril, and tropomyosin slides away from actin.

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

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When an impulse arrives at the knob of the motor neuron, calcium


A) enters through active transport pumps and triggers the release of transmitter.
B) enters through voltage-gated channels and triggers the release of transmitter.
C) exits through active transport pumps and brings transmitter with it.
D) exits through voltage-gated channels and triggers transmitter release.
E) is released from synaptic vesicles.

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

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Fibers from one motor unit


A) are clustered together within one fascicle of the muscle.
B) are dispersed throughout most of the muscle.

C) A) and B)
D) undefined

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The floor of the pelvic cavity includes skeletal muscles that function to support organs in that cavity.

A) True
B) False

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The multiple nuclei in skeletal muscle cells are the result of the


A) fusion of myoblasts.
B) cytokinesis of embryonic satellite cells.
C) spontaneous development of nuclei in embryonic cells.
D) stimulation of fibroblasts by hormones.
E) action of testosterone on mesenchyme cell.

F) C) and E)
G) B) and D)

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When a muscle relaxes,


A) crossbridges form and muscle extensibility returns the muscle to rest length.
B) crossbridges form and muscle elasticity returns the muscle to rest length.
C) crossbridges stop forming and muscle elasticity returns the muscle to rest length.
D) crossbridges stop forming and muscle extensibility returns the muscle to rest length.

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

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The junction between an axon and the muscle fiber itself is called a ________ junction.

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________ muscle fibers have large myoglobin stores, slow contraction velocity, and the highest resistance to fatigue.

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Muscles that are used for precisely controlled movements generally contain large motor units.

A) True
B) False

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The connections between the nervous system and skeletal muscle allow for voluntary control of movement.

A) True
B) False

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During REM sleep, muscle tone decreases significantly.

A) True
B) False

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Each skeletal muscle is composed of ________, which are bundles of muscle fibers.

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A drug that inhibited acetylcholinesterase would result in


A) a failure to stimulate the muscle due to decreased ACh release.
B) enhanced stimulation of the muscle due to decreased ACh breakdown.
C) enhanced stimulation of the muscle due to enhanced ACh release.
D) poor muscle stimulation due to enhanced ACh breakdown.

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

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