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1 | |
According to the sliding filament mechanism of skeletal-muscle contraction, during contraction: |
| | A) | The thick filaments stay the same size but the thin filaments shorten. |
| | B) | The sarcomeres shorten. |
| | C) | The thin filaments stay the same size but the thick filaments shorten. |
| | D) | Both thick and thin filaments shorten. |
| | E) | None of the above occurs. |
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2 | |
Which of the following is an important function of ATP in skeletal muscle? |
| | A) | It is required for the dissociation of actin from myosin. |
| | B) | It is hydrolyzed by the ATPase that pumps calcium ions into the sarcoplasmic reticulum. |
| | C) | It is used for the phosphorylation of myosin. |
| | D) | A and B. |
| | E) | A, B and C. |
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3 | |
At the neuromuscular junction, |
| | A) | the release of acetylcholine from the motor neuron causes an EPP in the motor end plate. |
| | B) | acetylcholinesterase inhibits repolarization of the motor end plate. |
| | C) | summation of end-plate potentials is required to trigger an action potential in the muscle membrane. |
| | D) | A and B. |
| | E) | A and C. |
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4 | |
Which of the following statements regarding the action of curare at the neuromuscular junction is true? |
| | A) | Curare is an acetylcholine agonist. |
| | B) | Curare binds to acetylcholine receptors. |
| | C) | Curare inhibits acetylcholinesterase. |
| | D) | Curare inhibits acetylcholine release from motor neuron terminals. |
| | E) | A and B. |
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5 | |
Which of the following statements is true with regard to types of skeletal-muscle contraction? |
| | A) | In an isotonic contraction, the load equals the tension produced. |
| | B) | In an isotonic contraction, the load exceeds the tension produced. |
| | C) | In a lengthening contraction, the tension produced exceeds the load. |
| | D) | Isotonic contractions begin as isometric contractions. |
| | E) | None of the above is true. |
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6 | |
Which of the following is a correct comparison of type I (slow-oxidative) skeletal-muscle fibers and type II B (fast-glycolytic) skeletal-muscle fibers? |
| | A) | Type I fibers have fewer mitochondria. |
| | B) | Type I fibers fatigue faster. |
| | C) | Type I fibers store more glycogen. |
| | D) | Type I fibers can generate more tension. |
| | E) | Type I fibers have a smaller diameter. |
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7 | |
Which of the following statements is true? |
| | A) | Nervous stimulation of smooth muscle is always excitatory, whereas nervous stimulation of skeletal muscle may be excitatory or inhibitory. |
| | B) | The contractile activity of smooth muscle may be affected by hormones. |
| | C) | Smooth muscle may be innervated by both sympathetic and parasympathetic neurons. |
| | D) | A and B. |
| | E) | B and C. |
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8 | |
Which of the following descriptions of skeletal- and smooth-muscle contraction is correct? |
| | A) | Skeletal-muscle contraction requires the influx of extracellular Ca2+, whereas smooth-muscle contraction does not. |
| | B) | Skeletal-muscle contraction involves interactions between thick and thin filaments, whereas smooth-muscle contraction does not. |
| | C) | Skeletal-muscle contraction results from cross-bridge cycling, whereas smooth-muscle contraction does not. |
| | D) | Smooth-muscle contraction requires release of Ca2+ from sarcoplasmic reticulum, whereas skeletal-muscle contraction does not. |
| | E) | The site of calcium regulation of skeletal-muscle contraction is on the thin filament, whereas in smooth-muscle contraction it is on the thick filament. |
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9 | |
Which of the following statements regarding myasthenia gravis is true? |
| | A) | It is caused by disuse atrophy. |
| | B) | It is caused by a genetic defect in the acetylcholinesterase pathway. |
| | C) | It is caused by a genetic lack of the protein, dystrophin. |
| | D) | It is caused by a virus that attacks motor neurons. |
| | E) | It is an autoimmune disease that attacks the neuromuscular junction. |
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10 | |
Muscles in the back have a higher proportion of fast-glycolytic fibers than do muscles in the arms. |
| | A) | True |
| | B) | False |
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11 | |
Muscles in the hands have smaller motor units than muscles in the back. |
| | A) | True |
| | B) | False |
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12 | |
The biceps muscle is an extensor, and its antagonist, the triceps, is a flexor. |
| | A) | True |
| | B) | False |
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