Question 1

Which of the following best describes the function of dystrophin in skeletal muscle fibers?

Accepted Answer

It connects the sarcomere to the sarcolemma, helping transmit tension generated by the sarcomere to the muscle fiber membrane.

Question 2

During muscle contraction, which of the following changes occur in the sarcomere?

Accepted Answer

The I band and H zone both decrease in width, while the A band remains the same.

Question 3

Which of the following events occurs first at the neuromuscular junction (NMJ) to initiate muscle contraction?

Accepted Answer

Acetylcholine is released from the synaptic vesicles into the synaptic cleft.

Question 4

What is the primary role of the sarcoplasmic reticulum (SR) in skeletal muscle contraction?

Accepted Answer

To store and release calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$necessary for muscle contraction.

Question 5

Which of the following best explains the role of ATP in the cross-bridge cycle of muscle contraction?

Accepted Answer

ATP hydrolysis energizes the myosin head, allowing it to bind to actin and perform a power stroke.

Question 6

A patient with a genetic defect in the protein dystrophin is most likely to experience which of the following symptoms?

Accepted Answer

Progressive muscle weakness due to impaired transmission of force from sarcomeres to the sarcolemma.

Question 7

Which of the following statements about the myosin molecule is correct?

Accepted Answer

The myosin head contains binding sites for both actin and ATP.

Question 8

What is the effect of calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$binding to troponin during muscle contraction?

Accepted Answer

It causes tropomyosin to move away from the myosin-binding sites on actin, allowing cross-bridge formation.

Question 9

Which of the following best describes the 'power stroke' in the sliding filament mechanism?

Accepted Answer

The myosin head pivots, pulling the thin filament toward the center of the sarcomere.

Question 10

Which of the following best explains why muscle relaxation occurs after contraction?

Accepted Answer

Calcium ions are actively transported back into the sarcoplasmic reticulum, causing tropomyosin to cover the myosin-binding sites on actin.

Question 11

During a sustained muscle contraction (tetanus), which of the following is true regarding calcium ion ($$\mathrm{Ca$$^{2+}$$}) $$levels in the sarcoplasm?

Accepted Answer

Calcium ion concentration remains elevated, allowing continuous cross-bridge cycling.

Question 12

Which of the following best describes the function of creatine phosphate in muscle metabolism?

Accepted Answer

It donates a phosphate group to ADP to rapidly regenerate ATP during the initial seconds of muscle contraction.

Question 13

A muscle fiber is stimulated at a frequency that allows partial relaxation between contractions. Which term best describes this phenomenon?

Accepted Answer

Unfused (incomplete) tetanus

Question 14

Which of the following is a correct sequence of events in excitation-contraction coupling?

Accepted Answer

Release of acetylcholine → depolarization of sarcolemma → release of $$\mathrm{Ca$$^{2+}$$}$$ from SR → binding of $$\mathrm{Ca$$^{2+}$$} to $$troponin

Question 15

Which of the following best explains why heavy breathing continues after strenuous exercise?

Accepted Answer

To replenish oxygen stores in myoglobin and convert lactic acid back to pyruvate.

Muscular and Nervous Tissue: Structure, Function, and Integration in the Human Body

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