Question 1

Which of the following best explains why skeletal muscle fibers are multinucleated?

Accepted Answer

They are formed by the fusion of multiple embryonic cells, resulting in a single cell with many nuclei.

Question 2

A patient is experiencing muscle fatigue during intense exercise. Which of the following is NOT a direct physiological factor contributing to muscle fatigue?

Accepted Answer

Psychological tiredness

Question 3

Which of the following statements about the sliding filament theory is correct?

Accepted Answer

Sarcomeres shorten as actin and myosin filaments slide past each other, increasing their overlap.

Question 4

During skeletal muscle contraction, what is the role of troponin?

Accepted Answer

It binds to calcium, causing a conformational change that moves tropomyosin and exposes myosin binding sites on actin.

Question 5

Which of the following best describes the difference between single-unit and multi-unit smooth muscle?

Accepted Answer

Single-unit smooth muscle cells are joined by gap junctions and contract together, while multi-unit smooth muscle cells contract independently.

Question 6

A drug blocks the release of calcium from the sarcoplasmic reticulum in skeletal muscle. What is the most immediate effect on muscle contraction?

Accepted Answer

Tropomyosin will continue to block myosin binding sites on actin, preventing contraction.

Question 7

Which of the following is TRUE regarding the source of calcium for contraction in smooth muscle?

Accepted Answer

Calcium enters the cytosol from both the extracellular fluid and the sarcoplasmic reticulum.

Question 8

Which of the following best explains why smooth muscle can sustain contractions for extended periods without fatiguing?

Accepted Answer

Smooth muscle uses less energy to generate and maintain force and contracts more slowly.

Question 9

A person is unable to perform fine motor movements with their eyes. Which of the following is the most likely explanation based on motor unit recruitment?

Accepted Answer

Their eye muscles have too many muscle cells per motor unit, reducing fine control.

Question 10

Which of the following events occurs FIRST during skeletal muscle contraction after acetylcholine is released at the neuromuscular junction?

Accepted Answer

Sodium ions enter the muscle cell, causing depolarization.

Question 11

Which of the following is a key difference between skeletal and smooth muscle contraction mechanisms?

Accepted Answer

Skeletal muscle contraction is initiated by troponin binding to calcium, while smooth muscle contraction is initiated by phosphorylation of myosin light chains.

Question 12

Which of the following best describes the process of muscle relaxation in smooth muscle?

Accepted Answer

Calcium is pumped back into the sarcoplasmic reticulum and out of the cell, causing myosin light chains to be dephosphorylated.

Question 13

A patient is diagnosed with a disease that prevents the phosphorylation of myosin light chains in smooth muscle. What is the most likely effect?

Accepted Answer

Smooth muscle contraction will be impaired because myosin ATPase activity will not increase.

Question 14

Which of the following is NOT a characteristic of cardiac muscle?

Accepted Answer

Multinucleated cells

Question 15

Which of the following best explains why smooth muscle lacks striations?

Accepted Answer

The contractile fibers in smooth muscle are not arranged in sarcomeres.

Question 16

Which of the following is TRUE regarding the control of smooth muscle contraction?

Accepted Answer

Smooth muscle contraction can be initiated by both electrical and chemical signals.

Question 17

Which of the following best describes the function of T-tubules in skeletal muscle?

Accepted Answer

They transmit depolarization events throughout the muscle cell to ensure simultaneous contraction of all myofibrils.

Question 18

A muscle is stimulated so rapidly that it does not have time to relax between stimuli, resulting in a sustained contraction. What is this phenomenon called?

Accepted Answer

Tetanus

Question 19

Which of the following is a correct sequence of events in skeletal muscle contraction?

Accepted Answer

Acetylcholine release → Na+ influx → Ca++ release from SR → Troponin binds Ca++ → Tropomyosin moves → Myosin binds actin

Question 20

Which of the following best explains why recruitment of motor units increases the strength of skeletal muscle contraction?

Accepted Answer

More motor units activated means more muscle fibers contract, generating greater force.

Muscle Tissue: Structure, Function, and Physiology

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