Question 1

Which of the following best describes the microscopic structure of a skeletal muscle fiber?

Accepted Answer

Elongated cell, multiple peripheral nuclei, striated, contains myofibrils and mitochondria

Question 2

During excitation-contraction coupling in skeletal muscle, which event directly triggers the release of Ca$$^{2+}$$ from the sarcoplasmic reticulum?

Accepted Answer

Depolarization of the T-tubule membrane

Question 3

Which statement about the neuromuscular junction is correct?

Accepted Answer

It is the site where acetylcholine is released from the motor neuron to stimulate the muscle fiber

Question 4

Which of the following best explains the difference between isotonic and isometric contractions?

Accepted Answer

Isotonic contractions change muscle length while maintaining constant tension; isometric contractions generate force without changing muscle length

Question 5

A patient is unable to produce smooth, graded muscle contractions. Which process is most likely impaired?

Accepted Answer

Temporal summation and motor unit recruitment

Question 6

Which muscle type is most resistant to fatigue and why?

Accepted Answer

Slow oxidative fibers, because they have abundant mitochondria and use aerobic metabolism

Question 7

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

Accepted Answer

Skeletal muscle fibers are voluntary and striated; smooth muscle fibers are involuntary and non-striated

Question 8

Which equation best represents the relationship between force (F), cross-sectional area (A), and tension (T) in a muscle fiber?

Accepted Answer

$$F = T 	imes A$$

Question 9

What is the primary role of ATP in the cross-bridge cycle?

Accepted Answer

To detach the myosin head from actin and energize the myosin head for the next power stroke

Question 10

Which of the following best explains rigor mortis?

Accepted Answer

Ca$$^{2+}$$ leaks into the cytosol, myosin binds actin, but lack of ATP prevents cross-bridge detachment

Question 11

Which structure in the muscle fiber conducts action potentials from the surface into the interior of the cell?

Accepted Answer

Transverse (T) tubules

Question 12

Which protein complex regulates the exposure of myosin binding sites on actin in response to Ca$$^{2+}$$?

Accepted Answer

Tropomyosin-troponin complex

Question 13

A muscle fiber is stretched beyond its optimal length before contraction. What will happen to the force generated?

Accepted Answer

Force will decrease due to reduced overlap between thick and thin filaments

Question 14

Which of the following best describes the arrangement of thick and thin filaments in a sarcomere?

Accepted Answer

Thin filaments are anchored to the Z-disc; thick filaments are anchored to the M-line

Question 15

Which process is responsible for the removal of Ca$$^{2+}$$ from the cytosol during muscle relaxation?

Accepted Answer

Active transport by Ca$$^{2+}$$ ATPases into the sarcoplasmic reticulum

Question 16

Which of the following is true regarding motor unit recruitment?

Accepted Answer

Smaller motor units are recruited first, followed by larger ones as more force is needed

Question 17

Which equation best represents the ATP hydrolysis reaction catalyzed by myosin ATPase?

Accepted Answer

$$ATP ightarrow ADP + Pi + 	ext{energy}$$

Question 18

Which of the following is a function of satellite cells in skeletal muscle?

Accepted Answer

Proliferate and fuse to regenerate muscle fibers after injury

Question 19

Which property allows muscle tissue to return to its resting length after being stretched?

Accepted Answer

Elasticity

Question 20

Which of the following best describes the sliding filament theory?

Accepted Answer

Muscle contraction occurs when thin filaments slide past thick filaments, shortening the sarcomere

Skeletal Muscle: Structure, Function, and Physiology

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