Question 1

Which of the following best describes the role of titin in skeletal muscle fibers?

Accepted Answer

Titin provides elastic recoil and holds thick filaments in place within the sarcomere.

Question 2

A patient with Duchenne muscular dystrophy has a mutation in the gene encoding dystrophin. What is the primary consequence of this mutation at the cellular level?

Accepted Answer

Disrupted linkage between the cytoskeleton and the extracellular matrix, leading to muscle fiber fragility.

Question 3

Which of the following is TRUE regarding the differences between skeletal, cardiac, and smooth muscle?

Accepted Answer

Skeletal muscle is striated and voluntary, while cardiac muscle is striated and involuntary.

Question 4

During excitation-contraction coupling in skeletal muscle, what is the role of the T-tubules?

Accepted Answer

They transmit the action potential deep into the muscle fiber, triggering calcium release from the sarcoplasmic reticulum.

Question 5

Which of the following best describes the sliding filament mechanism of muscle contraction?

Accepted Answer

Thin filaments slide past thick filaments, causing sarcomeres to shorten while filament lengths remain unchanged.

Question 6

What is the correct sequence of events in the cross-bridge cycle during muscle contraction?

Accepted Answer

Myosin attaches to actin, power stroke occurs, ATP binds to myosin, myosin detaches from actin.

Question 7

Which of the following equations correctly represents the relationship between force ($$F$$), cross-sectional area ($$A$$), and stress ($$\sigma) in $$muscle tissue?

Accepted Answer

$$F = \sigma 	imes A$$

Question 8

A muscle fiber is described as a syncytium. What does this mean?

Accepted Answer

It is formed by the fusion of multiple cells, resulting in many nuclei within one cell.

Question 9

Which of the following statements about myosin heads is CORRECT?

Accepted Answer

Myosin heads contain ATPase activity and bind to actin during contraction.

Question 10

Which connective tissue layer surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 11

What is the primary function of myoglobin in skeletal muscle cells?

Accepted Answer

To bind oxygen for use in aerobic metabolism.

Question 12

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

Accepted Answer

Calcium ions are actively pumped back into the sarcoplasmic reticulum, causing tropomyosin to block myosin binding sites on actin.

Question 13

Which of the following is a functional characteristic of muscle tissue that allows it to respond to a stimulus?

Accepted Answer

Excitability (Responsiveness)

Question 14

A muscle fiber at rest has low intracellular calcium concentration. What is the state of the myosin binding sites on actin?

Accepted Answer

They are blocked by tropomyosin, preventing cross-bridge formation.

Question 15

Which of the following best describes the role of troponin in muscle contraction?

Accepted Answer

Troponin binds calcium ions, causing a conformational change that moves tropomyosin away from myosin binding sites on actin.

Question 16

Which of the following is TRUE regarding the arrangement of myofilaments in a sarcomere?

Accepted Answer

Thin filaments are anchored to the Z disc, while thick filaments are anchored to the M line.

Question 17

Which of the following is a correct description of the sarcolemma?

Accepted Answer

The plasma membrane of the muscle cell.

Question 18

If a muscle fiber has a diameter of $$50\ \mu m$$ and a length of $$5\ cm$$, what is its approximate volume in $$mm^3$$? (Assume the fiber is a cylinder. Use $$V = \pi r^2$ h)$$

Accepted Answer

$$V \approx 98\ mm^3$

Question 19

Which of the following is a function of skeletal muscle that is essential for homeostasis?

Accepted Answer

Generation of heat to maintain body temperature.

Question 20

Which of the following statements about F-actin and G-actin is CORRECT?

Accepted Answer

G-actin polymerizes to form F-actin, which is the filamentous structure in thin filaments.

Cellular Physiology of Muscle: Structure, Function, and Mechanisms

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