Question 1

Which of the following correctly describes the hierarchical organization of skeletal muscle from largest to smallest structure?

Accepted Answer

Muscle, fascicle, muscle fiber, myofibril, myofilament

Question 2

During muscle contraction, which region of the sarcomere shortens while the A band remains unchanged?

Accepted Answer

H zone and I band

Question 3

Which protein directly binds calcium ions to initiate the exposure of myosin-binding sites on actin?

Accepted Answer

Troponin

Question 4

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

Accepted Answer

Storing and releasing calcium ions ($$\mathrm{Ca$$^{2+}$$})$$

Question 5

Which of the following best describes the sliding filament theory?

Accepted Answer

Actin filaments slide over myosin filaments, shortening the sarcomere

Question 6

Which event occurs first during excitation-contraction coupling in skeletal muscle?

Accepted Answer

Binding of acetylcholine to receptors on the motor end plate

Question 7

A patient experiences muscle soreness and elevated plasma creatine kinase (CK) levels 48 hours after running downhill. What is the most likely cause?

Accepted Answer

Eccentric muscle contractions causing contraction-induced injury

Question 8

Which of the following is a correct sequence of events in the cross-bridge cycle?

Accepted Answer

ATP binds to myosin, myosin detaches from actin, myosin head cocks, myosin binds to actin

Question 9

Which of the following best explains why antioxidants in the diet can reduce muscle damage after intense exercise?

Accepted Answer

Antioxidants minimize calcium-induced damage, resulting in less LDH release

Question 10

Which of the following is a function of cytokines such as interleukin-6 (IL-6) in skeletal muscle repair?

Accepted Answer

Stimulating the proliferation of satellite cells

Question 11

A muscle fiber is stimulated to contract, but the sarcoplasmic reticulum fails to release $$\mathrm{Ca$$^{2+}$$}. $$What is the most immediate effect?

Accepted Answer

Troponin does not change conformation, and myosin-binding sites on actin remain covered

Question 12

Which of the following best describes the role of satellite cells in muscle regeneration after injury?

Accepted Answer

They fuse to form new muscle fibers

Question 13

Which of the following is true regarding the changes in sarcomere structure during maximal contraction?

Accepted Answer

The H zone disappears and the I band narrows

Question 14

Which of the following best explains why trained athletes experience less contraction-induced muscle injury compared to untrained individuals?

Accepted Answer

They have a more homogeneous population of sarcomeres

Question 15

Which of the following is a direct result of increased $$\mathrm{Ca$$^{2+}$$}$$ concentration in the sarcoplasm during muscle contraction?

Accepted Answer

Troponin changes shape, moving tropomyosin and exposing myosin-binding sites on actin

Question 16

Which of the following best describes the role of fibroblast growth factor (FGF) and insulin-like growth factor (IGF-1) after muscle injury?

Accepted Answer

They recruit white blood cells and activate satellite cells for muscle repair

Question 17

Which of the following is a characteristic of contraction-induced muscle injury?

Accepted Answer

It is highly focal and localized at the sarcomere level

Question 18

Which of the following best explains why hypoxia alone does not cause muscle damage, but hypoxia combined with contraction does?

Accepted Answer

Contraction increases intracellular $$\mathrm{Ca$$^{2+}$$}$$, leading to greater LDH release and muscle damage

Question 19

Which of the following is the correct order of events during muscle repair after contraction-induced injury?

Accepted Answer

Degeneration, activation of satellite cells, alignment and fusion, formation of primary myotube, maturation

Structure and Function of Skeletal Muscle: Organization, Contraction, and Repair

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