Question 1

Which of the following best describes the role of the sarcoplasmic reticulum (SR) in skeletal muscle contraction?

Accepted Answer

It stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$necessary for muscle contraction.

Question 2

During the sliding filament model of muscle contraction, which event directly causes the sarcomere to shorten?

Accepted Answer

Myosin heads pivot, pulling actin filaments toward the M line.

Question 3

A patient is diagnosed with myasthenia gravis. Which of the following best explains the physiological basis of their muscle weakness?

Accepted Answer

Loss of acetylcholine receptors at the neuromuscular junction impairs action potential generation in muscle fibers.

Question 4

Which of the following equations correctly represents the reaction catalyzed by creatine kinase in muscle cells?

Accepted Answer

$$\mathrm{ADP + CP \rightarrow ATP + C}$$

Question 5

Which of the following best describes the function of troponin in skeletal muscle contraction?

Accepted Answer

It binds calcium ions, causing a conformational change that moves tropomyosin and exposes actin's active sites.

Question 6

A muscle fiber is stimulated at a frequency that does not allow complete relaxation between stimuli, resulting in increasing tension. What is this phenomenon called?

Accepted Answer

Wave summation

Question 7

Which of the following statements about fast-twitch (Type II-B) muscle fibers is correct?

Accepted Answer

They fatigue rapidly because most ATP is produced anaerobically.

Question 8

What is the primary source of ATP for skeletal muscle during peak activity levels?

Accepted Answer

Glycolysis

Question 9

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

ATP is depleted, preventing detachment of myosin heads from actin.

Question 10

A muscle is contracting but its length does not change and the tension never exceeds the load. What type of contraction is this?

Accepted Answer

Isometric contraction

Question 11

Which of the following best describes the role of titin in the sarcomere?

Accepted Answer

It connects thick filaments to Z lines, helping maintain sarcomere structure and elasticity.

Question 12

Which of the following is a function of skeletal muscle that is NOT shared by cardiac or smooth muscle?

Accepted Answer

Voluntary movement of the body by pulling on bones

Question 13

A patient presents with sustained, powerful muscle contractions after a deep puncture wound. Which condition is most likely responsible?

Accepted Answer

Tetanus caused by Clostridium tetani toxin

Question 14

Which of the following best describes the process of recruitment in skeletal muscle contraction?

Accepted Answer

Increasing the number of active motor units to produce greater tension

Question 15

Which of the following best explains why muscle tension decreases when sarcomeres are stretched beyond their optimal length?

Accepted Answer

There is less overlap between thick and thin filaments, reducing the number of cross-bridges that can form.

Question 16

Which of the following is a correct statement about the Cori cycle during muscle recovery?

Accepted Answer

Lactate produced by muscles is converted to glucose in the liver, which is then returned to muscle cells.

Question 17

Which of the following best describes the function of the perimysium in skeletal muscle?

Accepted Answer

It divides the muscle into fascicles and contains blood vessels and nerves.

Question 18

Which of the following is a characteristic of slow-twitch (Type I) muscle fibers?

Accepted Answer

They have high myoglobin content and are resistant to fatigue.

Question 19

Which of the following best explains the effect of botulinum toxin on skeletal muscle function?

Accepted Answer

It blocks the release of acetylcholine at the neuromuscular junction, preventing muscle contraction.

Skeletal Muscle Tissue: Structure, Function, and Physiology

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