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 Ca$$^{2+}$$ ions, which are essential for initiating muscle contraction.

Question 2

A patient presents with muscle stiffness several hours after death. Which of the following best explains the physiological cause of rigor mortis?

Accepted Answer

ATP is no longer produced, preventing detachment of myosin heads from actin, resulting in sustained cross-bridge formation.

Question 3

Which connective tissue sheath surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 4

During the sliding filament model of contraction, what happens to the H zone and I band as the sarcomere shortens?

Accepted Answer

Both the H zone and I band decrease in width.

Question 5

Which of the following is the correct sequence of events for excitation-contraction (E-C) coupling in skeletal muscle?

Accepted Answer

Action potential propagates along sarcolemma → T tubules depolarize → Ca$$^{2+}$$ released from SR → Ca$$^{2+}$$ binds to troponin → Cross-bridge formation

Question 6

Which of the following muscle types is characterized by single, fusiform, uninucleate cells with no striations?

Accepted Answer

Smooth muscle

Question 7

A muscle fiber is stimulated by a single action potential and then relaxes completely before the next stimulus. What is this response called?

Accepted Answer

Muscle twitch

Question 8

Which of the following best explains why fast glycolytic fibers fatigue more quickly than slow oxidative fibers during intense exercise?

Accepted Answer

They rely primarily on anaerobic glycolysis, which produces ATP rapidly but inefficiently.

Question 9

Which of the following equations correctly represents the direct phosphorylation of ADP by creatine phosphate in skeletal muscle?

Accepted Answer

$$\mathrm{Creatine\ phosphate + ADP \rightarrow Creatine + ATP}$$

Question 10

Which of the following is a unique feature of cardiac muscle compared to skeletal and smooth muscle?

Accepted Answer

Branching chains of cells connected by intercalated discs

Question 11

A muscle is stretched to 150% of its resting length before contraction. What is the expected effect on the force of contraction, and why?

Accepted Answer

Force decreases because thick and thin filaments do not overlap enough for cross-bridge formation.

Question 12

Which of the following best describes the mechanism by which smooth muscle contraction is initiated?

Accepted Answer

Ca$$^{2+}$$ binds to calmodulin, activating myosin light chain kinase, which phosphorylates myosin heads.

Question 13

Which of the following is true regarding the recruitment of motor units during skeletal muscle contraction?

Accepted Answer

Motor units with smaller muscle fibers are recruited first, followed by larger units as stimulus intensity increases.

Question 14

Which of the following best explains why muscle tone is important for the body?

Accepted Answer

It keeps muscles firm, healthy, and ready to respond to stimulation.

Question 15

Which of the following is a characteristic of multiunit smooth muscle?

Accepted Answer

It consists of independent muscle fibers that are innervated by the autonomic nervous system and rarely exhibit gap junctions.

Question 16

Which of the following best describes the process of wave (temporal) summation in skeletal muscle?

Accepted Answer

Successive stimuli are delivered before the muscle can relax completely, resulting in increased force of contraction.

Question 17

Which of the following is the main fuel source for muscle contraction after 30 minutes of moderate exercise?

Accepted Answer

Fatty acids

Question 18

Which of the following is NOT a function of skeletal muscle?

Accepted Answer

Secretion of hormones

Question 19

Which of the following best explains why smooth muscle can maintain contraction for prolonged periods with little energy cost?

Accepted Answer

Smooth muscle myofilaments may latch together, and ATPases are slower than in skeletal muscle.

Muscles and Muscle Tissue: Structure, Function, and Physiology

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