Question 1

Which property of muscle tissue allows it to return to its original length after being stretched, and which protein in the sarcomere is primarily responsible for this function?

Accepted Answer

Elasticity; titin

Question 2

A patient suffers a deep laceration that severs the perimysium of a skeletal muscle. Which of the following structures is most directly affected by this injury?

Accepted Answer

Bundles of muscle fibers (fascicles)

Question 3

During muscle contraction, which of the following changes occur in the sarcomere according to the sliding-filament theory?

Accepted Answer

The H band and I band narrow, and Z lines move closer together

Question 4

Which sequence correctly describes the events at the neuromuscular junction leading to muscle contraction?

Accepted Answer

Action potential arrives → ACh released → ACh binds to receptors → Na+ enters cell → action potential generated

Question 5

A muscle fiber is stimulated repeatedly at a frequency greater than 50 times per second, resulting in increased tension due to the summation of twitches. What is this phenomenon called?

Accepted Answer

Wave summation

Question 6

Which equation represents the conversion of ADP to ATP using creatine phosphate, catalyzed by creatine kinase?

Accepted Answer

$$\mathrm{ADP} + \mathrm{CP} \xrightarrow{\mathrm{CK}} \mathrm{ATP} + \mathrm{creatine}$$

Question 7

A weightlifter performs a 50-meter dash and experiences muscle hypertrophy. Which type of muscle fibers are primarily used, and which metabolic pathway is most important during this activity?

Accepted Answer

Fast fibers; anaerobic glycolysis

Question 8

Which of the following best explains why cardiac muscle cells cannot undergo tetanic contractions?

Accepted Answer

Cardiac muscle cells have long refractory periods that prevent wave summation

Question 9

A patient with severe muscle fatigue is found to have a decline in blood pH and pain. Which of the following is most likely contributing to their fatigue?

Accepted Answer

Accumulation of lactate and depletion of metabolic reserves

Question 10

Which of the following statements about smooth muscle tissue is correct?

Accepted Answer

Smooth muscle cells lack sarcomeres and have scattered thick filaments with many myosin heads

Question 11

During the contraction cycle, what event occurs immediately after the myosin head pivots toward the M line (power stroke)?

Accepted Answer

Myosin head binds ATP and detaches from actin

Question 12

Which of the following best describes the relationship between load and speed of contraction in skeletal muscle?

Accepted Answer

The heavier the load, the longer it takes for movement to begin and the less the muscle shortens

Question 13

Which of the following is a function of the sarcoplasmic reticulum (SR) in skeletal muscle fibers?

Accepted Answer

Storing and releasing calcium ions for muscle contraction

Question 14

A muscle fiber is at its maximum tension when the maximum number of cross-bridges is formed. Which sarcomere condition allows this?

Accepted Answer

Zone of overlap between thick and thin filaments is large

Question 15

Which of the following best describes the process of muscle relaxation after contraction?

Accepted Answer

Calcium ions are pumped back into the SR, troponin returns to its original position, and active sites are re-covered by tropomyosin

Question 16

Which of the following is true regarding muscle tone?

Accepted Answer

Muscle tone stabilizes positions of bones and joints without causing movement

Question 17

Which of the following hormones does NOT directly increase metabolic activities in skeletal muscles?

Accepted Answer

Insulin

Question 18

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

Accepted Answer

Isotonic contractions change muscle length with constant tension; isometric contractions produce tension without changing muscle length

Question 19

Which of the following is a unique feature of cardiac muscle cells compared to skeletal muscle fibers?

Accepted Answer

Cardiac muscle cells are branched, have a single nucleus, and are connected by intercalated discs

Muscle Tissue: Structure, Function, and Physiology

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