Question 1

Which of the following best explains why maximum tension in a skeletal muscle fiber is produced at an optimal sarcomere length?

Accepted Answer

Because the zone of overlap between thick and thin filaments is large, but the thin filaments do not extend across the sarcomere’s center, allowing maximal cross-bridge interactions.

Question 2

During a biceps curl, as shown in the images, which type of muscle contraction occurs when the muscle shortens while lifting the weight?

Accepted Answer

Concentric contraction

Question 3

A muscle fiber is stimulated repeatedly at a frequency that does not allow complete relaxation between stimuli, resulting in a sustained but wavering contraction. What is this phenomenon called?

Accepted Answer

Wave summation

Question 4

Which of the following equations correctly represents the reaction catalyzed by creatine kinase during muscle contraction?

Accepted Answer

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

Question 5

Which muscle fiber type is most resistant to fatigue and why?

Accepted Answer

Slow fibers, because they contain many mitochondria, extensive capillaries, and high myoglobin content.

Question 6

A patient is experiencing muscle fatigue after intense exercise. Which of the following is the primary cause of this fatigue at the cellular level?

Accepted Answer

Accumulation of hydrogen ions from ATP hydrolysis, increasing cytosol acidity and inhibiting contraction

Question 7

Which of the following best describes the process of muscle hypertrophy?

Accepted Answer

The enlargement of muscle fibers through increased mitochondria, myofibrils, glycogen reserves, and glycolytic enzymes

Question 8

During moderate activity, which metabolic pathway is primarily responsible for ATP production in skeletal muscle fibers?

Accepted Answer

Aerobic metabolism of glucose from stored glycogen

Question 9

Which of the following statements about isometric contractions is correct?

Accepted Answer

The muscle length remains constant while tension increases.

Question 10

A muscle fiber is stretched so that there is no overlap between thick and thin filaments. What is the result?

Accepted Answer

No active tension can be produced because cross-bridge interactions cannot occur.

Question 11

Which of the following best explains the concept of 'recruitment' in muscle contraction?

Accepted Answer

The activation of motor units starting from the smallest, slowest to the largest, most powerful units as more force is needed.

Question 12

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

Accepted Answer

Use of calmodulin and myosin light chain kinase for contraction

Question 13

Which of the following best describes the role of myoglobin in slow muscle fibers?

Accepted Answer

It binds oxygen, allowing sustained aerobic metabolism.

Question 14

During the recovery period after intense exercise, which process is primarily responsible for the removal and recycling of lactate?

Accepted Answer

Lactate is converted to pyruvate in the liver, which can then be used to synthesize glucose.

Question 15

Which of the following best describes the effect of increasing the load on a muscle during isotonic contraction?

Accepted Answer

The speed of contraction decreases as the load increases.

Question 16

Which of the following is a characteristic of cardiac muscle tissue but not skeletal muscle tissue?

Accepted Answer

Presence of intercalated discs

Question 17

A muscle is repeatedly stimulated at a frequency that allows complete relaxation between contractions. What is the expected outcome?

Accepted Answer

Treppe, with a gradual increase in peak tension with each stimulus.

Question 18

Which of the following best explains why fast fibers fatigue more quickly than slow fibers?

Accepted Answer

Fast fibers have fewer mitochondria and rely more on anaerobic glycolysis.

Question 19

Which of the following is the correct sequence of energy source utilization in a muscle fiber during a 2-minute sprint?

Accepted Answer

ATP stores → Creatine phosphate → Anaerobic glycolysis → Aerobic metabolism

Muscle Physiology: Mechanisms of Contraction, Metabolism, and Fiber Types

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