Question 1

A marathon runner, such as the one shown crossing the finish line in the first image, relies primarily on which type of skeletal muscle fiber during a race, and why?

Accepted Answer

Slow twitch oxidative fibers, because they are fatigue-resistant and support aerobic metabolism.

Question 2

Which of the following best explains why sprinters, like those shown in the second image, have a higher percentage of fast twitch muscle fibers compared to marathon runners?

Accepted Answer

Fast twitch fibers are larger in diameter and contract rapidly, producing powerful, short bursts of force.

Question 3

Referencing the table of muscle fiber properties, which muscle fiber type has the highest myoglobin content and what is the physiological significance of this?

Accepted Answer

Slow fibers; high myoglobin content allows for sustained aerobic metabolism and resistance to fatigue.

Question 4

A muscle biopsy shows a predominance of small, darkly stained fibers under the microscope. What can you infer about the function of this muscle?

Accepted Answer

It is specialized for sustained, endurance activities and resists fatigue.

Question 5

Which of the following best describes the change in muscle cell diameter during hypertrophy and atrophy?

Accepted Answer

Hypertrophy increases the diameter of existing muscle fibers; atrophy decreases the diameter of existing muscle fibers.

Question 6

During intense, brief exercise such as weightlifting (as shown in the image), which energy system is primarily used after ATP and creatine phosphate (CP) reserves are depleted?

Accepted Answer

Anaerobic glycolysis

Question 7

Which of the following equations best represents the process of anaerobic glycolysis in muscle cells?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} \rightarrow 2\ \mathrm{C_3H_6O_3} + 2\ \mathrm{ATP}$$

Question 8

Aging leads to a decrease in muscle strength and endurance. Which of the following is NOT a primary reason for this decline?

Accepted Answer

Increase in the number of muscle fibers

Question 9

Which of the following best explains why cardiac muscle cells are able to contract in a coordinated fashion?

Accepted Answer

They are connected by intercalated discs containing gap junctions and desmosomes.

Question 10

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

Accepted Answer

Ability to undergo plasticity, adapting to new lengths while retaining contractile ability

Question 11

A patient presents with muscle weakness and is found to have a genetic disorder affecting the X chromosome. Which muscular disorder is most likely?

Accepted Answer

Duchenne’s muscular dystrophy

Question 12

Which of the following best describes the control of contraction in cardiac muscle tissue?

Accepted Answer

Controlled by pacemaker cells and modulated by the autonomic nervous system

Question 13

Which of the following would most likely result in muscle atrophy?

Accepted Answer

Long-term immobilization of a limb

Question 14

A person is exposed to a nerve gas that inhibits acetylcholinesterase. What type of paralysis would most likely result?

Accepted Answer

Spastic paralysis due to continuous stimulation of muscle fibers

Question 15

Which of the following best describes the energy source for cardiac muscle contraction?

Accepted Answer

Aerobic metabolism with high myoglobin and mitochondria content

Question 16

Which of the following is a secondary muscular system disorder?

Accepted Answer

Electrolyte imbalance due to kidney disease

Question 17

Which of the following best explains why slow twitch muscle fibers appear darker under the microscope?

Accepted Answer

They have a higher concentration of myoglobin and more mitochondria.

Question 18

Which of the following best describes the effect of aerobic endurance training on skeletal muscle fibers?

Accepted Answer

Increases capillary supply and mitochondrial content in intermediate fibers.

Question 19

Which of the following is true regarding the length-tension relationship in smooth muscle?

Accepted Answer

Smooth muscle can adapt to new lengths and still contract effectively (plasticity).

Muscle Performance, Fiber Types, and Muscle Tissue Comparison

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