Question 1

Which of the following best describes the fate of pyruvate produced during glycolysis in muscle fibers when oxygen is NOT abundant?

Accepted Answer

Pyruvate is converted into lactic acid, some of which diffuses into the bloodstream.

Question 2

A patient is experiencing muscle fatigue after 45 seconds of intense exercise. Which energy source is now the predominant provider of ATP in their muscle fibers?

Accepted Answer

Oxidative (aerobic) catabolism

Question 3

Which of the following statements about the length-tension relationship in skeletal muscle is CORRECT?

Accepted Answer

Maximal tension is produced when the sarcomere is at its optimal length, allowing for maximal crossbridge formation.

Question 4

Which of the following best explains why fused (complete) tetanus generates more tension than unfused (incomplete) tetanus?

Accepted Answer

Calcium ion concentration in the cytosol remains high, allowing more crossbridges to form.

Question 5

A muscle fiber is stimulated 90 times per second. Which of the following best describes the resulting contraction?

Accepted Answer

Fused (complete) tetanus

Question 6

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

Accepted Answer

They are small to intermediate in diameter and can maintain extended periods of contraction.

Question 7

Which of the following best describes the role of myoglobin in muscle fibers during oxidative catabolism?

Accepted Answer

Myoglobin binds and releases oxygen as needed for mitochondrial ATP production.

Question 8

A patient presents with muscle paralysis after eating improperly canned food. Which mechanism best explains the effect of the toxin involved?

Accepted Answer

The toxin blocks acetylcholine release at the neuromuscular junction, preventing muscle contraction.

Question 9

Which of the following equations correctly represents the net ATP yield from glycolysis of one glucose molecule?

Accepted Answer

$$2 	ext{ ATP}$$

Question 10

During a muscle twitch, which period corresponds to the time when calcium ions are actively pumped back into the sarcoplasmic reticulum?

Accepted Answer

Relaxation period

Question 11

Which of the following best explains why muscle fibers can sustain contraction for hours during aerobic exercise?

Accepted Answer

Oxidative catabolism in mitochondria provides continuous ATP as long as oxygen and fuels are available.

Question 12

Which of the following is TRUE regarding wave summation in muscle fibers?

Accepted Answer

It results in twitches with progressively greater tension due to incomplete calcium reuptake.

Question 13

A muscle fiber is overly shortened before contraction. What is the expected effect on tension production?

Accepted Answer

Tension production is reduced because there is little room for thin filaments to be pulled together.

Question 14

Which of the following best describes the difference between fast-twitch and slow-twitch muscle fibers?

Accepted Answer

Fast-twitch fibers have high myosin ATPase activity and fatigue quickly; slow-twitch fibers have low myosin ATPase activity and are resistant to fatigue.

Question 15

Which of the following is a direct result of the Clostridium tetani toxin in the nervous system?

Accepted Answer

Excessive stimulation of skeletal muscles resulting in tetanic spasms.

Question 16

Which of the following best explains why Botox® injections can reduce the appearance of facial wrinkles?

Accepted Answer

Botox® blocks acetylcholine release, relaxing facial muscles and reducing movement.

Muscle Fiber Energy Sources and Tension Production

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