Question 1

Which of the following best describes central fatigue in skeletal muscle?

Accepted Answer

It is a sensation of tiredness and a desire to cease activity, primarily mediated by the brain.

Question 2

During a 100-meter sprint, which energy source is most rapidly depleted in skeletal muscle?

Accepted Answer

Creatine phosphate

Question 3

Which of the following is a characteristic of Type I skeletal muscle fibres?

Accepted Answer

High mitochondrial density and slow ATPase activity

Question 4

A patient experiences muscle weakness after repeated stimulation. Laboratory tests show increased extracellular potassium ($$K^+) in $$the T-tubule region. Which process is most likely impaired?

Accepted Answer

Excitation-contraction coupling due to altered threshold for action potentials

Question 5

Which equation best represents the relationship between muscle force ($$F) $$and the number of cross-bridges formed ($$N_{cb}$$)?

Accepted Answer

$$F = N_{cb} 	imes f_{cb}$$

Question 6

Which of the following changes would most likely increase the tension developed by a single muscle fibre?

Accepted Answer

Increasing the diameter of the muscle fibre

Question 7

A marathon runner relies primarily on which pathway for ATP production during the race?

Accepted Answer

Aerobic metabolism

Question 8

Which of the following is a direct effect of peripheral fatigue on muscle contraction?

Accepted Answer

Reduced release and reuptake of $$Ca^{2+} by $$the sarcoplasmic reticulum

Question 9

Which type of skeletal muscle fibre is most resistant to fatigue and why?

Accepted Answer

Type I, because of high oxidative capacity and abundant mitochondria

Question 10

If a muscle fibre is stimulated at a frequency that does not allow relaxation between twitches, what is the resulting contractile response called?

Accepted Answer

Fused tetanus

Question 11

Which of the following best explains why increasing the rate of action potentials in a muscle fibre increases tension?

Accepted Answer

It causes more calcium to be released from the sarcoplasmic reticulum before previous calcium is re-sequestered.

Question 12

Which of the following is NOT a determinant of force/tension development in an entire skeletal muscle?

Accepted Answer

Amount of acetylcholine stored in mitochondria

Question 13

A muscle fibre with few mitochondria, high glycogen stores, and rapid ATPase activity is most likely classified as:

Accepted Answer

Type IIX (fast glycolytic)

Question 14

Which of the following would most likely occur if the accumulation of inorganic phosphate ($$Pi) in $$the muscle fibre increases during intense exercise?

Accepted Answer

Slowed release of $$Pi$$ and ADP during the cross-bridge cycle

Question 15

Which of the following best describes the effect of initial resting length on muscle tension development?

Accepted Answer

Tension is maximized when actin and myosin filaments have optimal overlap.

Question 16

Which process is most likely to be the limiting factor in muscle fatigue during prolonged, submaximal exercise?

Accepted Answer

Failure of excitation-contraction coupling

Question 17

Which of the following is true regarding the duration of a muscle action potential ($$t_{AP}) $$and a muscle twitch ($$t_{twitch}$$)?

Accepted Answer

$$t_{AP} \u003c t_{twitch}$$

Question 18

Which of the following would most likely result from a decrease in the number of motor units activated in a muscle?

Accepted Answer

Decreased muscle tension

Question 19

Which of the following is a plausible consequence of decreased acetylcholine synthesis at the neuromuscular junction during repeated maximal stimulation?

Accepted Answer

Reduced transmitter release leading to decreased muscle activation

Question 20

Which of the following best explains why Type IIA muscle fibres are considered 'fast oxidative-glycolytic'?

Accepted Answer

They possess both high mitochondrial content and rapid ATPase activity.

Skeletal Muscle Fatigue, Fibre Types, and Force Development

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