Question 1

Which of the following best describes the role of calcium ions ($$\mathrm{Ca$$^{2+}$$}) in $$skeletal muscle contraction?

Accepted Answer

They bind to troponin, causing tropomyosin to move and expose myosin-binding sites on actin.

Question 2

During the sliding filament model of muscle contraction, which of the following changes occur in the sarcomere?

Accepted Answer

I bands shorten, Z discs move closer together, and H zones disappear.

Question 3

A patient is diagnosed with myasthenia gravis. Which of the following best explains the physiological basis of their muscle weakness?

Accepted Answer

Autoimmune destruction of ACh receptors on the muscle fiber membrane.

Question 4

Which of the following best describes an isometric muscle contraction?

Accepted Answer

The muscle tension increases but does not exceed the load, so the muscle does not shorten.

Question 5

Which metabolic pathway provides the greatest yield of ATP per glucose molecule during muscle contraction?

Accepted Answer

Aerobic respiration, yielding 30 ATP per glucose.

Question 6

A sprinter begins a 100-meter dash. Which energy system is primarily used during the first 6 seconds of maximal effort?

Accepted Answer

Phosphagen system (creatine phosphate)

Question 7

Which of the following is a characteristic of slow-twitch muscle fibers?

Accepted Answer

They are resistant to fatigue and well adapted for aerobic respiration.

Question 8

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

ATP is no longer produced, so calcium cannot be pumped back into the SR and myosin heads cannot detach from actin.

Question 9

Which of the following is true regarding the cross bridge cycle in muscle contraction?

Accepted Answer

ATP hydrolysis cocks the myosin head, preparing it for the next power stroke.

Question 10

Which of the following factors does NOT contribute to muscle fatigue during prolonged exercise?

Accepted Answer

Increased density of blood capillaries

Question 11

Which of the following best describes the difference between concentric and eccentric isotonic contractions?

Accepted Answer

Concentric contractions shorten the muscle as it does work, while eccentric contractions lengthen the muscle as it generates force.

Question 12

Which of the following is a direct result of acetylcholine (ACh) binding to its receptors on the sarcolemma at the neuromuscular junction?

Accepted Answer

Generation of an end plate potential (EPP)

Question 13

Which of the following adaptations is most likely to occur in skeletal muscle as a result of endurance (aerobic) exercise?

Accepted Answer

Increase in glycogen stores, mitochondria, and capillary density

Question 14

A weightlifter is performing a biceps curl. As he lifts the weight, which type of muscle contraction is primarily occurring in the biceps brachii?

Accepted Answer

Concentric isotonic contraction

Question 15

Which of the following is the correct sequence of events in excitation-contraction coupling?

Accepted Answer

ACh released from axon terminal → End plate potential generated → Action potential travels along sarcolemma → Ca$$^{2+}$$ released from SR → Cross bridge formation

Question 16

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

Accepted Answer

They rely primarily on anaerobic fermentation, which produces less ATP per glucose.

Question 17

Which of the following is NOT a function of ATP in muscle contraction?

Accepted Answer

Binding to troponin to expose myosin-binding sites on actin

Question 18

Which of the following would most likely increase a person's muscular strength?

Accepted Answer

Resistance training, such as weight lifting

Question 19

Which of the following is a real-life example of an eccentric isotonic contraction?

Accepted Answer

Lowering a book slowly onto a table

Question 20

Which of the following best describes the role of the phosphagen system in muscle metabolism?

Accepted Answer

It provides a rapid source of ATP for short bursts of intense activity by transferring a phosphate from creatine phosphate to ADP.

The Muscular System: Mechanisms of Skeletal Muscle Contraction and Physiology

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