Question 1

Which of the following best explains why skeletal muscle fibers appear striated under a microscope?

Accepted Answer

The arrangement of thick and thin myofilaments into sarcomeres, creating alternating dark (A) and light (I) bands.

Question 2

A patient suffers from muscle weakness and is diagnosed with a disorder affecting the sarcoplasmic reticulum. Which process is most directly impaired?

Accepted Answer

Release and reuptake of $$\mathrm{Ca$$^{2+}$$}$$ ions necessary for muscle contraction and relaxation.

Question 3

During a muscle contraction, which event occurs immediately after $$\mathrm{Ca$$^{2+}$$}$$ binds to troponin?

Accepted Answer

Tropomyosin shifts, exposing myosin-binding sites on actin.

Question 4

Which of the following best describes the difference between isometric and isotonic muscle contractions?

Accepted Answer

Isometric contractions generate tension without changing muscle length; isotonic contractions change muscle length while tension remains constant.

Question 5

A sprinter relies primarily on which energy pathway during a 10-second race, and what is the net ATP yield from this pathway per glucose molecule?

Accepted Answer

Anaerobic glycolysis; $$2$$ ATP

Question 6

Which muscle fiber type would you expect to be most abundant in the legs of a marathon runner, and why?

Accepted Answer

Slow oxidative fibers, because they are fatigue-resistant and rely on aerobic metabolism.

Question 7

Which of the following best explains why cardiac muscle cannot undergo tetanus?

Accepted Answer

Cardiac muscle has a long refractory period, preventing summation of contractions.

Question 8

A person is unable to perform fine motor movements with their fingers. Which aspect of motor unit organization is most likely affected?

Accepted Answer

Loss of small motor units, which are responsible for precise control.

Question 9

Which of the following events occurs during the relaxation phase of a muscle twitch as seen on a myogram?

Accepted Answer

$$\mathrm{Ca$$^{2+}$$} is $$pumped back into the sarcoplasmic reticulum.

Question 10

Which of the following best describes the role of creatine phosphate in muscle cells during the initial seconds of intense exercise?

Accepted Answer

It directly donates a phosphate group to ADP to rapidly regenerate ATP.

Question 11

Which of the following is TRUE regarding smooth muscle contraction?

Accepted Answer

Smooth muscle contraction is slow, involves calmodulin for calcium binding, and can maintain tension with minimal ATP use.

Question 12

Which of the following best explains the 'all-or-none' principle in skeletal muscle fibers?

Accepted Answer

A muscle fiber contracts maximally if stimulated above threshold; otherwise, it does not contract at all.

Question 13

Which of the following is a function of the perimysium in skeletal muscle?

Accepted Answer

It surrounds fascicles and contains blood vessels and nerves.

Question 14

A patient with damage to the lower motor neurons exhibits flaccid paralysis. Which term best describes their muscle tone?

Accepted Answer

Hypotonic

Question 15

Which of the following best describes the sequence of events in the sliding filament theory of muscle contraction?

Accepted Answer

Action potential travels down sarcolemma, $$\mathrm{Ca$$^{2+}$$} is $$released, myosin binds to actin, sarcomere shortens.

Question 16

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

Accepted Answer

Self-excitation and presence of intercalated discs with gap junctions.

Question 17

Which of the following best explains why muscle fatigue occurs during intense anaerobic exercise?

Accepted Answer

Depletion of oxygen and accumulation of lactic acid reduce the muscle's ability to generate ATP.

Question 18

Which of the following is TRUE regarding the role of ATP in muscle contraction and relaxation?

Accepted Answer

ATP is required for detaching myosin heads from actin, pumping $$\mathrm{Ca$$^{2+}$$}$$ back into the SR, and maintaining ion gradients.

Question 19

Which of the following best describes the effect of wave summation on muscle contraction?

Accepted Answer

It increases the force of contraction by stimulating the muscle before it fully relaxes.

Question 20

Which of the following statements about muscle atrophy is correct?

Accepted Answer

It can be reversible if muscle activity is restored before muscle tissue is replaced by collagen.

Muscle Tissue: Structure, Function, and Physiology

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