Question 1

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

Accepted Answer

Calcium ions bind to troponin, causing the troponin–tropomyosin complex to shift and expose myosin binding sites on actin.

Question 2

A patient is unable to relax their muscles after a contraction. Which of the following is the most likely explanation based on the sliding filament mechanism?

Accepted Answer

There is a lack of ATP to detach myosin heads from actin.

Question 3

Which of the following statements about slow-twitch muscle fibers is correct?

Accepted Answer

They are well-supplied with blood vessels and are used for endurance activities.

Question 4

During a biceps curl, the biceps brachii contracts while the triceps brachii relaxes. What type of muscle relationship is this an example of?

Accepted Answer

Antagonistic muscles

Question 5

Which process provides the fastest way for muscle cells to regenerate ATP during the initial seconds of intense exercise?

Accepted Answer

Transfer of a phosphate group from creatine phosphate to ADP

Question 6

A laboratory myogram shows a muscle fiber receiving rapid, repeated stimuli, resulting in a sustained, maximal contraction. What is this phenomenon called?

Accepted Answer

Tetanus

Question 7

Which of the following best explains why cardiac muscle cells can contract in a coordinated fashion without direct nerve stimulation?

Accepted Answer

They have intercalated discs with gap junctions that allow electrical impulses to pass between cells.

Question 8

Which of the following is true regarding isometric muscle contractions?

Accepted Answer

The muscle generates force but does not shorten, and no movement occurs.

Question 9

A genetic defect in the dystrophin protein leads to muscle cell membrane instability and muscle wasting. Which disease does this describe?

Accepted Answer

Muscular dystrophy

Question 10

Which of the following best describes the 'all-or-none' principle in skeletal muscle physiology?

Accepted Answer

Individual muscle cells contract completely or not at all in response to a stimulus.

Question 11

Which of the following is a function of smooth muscle but NOT skeletal muscle?

Accepted Answer

Regulating blood vessel diameter

Question 12

Which of the following steps occurs FIRST during the activation of a skeletal muscle fiber?

Accepted Answer

Acetylcholine is released from the motor neuron at the neuromuscular junction.

Question 13

A person is performing a plank exercise, holding their body in a fixed position. Which type of muscle contraction is primarily occurring in their core muscles?

Accepted Answer

Isometric contraction

Question 14

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

Accepted Answer

They have fewer mitochondria and rely more on anaerobic metabolism.

Question 15

Which of the following is NOT a function of skeletal muscle?

Accepted Answer

Maintaining blood vessel diameter

Question 16

Which of the following best describes the role of ATP in muscle relaxation?

Accepted Answer

ATP is required to pump calcium ions back into the sarcoplasmic reticulum.

Question 17

Which of the following would most likely result from overstretching a muscle during physical activity?

Accepted Answer

Pulled muscle

Question 18

Which of the following is a characteristic of cardiac muscle but NOT skeletal muscle?

Accepted Answer

Presence of intercalated discs

Question 19

A person receives a puncture wound and later develops sustained, forceful muscle contractions throughout the body. Which condition is most likely responsible?

Accepted Answer

Tetanus

Question 20

Which of the following best explains why endurance training increases muscle fatigue resistance?

Accepted Answer

It increases the blood supply, mitochondria, and myoglobin content in muscle cells.

The Muscular System: Structure, Function, and Physiology

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