Question 1

Which of the following best describes the role of the sarcoplasmic reticulum (SR) in skeletal muscle contraction?

Accepted Answer

It stores and releases calcium ions ($\mathrm{Ca^{2+}}$) necessary for muscle contraction.

Question 2

A patient is unable to relax their muscles after contraction, resulting in continuous muscle stiffness. Which of the following is the most likely explanation at the molecular level?

Accepted Answer

Calcium ions ($\mathrm{Ca^{2+}}$) are not being actively transported back into the sarcoplasmic reticulum.

Question 3

Which connective tissue layer directly surrounds individual muscle fibers and contains capillaries and nerve fibers?

Accepted Answer

Endomysium

Question 4

During a sustained, moderate-intensity exercise, which metabolic pathway is primarily responsible for ATP production in skeletal muscle fibers?

Accepted Answer

Aerobic metabolism in the mitochondria

Question 5

Which of the following statements about fast-twitch (white) muscle fibers is correct?

Accepted Answer

They fatigue rapidly due to fewer mitochondria and less myoglobin.

Question 6

A muscle is contracting isometrically. Which of the following best describes what is happening?

Accepted Answer

The muscle develops tension but does not change length.

Question 7

Which of the following events occurs first at the neuromuscular junction to initiate muscle contraction?

Accepted Answer

An action potential arrives at the axon terminal of the motor neuron.

Question 8

Which of the following best explains why cardiac muscle cells are resistant to fatigue?

Accepted Answer

They have abundant mitochondria and rely almost exclusively on aerobic metabolism.

Question 9

A marathon runner is experiencing muscle fatigue near the end of a race. Which of the following is most likely occurring in their muscle fibers?

Accepted Answer

Glycogen stores are depleted, and lactic acid is accumulating due to increased reliance on anaerobic glycolysis.

Question 10

Which of the following best describes the 'all-or-none' principle of muscle fiber contraction?

Accepted Answer

If a muscle fiber contracts, it contracts completely; there is no partial contraction of a single fiber.

Question 11

Which of the following is a function unique to smooth muscle tissue compared to skeletal muscle tissue?

Accepted Answer

It can sustain long, wave-like contractions in hollow organs.

Question 12

Which of the following best explains the physiological basis for muscle tone in resting skeletal muscle?

Accepted Answer

Some motor units are always active, even when the entire muscle is not contracting.

Question 13

During the recovery period after intense exercise, which process in the liver helps restore muscle energy reserves?

Accepted Answer

Conversion of lactic acid to pyruvic acid, then to glucose (Cori cycle)

Question 14

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

Accepted Answer

Thin filaments slide toward the center of the sarcomere, shortening the muscle fiber.

Question 15

A patient with a genetic mutation affecting myoglobin production would most likely experience which of the following symptoms during prolonged exercise?

Accepted Answer

Rapid muscle fatigue due to decreased oxygen storage in muscle fibers.

Question 16

Which of the following best explains why the tension produced by a whole skeletal muscle can be graded, rather than all-or-none?

Accepted Answer

Different numbers of motor units can be recruited depending on the required force.

Question 17

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

Accepted Answer

Cells are connected by intercalated discs containing gap junctions.

Question 18

Which of the following best describes the function of acetylcholinesterase at the neuromuscular junction?

Accepted Answer

It breaks down acetylcholine, terminating the signal for muscle contraction.

Question 19

Which of the following best explains why smooth muscle can maintain contractions for long periods without fatigue?

Accepted Answer

It uses less ATP and contracts more slowly than skeletal muscle.

Question 20

A person is holding a heavy object steady without moving it. Which type of muscle contraction is primarily occurring in their biceps brachii?

Accepted Answer

Isometric contraction

Muscle Tissue: Structure, Function, and Organization

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