Question 1

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

Accepted Answer

They bind to troponin, causing a conformational change that moves tropomyosin and exposes binding sites on actin.

Question 2

A patient is experiencing muscle weakness due to a lack of acetylcholinesterase at the neuromuscular junction. What is the most likely physiological consequence?

Accepted Answer

Prolonged muscle contraction due to continuous stimulation by acetylcholine.

Question 3

Which connective tissue sheath surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 4

During a high-intensity, short-duration activity such as sprinting, which metabolic pathway provides the initial source of ATP for muscle contraction?

Accepted Answer

Direct phosphorylation of ADP by creatine phosphate

Question 5

Which of the following is a characteristic unique to cardiac muscle tissue?

Accepted Answer

Branching, striated cells with intercalated discs

Question 6

A muscle is stretched to 150% of its resting length. According to the length-tension relationship, what is the expected effect on force generation?

Accepted Answer

Force generation decreases because there is less overlap between thick and thin filaments.

Question 7

Which of the following best explains why smooth muscle can maintain contraction for long periods with minimal energy expenditure?

Accepted Answer

Smooth muscle contraction is slower and requires less ATP.

Question 8

Which of the following events occurs first during excitation-contraction coupling in skeletal muscle?

Accepted Answer

Generation of an action potential in the sarcolemma

Question 9

A patient with a genetic defect in the protein dystrophin is most likely to experience which of the following?

Accepted Answer

Progressive muscle weakness due to instability of the sarcolemma

Question 10

Which muscle fiber type is most resistant to fatigue and is primarily used during endurance activities?

Accepted Answer

Slow oxidative fibers

Question 11

Which of the following best describes the function of a synergist muscle?

Accepted Answer

It assists the prime mover by adding extra force to the same movement.

Question 12

A patient is unable to relax their muscles after contraction, resulting in continuous stiffness. Which molecule is most likely deficient?

Accepted Answer

ATP

Question 13

Which of the following statements about the sliding filament model of muscle contraction is correct?

Accepted Answer

Myosin heads bind to actin, pulling thin filaments toward the center of the sarcomere.

Question 14

Which of the following is the correct order of events at the neuromuscular junction leading to muscle fiber excitation?

Accepted Answer

Action potential arrives at axon terminal, calcium enters axon terminal, acetylcholine is released, acetylcholine binds to receptors on the sarcolemma.

Question 15

Which of the following best explains why muscle tone is important for posture?

Accepted Answer

It keeps muscles firm and ready to respond to stimulation, maintaining posture and joint stability.

Question 16

Which of the following muscle arrangements allows for the greatest range of motion but the least power?

Accepted Answer

Parallel

Question 17

A person is performing a biceps curl. Which muscle acts as the antagonist during the upward (flexion) phase?

Accepted Answer

Triceps brachii

Question 18

Which of the following is a unique feature of single-unit (visceral) smooth muscle?

Accepted Answer

Cells are connected by gap junctions, allowing coordinated contraction.

Question 19

Which of the following best describes the function of the sarcoplasmic reticulum in skeletal muscle fibers?

Accepted Answer

It stores and releases calcium ions necessary for muscle contraction.

Question 20

A muscle is named 'flexor carpi radialis longus.' Which of the following characteristics does this name indicate?

Accepted Answer

It is a long muscle that flexes the wrist on the radial side.

The Muscular System: Structure, Function, and Physiology

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