Question 1

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

Accepted Answer

Myosin heads bind to actin, pulling the thin filaments toward the M line, shortening the sarcomere.

Question 2

What is the role of acetylcholine (Ach) at the neuromuscular junction?

Accepted Answer

It binds to receptors on the muscle cell membrane, initiating an action potential.

Question 3

Which structure is the basic contractile unit of a muscle fiber?

Accepted Answer

Sarcomere

Question 4

During muscle contraction, what happens immediately after calcium ions bind to the troponin complex?

Accepted Answer

Tropomyosin shifts, exposing the myosin-binding sites on actin.

Question 5

Which of the following is TRUE about the energy sources for muscle contraction?

Accepted Answer

Creatine phosphate rapidly donates a phosphate to ADP to regenerate ATP.

Question 6

A patient is unable to relax their muscles after death, resulting in rigor mortis. Which of the following best explains this phenomenon?

Accepted Answer

ATP is no longer produced, so myosin heads cannot detach from actin.

Question 7

Which muscle type is characterized by being striated, involuntary, and containing intercalated disks?

Accepted Answer

Cardiac muscle

Question 8

Which of the following best describes the difference between slow-twitch and fast-twitch muscle fibers?

Accepted Answer

Slow-twitch fibers are more resistant to fatigue and are used for endurance activities.

Question 9

Which of the following is a function of the sarcoplasmic reticulum in muscle fibers?

Accepted Answer

It stores and releases calcium ions necessary for muscle contraction.

Question 10

A person receives a deep puncture wound and later develops muscle spasms and rigidity. Which disease is most likely, and what is the cause?

Accepted Answer

Tetanus, caused by a bacterial toxin from Clostridium tetani.

Question 11

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

Accepted Answer

It increases the number of mitochondria and myoglobin in muscle fibers.

Question 12

Which of the following is NOT a characteristic of smooth muscle?

Accepted Answer

It is striated.

Question 13

What is the function of intercalated disks in cardiac muscle?

Accepted Answer

They allow action potentials to pass rapidly from cell to cell.

Question 14

Which of the following best describes the role of ATP in the cross-bridge cycle during muscle contraction?

Accepted Answer

ATP binds to myosin, causing it to detach from actin after the power stroke.

Question 15

Which of the following is a correct sequence of events in skeletal muscle contraction?

Accepted Answer

Action potential → Ca$$^{2+}$$ release → Troponin activation → Cross-bridge formation

Question 16

Which of the following best explains why muscle fibers are multinucleate?

Accepted Answer

They are formed by the fusion of multiple precursor cells during development.

Question 17

Which of the following is an example of antagonistic muscle action?

Accepted Answer

The biceps brachii flexes the arm while the triceps brachii extends it.

Question 18

Which of the following best describes the effect of a tetanus toxin on muscle contraction?

Accepted Answer

It causes continuous, forceful muscle contractions by blocking inhibitory signals.

Question 19

Which of the following is a correct statement about muscle twitch and tetanus?

Accepted Answer

A muscle twitch is a single contraction-relaxation cycle, while tetanus is a sustained maximal contraction.

Question 20

Which of the following best explains why eccentric exercise is more likely to cause delayed onset muscle soreness (DOMS)?

Accepted Answer

Eccentric contractions lengthen the muscle under tension, causing more microscopic damage to fibers.

The Muscular System: Structure, Function, and Contraction Mechanisms

Study Guide - Practice Questions