Question 1

Which of the following statements best describes the role of calcium ions ($$Ca^{2+}) in $$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 contraction, resulting in continuous muscle stiffness. Which of the following is the most likely explanation for this condition?

Accepted Answer

There is a deficiency of ATP, preventing myosin heads from detaching from actin.

Question 3

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

Accepted Answer

Isotonic contractions involve muscle shortening and movement, while isometric contractions generate force without changing muscle length.

Question 4

During a sprint, which type of muscle fibers are primarily recruited and why?

Accepted Answer

Fast-twitch fibers, because they contract quickly and can generate high force using anaerobic metabolism.

Question 5

Which of the following best explains why cardiac muscle cells can contract in the absence of nerve stimulation?

Accepted Answer

Cardiac muscle cells have pacemaker cells that generate spontaneous electrical impulses.

Question 6

A person is performing a bicep curl. Which of the following best describes the roles of synergistic and antagonistic muscles during this movement?

Accepted Answer

Synergistic muscles work together to flex the elbow, while antagonistic muscles (like the triceps) oppose the movement by extending the elbow.

Question 7

Which of the following is a correct sequence of events in the sliding filament mechanism of muscle contraction?

Accepted Answer

Calcium binds to troponin, troponin–tropomyosin complex shifts, myosin binds to actin, myosin heads bend, sarcomere shortens.

Question 8

Which of the following best explains why smooth muscle is able to sustain contractions for long periods without fatigue?

Accepted Answer

Smooth muscle cells are partially contracted all the time and contract very slowly, minimizing energy use.

Question 9

A laboratory myogram shows a muscle twitch with a prolonged contraction phase and no relaxation. Which of the following best describes this phenomenon?

Accepted Answer

Tetanic contraction (tetanus), where high-frequency stimulation maintains maximum contraction.

Question 10

Which of the following best describes the all-or-none principle as it applies to muscle cells?

Accepted Answer

A muscle cell either contracts completely or not at all in response to a stimulus.

Question 11

Which of the following is a primary source of ATP for muscle contraction during the first few seconds of intense activity?

Accepted Answer

Hydrolysis of creatine phosphate

Question 12

A person with Duchenne muscular dystrophy experiences progressive muscle weakness. Which of the following best explains the underlying cause?

Accepted Answer

A genetic defect leads to abnormal dystrophin, causing calcium leakage and destruction of muscle proteins.

Question 13

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

Accepted Answer

Fast-twitch fibers have fewer mitochondria and rely more on anaerobic metabolism, leading to rapid ATP depletion.

Question 14

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

Accepted Answer

It stores and releases calcium ions necessary for muscle contraction.

Question 15

A person is experiencing muscle cramps after intense exercise on a hot day. Which of the following is the most likely physiological cause?

Accepted Answer

Dehydration and ion imbalances disrupt normal muscle contraction and relaxation.

Question 16

Which of the following best explains why muscle mass and strength increase with resistance training?

Accepted Answer

Resistance training builds more myofibrils, especially in fast-twitch fibers, increasing muscle mass and strength.

Question 17

Which of the following is true regarding the arrangement of actin and myosin filaments in smooth muscle?

Accepted Answer

They are arranged in criss-crossed bundles, resulting in no striations.

Question 18

Which of the following best describes the process of recruitment in muscle contraction?

Accepted Answer

Recruitment is the activation of additional motor units to increase muscle force.

Question 19

Which of the following best explains why the heart can continue to beat even if all nerve connections to it are severed?

Accepted Answer

Cardiac muscle cells are connected by gap junctions and have pacemaker cells that generate rhythmic contractions.

Question 20

A person receives a deep puncture wound and later develops severe, sustained muscle contractions. Which of the following is the most likely diagnosis and cause?

Accepted Answer

Tetanus, caused by a bacterial toxin from Clostridium tetani.

Chapter 6 The Muscular System: Structure, Function, and Disorders

Study Guide - Practice Questions

Study Guide - Flashcards