Question 1

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

Accepted Answer

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

Question 2

During the sliding filament theory of muscle contraction, which event directly follows the binding of calcium ions to troponin?

Accepted Answer

Tropomyosin shifts to expose myosin-binding sites on actin.

Question 3

Which connective tissue layer surrounds individual muscle fibers (cells) in skeletal muscle?

Accepted Answer

Endomysium

Question 4

A patient presents with muscle weakness and is found to have a defect in acetylcholinesterase. What is the most likely effect on muscle contraction?

Accepted Answer

Prolonged muscle contraction due to excess acetylcholine in the synaptic cleft.

Question 5

Which of the following correctly lists the order of muscle organization from smallest to largest?

Accepted Answer

Myofilament, sarcomere, myofibril, myofiber, fascicle, named muscle, muscle group

Question 6

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

Accepted Answer

Presence of intercalated discs with gap junctions and desmosomes

Question 7

A muscle fiber is stimulated by a single action potential, resulting in a brief contraction followed by relaxation. This response is called:

Accepted Answer

A twitch

Question 8

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

Lack of ATP prevents detachment of myosin heads from actin, causing sustained contraction.

Question 9

Which type of muscle fiber is most resistant to fatigue and is primarily used for maintaining posture?

Accepted Answer

Slow oxidative fibers

Question 10

Which of the following statements about smooth muscle contraction is correct?

Accepted Answer

Calcium binds to calmodulin, which activates myosin light chain kinase (MLCK).

Question 11

A person is holding a heavy box without moving it. Which type of muscle contraction is primarily occurring in the arm muscles?

Accepted Answer

Isometric contraction

Question 12

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

Accepted Answer

When a muscle fiber is stimulated above threshold, it contracts fully; below threshold, it does not contract at all.

Question 13

Which of the following is a major cause of muscle fatigue during intense exercise?

Accepted Answer

Accumulation of lactic acid and depletion of ATP

Question 14

Which lever system is most common in the human body and is exemplified by the elbow joint during a biceps curl?

Accepted Answer

Third-class lever

Question 15

Which of the following best explains why smooth muscle can sustain contractions for longer periods than skeletal muscle?

Accepted Answer

Smooth muscle uses less ATP and has slower crossbridge cycling.

Question 16

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

Accepted Answer

Production of hormones

Question 17

A marathon runner is able to maintain activity for hours. Which muscle fiber type is most abundant in their leg muscles?

Accepted Answer

Slow oxidative fibers

Question 18

Which of the following best describes the role of creatine phosphate in muscle contraction?

Accepted Answer

It rapidly donates a phosphate group to ADP to regenerate ATP during the first few seconds of intense activity.

Question 19

Which of the following statements about motor units is correct?

Accepted Answer

A single motor neuron and all the muscle fibers it innervates form a motor unit.

Question 20

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

Accepted Answer

Isotonic contractions change muscle length, while isometric contractions maintain muscle length.

The Muscular System: Structure, Function, and Physiology

Study Guide - Practice Questions