Question 1

Which of the following best describes the role of the sodium-potassium pump ($$\mathrm{Na^+/K^+}$$ ATPase) in skeletal muscle fibers?

Accepted Answer

It moves three sodium ions out of the cell and two potassium ions in, using ATP hydrolysis to maintain ion gradients.

Question 2

A patient presents with muscle weakness and a waddling gait. Genetic testing reveals a mutation in the dystrophin gene. Which of the following best explains the pathophysiology of this condition?

Accepted Answer

Defective dystrophin disrupts the anchoring of the sarcolemma to the endomysium, causing muscle fiber death and replacement with connective tissue.

Question 3

During the contraction phase of a muscle twitch, which event occurs at the molecular level?

Accepted Answer

Myosin heads bind to actin, forming crossbridges, and perform power strokes to pull thin filaments toward the M line.

Question 4

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

Accepted Answer

ATP is no longer available to pump calcium ions into the sarcoplasmic reticulum, so myosin heads remain bound to actin.

Question 5

A muscle fiber is stimulated 100 times per second, and the tension remains at a maximum without relaxation. What is this phenomenon called?

Accepted Answer

Fused (complete) tetanus

Question 6

Which of the following is a property unique to cardiac muscle tissue compared to skeletal and smooth muscle?

Accepted Answer

Presence of intercalated discs containing gap junctions and desmosomes

Question 7

Which process provides the greatest amount of ATP for sustained muscle activity lasting several minutes or more?

Accepted Answer

Oxidative (aerobic) catabolism in the mitochondria

Question 8

Which of the following best describes the sequence of events at the neuromuscular junction leading to muscle fiber excitation?

Accepted Answer

Calcium enters the axon terminal, triggering exocytosis of synaptic vesicles containing acetylcholine.

Question 9

Which of the following is true regarding the length-tension relationship in skeletal muscle?

Accepted Answer

Maximum tension is produced at optimal sarcomere length, where there is maximal overlap between thick and thin filaments without excessive crowding.

Question 10

A patient receives an injection of botulinum toxin (Botox®) for cosmetic purposes. Which of the following best describes the mechanism of action of this toxin?

Accepted Answer

It blocks the release of acetylcholine from motor neurons, preventing muscle contraction.

Question 11

Which of the following best explains why endurance training increases resistance to muscle fatigue?

Accepted Answer

It increases the amount of oxidative enzymes, mitochondria, and blood vessels in muscle fibers.

Question 12

Which of the following is a distinguishing feature of smooth muscle contraction compared to skeletal muscle contraction?

Accepted Answer

Smooth muscle contraction is regulated by the calcium-calmodulin complex activating myosin light-chain kinase.

Question 13

Which of the following best describes the role of myoglobin in skeletal muscle fibers?

Accepted Answer

It binds and stores oxygen for use during oxidative catabolism.

Question 14

Which of the following is a correct sequence of events in the crossbridge cycle during muscle contraction?

Accepted Answer

Myosin head binds to actin, ATP hydrolysis cocks the head, power stroke occurs, ATP binds to detach myosin.

Question 15

Which of the following best explains why muscle fibers fatigue during intense exercise?

Accepted Answer

Depletion of key metabolites, decreased oxygen availability, and accumulation of ADP and phosphate ions contribute to muscle fatigue.

Question 16

Which of the following is true regarding the difference between single-unit and multi-unit smooth muscle?

Accepted Answer

Single-unit smooth muscle cells are connected by gap junctions and contract together, while multi-unit smooth muscle cells contract independently.

Question 17

A person is holding a heavy box with their arms stationary and not moving. Which type of muscle contraction is primarily occurring in their arm muscles?

Accepted Answer

Isometric contraction

Question 18

Which of the following best describes the function of titin in the sarcomere?

Accepted Answer

It acts as a spring, providing elasticity and helping the muscle fiber return to its original length after stretching.

Question 19

Which of the following best explains why creatine supplementation may improve performance in short bursts of high-intensity activity?

Accepted Answer

Creatine phosphate donates a phosphate group to ADP, rapidly regenerating ATP during short, intense activity.

Muscle Tissue and Physiology: Structure, Function, and Mechanisms

Study Guide - Practice Questions

Study Guide - Flashcards