What structure in skeletal muscle cells functions in calcium storage?
Myofibrillar network
Sarcoplasmic reticulum
T tubules
Mitochondria
Intermediate filament network
The Correct Answer is B
Choice A reason: The myofibrillar network refers to the arrangement of actin and myosin filaments responsible for muscle contraction. While essential for force generation, it does not store calcium. Its role is mechanical, not regulatory in terms of calcium ion concentration.
Choice B reason: The sarcoplasmic reticulum is a specialized form of smooth endoplasmic reticulum found in muscle cells. It functions as the primary site for calcium storage and release during muscle contraction. Upon stimulation, it releases calcium ions into the cytosol, initiating the interaction between actin and myosin filaments. This makes it the central regulator of calcium dynamics in skeletal muscle.
Choice C reason: T tubules (transverse tubules) are invaginations of the sarcolemma that help propagate action potentials into the interior of the muscle fiber. They facilitate communication between the sarcolemma and the sarcoplasmic reticulum but do not store calcium themselves.
Choice D reason: Mitochondria are responsible for ATP production through oxidative phosphorylation. Although they can buffer calcium to some extent, they are not the primary calcium storage organelle in skeletal muscle cells.
Choice E reason: The intermediate filament network provides structural support and maintains the integrity of the cell’s shape. It does not have a role in calcium storage or release during muscle contraction.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A reason: Actin is a structural protein that forms the thin filaments in muscle fibers. While it interacts with myosin during contraction, it does not bind calcium directly.
Choice B reason: Tropomyosin is a regulatory protein that blocks the myosin-binding sites on actin in a resting muscle. It shifts position when calcium binds to troponin but does not itself bind calcium.
Choice C reason: Titin is a large elastic protein that helps maintain the structural integrity of the sarcomere and contributes to passive elasticity. It does not function as a calcium receptor.
Choice D reason: Troponin is the correct answer. It is a regulatory protein complex associated with the thin filament. When calcium ions bind to troponin, it induces a conformational change that moves tropomyosin away from actin’s binding sites, allowing muscle contraction to occur.
Choice E reason: Dystrophin is a structural protein that connects the cytoskeleton of muscle fibers to the extracellular matrix. It is important for muscle integrity but does not bind calcium.
Correct Answer is C
Explanation
Choice A reason: Muscle relaxation is primarily governed by the removal of calcium ions from the sarcoplasm and the cessation of neural stimulation. Wave summation, on the other hand, is a mechanism that enhances contraction, not relaxation.
Choice B reason: While wave summation can contribute to sustained contractions, it does not directly prevent fatigue. In fact, repeated summation without rest can lead to fatigue due to depletion of energy stores and accumulation of metabolic byproducts.
Choice C reason: Wave summation increases the force of muscle contraction by layering successive stimuli before the muscle has fully relaxed. This results in a stronger, more sustained contraction due to residual calcium and continued cross-bridge cycling. It is a key physiological mechanism for producing smooth and powerful movements.
Choice D reason: Calcium ion release is essential for initiating muscle contraction. Wave summation does not reduce calcium release; rather, it builds on residual calcium from previous stimuli to enhance contraction force.
Whether you are a student looking to ace your exams or a practicing nurse seeking to enhance your expertise , our nursing education contents will empower you with the confidence and competence to make a difference in the lives of patients and become a respected leader in the healthcare field.
Visit Naxlex, invest in your future and unlock endless possibilities with our unparalleled nursing education contents today
Report Wrong Answer on the Current Question
Do you disagree with the answer? If yes, what is your expected answer? Explain.
Kindly be descriptive with the issue you are facing.