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Multiple Choice
Which muscle fiber component is responsible for storing and releasing calcium ions during muscle contraction?
A
Sarcolemma
B
Sarcoplasmic reticulum
C
T-tubule
D
Myofibril
Verified step by step guidance
1
Step 1: Understand the role of calcium ions in muscle contraction. Calcium ions are essential for initiating the interaction between actin and myosin filaments, which leads to muscle contraction.
Step 2: Identify the structure responsible for storing and releasing calcium ions. The sarcoplasmic reticulum is a specialized organelle in muscle fibers that stores calcium ions and releases them when triggered by an action potential.
Step 3: Differentiate the sarcoplasmic reticulum from other components listed in the problem. The sarcolemma is the plasma membrane of the muscle cell, the T-tubules are invaginations of the sarcolemma that help transmit action potentials, and myofibrils are the contractile units of the muscle fiber.
Step 4: Recognize the connection between the T-tubules and the sarcoplasmic reticulum. When an action potential travels down the T-tubules, it triggers the sarcoplasmic reticulum to release calcium ions into the cytoplasm.
Step 5: Conclude that the sarcoplasmic reticulum is the correct answer because it is directly responsible for storing and releasing calcium ions during muscle contraction.