The function of the T tubules in muscle contraction is to:
a. Make and store glycogen
b. Release Ca²⁺ into the cell interior and then pick it up again
c. Transmit the action potential deep into the muscle cells
d. Form proteins

Verified step by step guidance

Step 1: Understand the role of T tubules in muscle cells. T tubules, or transverse tubules, are invaginations of the sarcolemma (muscle cell membrane) that penetrate into the cell's interior.

Step 2: Recall that muscle contraction is initiated by an action potential traveling along the sarcolemma and then into the muscle fiber through the T tubules.

Step 3: Recognize that the T tubules help transmit the electrical signal (action potential) deep into the muscle fiber, ensuring that the signal reaches all parts of the muscle cell quickly and uniformly.

Step 4: Differentiate the function of T tubules from other structures: for example, the sarcoplasmic reticulum releases and reabsorbs Ca²⁺, glycogen is stored in the cytoplasm, and proteins are synthesized by ribosomes.

Step 5: Conclude that the primary function of T tubules is to transmit the action potential deep into the muscle cells, which corresponds to option c.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

T Tubules Structure and Location

T tubules are invaginations of the muscle cell membrane (sarcolemma) that penetrate into the cell's interior. They allow electrical signals to reach deep inside muscle fibers, ensuring coordinated contraction throughout the cell.

Role of Action Potentials in Muscle Contraction

Action potentials are electrical impulses that trigger muscle contraction. When transmitted along the sarcolemma and into the T tubules, they initiate the release of calcium ions from the sarcoplasmic reticulum, which is essential for muscle fiber activation.

Calcium Ion Release and Muscle Contraction

Calcium ions released inside muscle cells bind to regulatory proteins on actin filaments, enabling cross-bridge formation with myosin. This interaction causes muscle contraction. After contraction, calcium is pumped back to allow relaxation.

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