Final answer:
The T-tubules in skeletal muscle serve to conduct electrical impulses deep into the cell, triggering the release of calcium from the Sarcoplasmic Reticulum and initiating muscle contraction.
Step-by-step explanation:
The T-tubules (transverse tubules) in skeletal muscle function to promote an electrical impulse to travel deep into the muscle cell. These tubules are periodic invaginations of the sarcolemma that facilitate the propagation of an action potential into the cell's interior. The action potential triggers the opening of calcium channels in the membrane of the adjacent Sarcoplasmic Reticulum (SR), leading to the release of calcium ions (Ca++) into the sarcoplasm. The increased calcium concentration initiates the contraction of muscle fibers by activating the contractile units, or sarcomeres, within the myofibrils.
The T-tubules along with two terminal cisternae of the SR form a triad, which ensures that the action potential reaches the SR regardless of the muscle fiber's diameter. This system is essential for the efficient and coordinated contraction of skeletal muscle fibers, as it allows the electrical impulses to be quickly distributed throughout the muscle cell.