What is the purpose of the T tubule in muscle fibers?

The T tubule, or transverse tubule, plays a crucial role in muscle contraction by transmitting action potentials deep into the muscle fiber. When a muscle fiber is stimulated by a nerve impulse, the action potential travels along the sarcolemma (the muscle cell membrane) and into the T tubules. This system of tubules extends from the surface of the muscle cell into its interior, allowing the action potential to rapidly reach the interior of the fiber.

As the action potential travels through the T tubules, it causes the nearby sarcoplasmic reticulum to release calcium ions into the cytoplasm of the muscle fiber. The presence of calcium ions is essential for the interaction between actin and myosin filaments, which ultimately leads to muscle contraction. Therefore, the primary function of T tubules is to ensure that the electrical signal representing the initiation of muscle contraction effectively reaches all parts of the muscle fiber, enabling a coordinated contraction.

The other options do not accurately describe the specific role of T tubules. Energy storage happens in mitochondria and in the form of phosphocreatine. Muscle tissue repair is a function of satellite cells, not T tubules. Calcium storage is primarily the function of the sarcoplasmic reticulum, which works in