Context: Transverse tubules (T-tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronising calcium release throughout the cell. T-tubule structure may be affected by disease, potentially contributing to heart failure and arrhythmias. Although these structures were first seen in 1897, research into T-tubule biology is ongoing.

Question: t or transverse tubules in skeletal muscle function to?
Steam of consciousness below:
The relevant information to answer the above question is: With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.
So, the answer is permit rapid transmission of the action potential into the cell , and also play an important role in regulating cellular calcium concentration.