provide a means of rapidly transmitting the action potential from the surface into the central portions of the muscle fiber
Explanation:
T-tubules or Transverse tubules are the tube-like structures present in the muscle fibers.
The T tubules are formed by the modification in the plasma membrane of the cell and therefore arise from the surface of the muscle cell. The T tubules then pass through the muscle and enter the inner core of the muscle that is near to the sarcoplasmic reticulum.
The main function of the T tubules is to carry forward the action potential from the synaptic junction to the muscle where it triggers the release of the calcium from the muscle.
