MICROANATOMY

Detailed explanation-1: -However, smooth muscle fibers are much smaller in all dimensions than skeletal muscle cells. T-tubules are not required to reach the interior of the cell and therefore not necessary to transmit an action potential deep into the fiber.

Detailed explanation-2: -Without T-tubules, the muscle could not be signaled by the brain to contract, as T-tubules help signal within the cell to contract. T-tubules activate release of calcium from the sarcoplasmic reticulum, which allows for the contraction of muscle fibers by unblocking the F-actin binding site on myosin.