What Is the Function of the Transverse Tubules in a Skeletal-Muscle

Multiple Choice

What is the function of the transverse tubules in a skeletal-muscle fiber?

A) They store the calcium ions that are the main source of activation for the cross-bridge cycle.
B) They form the Z lines that mark the end of each sarcomere.
C) They allow action potentials to propagate deep into the center of skeletal muscle cells.
D) They manufacture and store ATP.
E) They run in parallel with the myofibrils, and have abundant Ca²⁺-ATPase proteins for pumping Ca²⁺ back into the sarcoplasmic reticulum.