<prompt> Which of the following is true regarding the action potential of skeletal muscle?It spreads inward to all pas of the muscle the T-tubulesIt has a prolonged plateau phaseIt causes the immediate uptake of Ca2 into the lateral sacs of the sarcoplasmic reticulumIt is longer than the action potential of cardiac muscle  <response>: Depolarization of the muscle fibers is essential for initiating muscle contraction. The action potential of skeletal muscle is transmitted to all of the fibrils along T-tubules, triggering the release of Ca2 from the lateral sacs of the sarcoplasmic reticulum next to the T-system. The electrical events in skeletal muscle and the ionic fluxes underlying them are similar to those in nerve. In contrast, the action potential in cardiac muscle is longer and has a prolonged plateau phase. 