Action Potentials without Contraction in Frog Skeletal Muscle Fibers with Disrupted Transverse Tubules

Action potentials, with no accompanying contraction, were recorded from muscle fibers in which the transverse tubular system had been disrupted. The results show that action potentials require an intact transverse tubular system to cause contraction. Furthermore, both the after-depolarization following a single action potential and the slower, late afterpotential following a train of action potentials were absent in this preparation. Therefore, both phenomena must normally involve the transverse tubular system.