Final answer:
True, muscle action potentials can continue even when there is slack in a contracted muscle. This continuation is supported by the mechanisms of ATP usage in cross-bridge cycling for contraction and relaxation, and the presence of latch-bridges in smooth muscles allowing for sustained muscle tone with minimal ATP.
Step-by-step explanation:
True, Action Potentials (AP) continue even when there is slack when the muscle is contracted.
During muscle contraction, the sliding filament model illustrates that sarcomere shortening occurs as the thick and thin filaments interact. This process relies on ATP to fuel cross-bridge cycling and the movement of myosin heads along actin filaments, which in turn pulls Z lines closer together. However, even in the absence of ATP, as observed in rigor mortis, myosin heads remain bound to actin, maintaining the contracted state of the muscle. ATP is also essential for muscle relaxation; it is required for the active transport of Ca++ ions back into the sarcoplasmic reticulum (SR), reducing calcium levels in the sarcoplasm, ultimately leading to muscle relaxation.
Tetanus and treppe are phenomena where sustained or progressively stronger contractions occur respectively, and in smooth muscle, latch-bridges allow for prolonged contractions without continual use of ATP. In all cases, the role of ATP is central to muscle function: it enables contraction, stretching, and relaxation phases of muscle activity.