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how does relaxation of the muscle occur according to the sliding filament theory

When Ca²⁺ is pumped back into the sarcoplasmic reticulum, troponin‑tropomyosin blocks the myosin‑binding sites on actin, cross‑bridges detach, and the actin and myosin filaments slide apart, allowing the muscle to relax.

what are the three sources of ATP regeneration in the muscle

Creatine phosphate (phosphocreatine) system, anaerobic glycolysis (lactate production), and aerobic oxidative phosphorylation in mitochondria.

what are the four steps of the contraction cycle that occurs after the myosin binding site on the actin has been exposed

o ATP hydrolysis o Attachment of myosin to actin to form cross linkages o Power stroke o Detachment of myosin from actin

function of tropomyosin strand

It blocks myosin‑binding sites on actin in relaxed muscle, and shifts to expose those sites when Ca²⁺ binds troponin, thereby regulating contraction.

What is the name of the voltage-dependent calcium channels in the T-tubule membrane that sense changes in membrane voltage during muscle excitation?

Dihydropyridine receptors (DHPRs) (L-Type voltage-gated calcium channels.)