Sarcomere Length-Tension Simulator

This simulator builds one sarcomere from its real ultrastructure — hexagonally packed thick (myosin) filaments surrounded by thin (actin) filaments anchored to Z-discs at each end — and lets you drag the Z-discs apart or together to change sarcomere length directly. As overlap between the filament sets changes, the simulator plots your live position on the classic Gordon–Huxley–Julian length-tension curve: force climbs through the ascending limb, reaches a plateau of maximal myosin-head engagement near 2.0–2.25 μm, and falls back to zero on the descending limb as filaments pull apart entirely. A separate calcium-activation control gates how many myosin heads actually cycle through attachment, power stroke and detachment at any instant, so you can see length-dependent overlap and Ca²⁺-dependent activation combine into one active-tension readout, exactly as they do in a real muscle fiber.