Sliding Filament Theory (6 Steps)

The sarcoplasmic reticulum stimulated to release calcium ions

Calcium ions bind to troponin - causes troponin to drag tropomyosin off cross bridge binding sites -cross bridges bind to actin

Cross bridges (on myosin) pull on actin (power stroke) - actin filaments slide to middle of sarcomere -muscle shortens & contracts

Cross bridge detaches from binding sites on actin

Muscle fiber lengthens & relaxes

Calcium ions actively pumped back into sarcoplasmic reticulum -troponin released from tropomyosin - tropomyosin covers cross bridge binding sites