steps of a muscle contraction 1-6

step 4

Myosin heads bind to actin binding site making a cross bridge

step 5

Myosin heads do a powerstroke (using ADP and P) which slides actin and decreases length of sarcomere (Z line to Z line)

step 3

Troponin changes shape and exposes actin binding site

step 2

Calcium binds to troponin

step 1

Calcium ions rush into muscle fibers

step 6

ATP causes release of myosin head from actin binding site (cross the myosin head is free to repeat the cycle as long as calcium is in and the ATP available)