12 steps of muscle contraction

Step 9

Myosin 'hinge' shortens, pulling actin filaments toward the center of the sarcomere

Step 12

Myosin head binds to another active site farther down the actin strand; the hinge shortens again pulling actin even closer to the midline

Step 8

Myosin heads bind to active sites

Step 11

Myosin hinge lengthens while unattached

Step 7

When troponin turns it pulls on the tropomyosin, moving the strand and uncovering active sites on actin molecules

Step 6

Binding causes troponin to change shape

Step 3

Binding of ACh causes an action potential to spread across the sarcolemma and into the T-tubules

Step 5

Ca2 binds to troponin

Step 1

Motor neurons release ACh into synapse

Step 4

Action potential causes the release of calcium ions from the sarcoplasmic reticulum

Step 2

ACh travels across the synapse and binds to ACh receptors on the sarcolemma

Step 10

ATP is used to break the actin myosin bond