# data[].attributes.body
Step 4: New ATP is split into ADP and P, cocking of myosin head occurs.

# data[].attributes.body
Step 3: New ATP attaches to myosin head, cross bridge detaches.

# data[].attributes.body
step 2: The myosin head pivots and bends as it pulls on the actin filament sliding it toward the M- line, also known as the working stroke.

# data[].attributes.body
step 1: The myosin cross bridges attaches to actin myofilament.

# data[].attributes.body
Step 3 and 4: Ca2+ combines with troponin and removes the blocking action of tropomyosin by changing the shape of the actin so that the myosin binding sites is exposed. Myosin binds to actin that forms cross bridges and contraction begins.

# data[].attributes.body
Step 2: Transmission of the action potential along the T tubules cause the adjacent sarcoplasmic reticulum (SR) to release Ca2+ which flows into the cytosol.

# data[].attributes.body
Step 1:  The action potential moves down the sarcolemma and down the T tubules (protrusion of the sarcolemma that produce deep into the muscle cell

# data[].attributes.body
The brain sends a nerve impulse (action potential) through the motor unit down to a neuromuscular junction (axon terminal). The nerve impulse causes voltage gated calcium ion channels to open which allow calcium ions to enter the neuron. The increase in calcium stimulates the release of acetylcholine. ACh binds to an ACh receptor sight and activates voltage gated Na+ channels which pumps Na+ in and K+ out. More Na+ is pumped out causing the cell interior to become depolarized. Initial depolarization spreads to adjacent areas, opening voltage gated sodium channels and eventually initiating an action potential that moves along the lengths of the sarcolemma. Na+ concentrations caused by depolarization stimulate a change in membrane permeability by opening voltage gated K+ pumps which allow K+ to diffuse across the sarcolemma out of the muscle fiber, also known as repolarization.