cross bridge + Sliding filament theory + riggor

4 main steps of cross bridge

• myosin bound to actin

• Pi + ADP falls off

• ATP binds to myosin

• Myosin goes from low to high energy

Step 1 - Myosin is bound to actin

• myosin has bridged a gap between thick and thin filaments

• ADP and inorganic phosphate bind to myosin head

Step 2 - Pi + ADP fall off 

• myosin goes from high to low energy = power stroke

• pulls thin filament + causes shortening

step 3 - ATP binds to myosin head 

• Myosin breaks away from the actin

• cross bridge detaches

step 4 - myosin goes from low energy to high energy

• Myosin breaks down ATP through ATP hydrolysis 

• Mysoin can now from a new crossbridge

1

2

3

4

Sliding filament theory

thin filaments slide past the thick filament & actin and myosin overlap

A bands get _____ when sliding

larger

I bands get _____ when sliding

smaller

At full contraction what is seen?

• A band

• M line

filaments slide through _______

cross bridge cycling

riggor mortis

stiffness after death

without ATP myosin cannot ______

detatch from actin

Stiffness disappears as muscle protiens ______

break down