Muscle Contraction Cycle (12 step)

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Step 10

P flies off and myosin head binds to binding site on actin

Step 12

Repeat 8-11 until the Ca+2 comes off the TT complex

Step 7

This shape change pulls tropomyosin away from myosin-binding sites on actin

Step 2

acetylcholine (ACh) release from vesicles on motor neuron

Step 6

Ca+2 attaches to troponin of TT complex and changes its shape

Step 5

Ca+2 floods sarcoplasm, AChE degrades ACh

Step 1

Motor neuron sends action potential (nerve impulse) to the muscle

Step 4

Action potential opens active transport pumps of sarcoplasmic reticulum

Step 9

ATP use on myosin head in presence of Mg+ splits ATP into ADP+P which energizes myosin head (swings forward)

Step 3

ACh binds to receptors on muscle membrane & activates 2nd action potential, now on muscle

Step 11

ADP is pushed off + myosin head is de-energized (pulling actin forward) non myosin swivels back to resting state

Step 8

ATP attaches to ATP binding site on myosin crossbridge

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