Fill in the Blanks Muscle contraction stepsOnline version order and explanation of muscle contractions by Rachel Beal 1 ATP Acetylcholine myosin glycogen junctio sacromeres neuromuscular energy actin is released from a neuron ending into the synaptic cleft at the 2 cross Acetylcholine ATP potassium calcium bridges cytoplasm receptors binds to and stimulates the action potentia l 3 sarcoplasmic tubules contraction stimulation channels troponin energy potassium reticulu T calcium actin The action potential travels down the sarcolemma and - and activates the in the 4 muscl actin myosin calcium cell ATP muscle potassium The sarcoplasmic reticulum releases into the 5 ATP acetylcholine calcium Calcium glycogen potassium troponin tropomyosin myosin actin binds to which shifts so that binding sites on are expose d 6 potassium cross ATP Myosin bridge action-potential troponin calcium heads bind to actin , forming - 7 cytoplasm potassium sarcoplasmic reticulum calcium neuromuscular junction actin muscle cell sarcomeres Using the chemical energy contained in ATP , myosin heads pull filaments together within the , and shorten s 8 myosin ends actin calcium cytoplasm ATP muscle sarcoplasmic reticulum heads potassium New is used to detach and move them back into position for another power strok e 9 calcium begins moves atp ends actin action potential potassium reticulu sarcoplasmic muscle energy The relaxes when stimulation , and the is pumped back into the