Fill in the missing steps fоr skeletаl muscle cоntrаctiоn by writing the correct number in the blаnk (write only the number; not the whole statement). acetylcholine diffuses across the synaptic cleft and binds receptors on the muscle fiber neuron axon terminal releases acetylcholine by exocytosis myosin head pivots, pushing thin filament toward center of sarcomere (power stroke) exposes active site on actin (thin filament) action potential releases calcium from sarcoplasmic reticulum sarcomere shortens Neuron fires an action potential -> -> -> muscle fiber fires an action potential -> -> -> myosin head binds actin (cross-bridge formation)-> -> -> myofibril shortens -> muscle fiber shortens -> muscle shortens (contracts)