Sliding filament theory

A nerve impulse is received at the neuromuscular junction this causes Ca2+ ions to be released from the sarcoplasmic reticulum the Ca2+ ions diffuse through the sarcoplasm bind to troponin changing its shape and position which displaces tropomyosin exposing the actin binding sites myosin heads and actin filaments can now form a cross bridge the hydrolysis of ATP provides energy for the myosin heads to pull on the actin filaments and the sarcomere shortens ATP then binds to the myosin head to break the cross bridge and cock the myosin head back for another power stroke this happens along the whole actin filament when the nerve impulse stops ATP is used to actively transport Ca2+ back into the sarcoplasmic reticulum