Sliding Filament Theory

Muscle contraction occurs by the sliding of thin filaments (actin) over thick filaments (myosin); Motor neuron releases Acetylcholine, triggering an action potential; Ca2+ is released from sarcoplasmic reticulum, binds to Troponin, exposing myosin-binding sites on actin; Myosin head binds (using ATP), forming a cross-bridge and pulling actin inwards.