<P> Smooth muscle contraction is caused by the sliding of myosin and actin filaments ( a sliding filament mechanism ) over each other . The energy for this to happen is provided by the hydrolysis of ATP . Myosin functions as an ATPase utilizing ATP to produce a molecular conformational change of part of the myosin and produces movement . Movement of the filaments over each other happens when the globular heads protruding from myosin filaments attach and interact with actin filaments to form crossbridges . The myosin heads tilt and drag along the actin filament a small distance ( 10 - 12 nm ) . The heads then release the actin filament and then changes angle to relocate to another site on the actin filament a further distance ( 10 - 12 nm ) away . They can then re-bind to the actin molecule and drag it along further . This process is called crossbridge cycling and is the same for all muscles ( see muscle contraction ) . Unlike cardiac and skeletal muscle , smooth muscle does not contain the calcium - binding protein troponin . Contraction is initiated by a calcium - regulated phosphorylation of myosin , rather than a calcium - activated troponin system . </P>
<P> Smooth muscle contraction is caused by the sliding of myosin and actin filaments ( a sliding filament mechanism ) over each other . The energy for this to happen is provided by the hydrolysis of ATP . Myosin functions as an ATPase utilizing ATP to produce a molecular conformational change of part of the myosin and produces movement . Movement of the filaments over each other happens when the globular heads protruding from myosin filaments attach and interact with actin filaments to form crossbridges . The myosin heads tilt and drag along the actin filament a small distance ( 10 - 12 nm ) . The heads then release the actin filament and then changes angle to relocate to another site on the actin filament a further distance ( 10 - 12 nm ) away . They can then re-bind to the actin molecule and drag it along further . This process is called crossbridge cycling and is the same for all muscles ( see muscle contraction ) . Unlike cardiac and skeletal muscle , smooth muscle does not contain the calcium - binding protein troponin . Contraction is initiated by a calcium - regulated phosphorylation of myosin , rather than a calcium - activated troponin system . </P>
the involuntary movement of smooth muscles is called
the involuntary movement of smooth muscles is called
contraction
contraction