Micropikes and filopodia are thin projections of plasma membrane supported by actin bundles. Actin, Myosin and Cell Movement Actin filaments, usually in association with myosin, are responsible for many types of cell movements. Interactions of actin and myosin are responsible for muscle contraction, cell division, cell crawling, etc. Muscle fibers are single large muscle cells. The cytoplasm of muscle fibers contains mostly myofibrils .
Myofibrils consist of myosin filaments and actin filaments .
Sarcormeres are structural units within the myofibrils defined by Z disc, actin, myosin, nebulin and titin. The type of myosin in muscle is myosin II which consist of a globular head that binds to actin and a tail which binds to other myosin molecules. The globular head also binds and hydrolyses ATP providing energy to drive filament sliding. An example is the contractile ring in cytokinesis. This contractile ring consists of actin filaments and myosin II present underneath the plasma membrane.