The microfilament system is a network of filaments 6 nanometers (nm) in diameter that are important for anchoring plasma membrane proteins, for producing cell movement, and for cell division. The base filament is composed of a protein called actin that is 42 kilodaltons (kd) in weight.
It is divided into two subgroups; the single-unit (unitary) and multiunit smooth muscle. Within single-unit cells, the whole bundle or sheet contracts as a syncytium (i.e. a multinucleate mass of cytoplasm that is not separated into cells).mooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, regulation of contraction, and excitation-contraction coupling. Smooth muscle cells known as myocytes, have a fusiform shape and, like striated muscle, can tense and relax.
1 Commonality between smooth and cardiac muscle types. 2  The type of muscle under voluntary control. 3  Which type of muscle moves your tongue. 4  Striated muscles.  Where you would be most likely to find smooth muscles in the body.