Some body systems are more affected than others based on their normal turnover rate. For instance, the cells of the gastrointestinal lining and blood forming system have rapid turnover rates and are therefore susceptible to the inhibition of mitosis caused by the chemotherapy agents. Microtubules provide the necessary intracellular highway system for the movement of organelles and vesicles from one place to another. Molecular motors such as dynien and kinesin transport packages along this highway in an energy requiring process. Microfilaments Actin and myosin are microfilament proteins responsible for contraction in muscle cells .
All cells have actin in some form.
Myosin in motile nonmuscle cells is present in unpolymerized form. It polymerizes only to participate in cell movement. In most cells, microfilaments form thin sheath just under the cell membrane that is associated with the cellular functions of endocytosis, exocytosis and cell movement. Microfilaments are involved with the movement of vesicles, granules and cytoplasmic organelles. Intermediate Filaments Intermediate filaments have an average diameter of about 10 nm and are made of several proteins dependent on the cell or tissue type.