MFs in the nervous system appear to have a variety of functions. The neuronal membrane cytoskeleton plays a role in maintaining the distribution of plasma membrane proteins, establishing cell morphologies and segregating axonal and dendritic proteins into their respective compartments [20]. MFs and the membrane cytoskeleton also mediate the interactions between neurons and the external world, including extracellular matrix components and neighboring cells (see Chap. 7). In neurons and glia, cell adhesion sites, such as tight junctions and focal adhesion plaques, interact with the MF cytoskeleton either directly or indirectly. The cortical MF meshwork also restricts access of organelles to the plasma membrane and is involved in both regulated and constitutive secretion (see Chap. 9). Finally, MFs are the basis of filopodia and lamellipodia that are essential for cell migration, growth cone motility and myelination.