FIGURE 9.

Schematic of cytoskeleton-driven spreading coupled to membrane tension. F-actin is sketched as green lines which (i) drive with a force f against the membrane while being anchored by focal adhesions at the other end. Newton's law of action-reaction equates f near adhesion sites with cell tractions (Lo et al., 2000), while balancing f at the plasma membrane by the tension τ_o. Slight increases in this tension—driven by the cytoskeleton (see Fig. 6, inset)—will tend to reinforce spreading (ii) by driving into adhesive contact plasma membrane reservoirs such as vesicles widely known in platelets (Grouse et al., 1990). Such recruitment processes tend to relax any increases in tension back to τ_o.