FIGURE 2:

Balance of forces in a dendritic filopodium described by the minimal model. The model captures five essential processes: 1) polymerization of F-actin at the tip of the filopodium; 2) binding and unbinding of myosin to F-actin; 3) isotropic contractile stresses exerted by bound myosin on F-actin; 4) viscous flow of F-actin (ARF) induced by these contractile stresses and membrane tension; and 5) friction between the filopodium and the substrate due to adhesion. Bound myosin contractile stress is shown by blue arrows, σ₀ and m_b; v_p, polymerization rate, direction indicated by green arrow, ζv, the substrate adhesion force, is denoted by the red arrows, and the black arrow is β v, the resistance force at the base due to the microtubule network inside the dendrite. Unbound myosin freely diffuses inside the filopodium.