Figure 3. Filament force density profiles as in Equation 3.

(a) The crosslink density ${\rho }_c$ is suppressed near the plus end, implying that the crosslink force $f_c<0$ is predominantly applied to the right-hand-side of the filament. (b) When motors are faster than treadmilling ($v_m>v_t$), they are depleted from the minus end and right-directed motor forces are predominantly applied on the left-hand side of the filament. As schematized on the right-hand-side, the fact that the crosslink force (dark blue arrow) is applied more to the right than the motor force (light blue arrow) implies that the filament is under compression. (c) When $v_t$ barely exceeds $v_m$, motor forces are applied relatively uniformly over the filament, which also results in filament compression. (d) When $v_t\gg v_m$, the motor depletion zone is larger than the crosslink depletion zone and motor forces are significantly shifted to the right. The filament is tensed in that case.