Figure 2.
A segment of the rod-fiber assembly showing the tension (T) in the fiber and its position relative to the centerline of the rod. The segment length in the discretized model is given by ls = L/Ns where L is the length of the rod and Ns is the number of segments. The force acting on the centerline (Fs) is parallel to T and exerts shear and compression forces. The moment (Ms) of the tension is perpendicular to r and Fs, and generates bend and twist couples. The rest length of the spasmoneme segment in its calcium-free state is le and its rest length in the calcium-bound state is lc; its time-dependent length, l, varies between le and lc. The force and couple acting on the bottom plane are not shown.