Fig. 3. Model output for small (A,C) and large (B,D) light levator fibers using parameters in Table 1. The small fibers were modeled assuming a uniform distribution of mitochondria, while the large fibers were modeled assuming only subsarcolemmal mitochondria (Boyle et al., 2003). The temporally and spatially resolved concentrations of AP and ATP during a contraction–recovery cycle are shown. The arrows indicate where mild gradients exist in the large fibers. For AP, the gradients are not obvious due to the scaling of the concentration axis, but they are of a magnitude similar to that seen in ATP. ADP, Arginine and P_i are not shown, but the concentrations change in reciprocal fashion to that of AP.