Figure 3.

Simulations of a swimming sperm in a 3-dimensional viscous fluid where the CatSper-mediated Ca²⁺ dynamics are accounted for and are coupled to the preferred curvature. The solid black circle denotes the head side of the flagellum. Velocity vectors for the local fluid velocity are depicted in the plane of the beating flagellum and the calcium concentration along the length of the flagellum is shown. After application 8-Br-cAMP, the Ca²⁺ profiles (as in Fig. 2) are determined by the partial differential equations accounting for release of Ca²⁺ from the RNE. These Ca²⁺ concentrations are then used to define a preferred curvature for the flagellar waveform using a modified Hill function for the amplitude. From left to right, top row: t = 0, 1, 2 s and bottom row: t = 4, 6, 8 s. Note how the waveform is modified as the Ca²⁺ concentration increases.