ncts

Complex fluids flow in complex ways in complex structures. Transport of water and various organic and inorganic molecules in the central nervous system (CNS) is important in a wide range of biological and medical processes, “Brain extracellular space: The final frontier of neuroscience”. However, the exact driving mechanisms are often not known. In this talk, we investigate flows induced by action potentials in an optic nerve as a prototype of the CNS. Different from traditional fluid dynamics problems, flows in biological tissues such as the CNS are coupled with ion transport. It is driven by osmosis created by the concentration gradient of ionic solutions, which in turn influence the transport of ions. Our mathematical model is based on the known structural and biophysical properties of the experimental system used by the Harvard group. Asymptotic analysis and numerical computation show the significant role of water in convective ion transport. The full model (including water) and the electro-diffusion model (excluding water) are compared in detail to reveal an interesting interplay between water and ion transport. In the full model, convection due to water flow dominates inside the glial domain. This water flow in the glia contributes significantly to the spatial buffering of potassium in the extracellular space. Convection in the extracellular domain does not contribute significantly to spatial buffering. Electro-diffusion is the dominant mechanism for flows confined to the extracellular domain. This work is collaborated with Yi Zhu, Robert Eisenberg and Huaxiong Huang.