Complex sentence: Sodium is also important in neuron function and osmoregulation between cells and the extracellular fluid, their distribution mediated in all animals by Na +/K +-ATPase; hence, sodium is the most prominent cation in extracellular fluid.
Split into simpler sentences: Sodium is also important in neuron function and osmoregulation between cells and the extracellular fluid; their distribution is mediated in all animals by Na +/K +-ATPase. Hence, sodium is the most prominent cation in extracellular fluid.