Membrane transport refers to the mechanisms by which solutes cross the plasma membrane, but there are additional prokaryotic cell structures through which a solute would pass when entering or exiting a cell. sequence the path of a solute from the external environment to the cytoplasm of a prokaryotic cell.

Na+ loss through sweet plus the dilution has lowered na+ concentration outside of neurons, altering the na+ equilibrium potential. sodium exists more outside the cells than inside. when na+ is lost by sweat plus the dilution( because they drink a lot of water) changes the concentration outside the cell, forcing the water to enter the cell and attempt to balance the concentration inside/outside.the problem is that the abundance of water will cause the cells to swell. most cells can adapt, however, the brain cells can't that's why the runner has confusion and can't control the muscles.  if not treated and this occurs in less than 48 hours, it can be immediately fatal .