When the cell excretes sodium from within, against the natural tendency of matter, it is performing

When the cell is removing and or excreting sodium from within the cell, against the natural tendency of matter, it is performing a type of active transport, called exocytosis, I believe. The sodium ions become associated with membrane enclosed structures called vacuoles, from the Golgi apparatus and later merge with the cell membrane of the cell to dispose the sodium carried within the vacuoles.

Generally travels west to east but often shifts to north and south