Intracellular

The term intracellular refers to everything that is contained inside the plasma membrane that seperates a cell from its environment. The intracellular components of the cell include the membrane bound organelles (i.e. the mitochondria) and cytoplasm. The term "intra" means "within" and so the term intracellular means "within cell".

The intracellular medium of a cell is often referred to when discussing the differences in concentration of ions between the extracellular and intracellular fluids. For example, the intracellular fluid contains higher concentrations of potassium ions but lower levels of sodium ions in comparison to the extracellular medium. These differences are important in many cellular functions such as generating action potentials.