The tendency of biologic tissues and processes
to maintain a constancy of
environment consistent with their vitality and well being. For cells to maintain their
stability or equilibrium, the cell membranes must be in continuous interaction with
both the internal (intracellular) environment and the external (extracellular)
environment. When the equilibrium of any component is disturbed, the interaction
permits automatic readjustment by giving rise to stimuli that result in restoration of
the equilibrium.