There is a biochemical and anatomical difference. Exhausted would implies that there is no available energy for the task at hand and enervated would suggest that the intended task lack the nervous potential to be actuated. That said, in popular discourse, there is not much difference between the two.
Systems theory has also been developed within sociology. An important figure in the sociological systems perspective as developed from GST is Walter Buckley (who from Bertalanffy's theory). Niklas Luhmann is also predominant in the literatures for sociology and systems theory.
Systems analysis. Systems analysis is the branch of systems science that analyzes systems, the interactions within those systems, and/or interaction with its environment, often prior to their automation as computer models. This field is closely related to operations research.