Evaluate the endogenous reasons of business cycle

In certain schools of economics, business cycles - - the ebb and flow of business and economic health - - are said to be tied to endogenous and exogenous factors. Endogenous factors are considered internal forces and occur entirely within a particular model, while exogenous factors are considered external and occur entirely outside a particular model. Both endogenous and exogenous factors exert influence on the way a business, and the economy as a whole, behaves.