The functional role of the visceral nervous system. A critical evaluation of Cannon's "homeostatic" and "emergency" theories.
Cannon's view of the sympatico-adrenal system's functional role, the homeostatic concept and model, has been reexamined. The living being is an "open system" in which homeostasis, constancy of the internal psycho-chemical conditions, is essential for survival. This constancy is threatened by endangering stimuli. To safeguard it, physiological regulatory processes, work for stability, utility, and coordination: the body is wise. Along this teleological view, the sympathetic nervous system is the most important homeostatic agent. Sympathectomized animals, however, showed no evidence of instability of the fluid matrix. Cannon concluded that the sympathetic system is not essential for life and in emergency function is its main value for the individual. Homeostatic and emergency theory, when analyzed, reveal profoundly contradictory aspects. Emergency function cannot be interpreted homeostatically, because, in emergencies, is the sympathetic system which promotes changes, rather than resists them. Sympathectomized animals do not lack constancy of the fluid matrix; they lack rather the possibility to compensate, along patterns of responses, the internal organization of the visceral apparatus. In strong emotional reactions, moreover, it is the sympathetic system itself which may induce marked derangements in visceral function that damage the organism's stability. The a priori accepted view that all physiological regulatory processes, by necessity, work for the welfare of the body - the teleological explanation - masked the experimental evidence. The conclusion is drawn that homeostatic and emergency theories described only in part the functional role of the sympathetic nervous system in all its possible functional expressions.
D000313:Adrenal Medulla / Q000502:physiology; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D002415:Cats; D004285:Dogs; D004644:Emotions / Q000502:physiology; D006706:Homeostasis; D013562:Sympathectomy; D013564:Sympathetic Nervous System / Q000502:physiology