The author studies symptoms which are not neurological and which regulation could be central or peripheral; referring to the central regulation, the author implies the psychic as well as the neural one. The same symptom may be exteriorized and activated by different factors; thus the asthmatic crisis or the convulsive attack may be initiated or inhibited by factors which are extrinsic to the syndrome. The activating or inhibiting central regulation will be a pathogenic or therapeutic factor, even decisive, without any link whatsoever with the cause of the symptom; conversely, symptoms which have been initially brought about by central dysregulation can become autochtonous and the dysregulation then is no longer central but peripheral and autonomic and sometimes irreversible. It is also certain that each symptom can evolve independently from the other not only to get better but also to get worse. The simultaneousness and pathogenic identity do not mean evolutional equivalence. As symptoms can develop adding successive physiological links that are not intrinsic to them, these extrinsic links take on a pathogenic role, sometimes passing to command the symptoms though extraneous to their causality: the symptomatic phenomenon, previously peripheral, has gained central regulation which is an additional link, extraneous but a decisive one. In this way, the symptom that was "specific" becomes "non-specific"; instead of cause the factor is important. And the importance of the factor can rise so much to decide the evolution, including the irreversibility, and the cause is no longer found. In the chain of reactions that the symptom keeps on organizing, any link may becomes the trigger and the most important. Central and peripheral regulation of the psychosomatic symptom is the expression of this possibility.