Vegetative nervous system and syncopes.

The vegetative nervous system (VNS) plays a prominent role in many syncopes according to either organic or (days)functional pathogenetic mechanism. Vasovagal syncopes are typically (dys)functional and related to both vasodepression and cardioinhibition, whereas syncopes due to autonomic failure (AF) show a clearly organic pathogenesis and are related to the impairment of baroceptor control on arterial blood pressure. The differences between (dys)functional and organic vegetative syncopes are discussed. AF is a model for studying the effects of chronic vegetative insufficiency in man and makes it possible to speculate on the functional role of the VNS. Vasovagal syncopes seem to be inhibitory integrated vegetative-somatic behaviours, with a protective and adaptive functional role.