The visceral nervous system as a mediator of psychosocial risk factors: therapeutic implications of its specific organization.

The visceral (autonomic) nervous system is one of the most important mediators between mind and viscera. Its organization has conventionally been attributed to the dominance of the brain, with the sympathetic and parasympathetic systems performing solely outflow functions. However, since the reflex arc appears to be the functional unit of these systems, their organization may be based on local reflexes, modulated by higher nervous structures. Visceral nervous activity therefore reflects both the central excitatory state and local input from the viscera. Moreover, the sympathetic and parasympathetic systems do not exert reciprocal control more or less independently, as used to be thought. In the heart, visceral afferent impulses carried by the vagus and sympathetic nerves each reflexly influence both sympathetic and vagal outflow. Recognition of this pattern of reflex control appears to have implications for beta-adrenergic blockade.