The general visceral afferent fibers (GVA) conduct sensory impulses (usually pain or reflex sensations) from the viscera, glands, and blood vessels to the central nervous system. They are considered to be part of the visceral nervous system, not the autonomic nervous system. However, unlike the efferent fibers of the autonomic nervous system, the afferent fibers are not classified as either sympathetic or parasympathetic.