Autonomic nervous system definition

The autonomic nervous system is by definition that part of the nervous system that innervates smooth muscle, cardiac muscle and glands. It is thus a motor system. Perception arising from the viscera involves pathways similar to those arising from the body surface and skeletal muscle. Thus there are visceral afferent fibres that pass from the viscera to the central nervous system. Such impulses then ascend the spinal cord to the thalamus and are thence relayed to the post-central gyrus of the brain (or sensory cortex). Visceral reflex arcs use visceral afferent fibres to convey impulses to the cord, but the efferent limb of such a visceral reflex is the autonomic nervous system. Although visceral reflexes are under higher central control, it is usually impossible to bring them under the control of the will. 

This question deserves a fuller treatment than I can give it here. The answer, I think, is connected with the fact that breathing is an automatic response, controlled by the autonomic nervous system. Appetites, acquired and unacquired, are sustained by reward.34 In contrast, I suppose, the desire to breathe and the discomfort of not breathing do not involve the brain s reward system in the same way, but I am not sure how to incorporate these observations into a satisfactory definition of the appetitive. 

The definition of receptors as specific sites for drug action owes much to the work of John Newton Langley [ 1852-1925 ] and Paul Ehrlich [ 1854-1915 ]. Their separate work on the autonomic nervous system and toxins and chemotherapeutic agents led to the concept of a receptor that possesses both recognition and transduction components and of chemotherapeutic molecules possessing discrete molecular features subserving specific functions ... 

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