Most of the neural pathways in the enteric plexuses lack direct preganglionic inputs and can operate independently of central control. This traditional terminology is confusing and we use the term "autonomic motoneurons" or "final motoneurons" for the ganglionic cells.Ĭomplex autonomic ganglia in the walls of the stomach and small intestine are separately classified as the enteric nervous system. The motor neurons in the autonomic ganglia are sometimes referred to as "postganglionic neurons". Post-ganglionic axonal processes of motor neurons in the autonomic ganglia innervate organs and tissues throughout the body (eyes, salivary glands, heart, stomach, urinary bladder, blood vessels, etc). In this respect preganglionic autonomic motor neurons are clearly distinguished from somatic motor neurons that project from the CNS directly to the innervated tissue (skeletal muscle), without any intervening ganglia. There are also CNS components of the ANS, including brainstem and spinal autonomic preganglionic neurons that project to the autonomic motor neurons in the peripheral ganglia. Autonomic pathways, together with somatic motor pathways to skeletal muscle and neuroendocrine pathways, are the means whereby the central nervous system (CNS) sends commands to the rest of the body. The term autonomic nervous system (ANS) refers to collections of motor neurons (ganglia) situated in the head, neck, thorax, abdomen, and pelvis, and to the axonal connections of these neurons (Figure 1). Figure drawn by the authors, incorporating material from Gray's Anatomy 31st Edition 1954, and from Cannon and Rosenblueth Physiology of the Autonomic Nervous System, 1937. Figure 1: Summary of sympathetic (A) and parasympathetic (B) autonomic neural outflows from the central nervous system.
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