Overview of the Anatomy, Physiology, and Pharmacology of the Autonomic Nervous System

Abstract

Comprised of the sympathetic nervous system, parasympathetic nervous system, and enteric nervous system, the autonomic nervous system (ANS) provides the neural control of all parts of the body except for skeletal muscles. The ANS has the major responsibility to ensure that the physiological integrity of cells, tissues, and organs throughout the entire body is maintained (homeostasis) in the face of perturbations exerted by both the external and internal environments. Many commonly prescribed drugs, over-the-counter drugs, toxins, and toxicants function by altering transmission within the ANS. Autonomic dysfunction is a signature of many neurological diseases or disorders. Despite the physiological relevance of the ANS, most neuroscience textbooks offer very limited coverage of this portion of the nervous system. This review article provides both historical and current information about the anatomy, physiology, and pharmacology of the sympathetic and parasympathetic divisions of the ANS. The ultimate aim is for this article to be a valuable resource for those interested in learning the basics of these two components of the ANS and to appreciate its importance in both health and disease. Other resources should be consulted for a thorough understanding of the third division of the ANS, the enteric nervous system. © 2016 American Physiological Society. Compr Physiol 6:1239-1278, 2016.

Evidence for a direct effect of the autonomic nervous system on intestinal epithelial stem cell proliferation

“…As the effects of the SNS and PNS are usually thought of as antagonistic, opposing effects of NE and ACh on cyclin D1 might be expected. However, a more nuanced description of the ANS includes cooperative function of the SNS and PNS on certain organs (e.g., iris muscles in the eye and sexual organs (Wehrwein et al 2016)). This SNS and PNS cooperation is also seen in regard to control of cell proliferation, as NE and ACh both increase proliferation of hepatic myofibroblastic stellate cells, reflecting the dual participation of the SNS and PNS in liver regeneration after injury (Oben et al 2003a,b).…”

“…This may be a strategy for the ANS to inhibit proliferation during specific body states. When sympathetic tone is high, the SNS coordinates an overall decrease in energy and resources to the intestine (Browning and Travagli 2014;Wehrwein et al 2016), which may subsequently limit the energy available for cell proliferation. In contrast, PNS tone is increased during digestion, which is accompanied by increased cellular metabolism and subsequent reactive oxygen species (ROS) byproducts (Granger et al 2015).…”

Brainstem dysfunction in critically ill patients

“…The ANS plays a key role in homeostasis and allostasis by controlling vital functions and the immune system [46] and is composed of sympathetic (e.g., noradrenergic) and parasympathetic (e.g., cholinergic) systems. Sympathetic effects originate from the spinal cord (D1 to L3), while parasympathetic neuronal cell bodies are present in the nuclei of cranial nerves III (Edinger Westphal nuclei), VII, IX, and X and the sacral spinal cord (S2 to S4).…”

Comparison of the 3-D patterns of the parasympathetic nervous system in the lung at late developmental stages between mouse and chicken

“…Like other organs in the body, the lung physiology is governed by the autonomic nervous system, which is composed of sympathetic- and parasympathetic neurons (McCorry, 2007; Wehrwein et al, 2016; Karemaker, 2017). Previous studies, predominantly in mammals, reveal that the parasympathetic nervous system is particularly important in lung physiology, whereas the sympathetic nervous system plays less important roles (Mazzone and Canning, 2013).…”