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The Autonomic Nervous System and Adrenergic Receptors in Pediatric Practice
Jeffrey S. Rubenstein MD1
1 Chief, Division of Pediatric Critical Care, Department of Pediatrics, University of Rochester School of Medicine & Dentistry, Rochester, NY.
The last 20 years have seen an explosion in our knowledge of the autonomic nervous system and our ability to manipulate its parasympathetic and sympathetic portions pharmacologically to achieve therapeutic goals. This article will briefly review the structure and function of the autonomic nervous system, with particular focus on the sympathetic branch. Included in the review is a discussion of the major receptors of the sympathetic system, concentrating on their intracellular mechanism of action, their effects on major target organ systems, and some commonly used pharmacologic agents that influence these organ systems through their actions on sympathetic receptors.
Structure and Function of the System
The autonomic (or involuntary) nervous system innervates the heart, visceral organs, blood vessels, smooth muscles, and glands. It can be divided functionally into the parasympathetic and sympathetic systems, which have opposing functions. All autonomic nerve pathways consist of two nerves in sequence. Presynaptic nerves begin in the central nervous system and transmit impulses to the postsynaptic nerves. Postsynaptic nerves then carry impulses to the effector organ.
Actions of the parasympathetic nervous system include bradycardia, vasodilation in skeletal muscle and skin, contraction of bronchial smooth muscle, increased gastrointestinal motility, pupillary miosis, and contraction of the bladder detrusor coupled with relaxation of the bladder trigone (necessary for spontaneous voiding).
