The sympathoadrenal system is a physiological connection between the sympathetic nervous system and the adrenal medulla and is crucial in an organism's physiological response to outside stimuli. When the body receives sensory information, the sympathetic nervous system sends a signal to preganglionic nerve fibers, which activate the adrenal medulla through acetylcholine. Once activated, norepinephrine and epinephrine are released directly into the blood by adrenomedullary cells where they act as the bodily mechanism for "fight-or-flight" responses. Because of this, the sympathoadrenal system plays a large role in maintaining glucose levels, sodium levels, blood pressure, and various other metabolic pathways that couple with bodily responses to the environment. During numerous diseased states, such as hypoglycemia or even stress, the body's metabolic processes are skewed. The sympathoadrenal system works to return the body to homeostasis through the activation or inactivation of the adrenal gland. However, more severe disorders of the sympathoadrenal system such as pheochromocytoma (a tumor on the adrenal medulla) can affect the body's ability to maintain a homeostatic state. In these cases, curative agents such as adrenergic agonists and antagonists are used to modify epinephrine and norepinephrine levels released by the adrenal medulla.
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Preganglionic nerve fibers in the context of Group B nerve fiber
Group B nerve fibers are one of the three classes of nerve fiber as generally classified by Erlanger and Gasser. They are moderately myelinated, which means less myelinated than group A nerve fibers, and more myelinated than group C nerve fibers. They have a medium conduction velocity of 3 to 14 m/s. They are usually general visceral afferent fibers and preganglionic nerve fibers of the autonomic nervous system. They are used in Bainbridge reflex as afferents.