Adrenergic and Cholinergic Systems
The transmission of impulses is mediated in the sympathetic nervous system by norepinephrine, and in the parasympa-thetic nervous system by acetylcholine. The sympathetic nervous system is therefore alsoknown as the adrenergic system and the para-sympathetic nervous system as thecholiner-gic system. All preganglionic fibers of thesympathetic nervous system are choliner-gic, and only the postganglionic fibers are noradrenergic. The postgan-glionic sympathetic fibers innervating the sweat glands of the skin are also cholinergic.
The antagonism between sympathetic and parasympathetic nervous systems is clearly apparent for some organs (heart, lungs). Other organs are regulated by the increased or decreased tone of just one system. Thus, the adrenal glands and the uterus are sup-plied only by sympathetic fibers (the adrenal gland as paraganglion is supplied by preganglionic fibers). The func-tion of the urinary bladder is regulated by parasympathetic fibers; the role of sympa-thetic fibers in this control is disputed.