In the sympathetic division, neurons are mostly adrenergic (that is, epinephrine and norepinephrine function as the primary neurotransmitters). Notable exceptions to this rule include the sympathetic innervation of sweat glands and arrectores pilorum muscles where the neurotransmitter at both pre and post ganglionic synapses is acetylcholine. Another notable structure is the medulla of the adrenal gland, where chromaffin cells function as modified post-ganglionic nerves. Instead of releasing epinephrine and norepinephrine into a synaptic cleft, these cells of the adrenal medulla release the catecholamines into the blood stream as hormones.[1] Like other components of the sympathetic nervous system, all of these exceptions are still stimulated by cholinergic preganglionic fibers.
^Noback C, Ruggiero DA, Demarest RJ, Strominger NL (2005). The Human Nervous System: Structure and Function (6th ed.). New Jersey: Humana Press. ISBN978-1588290403.
^Costanzo, Linda (2014). BRS Physiology (6th ed.). LWW. ISBN9781451187953.