In the autonomic nervous system, fibers from the ganglion to the effector organ are called postganglionic fibers.
The neurotransmitters of postganglionic fibers differ:
In the parasympathetic division, neurons are cholinergic.
In the sympathetic division, neurons are mostly adrenergic that is, epinephrine and norepinephrine function as the primary neurotransmitters.
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.
The medulla of the adrenal gland, where chromaffin cells function as modified post-ganglionic nerves., release the catecholamines into the blood stream as hormones.
In both divisions of the autonomic nervous system, postganglionic neurons express nicotinic acetylcholine receptors to receive signals from preganglionic neurons.