Postganglionic nerve fibers
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|Nerve: Postganglionic fibers|
Sympathetic connections of the ciliary and superior cervical ganglia.
The neurotransmitters of postganglionic fibers differ:
- In the parasympathetic division, neurons are cholinergic (that is, acetylcholine is the primary neurotransmitter.)
- In the sympathetic division, neurons are mostly adrenergic (that is, epinephrine and norepinephrine function as the primary neurotransmitters.) Two exceptions to this rule are the sympathetic innervation of sweat glands and arrectores pilorum muscles where the neurotransmitter at both pre and post ganglionic synapses is acetylcholine and the vessels in the renal cortex where dopamine is used as the main neurotransmitter. Another exception is the sympathetic innervation of the medulla of the adrenal glands, which is accomplished by preganglionic fibers, and subsequently uses acetylcholine as a neurotransmitter. The cells of the adrenal medulla are actually modified postganglionic neurons which secrete epinephrine and norepinephrine directly into the blood stream rather than into a synapse.
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