postganglionic fiber

(noun)

In the autonomic nervous system, these are the fibers that run from the ganglion to the effector organ.

Related Terms

Examples of postganglionic fiber in the following topics:

  • Postganglionic Neurons

    • In the autonomic nervous system, fibers from the ganglion to the effector organ are called postganglionic fibers.
    • In the autonomic nervous system, fibers from the ganglion to the effector organ are called postganglionic fibers.
    • The neurotransmitters used by postganglionic fibers differ.
    • As a result, the postsynaptic parasympathetic nerve fibers are very short.
    • The postganglionic nerve then releases ACh to stimulate the muscarinic receptors of the target organ.

  • Preganglionic Neurons

    • In the autonomic nervous system (ANS), nerve fibers that connect the central nervous system to ganglia are known as preganglionic fibers.
    • The postganglionic neuron will then cross a synapse at the target organ.
    • Sympathetic preganglionic fibers tend to be shorter than parasympathetic preganglionic fibers because sympathetic ganglia are often closer to the spinal cord while parasympathetic preganglionic fibers tend to project to and synapse with the postganglionic fiber close to the target organ.
    • There are several locations where preganglionic neurons create synapses with their postganglionic neurons:
    • These are the preganglionic neurons that synapse with the postganglionic neurons in these locations :

  • Sympathetic Nervous System

    • This response is also known as the sympathetico-adrenal response because the pre-ganglionic sympathetic fibers that end in the adrenal medulla—like all sympathetic fibers—secrete acetylcholine.
    • Preganglionic nerves from the spinal cord create a synapse at one end of the chain ganglia and the postganglionic fiber extends to an effector, typically a visceral organ, in the thoracic cavity.

  • Oculomotor (III) Nerve

    • The Edinger-Westphal nucleus supplies parasympathetic fibers to the eye via the ciliary ganglion, and controls the pupillae muscle (affecting pupil constriction) and the ciliary muscle (affecting accommodation).
    • Sympathetic postganglionic fibers also join the nerve from the plexus on the internal carotid artery in the wall of the cavernous sinus and are distributed through the nerve, for example, to the smooth muscle of levator palpebrae superioris.

  • Autonomic Ganglia

    • Preganglionic nerves from the spinal cord create a synapse end at one of the chain ganglia, and the postganglionic fiber extends to an effector, typically a visceral organ in the thoracic cavity.
    • This second neuron is referred to as the postganglionic or postsynaptic neuron.
    • As a result, the postsynaptic parasympathetic nerve fibers are very short.
    • The postganglionic fibers travel from the ganglion to the effector organ.

  • Submucosa

    • It also joins the mucosa to the bulk of underlying smooth muscle (fibers running circularly within layer of longitudinal muscle).
    • Tiny parasympathetic ganglia are scattered around forming the submucosal plexus (or "Meissner's plexus") where preganglionic parasympathetic neurons synapse with postganglionic nerve fibers that supply the muscularis mucosae.

  • Autonomic Plexuses

    • Autonomic plexuses are formed from sympathetic and parasympathetic fibers that innervate and regulate the overall activity of visceral organs.
    • Autonomic plexuses are formed from sympathetic postganglionic axons, parasympathetic preganglionic axons, and some visceral sensory axons.
    • The esophageal plexus is formed by nerve fibers from two sources: the branches of the vagus nerve and the visceral branches of the sympathetic trunk.
    • The esophageal plexus and the cardiac plexus contain the same types of fibers and are both considered thoracic autonomic plexus(es).

  • Autonomic Reflexes

    • The ANS is unique in that it requires a sequential two-neuron efferent pathway; the preganglionic neuron must first creat a synapse to a postganglionic neuron before innervating the target organ.
    • The preganglionic, or first neuron will begin at the outflow and will cross a synapse at the postganglionic, or second neuron's cell body.
    • The postganglionic neuron will then create a synapse at the target organ.
    • General visceral afferent sensations are mostly unconscious, visceral motor reflex sensations from hollow organs and glands that are transmitted to the CNS (see the following illustration for a depiction of a typical nerve fiber, including general visceral afferent fibers).
    • This schematic (but not anatomically correct) depiction of a typical spinal nerve indicates (1) somatic efferent fibers, (2) somatic afferent fibers, (3 to 5) sympathetic efferent fibers, and (6 and 7) sympathetic afferent fibers.

  • Dietary Fiber

    • Lignin, a major dietary insoluble fiber source, may alter the fate and metabolism of soluble fibers.
    • The term "fiber" is something of a misnomer since many types of so-called dietary fiber are not actually fibrous.
    • Dietary fiber is found in plants.
    • Fiber-rich plants can be eaten directly.
    • The plum's skin is a source of insoluble fiber while soluble fiber is in the pulp.

  • Function and Physiology of the Spinal Nerves

    • Acetylcholine is the preganglionic neurotransmitter for both divisions of the ANS, as well as the postganglionic neurotransmitter of parasympathetic neurons.
    • Acetylcholine is released from the axon terminal knobs of alpha motor neurons and received by postsynaptic receptors (nicotinic acetylcholine receptors) of muscles, thereby relaying the stimulus to contract muscle fibers.
    • Numbers indicate the types of nerve fibers: 1 somatic efferent, 2 somatic afferent, 3–5 sympathetic efferent, 6–7 sympathetic afferent.