preganglionic fiber

(noun)

In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers.

Related Terms

Examples of preganglionic fiber in the following topics:

  • Preganglionic Neurons

    • In the autonomic nervous system (ANS), nerve fibers that connect the central nervous system to ganglia are known as preganglionic fibers.
    • In the autonomic nervous system (ANS), fibers from the central nervous system to the ganglion are known as preganglionic fibers.
    • All preganglionic fibers, whether they are in the sympathetic nervous system (SNS) or in the parasympathetic nervous system (PSNS), are cholinergic—that is, these fibers use acetylcholine as their neurotransmitter—and are myelinated.
    • 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.
    • Another major difference between the two ANS systems is divergence, or the number of postsynaptic fibers a single preganglionic fiber creates a synapse with.

  • 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.
    • In the cranium, preganglionic fibers (cranial nerves III, VII, and IX) usually arise from specific nuclei in the central nervous system (CNS) and create a synapse at one of four parasympathetic ganglia: ciliary, pterygopalatine, otic, or submandibular.
    • In the autonomic nervous system, preganglionic fibers (shown in light blue) carry information from the CNS to the ganglion.

  • Facial (VII) Nerve

    • It also functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity, and it supplies preganglionic parasympathetic fibers to several head and neck ganglia.

  • The Stress Response

    • This response is also referred to as the sympatho-adrenal response of the body owing to the fact that the preganglionic sympathetic fibers that end in the adrenal medulla secrete acetylcholine, which activates the release of adrenaline and noradrenaline from the medulla.

  • 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.

  • 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.

  • 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.
    • The first neuron in this pathway is referred to as the preganglionic or presynaptic neuron.
    • As a result, the postsynaptic parasympathetic nerve fibers are very short.
    • The postganglionic fibers travel from the ganglion to the effector organ.

  • 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.
    • 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.

  • 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).

  • 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.