Myenteric plexus

Last updated
Myenteric plexus
Gray1071.png
The myenteric plexus from the rabbit. X 50.
GI Organization.svg
Details
Identifiers
Latin plexus myentericus, plexus Auerbachi
MeSH D009197
TA98 A14.3.03.041
TA2 6727
Anatomical terms of neuroanatomy
Layers of the GI Tract english.svg
This article is one of a series on the
Gastrointestinal wall
General structure
Specific
Organs

The myenteric plexus (or Auerbach's plexus) provides motor innervation to both layers of the muscular layer of the gut, having both parasympathetic and sympathetic input (although present ganglion cell bodies belong to parasympathetic innervation, fibers from sympathetic innervation also reach the plexus), whereas the submucous plexus provides secretomotor innervation to the mucosa nearest the lumen of the gut.

Contents

It arises from cells in the vagal trigone also known as the nucleus ala cinerea, the parasympathetic nucleus of origin for the tenth cranial nerve (vagus nerve), located in the medulla oblongata. The fibers are carried by both the anterior and posterior vagal nerves. The myenteric plexus is the major nerve supply to the gastrointestinal tract and controls GI tract motility. [1]

According to preclinical studies, 30% of myenteric plexus' neurons are enteric sensory neurons, thus Auerbach's plexus has also a sensory component. [2] [3]

Structure

A part of the enteric nervous system, the myenteric plexus exists between the longitudinal and circular layers of muscularis externa in the gastrointestinal tract. It is found in the muscles of the esophagus, stomach, and intestine.[ citation needed ]

The ganglia have properties similar to the central nervous system (CNS). These properties include presence of glia, interneurons, a small extracellular space, dense synaptic neuropil, isolation from blood vessels, multiple synaptic mechanisms and multiple neurotransmitters.

The myenteric plexus originates in the medulla oblongata as a collection of neurons from the ventral part of the brain stem. The vagus nerve then carries the axons to their destination in the gastrointestinal tract. [4]

They contain Dogiel cells. [5]

Function

The myenteric plexus functions as a part of the enteric nervous system (digestive system). The enteric nervous system can and does function autonomously, but normal digestive function requires communication links between this intrinsic system and the central nervous system. The ENS contains sensory receptors, primary afferent neurons, interneurons, and motor neurons. The events that are controlled, at least in part, by the ENS are multiple and include motor activity, secretion, absorption, blood flow, and interaction with other organs such as the gallbladder or pancreas. These links take the form of parasympathetic and sympathetic fibers that connect either the central and enteric nervous systems or connect the central nervous system directly with the digestive tract. Through these cross connections, the gut can provide sensory information to the CNS, and the CNS can affect gastrointestinal function. Connection to the central nervous system also means that signals from outside of the digestive system can be relayed to the digestive system: for instance, the sight of appealing food stimulates secretion in the stomach. [6]

Neurotransmitters

The enteric nervous system makes use of over 30 different neurotransmitters, most similar to those of the CNS such as acetylcholine, dopamine, and serotonin. More than 90% of the body's serotonin lies in the gut; as well as about 50% of the body's dopamine, which is currently being studied to further our understanding of its utility in the brain. [7] The heavily studied neuropeptide known as substance P is present in significant levels and may help facilitate the production of saliva, smooth muscle contractions, and other tissue responses.

Receptors

Since many of the same neurotransmitters are found in the ENS as the brain, it follows that myenteric neurons can express receptors for both peptide and non-peptide (amines, amino acids, purines) neurotransmitters. Generally, expression of a receptor is limited to a subset of myenteric neurons, with probably the only exception being expression of nicotinic cholinergic receptors on all myenteric neurons. One receptor that has been targeted for therapeutic reasons has been the 5-hydroxytryptamine (5-HT4) receptor. Activating this pre-synaptic receptor enhances cholinergic neurotransmission and can stimulate gastrointestinal motility. [8]

The enteric nervous system exhibits taste receptors similar to the ones in the tongue. The taste receptor TAS1R3 and the taste G protein gustducin are two of the most common. These receptors sense "sweetness" on the tongue and sense glucose in the enteric nervous system. These receptors help regulate the secretion of insulin and other hormones that are responsible for controlling blood sugar levels. [9]

Clinical significance

Hirschsprung's disease is a congenital disorder of the colon in which nerve cells of the myenteric plexus in its walls, also known as ganglion cells, are absent. Hirschsprung's disease is a form of functional low bowel obstruction due to failure of caudal migration of neuroblasts within developing bowel – this results in an absence of parasympathetic intrinsic ganglion cells in both Auerbach's and Meissner's plexuses. The distal large bowel from the point of neuronal arrest to the anus is continuously aganglionic. It is a rare disorder (1:5000), with prevalence among males being four times that of females. [10]

Achalasia is a motor disorder of the esophagus characterized by decrease in ganglion cell density in the myenteric plexus. The cause of the lesion is unknown. [11]

Myenteric plexi destruction has been found to be secondary to Chagas disease (T. cruzi infection sequelae). Destruction occurs in the esophagus, intestines, and ureters. This denervation can lead to secondary achalasia (lower esophageal sphincter will not open; loss of inhibitory neurons), megacolon, and megaureter, respectively.

Role in CNS disorders

Because the ENS is known as the "brain of the gut", due to its similarities with the CNS, researchers have been using colonic biopsies of Parkinson's patients to help better understand and manage Parkinson's disease. [12] PD patients are known to experience severe constipation due to GI tract dysfunction years before the onset of motor movement complications, which characterises Parkinson's disease. [13]

History

Leopold Auerbach, a neuropathologist, was one of the first to further research the nervous system using histological staining methods.[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Peripheral nervous system</span> Part of the nervous system excluding the brain and spinal cord

The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain and the spinal cord. The main function of the PNS is to connect the CNS to the limbs and organs, essentially serving as a relay between the brain and spinal cord and the rest of the body. Unlike the CNS, the PNS is not protected by the vertebral column and skull, or by the blood–brain barrier, which leaves it exposed to toxins.

<span class="mw-page-title-main">Vagus nerve</span> Cranial nerve X, for visceral innervation

The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that carries sensory fibers that create a pathway that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right vagus nerves—but they are typically referred to collectively as a single subsystem. The vagus is the longest nerve of the autonomic nervous system in the human body and comprises both sensory and motor fibers. The sensory fibers originate from neurons of the nodose ganglion, whereas the motor fibers come from neurons of the dorsal motor nucleus of the vagus and the nucleus ambiguus. The vagus was also historically called the pneumogastric nerve.

<span class="mw-page-title-main">Autonomic nervous system</span> Division of the nervous system supplying internal organs, smooth muscle and glands

The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the nervous system that operates internal organs, smooth muscle and glands. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, its force of contraction, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response.

<span class="mw-page-title-main">Parasympathetic nervous system</span> Division of the autonomic nervous system

The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

<span class="mw-page-title-main">Sympathetic nervous system</span> Part of the autonomic nervous system which stimulates fight-or-flight responses

The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

<span class="mw-page-title-main">Enteric nervous system</span> Vital system controlling the gastrointestinal tract

The enteric nervous system (ENS) or intrinsic nervous system is one of the main divisions of the peripheral nervous system (PNS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract. It is capable of acting independently of the sympathetic and parasympathetic nervous systems, although it may be influenced by them. The ENS is nicknamed the "second brain". It is derived from neural crest cells.

<span class="mw-page-title-main">Nervous tissue</span> Main component of the nervous system

Nervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the brain and spinal cord, and the peripheral nervous system (PNS) comprising the branching peripheral nerves. It is composed of neurons, also known as nerve cells, which receive and transmit impulses, and neuroglia, also known as glial cells or glia, which assist the propagation of the nerve impulse as well as provide nutrients to the neurons.

<span class="mw-page-title-main">Neuroeffector junction</span> Site where a motor neuron releases a neurotransmitter to affect a target cell

A neuroeffector junction is a site where a motor neuron releases a neurotransmitter to affect a target—non-neuronal—cell. This junction functions like a synapse. However, unlike most neurons, somatic efferent motor neurons innervate skeletal muscle, and are always excitatory. Visceral efferent neurons innervate smooth muscle, cardiac muscle, and glands, and have the ability to be either excitatory or inhibitory in function. Neuroeffector junctions are known as neuromuscular junctions when the target cell is a muscle fiber.

<span class="mw-page-title-main">Enterochromaffin cell</span> Cell type

Enterochromaffin (EC) cells are a type of enteroendocrine cell, and neuroendocrine cell. They reside alongside the epithelium lining the lumen of the digestive tract and play a crucial role in gastrointestinal regulation, particularly intestinal motility and secretion. They were discovered by Nikolai Kulchitsky.

<span class="mw-page-title-main">Megacolon</span> Medical condition

Megacolon is an abnormal dilation of the colon. This leads to hypertrophy of the colon. The dilation is often accompanied by a paralysis of the peristaltic movements of the bowel. In more extreme cases, the feces consolidate into hard masses inside the colon, called fecalomas, which can require surgery to be removed.

<span class="mw-page-title-main">Ciliary ganglion</span> Bundle of nerves, parasympathetic ganglion

The ciliary ganglion is a bundle of nerves, parasympathetic ganglion located just behind the eye in the posterior orbit. It is 1–2 mm in diameter and in humans contains approximately 2,500 neurons. The ganglion contains postganglionic parasympathetic neurons. These neurons supply the pupillary sphincter muscle, which constricts the pupil, and the ciliary muscle which contracts to make the lens more convex. Both of these muscles are involuntary since they are controlled by the parasympathetic division of the autonomic nervous system.

<span class="mw-page-title-main">Nerve plexus</span> Network of nerve fibres

A nerve plexus is a plexus of intersecting nerves. A nerve plexus is composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels. There are five spinal nerve plexuses, except in the thoracic region, as well as other forms of autonomic plexuses, many of which are a part of the enteric nervous system. The nerves that arise from the plexuses have both sensory and motor functions. These functions include muscle contraction, the maintenance of body coordination and control, and the reaction to sensations such as heat, cold, pain, and pressure. There are several plexuses in the body, including:

<span class="mw-page-title-main">Postganglionic nerve fibers</span> Fibers from the ganglion to the effector organ

In the autonomic nervous system, nerve fibers from the ganglion to the effector organ are called postganglionic nerve fibers.

<span class="mw-page-title-main">Celiac ganglia</span> Two large masses of nerve tissue in the upper abdomen

The celiac ganglia or coeliac ganglia are two large irregularly shaped masses of nerve tissue in the upper abdomen. Part of the sympathetic subdivision of the autonomic nervous system (ANS), the two celiac ganglia are the largest ganglia in the ANS, and they innervate most of the digestive tract.

Neurturin (NRTN) is a protein that is encoded in humans by the NRTN gene. Neurturin belongs to the glial cell line-derived neurotrophic factor (GDNF) family of neurotrophic factors, which regulate the survival and function of neurons. Neurturin’s role as a growth factor places it in the transforming growth factor beta (TGF-beta) subfamily along with its homologs persephin, artemin, and GDNF. It shares a 42% similarity in amino acid sequence with mature GDNF. It is also considered a trophic factor and critical in the development and growth of neurons in the brain. Neurotrophic factors like neurturin have been tested in several clinical trial settings for the potential treatment of neurodegenerative diseases, specifically Parkinson's disease.

Gastrointestinal physiology is the branch of human physiology that addresses the physical function of the gastrointestinal (GI) tract. The function of the GI tract is to process ingested food by mechanical and chemical means, extract nutrients and excrete waste products. The GI tract is composed of the alimentary canal, that runs from the mouth to the anus, as well as the associated glands, chemicals, hormones, and enzymes that assist in digestion. The major processes that occur in the GI tract are: motility, secretion, regulation, digestion and circulation. The proper function and coordination of these processes are vital for maintaining good health by providing for the effective digestion and uptake of nutrients.

The basal or basic electrical rhythm (BER) or electrical control activity (ECA) is the spontaneous depolarization and repolarization of pacemaker cells known as interstitial cells of Cajal (ICCs) in the smooth muscle of the stomach, small intestine, and large intestine. This electrical rhythm is spread through gap junctions in the smooth muscle of the GI tract. These pacemaker cells, also called the ICCs, control the frequency of contractions in the gastrointestinal tract. The cells can be located in either the circular or longitudinal layer of the smooth muscle in the GI tract; circular for the small and large intestine, longitudinal for the stomach. The frequency of contraction differs at each location in the GI tract beginning with 3 per minute in the stomach, then 12 per minute in the duodenum, 9 per minute in the ileum, and a normally low one contraction per 30 minutes in the large intestines that increases 3 to 4 times a day due to a phenomenon called mass movement. The basal electrical rhythm controls the frequency of contraction but additional neuronal and hormonal controls regulate the strength of each contraction.

The nervous system, and endocrine system collaborate in the digestive system to control gastric secretions, and motility associated with the movement of food throughout the gastrointestinal tract, including peristalsis, and segmentation contractions.

<span class="mw-page-title-main">Outline of the human nervous system</span> Overview of and topical guide to the human nervous system

The following diagram is provided as an overview of and topical guide to the human nervous system:

<span class="mw-page-title-main">Dogiel cells</span> Type of multipolar nerve cell

Dogiel cells, also known as cells of Dogiel, are a type of multipolar neuronal cells within the prevertebral sympathetic ganglia. They are named after the Russian anatomist and physiologist Alexandre Dogiel (1852–1922). Dogiel cells play a role in the enteric nervous system.

References

  1. ↑ Human Anatomy and Physiology, Marieb & Hoehn, seventh edition[ page needed ]
  2. ↑ Handbook of Experimental Pharmacology, Vol. 194: Sensory Nerves, Brendan J. Canning, Domenico Spina. Springer. Page 341.
  3. ↑ Costa, M; Brookes, S. J.; Hennig, G. W. (2000). "Anatomy and physiology of the enteric nervous system". Gut. 47 (90004): iv15–9, discussion iv26. doi:10.1136/gut.47.suppl_4.iv15. PMC   1766806 . PMID   11076898.
  4. ↑ Mazzuoli, Gemma; Schemann, Michael (2012). "Mechanosensitive Enteric Neurons in the Myenteric Plexus of the Mouse Intestine". PLOS ONE. 7 (7): e39887. Bibcode:2012PLoSO...739887M. doi: 10.1371/journal.pone.0039887 . PMC   3388088 . PMID   22768317.
  5. ↑ Stach, W (1979). "Differentiated vascularization of Dogiel's cell types and the preferred vascularization of type I/2 cells within plexus myentericus (Auerbach) ganglia of the pig (author's transl)". Anatomischer Anzeiger. 145 (5): 464–73. PMID   507375.
  6. ↑ Fujita, Shin; Nakanisi, Yukihiro; Taniguchi, Hirokazu; Yamamoto, Seiichiro; Akasu, Takayuki; Moriya, Yoshihiro; Shimoda, Tadakazu (2007). "Cancer Invasion to Auerbachʼs Plexus is an Important Prognostic Factor in Patients with pT3-pT4 Colorectal Cancer". Diseases of the Colon & Rectum. 50 (11): 1860–6. doi:10.1007/s10350-007-9072-8. PMID   17899273. S2CID   26109259.
  7. ↑ Pasricha, Pankaj Jay. "Stanford Hospital: Brain in the Gut - Your Health". YouTube . Archived from the original on 2021-12-22.
  8. ↑ Dickson, E. J.; Heredia, D. J.; Smith, T. K. (2010). "Critical role of 5-HT1A, 5-HT3, and 5-HT7 receptor subtypes in the initiation, generation, and propagation of the murine colonic migrating motor complex". AJP: Gastrointestinal and Liver Physiology. 299 (1): G144–57. doi:10.1152/ajpgi.00496.2009. PMC   2904117 . PMID   20413719.
  9. ↑ Margolskee, Robert F.; Dyer, Jane; Kokrashvili, Zaza; Salmon, Kieron S. H.; Ilegems, Erwin; Daly, Kristian; Maillet, Emeline L.; Ninomiya, Yuzo; Mosinger, Bedrich; Shirazi-Beechey, Soraya P. (2007). "T1R3 and gustducin in gut sense sugars to regulate expression of Na+-glucose cotransporter 1". Proceedings of the National Academy of Sciences. 104 (38): 15075–80. Bibcode:2007PNAS..10415075M. doi: 10.1073/pnas.0706678104 . JSTOR   25449086. PMC   1986615 . PMID   17724332.
  10. ↑ Tam, Paul K. H.; Garcia-Barceló, Mercè (2009). "Genetic basis of Hirschsprung's disease". Pediatric Surgery International. 25 (7): 543–58. doi:10.1007/s00383-009-2402-2. PMID   19521704. S2CID   27343466.
  11. ↑ Storch, W. B.; Eckardt, V. F.; Wienbeck, M; Eberl, T; Auer, P. G.; Hecker, A; Junginger, T; Bosseckert, H (1995). "Autoantibodies to Auerbach's plexus in achalasia". Cellular and Molecular Biology (Noisy-le-Grand, France). 41 (8): 1033–8. PMID   8747084.
  12. ↑ Shprecher, D. R.; Derkinderen, P. (2012). "Parkinson Disease: The Enteric Nervous System Spills its Guts". Neurology. 78 (9): 683, author reply 683. doi:10.1212/WNL.0b013e31824bd195. PMID   22371415.
  13. ↑ Lebouvier, Thibaud; Neunlist, Michel; Bruley Des Varannes, Stanislas; Coron, Emmanuel; Drouard, Anne; n'Guyen, Jean-Michel; Chaumette, Tanguy; Tasselli, Maddalena; Paillusson, Sébastien; Flamand, Mathurin; Galmiche, Jean-Paul; Damier, Philippe; Derkinderen, Pascal (2010). "Colonic Biopsies to Assess the Neuropathology of Parkinson's Disease and Its Relationship with Symptoms". PLOS ONE. 5 (9): e12728. Bibcode:2010PLoSO...512728L. doi: 10.1371/journal.pone.0012728 . PMC   2939055 . PMID   20856865.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.