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Encyclopedia > Sympathetic ganglion
Gray's FIG. 838– The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses.

The sympathetic nervous system (SNS) is part of the autonomic nervous system (ANS), which also includes the parasympathetic nervous system (PNS). Download high resolution version (503x800, 66 KB)From Grays Anatomy This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... Download high resolution version (503x800, 66 KB)From Grays Anatomy This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... An illustration from the 1918 edition Henry Grays Anatomy of the Human Body, commonly known as Grays Anatomy, is an anatomy textbook widely regarded as a classic work on human anatomy. ... This article or section is in need of attention from an expert on the subject. ... It has been suggested that Parasympatholytic be merged into this article or section. ...

Contents


Function

The sympathetic nervous system activates what is often termed the fight or flight response. This response is also known as sympathico-adrenal response of the body, as the pre-ganglionic sympathetic fibers that end in the adrenal medulla (but also all other sympathetic fibers) secrete acetylcholine, which activates the secretion of adrenaline (epinephrine) and to a lesser extent norepinephrine from it. Therefore, this response that acts primarily on the cardiovascular system is mediated directly via impulses transmitted through the sympathetic nervous system and indirectly via catecholamines secreted from the adrenal medulla. This article or section should include material from Fight-or-flight The flight or fight response, also called the acute stress response, was first described by Walter Cannon in the 1920s as a theory that animals react to threats with a general discharge of the sympathetic nervous system. ... In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers. ... In mammals, the adrenal glands are the triangle-shaped endocrine glands that sit atop the kidneys. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Epinephrine (INN) or adrenaline (BAN) is a hormone and a neurotransmitter. ... For the Deftones album; see Adrenaline (album). ... Norepinephrine or noradrenaline is a catecholamine and a phenethylamine with chemical formula C8H11NO3. ... The circulatory system or cardiovascular system is the organ system which circulates blood around the body of most animals. ... Catecholamines are chemical compounds derived from the amino acid tyrosine that act as hormones or neurotransmitters. ...


Western science typically looks at the SNS as an automatic regulation system, that is, one that operates without the intervention of conscious thought. Some evolutionary theorists suggest that the sympathetic nervous system operated in early man to maintain human survival (Origins of Consciousness, Robert Ornstein; et al.), as the sympathetic nervous system is responsible for priming the body for action.


Organization

Sympathetic nerves originate inside the vertebral column, toward the middle of the spinal cord in the intermediolateral cell column (or lateral horn), beginning at the first thoracic segment of the spinal cord and extending into the second or third lumbar segments. Because its cells begin in the thoracic and lumbar regions of the spinal cord, the SNS is said to have a thoracolumbar outflow. Axons of these nerves leave the spinal cord in the ventral branches (rami) of the spinal nerves, and then separate out as 'white rami' (so called from the shiny white sheaths of myelin around each axon) which connect to two chain ganglia extending alongside the vertebral column on the left and right. These elongated ganglia are also known as 'paravertebral ganglia' or 'sympathetic trunks'. In these hubs, connections (synapses) are made which then distribute the nerves to major organs, glands, and other parts of the body. [1] The vertebral column seen from the side Different regions (curvatures) of the vertebral column The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ... Cross-section through cervical spinal cord. ... Diagram of a tsetse fly, showing the head, thorax and abdomen The thorax is a division of an animals body, that lies between the head and the abdomen. ... In anatomy, lumbar is an adjective that means of or pertaining to the abdominal segment of the torso, between the diaphragm and the sacrum (pelvis). ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... In neuroscience, myelin is an electrically insulating phospholipid layer that surrounds the axons of many neurons. ... This is a dorsal root ganglion (DRG) from a chicken embryo (around stage of day 7) after incubation overnight in NGF growth medium stained with anti-neurofilament antibody. ... Illustration of the major elements in a prototypical synapse. ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues, which perform a specific function or group of functions. ... A gland is an organ in an animals body that synthesizes a substance for release such as hormones, often into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). ...


In order to reach the target organs and glands, the axons must travel long distances in the body, and, to accomplish this, many axons link up with the axon of a second cell. The ends of the axons do not make direct contact, but rather link across a space, the synapse. Illustration of the major elements in a prototypical synapse. ...


In the SNS and other components of the peripheral nervous system, these synapses are made at sites called ganglia. The cell that sends its fiber is called a preganglionic cell, while the cell whose fiber leaves the ganglion is called a postganglionic cell. As mentioned previously, the preganglionic cells of the SNS are located between the first thoracic segment and the second or third lumbar segments of the spinal cord. Postganglionic cells have their cell bodies in the ganglia and send their axons to target organs or glands. This is a dorsal root ganglion (DRG) from a chicken embryo (around stage of day 7) after incubation overnight in NGF growth medium stained with anti-neurofilament antibody. ...


The ganglia include not just the sympathetic trunks but also the superior cervical ganglion (which sends sympathetic nerve fibers to the head), and the celiac and mesenteric ganglia (which send sympathetic fibers to the gut). The superior cervical ganglion, the largest of the cervical ganglia, is placed opposite the second and third cervical vertebræ. It is of a reddish-gray color, and usually fusiform in shape; sometimes broad and flattened, and occasionally constricted at intervals; it is believed to be formed by the coalescence of... The Celiac Ganglia (semilunar ganglia) are two large irregularly shaped masses having the appearance of lymph glands and placed one on either side of the middle line in front of the crura of the diaphragm close to the suprarenal glands, that on the right side being placed behind the inferior...


Information transmission

Messages travel through the SNS in a bidirectional flow. Efferent messages can trigger changes in different parts of the body simultaneously. For example, the sympathetic nervous system can accelerate heart rate; widen bronchial passages; decrease motility (movement) of the large intestine; constrict blood vessels; cause pupil dilation, piloerection (goose bumps) and perspiration (sweating); and raise blood pressure. Afferent messages carry sensations such as heat, cold, or pain. Efferent nerve fibers carry information away from the brain. ... Heart rate is a term used to describe the frequency of the cardiac cycle. ... The bronchioles are the first airway branches that no longer contain cartilage. ... Motility is the ability to move spontaneously and independently. ... In anatomy of the digestive system, the colon is the part of the intestine from the cecum to the rectum. ... The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... The human eye The pupil is the central transparent area (showing as black). ... Dilation in physiological context may mean: pupil dilation (mydriasis) dilation of blood vessels (vasodilation) cervical dilation (or dilation of the cervix) in childbirth Dilation and curettage (surgical dilation) In mathematics: Dilation This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Goose bumps on a human Goose bumps (AE), also called goose pimples, goose flesh (BE), chicken skin (Hawaiian Pidgin), or cutis anserina, are the bumps on a persons skin at the base of body hairs which involuntarily develop when a person is cold or experiences strong emotions like fear. ... Sweating (also called perspiration or sometimes transpiration) is the loss of a watery fluid, consisting mainly of sodium chloride and urea in solution, that is secreted by the sweat glands in the skin of mammals. ... Blood pressure is the pressure exerted by the blood on the walls of the blood vessels. ... In nervous systems, afferent signals or nerve fibers carry information toward the brain. ...


The first synapse (in the sympathetic chain) is mediated by nicotinic receptors physiologically activated by acetylcholine, and the target synapse is mediated by adrenergic receptors physiologically activated by either norepinephrine or epinephrine. An exception is with sweat glands which receive sympathetic innervation but have muscarinic acetylcholine receptors which are normally characteristic of the PNS. Another exception is with certain deep muscle blood vessels, which have acetylcholine receptors and which dilate (rather than constrict) with an increase in sympathetic tone. The Sympathetic Chain is a series of interconnected sympathetic ganglia, belonging to the autonomic nervous system. ... Nicotinic Receptors form ion channels present in the plasma membrane of cells. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... An adrenergic is a drug, or other substance, which has effects similar to, or the same as, epinephrine (adrenaline). ... Muscarinic receptors are those membrane bound acetylcholine receptors that are more sensitive to muscarine than to nicotine. ...


See also

Nervous system - edit
Brain | Spinal cord | Central nervous system | Peripheral nervous system | Somatic nervous system | Autonomic nervous system | Sympathetic nervous system | Parasympathetic nervous system

  Results from FactBites:
 
IX. Neurology. 5e. The Trigeminal Nerve. Gray, Henry. 1918. Anatomy of the Human Body. (5634 words)
The ciliary ganglion is connected with the ophthalmic nerve; the sphenopalatine ganglion with the maxillary nerve; and the otic and submaxillary ganglia with the mandibular nerve.
In the sphenopalatine ganglion they form synapses with neurons whose postganglionic axons, vasodilator and secretory fibers, are distributed with the deep branches of the trigeminal to the mucous membrane of the nose, soft palate, tonsils, uvula, roof of the mouth, upper lip and gums, and to the upper part of the pharynx.
The branch of communication from the lingual to the forepart of the ganglion is by some regarded as a branch of distribution, through which filaments pass from the ganglion to the lingual nerve, and by it are conveyed to the sublingual gland and the tongue.
Thoracic Nerves (854 words)
The autonomic nerves are the fibres from the sympathetic chain, and the vagus nerve.
Post ganglionic fibres pass to the primary rami in grey rami communicantes to be distributed to the tissues.
Sympathetic fibres from T2-T6 of the thoracic sympathetic chain, and parasympathetic fibres from the vagus form the pulmonary plexus.
  More results at FactBites »

 
 

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