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 Post subject: Breathing and stress
PostPosted: Sun Aug 22, 2004 8:06 pm 
In today's fast-faced, anxiety-driven world, stress management has become paramount not just for individuals faced with excessive stress in their daily lives, but also for the owners and managers of businesses of all sizes. Researchers now believe that excessive stress is associated with 60-80 percent of all visits to doctors. Not only are numerous health problems associated with unnecessary stress, problems which are reflected in our growing health-care costs, but businesses of all kinds are faced with the increasing use of "sick time" by employees at all levels and the overall loss of corporate productivity.

There are, of course, many powerful tools for stress management, for turning on our parasympathetic nervous system--our "relaxation response." One of them--healthy breathing--is often overlooked. In fact, most of us take our breathing almost entirely for granted, not realizing that the way we breathe influences every aspect of our lives. The paragraphs that follow--which are taken from The Tao of Natural Breathing, by Dennis Lewis, explore some important issues associated with stress--especially the negative emotions often associated with it--and how healthy, natural breathing, can help us understand and free ourselves from these emotions.

From The Tao of Natural Breathing
"As troublesome as they are in our lives, it is clear—at least sometimes—that what we call “negative emotions” have important “survival” value. Many of our negative emotions are simply signals that something has gone wrong in our lives or that some action is necessary to avoid a potential problem. A student’s anxiety about an upcoming exam, or an executive’s anxiety about a financial report that is due the next day, can play a beneficial role in stimulating appropriate preparation, as long as the anxiety does not become so excessive that it causes fear and a lack of concentration. A woman’s anger toward a man who physically or psychologically abuses her may motivate her to leave the relationship or to find a healthier relationship with someone else, as long as it doesn’t become so strong that she becomes violent. A mother’s anger toward a teenage daughter who stays out all night may be what is necessary to motivate both mother and daughter to try to communicate with each other in a new way. Our lives are filled with many examples of how our so-called negative emotions, as long as they do not become excessive, can provide important information about what is happening in our lives—information that can help us take intelligent actions on behalf of ourselves and others. Unfortunately, many of our negative emotions seem to quickly reach a point where they have no apparent solution, and we frequently find ourselves unable to learn anything from them or to do anything about them. These emotions leave us with pounding hearts, contracted muscles, poor digestion, constipation, tension, and so on. Over time, these conditions can become chronic and can consume the energy we need for healing and for inner growth. Once these conditions become habitual, the parasympathetic branch of the autonomic nervous system, designed to put the brakes on the sympathetic nervous system, will have little power to bring about more than temporary relief—unless we can learn how to consciously turn it on for longer periods of time.

Learning to Turn On the Parasympathetic Nervous System

To learn how to turn on the parasympathetic nervous system, it is useful to know something about its organization. The neurons for this system reside mainly in certain cranial nerves, such as the vagus nerve, coming from the brain stem, and in the lower-back region of the spine. The parasympathetic ganglia do not run down the spine, but instead are located near the organs that they influence. Impulses coming from these ganglia reduce the heart rate, dilate the blood vessels, increase digestive peristalsis, and constrict the air passages in the lungs, and thus help the body slow down and restore itself. How can we intentionally turn on this system, our relaxation response, without the outside help of psychologists, massage therapists, and so on? The key is our attention. We know from experience that when we are tense or “stressed out” our attention—directed by the sympathetic nervous system—automatically focuses on the supposed cause of our tension, the compulsive thoughts and feelings that arise in relation to it, or the particular unpleasant physical symptoms we are experiencing. As a result, our experience of ourselves becomes so narrow that we cannot even imagine an alternative. To learn how to relax in such situations, we need to learn how to work actively with our attention, to widen it to include the parts of ourselves that are not in the grip of the negativity we are experiencing. One of the most effective ways to accomplish this is through self-sensing. According to Ernest Rossi, a pioneer in the field of mind/body interaction, “You simply close your eyes and tune into the parts of your body that are most comfortable. When you locate the comfort you simply enjoy it and allow it to deepen and spread throughout your body all by itself. Comfort is more than just a word or a lazy state. Really going deeply into comfort means that you have turned on your parasympathetic system—your natural relaxation response.”[i] As we shall see later, natural breathing plays an important role in learning how to go “deeply into comfort,” and thus in learning how to use our awareness to harmonize the aggressive and restorative functions of our nervous system.[ii] What’s more, since natural breathing massages our internal organs and relaxes our lower back, it has a beneficial influence on the parasympathetic nerves and ganglia in these areas. Unfortunately, most of us are not very good at sensing ourselves and have little awareness of the extent to which our perception and behavior are conditioned by emotions such as fear, anger, and anxiety. We have become so accustomed to high levels of stress and negativity in our lives that we take it as “normal,” not realizing the tremendous toll it takes on our health and vitality. The noise produced by this stress makes it almost impossible to hear the quiet, ever-present intelligence of our own bodies. Unable to experience this inner intelligence, we exacerbate our situation by seeking quick relief through excessive stimulation of some kind—alcohol, drugs, tobacco, caffeine, food, sex, television, and so on. Sometimes, when we wake up for a moment to the senselessness of our situation, we may try to deal rationally with the stresses we face. But our minds by themselves have little power to “figure out” effective solutions—especially in an “information society” that floods our consciousness with negative news and images from around the world. The end result is the accumulation of more and more tension, a sense of helplessness, and the eventual appearance of various chronic symptoms and ailments in our lives—many of which are not just the result of stresses we face, but also of the way we try to escape them.
Coping with the Effects of Stress Is Not the Solution

Unable to figure out effective solutions to the many stresses in our lives, we have over time learned various ways to “cope” with their effects on us instead. Some of us, for example, simply vent our negative emotions, especially anger, on others, believing that this is good for us. Recent studies suggest, however, that venting our anger causes us to get more angry, not less, and thus increases our health risks.[iii] What’s more, such an action simply spreads our negativity to others, adding to their own problems. The expression of negative emotions, however, is probably not nearly as prevalent as finding ways to avoid experiencing them. As children, some of us learned how to use fantasy and repression to shut ourselves off from the painful feelings of contradiction that we felt when our parents did not seem to accept us as we were, but rather demanded that we “grow up” according to their image. As adults, many of us have learned how to “swallow” our negative emotions and take refuge in what we consider to be our more positive ones. We have learned how to suppress our negative emotions in order to function in what we believe to be a reasonable way based on our self-image. But we know by the scientific law of conservation of energy that the neurochemical energy of these emotions cannot be destroyed—it can only be transformed. And we also know, if we look carefully, that this energy is often transformed into kinetic or mechanical energy that acts, without our awareness, on the nerves, tissues, structures, and movements of our bodies. The repression or suppression of emotions manifests itself not only in our postures and movements, but also in tensions buried deep in our bodies, tensions that consume our energy and undermine our physical and psychological health. By learning how to sense these tensions in ourselves, we will eventually come face-to-face with our mostly unconscious emotions of anger, worry, fear, anxiety, and so on. The goal is not to get rid of these so-called negative emotions—this would be both impossible and undesirable—but rather to find the courage to experience them fully, to open them to the transformative light of impartial awareness. From the Taoist perspective, when we become fully aware of our negative emotions without amplifying them or trying to defend ourselves against them, the neurochemical energy they activate in us can be transformed into the pure energy of vitality. As the Taoists might say, “clouds, rain, and lightening are as necessary to our environment as sunshine and calm. Without a harmonious balance of both kinds of weather, nature would become barren.” It is through our breath, especially through natural breathing, that we can begin to discover this dynamic harmony in ourselves. It is through deep, comfortable, natural breathing that we can begin to activate the parasympathetic nervous system and thus the process of healing—of becoming whole again."
Copyright 1996 by Dennis Lewis. This passage, from pages 58-62 of The Tao of Natural Breathing, may not be used for any commercial purpose.

Anyone who is interested in discovering how breathing can help with stress management should try the free breathing exercises and techniques on this website. You might also wish to read the article entitled Breathing Exercises, which discusses some of the dangers of breath control exercises, and the article entitled Hyperventilation & Health.



[i] Ernest Lawrence Rossi, The Psychobiology of Mind-Body Healing (New York: Norton, 1988), pp. 173-74.
[ii] Another effective way to turn on the parasympathetic nervous system is through special movement and awareness practices such as tai chi and chi kung. Among many other benefits, these practices can help release unnecessary tension in the back, especially in the spine, where the main neurons of the central nervous system reside. It is my experience that people with frequent lower back pain are often the same people who have trouble not only relaxing but even admitting that they need to relax. When carried out in the correct way, tai chi and chi kung increase relaxation not only by making the spine more flexible, but also through the deeper breathing that they promote.
[iii] For further information on the subject of anger, see David Sobel and Robert Ornstein, “Defusing Anger and Hostility,” Mental Medicine Update: The Mind/Body Newsletter, Vol. 4, No. 3 (1995).


Learn more about Free Your Breath, Free Your Life, the new book by Dennis Lewis due out from Shambhala Publications in May, 2004.

http://www.authentic-breathing.com/brea ... stress.htm


 
  
 
 Post subject: Autonomic nervous system
PostPosted: Sun Aug 22, 2004 8:08 pm 
The autonomic nervous system concentrates on maintaining homeostasis regardless of the changes in the internal environment, and on controlling the involuntary functions of organs, such as digestion, breathing, metabolism or blood pressure. Although these actions cannot be controlled by our will, they are influenced by our state of mind, and we can become aware of them, mainly when something does not work properly, causing us to feel pain.

The autonomic nervous system and the somatic nervous system comprise the peripheral nervous system. The somatic system regulates body functions which can be affected by our will, such as the motor functions of the skeletal muscle and the perception of sensory stimuli.

The autonomic nervous system is divided into three elements which act together, either in a synergistic or an antagonistic way. They are called the sympathetic, the parasympathetic, and the enteric systems. Sympathetic and parasympathetic systems are subdivisions of the efferent portion of the autonomic division.

The sympathetic system is responsible for the provision of energy needed especially in situations like hunger, fear, or extreme physical activity. Therefore the sympathetic neurons induce glycogenolysis in liver cells and lipolysis in the adipose tissue; raise blood pressure, heart rate, and the blood supply in the skeletal muscle at the expense of the gastrointestinal tract and the skin; and dilate both the pupils of the eyes and the bronchioles, providing the person with sufficient visibility and oxygen. Consequently, the sympathetic system operates to stimulate organs, and to mobilize energy.

After having mastered such a challenging situation, the body is exhausted and needs to rest, recover, and gain new energy. These tasks are under the control of the parasympathetic system, which lowers the heart rate and the blood pressure, diverts a great amount of blood back to the skin and the gastrointestinal tract, contracts the pupils of the eyes and the bronchioles, stimulates secretion in the salivary glands, and accelerates peristalsis. Basically, the parasympathetic nerves influence organs to restore and to save energy.

The enteric system is situated in the intestinal wall. Although it can operate independently, it is modulated by sympathetic and parasympathetic nerve fibers which are connected to its intramural plexus, the submucous, and the myenteric plexus. It regulates secretion in the enteric glands, regeneration of the intestinal epithelium, and the contraction of the smooth muscle cells and thus motility.

In contrast to the somatomotoric nerve fibres, which consist of only one neuron, the sympathetic and parasympathetic fibres have two: a preganglionic and a postganglionic nerve cell connected by a ganglion. Here, the nerve impulse is transferred from the preganglionic cell to the postganglionic by the chemical transmitter acetylcholine, which is released from the first neuron and binds to a nicotinic acetylcholine receptor of the second. This neuron then transfers the impulse to an effector cell--in most cases a smooth muscle cell or a gland cell--by using a second neurotransmitter, which is acetylcholine again in parasympathetic fibres and noradrenalin in the sympathetic nervous system. Preganglionic sympathetic fibres also end in the adrenal medulla, which can be regarded as the biggest sympathetic ganglion, but as there are no postganglionic cells, the adrenal gland releases the second neurotransmitter noradrenalin or, more often, adrenalin into the blood stream.

All somas of preganglionic autonomic nerve cells are situated in the central nervous system. As regards the sympathetic nervous system, they lie in the thoracal and lumbal segments of the spinal cord. The preganglionic parasympathetic cell bodies are situated in the brain stem (cranial parasympathetic) and in the sacral spinal cord (sacral parasympathetic). The axons of the sympathetic and sacral parasympathetic fibres leave the spinal cord through its ventral root, enter the spinal nerve and then the white communicating branch, and thence run to their further destination.

The sympathetic axons build a chain of 22 ganglions, the so-called trunk of the sympathetic nerve, on both sides of the spinal column, from where the splanchnic nerves run to the prevertebral ganglia, which lie in front of the aorta at the place where its unpaired visceral branches leave the large vessel. The left and right trunk of the sympathetic nerve fuse to an unpaired ganglion in the pelvic area. The organs innervated by sympathetic fibres are numerous and manifold and include heart, lungs, esophagus, stomach, small and large intestine, liver, gallbladder and genital organs.

All these organs are also innervated by the parasympathetic nervous system. The digestive system from the lower part of the colon downwards is regulated by the sacral parasympathetic fibres which form pelvic ganglia, and the upper parts of it are controlled by the vagus nerve, the biggest element of the cranial parasympathetic system, whose fibres, after having left the brain stem, accompany four cerebral nerves before they build the cranial parasympathetic ganglia, which innervate eye muscles and salivary glands.


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To be merged
The sympathetic nervous system [Fig. 1] innervates all the smooth muscles and the various glands of the body, and the striated muscle of the heart. The efferent sympathetic fibers which leave the central nervous system in connection with certain of the cranial and spinal nerves all end in sympathetic ganglia and are known as preganglionic fibers. From these ganglia postganglionic fibers arise and conduct impulses to the different organs. In addition, afferent or sensory fibers connect many of these structures with the central nervous system.


Figure 1: The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses. (After Schwalbe.)
The peripheral portion of the sympathetic nervous system is characterized by the presence of numerous ganglia and complicated plexuses. These ganglia are connected with the central nervous system by three groups of sympathetic efferent or preganglionic fibers, i. e., the cranial, the thoracolumbar, and the sacral. These outflows of sympathetic fibers are separated by intervals where no connections exist. The cranial and sacral sympathetics are often grouped together owing to the resemblance between the reactions produced by stimulating them and by the effects of certain drugs. Acetylcholine, for example, when injected intravenously in very small doses, produces the same effect as the stimulation of the cranial or sacral sympathetics, while the introduction of adrenalin produces the same effect as the stimulation of the thoracolumbar sympathetics. Much of our present knowledge of the sympathetic nervous system has been acquired through the application of various drugs, especially nicotine which paralyzes the connections or synapses between the preganglionic and postganglionic fibers of the sympathetic nerves. When it is injected into the general circulation all such synapses are paralyzed; when it is applied locally on a ganglion only the synapses occurring in that particular ganglion are paralyzed. Langley, 138 who has contributed greatly to our knowledge, adopted a terminology somewhat different from that used here and still different from that used by the pharmacologists. This has led to considerable confusion, as shown by the arrangement of the terms in the following columns. Gaskell has used the term involuntary nervous system.

Gray Langley Meyer and Gottlieb
Sympathetic nervous system Autonomic nervous system Vegetative nervous system
Cranio-sacral sympathetics Parasympathetics Autonomic
Oculomotor sympathetics Tectal autonomics Cranial autonomics
Facial sympathetics Bulbar autonomics
Glossopharyngeal sympathetics
Vagal sympathetics
Sacral sympathetics Sacral autonomics Sacral autonomics.
Thoracolumbar sympathetics Sympathetic Sympathetic.
Thoracic autonomic
Enteric Enteric Enteric.

The Cranial Sympathetics
The cranial sympathetics include sympathetic efferent fibers in the oculomotor, facial, glossopharyngeal and vagus nerves, as well as sympathetic afferent in the last three nerves.

The Sympathetic Efferent Fibers of the Oculomotor Nerve probably arise from cells in the anterior part of the oculomotor nucleus which is located in the tegmentum of the mid-brain. These preganglionic fibers run with the third nerve into the orbit and pass to the ciliary ganglion where they terminate by forming synapses with sympathetic motor neurons whose axons, postganglionic fibers, proceed as the short ciliary nerves to the eyeball. Here they supply motor fibers to the Ciliaris muscle and the Sphincter pupillæ muscle. So far as known there are no sympathetic afferent fibers connected with the nerve.

The Sympathetic Efferent Fibers of the Facial Nerve are supposed to arise from the small cells of the facial nucleus. According to some authors the fibers to the salivary glands arise from a special nucleus, the superior salivatory nucleus, consisting of cells scattered in the reticular formation, dorso-medial to the facial nucleus. These preganglionic fibers are distributed partly through the chorda tympani and lingual nerves to the submaxillary ganglion where they terminate about the cell bodies of neurons whose axons as postganglionic fibers conduct secretory and vasodilotar impulses to the submaxillary and sublingual glands. Other preganglionic fibers of the facial nerve pass via the great superficial petrosal nerve to the sphenopalatine ganglion where they form synapses with neurons whose postganglionic fibers are distributed with the superior maxillary nerve as vasodilator and secretory fibers to the mucous membrane of the nose, soft palate, tonsils, uvula, roof of the mouth, upper lips and gums, parotid and orbital glands.


Figure 2: Diagram of efferent sympathetic nervous system. Blue, cranial and sacral outflow. Red, thoracohumeral outflow. - -, Postganglionic fibers to spinal and cranial nerves to supply vasomotors to head, trunk and limbs, motor fibers to smooth muscles of skin and fibers to sweat glands. (Modified after Meyer and Gottlieb.)
There are supposed to be a few sympathetic afferent fibers connected with the facial nerve, whose cell bodies lie in the geniculate ganglion, but very little is known about them.


Figure 3: Sympathetic connections of the ciliary and superior cervical ganglia.
The Sympathetic Afferent Fibers of the Glossopharyngeal Nerve are supposed to arise either in the dorsal nucleus (nucleus ala cinerea) or in a distinct nucleus, the inferior salivatory nucleus, situated near the dorsal nucleus. These preganglionic fibers pass into the tympanic branch of the glossopharyngeal and then with the small superficial petrosal nerve to the otic ganglion. Postganglionic fibers, vasodilator and secretory fibers, are distributed to the parotid gland, to the mucous membrane and its glands on the tongue, the floor of the mouth, and the lower gums.

Sympathetic Afferent Fibers, whose cells of origin lie in the superior or inferior ganglion of the trunk, are supposed to terminate in the dorsal nucleus. Very little is known of the peripheral distribution of these fibers. The Sympathetic Efferent Fibers of the Vagus Nerve are supposed to arise in the dorsal nucleus (nucleus ala cinerea). These preganglionic fibers are all supposed to end in sympathetic ganglia situated in or near the organs supplied by the vagus sympathetics. The inhibitory fibers to the heart probably terminate in the small ganglia of the heart wall especially the atrium, from which inhibitory postganglionic fibers are distributed to the musculature. The preganglionic motor fibers to the esophagus, the stomach, the small intestine, and the greater part of the large intestine are supposed to terminate in the plexuses of Auerbach, from which postganglionic fibers are distributed to the smooth muscles of these organs. Other fibers pass to the smooth muscles of the bronchial tree and to the gall-bladder and its ducts. In addition the vagus is believed to contain secretory fibers to the stomach and pancreas. It probably contains many other efferent fibers than those enumerated above.


Figure 4 : Sympathetic connections of the sphenopalatine and superior cervical ganglia.
Sympathetic Afferent Fibers of the Vagus, whose cells of origin lie in the jugular ganglion or the ganglion nodosum, probably terminate in the dorsal nucleus of the medulla oblongata or according to some authors in the nucleus of the tractus solitarius. Peripherally the fibers are supposed to be distributed to the various organs supplied by the sympathetic efferent fibers.

The Sacral Sympathetics - The Sacral Sympathetic Efferent Fibers leave the spinal cord with the anterior roots of the second, third and fourth sacral nerves. These small medullated preganglionic fibers are collected together in the pelvis into the nervus erigentes or pelvic nerve which proceeds to the hypogastric or pelvic plexuses from which postganglionic fibers are distributed to the pelvic viscera. Motor fibers pass to the smooth muscle of the descending colon, rectum, anus and bladder. Vasodilators are distributed to these organs and to the external genitalia, while inhibitory fibers probably pass to the smooth muscles of the external genitalia. Afferent sympathetic fibers conduct impulses from the pelvic viscera to the second, third and fourth sacral nerves. Their cells of origin lie in the spinal ganglia.


Figure 5 : Sympathetic connections of the submaxillary and superior cervical ganglia.
The Thoracolumbar Sympathetics - The thoracolumbar sympathetic fibers arise from the dorso-lateral region of the anterior column of the gray matter of the spinal cord and pass with the anterior roots of all the thoracic and the upper two or three lumbar spinal nerves. These preganglionic fibers enter the white rami communicantes and proceed to the sympathetic trunk where many of them end in its ganglia, others pass to the prevertebral plexuses and terminate in its collateral ganglia. The postganglionic fibers have a wide distribution. The vasoconstrictor fibers to the bloodvessels of the skin of the trunk and limbs, for example, leave the spinal cord as preganglionic fibers in all the thoracic and the upper two or three lumbar spinal nerves and terminate in the ganglia of the sympathetic trunk, either in the ganglion directly connected with its ramus or in neighboring ganglia. Postganglionic fibers arise in these ganglia, pass through gray rami communicantes to all the spinal nerves, and are distributed with their cutaneous branches, ultimately leaving these branches to join the small arteries. The postganglionic fibers do not necessarily return to the same spinal nerves which contain the corresponding preganglionic fibers. The vasoconstrictor fibers to the head come from the upper thoracic nerves, the preganglionic fibers end in the superior cervical ganglion. The postganglionic fibers pass through the internal carotid nerve and branch from it to join the sensory branches of the various cranial nerves, especially the trigeminal nerve; other fibers to the deep structures and the salivary glands probably accompany the arteries.


Figure 6 : Sympathetic connections of the otic and superior cervical ganglia.
The postganglionic vasoconstrictor fibers to the bloodvessels of the abdominal viscera arise in the prevertebral or collateral ganglia in which terminate many preganglionic fibers. Vasoconstrictor fibers to the pelvic viscera arise from the inferior mesenteric ganglia. The pilomotor fibers to the hairs and the motor fibers to the sweat glands apparently have a distribution similar to that of the vasoconstrictors of the skin.

A vasoconstrictor center has been located by the physiologists in the neighborhood of the facial nucleus. Axons from its cells are supposed to descend in the spinal cord to terminate about cell bodies of the preganglionic fibers located in the dorsolateral portion of the anterior column of the thoracic and upper lumbar region.

The motor supply to the dilator pupillæ muscle of the eye comes from preganglionic sympathetic fibers which leave the spinal cord with the anterior roots of the upper thoracic nerves. These fibers pass to the sympathetic trunk through the white rami communicantes and terminate in the superior cervical ganglion. Postganglionic fibers from the superior cervical ganglion pass through the internal carotid nerve and the ophthalmic division of the trigeminal nerve to the orbit where the long ciliary nerves conduct the impulses to the eyeball and the dilator pupillæ muscle. The cell bodies of these preganglionic fibers are connected with fibers which descend from the mid-brain.

Other postganglionic fibers from the superior cervical ganglion are distributed as secretory fibers to the salivary glands, the lacrimal glands and to the small glands of the mucous membrane of the nose, mouth and pharynx. The thoracic sympathetics supply accelerator nerves to the heart. They are supposed to emerge from the spinal cord in the anterior roots of the upper four or five thoracic nerves and pass with the white rami to the first thoracic ganglion, here some terminate, others pass in the ansa subclavia to the inferior cervical ganglion. The postganglionic fibers pass from these ganglia partly through the ansa subclavia to the heart, on their way they intermingle with sympathetic fibers from the vagus to form the cardiac plexus. Inhibitory fibers to the smooth musculature of the stomach, the small intestine and most of the large intestine are supposed to emerge in the anterior roots of the lower thoracic and upper lumbar nerves. These fibers pass through the white rami and sympathetic trunk and are conveyed by the splanchnic nerves to the prevertebral plexus where they terminate in the collateral ganglia. From the celiac and superior mesenteric ganglia postganglionic fibers (inhibitory) are distributed to the stomach, the small intestine and most of the large intestine. Inhibitory fibers to the descending colon, the rectum and Internal sphincter ani are probably postganglionic fibers from the inferior mesenteric ganglion.

The thoracolumbar sympathetics are characterized by the presence of numerous ganglia which may be divided into two groups, central and collateral.

The central ganglia are arranged in two vertical rows, one on either side of the middle line, situated partly in front and partly at the sides of the vertebral column. Each ganglion is joined by intervening nervous cords to adjacent ganglia so that two chains, the sympathetic trunks, are formed. The collateral ganglia are found in connection with three great prevertebral plexuses, placed within the thorax, abdomen, and pelvis respectively.

The sympathetic trunks (truncus sympathicus; gangliated cord) extend from the base of the skull to the coccyx. The cephalic end of each is continued upward through the carotid canal into the skull, and forms a plexus on the internal carotid artery; the caudal ends of the trunks converge and end in a single ganglion, the ganglion impar, placed in front of the coccyx. The ganglia of each trunk are distinguished as cervical, thoracic, lumbar, and sacral and, except in the neck, they closely correspond in number to the vertebræ. They are arranged thus:

Cervical portion3 ganglia
Thoracic portion12 ganglia
Lumbar portion4 ganglia
Sacral portion4 or 5 ganglia
In the neck the ganglia lie in front of the transverse processes of the vertebræ; in the thoracic region in front of the heads of the ribs; in the lumbar region on the sides of the vertebral bodies; and in the sacral region in front of the sacrum.

Connections with the Spinal Nerves
Communications are established between the sympathetic and spinal nerves through what are known as the gray and white rami communicantes; the gray rami convey sympathetic fibers into the spinal nerves and the white rami transmit spinal fibers into the sympathetic. Each spinal nerve receives a gray ramus communicans from the sympathetic trunk, but white rami are not supplied by all the spinal nerves. White rami are derived from the first thoracic to the first lumbar nerves inclusive, while the visceral branches which run from the second, third, and fourth sacral nerves directly to the pelvic plexuses of the sympathetic belong to this category. The fibers which reach the sympathetic through the white rami communicantes are medullated; those which spring from the cells of the sympathetic ganglia are almost entirely non-medullated. The sympathetic nerves consist of efferent and afferent fibers, the origin and course of which are described on page 920). The three great gangliated plexuses (collateral ganglia) are situated in front of the vertebral column in the thoracic, abdominal, and pelvic regions, and are named, respectively, the cardiac, the solar or epigastric, and the hypogastric plexuses. They consist of collections of nerves and ganglia; the nerves being derived from the sympathetic trunks and from the cerebrospinal nerves. They distribute branches to the viscera.

Development
The ganglion cells of the sympathetic system are derived from the cells of the neural crests. As these crests move forward along the sides of the neural tube and become segmented off to form the spinal ganglia, certain cells detach themselves from the ventral margins of the crests and migrate toward the sides of the aorta, where some of them are grouped to form the ganglia of the sympathetic trunks, while others undergo a further migration and form the ganglia of the prevertebral and visceral plexuses. The ciliary, sphenopalatine, otic, and submaxillary ganglia which are found on the branches of the trigeminal nerve are formed by groups of cells which have migrated from the part of the neural crest which gives rise to the semilunar ganglion. Some of the cells of the ciliary ganglion are said to migrate from the neural tube along the oculomotor nerve.

This article is based on an entry from the 1918 edition of Gray's Anatomy, which is in the public domain. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.


http://www.wordiq.com/definition/Autono ... ous_system


 
  
 
 Post subject:
PostPosted: Mon Dec 13, 2004 1:22 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
A lot of thanks to Guest! It is exactly what I needed! The article was here a long time ago, but I did not read it... A shame on me! Wink
It really works! Very Happy

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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