The Sympathetic Nervous System

The idea of the sympathetic nervous system goes back almost 2000 years, to Galen, who believed and taught that this complex of nerves permitted animal spirits to travel from one organ to another, creating "sympathy" among them. Here we are especially concerned with the sympathetic nervous system as a part of what we now recognize as the autonomic nervous system (chapter 2 and figs. io.4a-b) because the sympathetic component is generally sedated by breathing and relaxation techniques. It activates the body globally when it is stimulated and it quiets the body down globally afterward. Stress is its stimulant, and preparation for "fight or flight" is its response. To that end it speeds the heart rate, opens the bronchial tree, stimulates the release of glucose from the liver, dilates the pupils, constricts arterioles in the digestive system and skin, dilates arterioles in the heart, and contracts sphincters in the gastrointestinal tract and in the urethra. All of these responses act together and in "sympathy" with one another—Galen had the right idea, after all—to gear up the body for emergencies. Only a few sympathetic reactions, such as orgasm and dilation of the pupils in dim light, occur in relative isolation. The parasympathetic nervous system, by contrast, affects the internal organs specifically and often in isolation.

We can see the operation of the sympathetic nervous system and how it orchestrates bodily processes during an ordinary sequence of postures fodowed by relaxation. The sympathetic nervous system, including one of its main endocrine components, the adrenal medulla, becomes activated by vigorous hatha yoga practices, especially standing stretches, sun salutations, and abdominopelvic exercises such as leglifting and agni sara. Relaxing in the corpse posture after an invigorating session of postures will then quiet this system and diminish the sympathetic effects on organs and tissues throughout the body.


The autonomic nervous system regulates body temperature, not only in thi core of the body where it affects the chest, abdomen, and pelvis, but also it tissues of the skin and extremities. When the sympathetic system ¡. activated, skin (especially in the hands and feet) becomes cold because it blood supply is diminished by vasoconstriction (chapter 2), and it become clammy because sweat glands flood the surface of the body with moistun When you lie down to relax, the sympathetic nervous system calms dosv: decreasing muscular tone in the smooth muscle that encircles arteries ai arterioles, which allows those vessels to dilate and causes blood supply the skin to increase and skin temperature to rise.

You would think this would make you feel warm, but that is not the ca because during relaxation, the skin temperature rises and radiates he and this causes the body to cool down. Ordinarily the internal temperatm regulating systems would then prompt you to shiver, but you curb tl 1 impulse, knowing that any movement would break the relaxation. rl 1 result is that you are chilly when you come out of the exercise, and the nt .t time you try to relax, your body does not remember the experience fonc But knowing in advance that the body will lose radiant heat during a 1< g relaxation, you can cover up—even a pillow placed on the chest ■< d abdomen can make a difference. This is a good example of how we n anticipate and accommodate to the peculiarities of the autonomic nerv is system—coddling it and letting it do its job rather than trying to bend 11 o our will.

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  • Myrtle
    Which part of the sympathetic nervous system is activated when you lie?
    7 years ago
  • monika
    How to relax the sympathetic nervous system?
    7 years ago

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