Parasympathetic and Sympathetic nervous systems

[Guest guest]

I'm posting on this because the background information will help some

readers get more out of the " Integrating the Traditional Chinese

Understanding of the Kidneys into Western Herbalism " article by Michael

Tierra, L.ac, O.M.D. over on acupuncture.com. It's also important to know

what these two divisions of the autonomic nervous system do if one is taking

a Western anatomy and physiology class, if one is planning on becoming a

chiropractor, or if one is interested in specializing in immune system

problems in herbalism. This also relates to the previous Yin - Yang

discussion.

 

The autonomic nervous system is made up of nerves which go to the organs. It

controls smooth muscles - like the heart, the glands, etc. - and it

regulates things like body temperature, breathing rate, pulse rate, blood

pressure, the pupils, salivation, and intestinal secretions.

 

The autonomic nervous system is automatic and autonomous for the most part.

One doesn't have to consciously force oneself to breathe or one's pupils to

dilate or constrict like one consciously decides to take a step or brush

one's teeth or lift a spoonful of food to one's mouth. Old terms for these

two nervous systems are the voluntary (you conscious decide to move

something) and the involuntary (you don't have to will your heart to beat).

 

For many years people in the West believed that people couldn't influence

the autonomic nervous system. Then along came some people from the East

like yoga masters and others who demonstated that they could slow or speed

heart rate at will, lower or elevate blood pressure at will, change their

body temperatures at will, etc., and many Westerners came to realize that

the autonomic nervous system isn't quite as autonomous as previously

believed. This was the beginning of things like bio-feedback and

visualization in the West. It also resulted in a new field in Western

medicine which studies the relationship between things like emotions, the

autonomic nervous system, and immune function. (Sorry, can't spell the very

long word for this field of medicine, and none of my old dictionaries and

books have it.)

 

The autonomic nervous system has two divisions - the sympathetic and

parasympathetic - and these two divisions do opposite things. The

parasympathetic is dominant when there is a need to " fight or flee " . The

parasympathetic division does its thing when a person is afraid or angry

gets startled in some way - like in a fight or an accident. The

parasympathetic is dominant when a person is calm and doing things like

reading a book, listening to soothing music, enjoying a pretty sunset, etc.

 

When the sympathetic division is dominant, it triggers things like dilating

the pupils (so one can see enemies or dangers better), dilating the

bronchioles in the lungs so one can have more air and energy to fight or

flee, raising heart rate, and directing blood flow away from the organs and

digestion to the muscles so the person can fight or run better. The

sympathetic division of the autonomic nervous system is a Yang type of

thing. Action, action, action. It speeds the person up. It activates. It

jazzes.

 

In contrast, the parasympathetic causes pupils to constrict, the bronchioles

to constrict, and heart rate to decrease. It's for quiet, non-threatening

times. Parasympathetic is Yin in nature - it calms. It also causes

salivary secretions to increase and intestinal secretions to increase. In

other words, it's geared toward improving digestion, and digestion is a

stage in the body creating its struction. Yin is building form.

 

These two divisions are opposites. They become dominant in turn, based on

what the needs of the moment are. Just like the Yin and Yang in the Taoist

symbol. Life is made possible by both, just like Yin and Yang are both

needed for life to be. The balance is constantly shifting in response to

current needs.

 

Tierra makes the point in his article that good health often is dependent on

a person being able to switch easily and quickly between the two divisions

as the need arises. Think of a cat lazing in the sun like he's comatose

suddenly springing into action and chasing a mouse. Or running from a dog.

At one point Tierra talks about herbalist, Steve Blake attributing Siberian

Ginseng's adaptogen (a Western classification of some herbs which increase

endurance and resistence) properties " as neither stimulating the

yang-sympathetic nor the yin-parasympathetic but improving the body's

aiblity to appropriately switch back and forth more efficiently and at a

faster rate. "

 

Another basic thing to remember is that sympathetic (yang) postganglionic

fibers secrete norepinephrine (noradrenalin), and they are called adrenergic

fibers. Acetylcholine is secreted by the postgangionic parasympathetic

fibers, and they are called cholingergic fibers.

 

A ganglionic fiber is the long tail or arm of a nerve cell. Sort of like a

long strand of spaghetti (the ganglionic fiber) attached to a meatball (the

cell body). (I'm trying to describe this without the aid of pictures for

people without a background in anatomy.) The cell body of these nerve cells

is in the brain or the spinal cord, and and the axon (the spaghetti-like

part) which also is called a preganglionic fiber leaves the spine and meets

up with with one or more fibers " whose cell bodies are housed within an

autonomic ganglion outside the brain or spinal cord. " (John W. Hole, Jr.,

Human Anatomy and Physiology, 2nd ed., p. 317) Think of the autonomic

gangions as a mass of spaghetti and meatballs outside the brain or spinal

cord. The preganglionic fiber from a nerve cell within the brain or spinal

cord branches out of the spinal cord and meets up with a mass of (ganglia)

nerve cells and their fibers, and the axons (fibers) from these ganglion are

called postganglionic fibers. The preganglionic fibers (before the

ganglion) from the nerve cell bodies in the brain or spinal cord) meet up

with these masses of nerve cells outside the spinal cord, and the nerve

fibers which go away from these ganglion are called post(after)ganglionic

fibers. The postganglionic fibers go to what are called " visceral

effectors " . What typically happens is that the postganglionic fiber will

return to a spinal nerve and then go with it to a visceral effector. A

" visceral effector " is a fancy term for a specialized cell within smooth

muscle (the heart muscle, the blood vessels, the glands, etc.) which is

affected by what the postganglionic fiber secretes. The sympathetic

postganglionic fibers secrete norephinephrine (noradrenalin) and jazz things

up. The parasympathetic postganglionic fibers secrete acetylcholine.

 

There is are exceptions to preganglion fibers from the brain and spinal cord

meeting up with the fibers of other nerve cells outside the brain and spinal

cord, and the postganglionic fibers of these nerve cells outside the central

nervous system going to the visceral effector. The most important one is a

bunch of preganglionic fibers that pass through the chain ganglia and go

into the medulla of both adrenal glands. There's no postganglionic middle

man here. These special preganglionic fibers secrete acetylcholine (like

all sympathetic and parasympathetic preganglion, but they end on special

cells in the medullas of the kidneys which release norepinephrine and

epinephrine.

 

Whenever the balance between the parasympathetic and the sympathetic and the

substances which their postganglionic fibers secrete (acetylcholine or

norepinephrine) gets messed up, health problems result.

 

There are a number of herbs as well as prescription drugs which can

influence the two divisions or the substances their postganglionic fibers

secrete. John W. Hole, Jr. writes in Human Anatomy and Physiology, " Many

drugs influence autonomic functions in a variety of ways. Some, like

epinephrine, have efvfects similar to norepinephrine. Others, like

ephedrine, stimulate the release of norepinephrine from sympathetic nerve

endings; still others, like reserpine, inhibit sympathetic activity by

preventing the synthesis of norepinephrine. Another group of drugs, which

includes pilocarpine, produce parasympathetic effects, and some, like

atropine, block the action of acetylcholine in visceral effectors. " (p.320)

In additon, chiropractor or DO adjustments can correct some problems (when

spinal misalignment is causing a nerve to be too active or not active

enough). Bio-feedback, relaxation, and visualization can affect the

autonomic nervous system. So can counseling in some instances.

 

Whey can problems arise in the autonomic nervous system or either of its too

divisions. Spinal misalignment is one way. For example, there is an

adjustment that chiropractors and DO can give which can open up the lungs in

cases of breathing difficulties. Another cause can be suppressed emotions.

Even though something which made a person very afraid happened 20 years or

more ago, if it was never fully faced and worked through, it can tilt the

person's sympathetic division towards being more active. Every time the

person sees or experiences something which reminds him or her even vaguely

of the original trauma (which never has been fully faced and resolved), the

person's sympathetic division gears him/her up for fighting or fleeing. In

a lot of cases, the reason why one division becomes too dominate and

inappropriately dominate is not known. According to the Tierra article, Yin

Deficiency may be one reason the sympathetic division becomes

inappropriately dominate.

 

The Tierra article also lists some herbs which appear to have effects on the

autonomic system and its divisions as well as adaptogen herbs which enable

the body to switch quickly and effectively between the two divisions as the

need arises. The article can be found at acupuncture.com.

 

Victoria

 

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