The Nervous System
The human nervous system has two main components, the central and autonomic nervous systems. The central nervous system is comprised of the brain, twelve pairs of cranial nerves, the spinal cord, and thirty-one pairs of spinal nerves. These have both afferent (sensory) and efferent (motor) fibers, for messages going into and out from the spinal cord and brain. [SB]
The autonomic nervous system includes the sympathetic and parasympathetic nervous systems. The former branches out from a trunk line of sympathetic ganglia along the spine. The later branches off from the Vagus nerve(10th cranial) which lies in front of the spine. The functions controlled by the autonomic nervous system are not normally under conscious control, but this may be changed by practices such as pranayama, or bio-feedback training. The former works in through the ability of either main nervous system to control the href="body.htm#breath"> breath. [SB]
The main nerve plexi are associated with the chakras. These are the Sacral, at the base of the spine, the Hypogastric, behind the genitals, the Solar, between the naval and the sternum, the Cardiac, around the heart, and the Pharyngeal, at the base of the throat. The upper three have both sympathetic and parasympathetic nerve feeds, while the lower two have mainly sympathetic nerves and only filaments from the vagus. A Nasociliary plexus associated with the Ajna chakra is also mentioned. [SB]
The sympathetic nervous system is activated in the fight or flight reactions. It prepares the body for action, and is stimulated by emergencies and various excitements. It tends to be involved in the expression of strong emotions, even positive ones. This system is centralized in the brain.[HB]
The parasympathetic nervous system is activated in the conservation withdrawal reactions. This system reverses the actions of the sympathetic system, slowing the body down and returning to a more normal level of operation. This system is distributed, having nerve clusters near the various organs.[HB]
These two systems are mutually exclusive, when one is up the other is down. They involve different nerve circuits and different neurotransmitters (norepinephrine and acetylcholine respectively).[HB]
Among other functions, the autonomic nervous system communicates directly with the immune system[EI].
There is a separate system for pain. Both special sensors and a priority set of nerves to convey the signals to the brain. [HB]
In yogic terms there are ten indryas, or organs. The five
sense organs, or jnanendriyas
(organs of knowledge) are the eyes, ears, nose, tongue, and skin.
The jnanendriyasare comprised of the sense
organs together with the nerves, nerve fluid, and the appropriate
seat in the brain. There are also five organs of action (karmendrya),
which are the mouth, the arms, the legs, the anus and the genitals.
The immune system is a complex system of cells and molecules
distributed throughout the body, which has the function of identifying
"foreign" substances and molecules and then rallying the bodies defenses
against them. It has a similar range of actions to the nervous system,
being able to send and receive signals, which can be excitatory or
inhibitory, and to remember and learn. Like the nervous system it
has sensors for monitoring external and internal conditions and can
respond to these by regulating body functions. It includes the the thymus gland, the spleen, the bone marrow,
and the lymph nodes. [HB]
There are two types of immunity, natural and acquired. Natural, or
innate" immunity is a function of all cells by which they react to tissue
damage via inflammatory processes which allow other cells or molecules
to come to their aid, in particular in order to fight and contain viruses.
Acquired immunity is embodied by the lymphocytes which are produced in
the bone marrow. They are modified either in the thymus (T-cells) or
in the bone marrow (B-cells) (fetal processes are somewhat different).
These cells patrol the blood stream looking for trouble in the form of
hostile cells, viruses, or other substances (collectively antigens),
which they then attack and destroy. There are a wide variety of T-cells
with different roles in these processes. There are also macrophages
(which consume antigens) and natural killer cells which attack tumor
and virus infected cells. [HB]
There are millions of types of lymphocytes in the infant some of
which match antigens which are a natural part of the body, and are
therefore turned off, the rest evolve to handle external antigens.
These have receptors that match to the various viruses, bacteria,
toxins, or other products of disease. Once matched that type clones
itself very rapidly, produces antibodies which combine with and
deactivate the antigen, and other types of cells (e.g. macrophages)
are marshaled. In a healthy system there are all sorts of potentially
troublesome antigens, viruses, mutated cancerous cells, toxins, etc.
but the immune system handles them before they become dangerous. It
is the weakening, or imbalance of the immune system that leads to
disease. As well as diseases where the immune system breaks down, or
fails to contain a threat, there are also "autoimmune" diseases where
it becomes over active, reacting to harmless antigens (allergies) or
even attacking parts of the body itself. Lupus is an extreme example
of these autoimmune diseases, in which the immune system reacts to
the bodies own DNA as an antigen. It appears to be affected by
psychological stress. [HB]
While stress of various sorts, both physical and mental is a
clear factor in disease of various types (see below) it appears
that it is the response to the stress
as much as the stress itself that is important.
The immune system is affected by psychological stress. It is
usually generally depressed by the loss of a loved one, a sudden
loss of job, natural disasters, or other events that cause a sudden,
and major change in the external environment, especially those that
affect the social network, or ones
sense of personal well being. It is through the connections between
the nervous and immune systems that the mind can directly affect the
health of the body. All of the components of the immune system are
well supplied with nerves. Removal of these nerves severely impedes
the immune response[EI}. The lymphocytes have receptors to a wide
range of hormones, neurotransmitters, and other nerve chemicals
that may serve to control various aspects of lymphocyte function.
Hormones that are released in response to stress dampen the
activity of the immune cells.
The most common chemical messengers in both the
brain and the immune system are densest in the areas the regulate
emotion.[EI]
There is evidence that left-handed
persons are more likely to suffer from immune system problems (mostly
of the thymus and bowels), as well as from migraine headaches. There
is other evidence that the proper functioning of the left hemisphere of the brain is related to
full immune system function. This may be due to the impact of "hostile"
emotions associated with the right
hemisphere. It is known that "hostile" rather than angry people
are most likely to suffer the heart attacks and strokes of the type A
personality. [HB]
The immune system also appears to depend on the hypothalamus, with evidence for two way
communication. Immune responses are correlated with increased activity
in the hypothalamus, while a damaged hypothalamus eliminates a known
immune response. Activation also significant changes in the levels
of the pituitary neurotransmitter norepinephrine, possibly due to
control from the hypothalamus. That the hypothalamus is involved in
the emotions suggests a pathway for the
linkage of emotional states and the strength of the immune system.
[HB]
The various neurohormones that are
released in response to physical or psychological stress that activate
the sympathetic nervous system, are known
to depress the immune system (e.g. corticosteroids). While natural
killer cells are apparently suppressed by the endorphins released in reaction to pain,
as well as mild stresses and loneliness. Those who cope "poorly"
with stress are generally found to have depressed immune systems.
Experiments with cancer in rats find that stress induced changes
in the immune system correlate with susceptibility to tumor growth.
When the stress was escapable the immune system was toughest, while
inescapable stress significantly depressed it. In people high
expectations (externally motivated) coupled with low performance
increases susceptibility to manifesting mononucleosis when infected
with Epstein-Barr virus. In people infected with herpes, their
depression about having the disease increased the likelihood of an
outbreak (a form of resistance).
Stresses related to a "need for power" also appear to depress
the immune system, probably due to increased activity of the
sympathetic nervous system. There is good evidence that the way
people deal with anger affects their susceptibility to cancer and
their ability to survive it. Suppression
of emotions, especially anger (fear) is highly correlated
with cancer and mortality. Those who fight are more likely to
survive, possibly because they were more in touch with the stress
and willing to express it.[HB]
There is somewhat less evidence that psychological factors can
boost the immune system, in part due to the possible differences
between fighting existing disease, and resisting its appearance to
begin with. Studies have shown that
hypnotized subjects could boost their immune systems, and that
relaxation programs for elderly also had a positive affect. Humor
is also associated with increased immune functions.
The phenomenon of blushing illustrates the connection between
emotions and the heart. Blushing is a
signal of increased blood pressure. It can occur "internally" as
well, i.e. without the outward signs of reddening. Studies show
that talking to someone raises the blood pressure slightly, but
talking to someone who is of "higher" status raises the blood
pressure much more. [The significant factor is probably not the
absolute status, but the perceived feeling of inferiority, which
makes one nervous and takes them off center.] [HB]
People with hypertension (high blood pressure) can learn to
control it through monitors that show them how it goes up and
down as they speak. Speaking about emotionally charged topics
can also lead to increases in blood pressure. In the classic
Type A people it is now felt that ongoing anger, or hostility,
which cuts one off from other people,
is the key factor. The hurriedness, or multitasking are not
necessarily correlated with heart troubles. The most endangered
are those who are often and easily angry, but hold it in. These
folks tend to be very judgmental,
particularly in thinking oneself superior to others.
Self-involvement is a recognized factor in heart disease and
hypertension. Self-centered and hostile people have higher
blood pressure and tend to react more strongly to stress or
challenge. The high levels of adrenaline
and high blood pressure, both damage the arteries. It
appears that it is selfishness behind business, rather than
business itself that is dangerous. Business in the service of others is not a
problem, as long as the motive is really to do service. [HB]
There are also heart attacks which are due to a sudden
upset, excitement, or shock. These may happen even to otherwise
healthy people and show an affect similar to that of the immune system. It is generally due to a
rapid, ineffectual, beating of the heart. This is thought to
be the result of emergency arousal, but uncertainty about the
best course of action, fight or flight. Thus both the sympathetic
and the parasympathetic nervous
systems may become activated, and the heart is torn between
conflicting messages, the heart speeds up, but its muscle tone
is relaxed. Studies with beta-blockers, and other drugs,
indicate that the controlling messages come from the brain, in
particular the frontal lobes
(stress interpretation and decision making) and the hypothalamus (which sends out fear
messages). These are cases where "the brain cannot make up its
mind", due to external or internal ambiguity of a charged
situation.[HB]
The heart is also a gland in that
it produces the hormone atrial
natriuretic factor (ANF) when the blood pressure rises. This
hormone affects kidney function, salt levels, and also the
pituitary . [GLE]
There is a great deal of evidence that people who are
connected to the world around them, through family, friends,
pets, or plants, are healthier and less likely to die or to
commit suicide. Strong social networks provide a stability
that can help to contract the effects of sudden environmental
changes, e.g. the death of loved ones, loss of a job, etc.
If the level of uncertainty, and the stress that goes with it
becomes too high, or too sustained, then a person is more
likely to become ill or to die. This need for social
connection is due in part to evolutionary factors. Man's
upright gate forced changes in the body including a heavier
pelvis with a smaller opening. Therefore a human baby's brain
is only 25% grown when it is born (compared to a baboon's 70%).
This means most of the brain forms after birth, resulting in
a long period of helplessness in which the infant needs to
attach to its mother. Bonding ensues. Because the mother
cannot provide enough food, while also taking care of one or
more infants, changes in sexuality lead to the more or less
permanent presence of a male who can provide food for a family.
I.e. the human family and social nature is in part an evolutionary
necessity. [HB]
The advantages of social bonding show up in the statistical
differences between men and women, in and out of marriage. This
is due to the more active role that women take in forming and
maintaining close relationships. In marriage men benefit from
this activity by their spouses. Social support and interaction
are found to benefit laboring mothers, and aged nursing home
residents. The later show increases in
anabolic hormones, which boost the body's overall health.[HB]
There is also the famous study of students watching Mother
Teresa serving the poor (tapah).
Even those who consciously stated they disliked her had their
immune systems boosted for at least an hour. The lack of connectedness
shows up in depression of the immune system
, leading to illness and cancer, as well as the coronary system, leading to heart disease
and heart attacks. [HB]
The breath ( prana) is a level
of energy that is very important as a link between the mind
and the body. Breathing is an interface between the central
and autonomic nervous systems, as either one can be used to
work the lungs. Through the practices of pranayama it is possible to
learn to control the autonomic functions. As we control our
breathing (i.e. the lungs) we also can control the heart. [SB]
In yoga the bodily functions are associated with breathing through either the right
or the left nostril. This shifts both the tempo of the
metabolism and the mind. When the right side dominates
the metabolism increases, while the mind is more focused
externally. In particular this is the mode for digestion,
elimination and physcial exercise. When the left side
dominates the metabolism is calmer and the mind can more
easily focus and turn inwards. This is also the
recommended state for performing
asanas. Many actions are traditionally recommended for
one state or the other. In order to open the desired side
pressing under the armpit of the opposite
side for several minutes will effect the change.
When napping after a meal, or first going to bed it is
best to lay on the left side. For general sleep the right
side is better. Laying on one side will naturally open up
the nostril on the other (upper) side. [SB]
There are three phases of breathing, diaphragmatic, thoracic, and
clavicular. Chest breathing is most common, but diaphragmatic is most
efficient, especially when the body is upright. This is because there
is more blood flowing through the bottom third of the lungs, due to
gravity, and so using the diaphram (pushing out the stomach muscles),
and using the lower lungs, leads to the most efficient transfer of
gases to and from the blood. This means that the heart can slow down.[SB]
The natural alternation of the breath from one nostril
to the other, on the order of two to three hours per side,
is also necessary. In the yogic literature it is reported
that if one side should dominate for as long has 24 hours
illness is likely to occur. The balance is necessary to
overall health. [SB]
The shape of the nasal passages is apparently quite
important. Significant changes can affect a persons personality
and moods. This illustrates the key role played by the breath
in the mental and emotional bodies as well as the physical.
The rhythm and regularity of breathing is also very powerful
and is related to emotion. The yogis have found that certain
emotions tend to generate certain breathing patterns. Conversely,
those breathing patterns will bring up the same emotions. This
is part of the power of
rebrithing. [SB]
The body normally releases toxins and waste in the urine and
the feces, in the exhaled air (mostly carbon dioxide), and in the
perspiration. At times they may also be expelled in saliva and
mucus, and in extreme cases through sores in the mouth or on the
skin. There are various practices, including fasting, internal
washes, and breathing exercises which facilitate these clearing
processes. This is part of the general process of seeing health
as the result of a good internal ecology rather than just a good
external ecology. Both are important.
The mucus membranes in the lungs and nasal passages have a
secondary function of expelling waste from the body. When other
channels are overwhelmed or plugged up, then these membranes will
increase their secretions, giving rise to a cold or other illness.
It is therefore important to bath these and help keep them clean.
[SB]
There are broadly two types of muscle fibers, Type I and Type II.
The first burns sugars and is meant for fast, short-term, action. This
is called anaerobic exercise and creates lactate. The second burns
fats and is meant for long-term ,
smoother action. It is called aerobic exercise and burns lactate
creating water and carbondioxide. There is a third energy pathway
that kick starts the fight or flight activity of the Type I fibers.
This is based on burning phosphagens and lasts typically for 30
seconds or so. [GLE]
See also these articles notes.
The Indryas or Organs of the Body
The Immune System
Immune and Nervous System Interaction
The Circulatory System
Social Connectedness and Illness
Breathing and Body Functions
Body Cleansing
Muscle Types
Working and Learning with the Body.
