The wisdom of creation acting through the process of evolution seldom discards any thing that is useful and has survival benefit. Unfit life forms or adaptations tends not to reproduce after their own kind, and eventually become extinct. As the growth of animated beings developed over the aeons Intelligence developed with them. Starting with but a small clot of cells sensitized to light or movement clustered around one end of a body, the brain evolved into what we regard as its lofty eminence today. It is not something, however, which merely exists to produce abstract thought and televisions. Rather, the brain is responsible for the maintenance of all life functions. As nature never throws away a working apparatus we carry within us, if you will, the brains of every life form on our family tree, beginning with the brain stem itself which we share with the early amphibians and reptiles. This part of the brain evolved five hundred million years ago,and is primarily concerned with the most fundamental life process of the organism, such as breathing, heart rate, and awareness of possible predators or food sources. This level of intelligence was, and still is all that is necessary for life in the seas and marshes. And in a certain way we could be considered to be alive, albeit on a vegetative level, if only the brain stem were operating. Life is tougher on land, and greater mental organization is necessary to survive. We share with all other mammals the limbic system of the brain which is primarily responsible for maintaining homeostasis. Homeostatic functions include body temperature , blood pressure and sugar levels, functions designed to maintain the life processes in the interior environment of the body. But this limbic system, or mammalian brain as it is frequently called, is involved in far more than homeostasis. It is also the seat of the emotions and the organizing center for our response to the environment. While the reptile may fight with cold fury to protect itself and its mating turf, mammalian life forms exhibit far more intricate patterns of territoriality, emotional pair bonding, and passionate responses to life,including decisions to flee or fight. Within the limbic system is the hypothalamus, the brain of the brain, which regulates body temperature,eating, drinking, sleeping, waking, hormone balances, heart rate sex and emotions. Through its control of the pituitary gland the hypothalamus controls the glandular activity of all the body functions. All this activity and these decisions are made by parts of the brain that can carry on completely without any conscious thought. That part of our life is the responsibility of a relative newcomer, the cerebral cortex, which has evolved within the last fifty million years, and is the distinctly human part of our brain profile. Language, perception and intelligence, which we regard as our most human attributes, therefore, take up only a small portion of our brain's functioning, while the vast and intricate processes of life continue without the need for any conscious thought.
It would be a mistake, however, to conclude that all these brain functions do not interrelate. The brains within brains are intimately conjoined and interactive. The cerebral cortex itself which is divided into right and left hemispheres communicates with itself via the massive corpus callosum. Information is stored within the brain in an almost web like fashion so that while one area may be predominantly occupied with one function, redundancies and scattered filings keep the brain functioning in the event of damage to one area. The significance of this system of operation to our health is profound. Since our brain systems are not isolated from one another, events that happen on one level of functioning can and do affect processes on other levels of functioning. When we worry about decisions we made yesterday in the stock market, for example, our brains go into a stress modality that affects hormones that affect glandular secretions that affect or depress the immune system, leaving it vulnerable to attack. Thoughts of joy or comfort as we rest in the love of our families can trigger endorphin responses that contribute to our well being. Knowing this, we can see that if we can affect the brain in a positive way we can do the same to our health. Let us take a look then at the factors which most affect our immune systems. Throughout the evolutionary development of our brain system, our ancestors were continually subject to alarming and exciting events which required immediate attention. During these acute moments of stress a survival system evolved which involved the raising of blood pressure and heart rate, the suppression of pain, the increasing of muscular tension, particularly on the side of the body opposite to the dominant hemisphere, and other physiological stimuli that prompted our ancestors to violent combat or headlong retreat. These highly adaptive and successful responses to acute stress are not helpful in dealing with endemic low level chronic stress. The brain's response to these real or perceived threats to its survival acts to keep us in an inappropriate stress state almost all of the time. In this stress state the vital production of neurotransmitters is negatively affected, which can compromise our immune functions. Left to continue at this level we can become increasingly prone to a host of ailments. The only real antidote to these ill effects is in finding ways to release or relieve the stress.