Your Behavior Can Affect Your Body
By Erika Cappelluti, M.D., Ph.D., F.C.C.P.
have an infection? Do you know why people feel depressed during an acute illness? How is it possible that low socioeconomic status can heighten a person’s susceptibility to infection? Did you know that your memory could be impaired by infection? The once anecdotal evidence to support these claims has been substantiated in recent years by rigorous scientific data. We have finally begun to recognize and understand the complex interplay between the endo- crine, immune and nervous systems within the human body. This field of study, known as Psychoneuroimmunology (PNI), has emerged as a result of a change in the way that the scientific and medical communities view the human being: as a complex whole, rather than a conglomerate of unrelated parts. As it turns out, these systems can influence one another in multidirectional fashion. Very simply put - your behavior can affect your body and your body can affect your behavior. Psychoneuroimmunology is a scientific
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demonstration of the unity of the organism but chiefly involves the immune, endocrine, and nervous systems. This integrative disci- pline was first described in 1980 by Robert Ader (Ader, 1981). It is “the study of behav- iorally associated immunologic changes and immunologically associated behavioral changes that result from reciprocal interac- tions among the nervous, endocrine, and immune systems.” It is a novel field of scien- tific inquiry for which supporting evidence has exploded in the past 2 decades. Since J. Edwin Blalock proposed a theory in 1985 about shared mediators and shared receptors in the immune and neuroendocrine systems, the field of PNI has made significant prog- ress (Blalock et al., 1985). There are now volumes of information available, some of which will be surveyed here.
20 Natural Nutmeg
ave you ever wondered why you’re more prone to infection when sleep- deprived and sleepier when you
The PNI Players:
Immune System The immune system is comprised of
many different cell types and large mol- ecules whose function is to maintain the integrity of the organism and fight patho- gens. It is the interface between the organ- ism and microscopic adversaries. The skin is the most obvious component, but the liver, thymus, spleen, lymph tissue, and bone marrow play substantial roles as well. At the cellular level, immunoglobulins, granulo- cytes, T-cells, B-cells, natural killer cells, and chemicals called cytokines and chemokines, keep infection at bay. However, the immune system does not function autonomously. There are hormones and peptides released by the endocrine glands that impact the im- mune system. This is one of the foundational principles of PNI.
Endocrine System
The endocrine system is essential for maintaining life and consists of the hypo- thalamus, pituitary gland, thyroid, para- thyroid and adrenal glands, reproductive organs, pancreas, pineal gland, and the thymus (also considered part of the immune system). The hormones and factors produced and secreted by these organs are numerous and involved in virtually every aspect of the organism. A partial list includes the follow- ing: oxytocin, dopamine, thyroid-stimulating hormone, growth hormone, prolactin, estro- gen, thyroid hormones, insulin-like growth factor, epinephrine, and beta endorphin. The release of hormones by the endocrine glands is largely under neural control, is subject to negative feedback, and is influenced by other hormones. We now know that sub- stances first discovered in the immune cells (e.g., cytokines) can alter endocrine activity
and are now known to be released by pitu- itary cells, endothelial cells, and cells of the nervous system (neurons and glial cells). Fur- thermore, leukocytes (a type of white blood cell that is crucial to fighting infection) have been shown to produce pituitary hormones and various other peptides that may influ- ence neuroendocrine activity. The complexity and multitude of recip- rocal influences between the endocrine and immune systems help explain the abundance of pathways for neuroimmune communica- tion. However, they also reinforce the notion that a simple model of hormonal immune effects does not exist.
Nervous System The nervous system is composed of
two major parts: the central nervous system (brain and spinal cord) and the peripheral nervous system (all neural elements outside of the brain and spinal cord). The peripheral nervous system (PNS) consists of sensory and motor pathways carrying information to and from the tissues of the body. The sensory pathways transmit signals FROM visceral or- gans, muscles, tendons, and skin. The motor pathways carry signals TO the muscles and the visceral organs. The visceral neural outflow is also
known as the autonomic nervous system (ANS) which is divided into the sympathetic and parasympathetic branches. Another major component of the ANS is the enteric nervous system (ENS), which is contained within the walls of the gastrointestinal tract. Simply put, the components of the ANS are not under voluntary control. The ANS con- trols things like sweating, constriction/dila- tion of blood vessels, and how quickly food moves through the gut. This is in contrast to the somatic nervous system which is under voluntary control and aids us in the use of our muscles.
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