Immune system and nervous system interactions in biopsychology

Immune Biopsychology

Interactions of the Human Immune System and Nervous System and their Implications on Biopsychology

This paper presents information obtained through a review of current knowledge and literature in the areas of immune system response and general nervous system functioning in the human body, and the interactions and influences that exist between these two systems. A general understanding of the immune system and some of its constituent arts its provided as necessary background information, as is a brief explanation of the nervous system and its functions in the body. A broad understanding of these systems and the mechanisms by which they function provides initial knowledge and a framework for examining the interactions that occur between these two systems and their effects on each other. These interactions are then discussed form a biopsychological perspective, noting the relationship that exists not only between mental and physiological health, but the physiological creation of (or at least influence of) mental health through such interactions.

Introduction

The human immune system is comprised of complex interactions of various cells, organs, and organ systems, coordinated through a variety of chemical and electronic messages that are in a constant state of transmittal. As the different mechanisms that protect the human body from both disease-causing foreign agents and internal stresses that reach less-than-optimal levels engage, other elements of human physiology and psychology are impacted upon, creating a complex cascade of often cyclical effects on the body and mind.

The nervous system is also highly complex n the variety of tasks it performs and in its extent throughout the body, though it is somewhat more straightforward than the immune system in terms of the basic activities it performs and the mechanisms by which it functions. Essentially serving as the communications network for the body in virtually all of its functions and actions, the nervous system has tremendous effects on the workings of other systems, and is generally instrumental in the continued functionality of every organ and organ system throughout the body. Because of this, damage to the nervous system or simple mis-firings in the vast array of its neurons on neurotransmitters can lead to a variety of issues in other systems throughout the body, including the immune system. Similar issues can occur in reverse, with damage to other organs or organ systems leading to nervous system disorders or symptoms. These interactions can have further impacts on the overall psychological as well as physiological health of the individuals that must deal with these situations.

Direct interactions between the nervous and immune systems of the human body are especially likely to have an impact on the physiological and psychological health of a given individual. Anecdotal evidence linking mood and other psychological features with certain diseases and symptoms has existed in most reputable medical texts since ancient times, and modern research continues to support many similar conclusions from a more objective and empirical perspective. As the mechanisms of the nervous system and the human immune system are investigated further and better understood, knowledge in this area continues to become more refined.

Biopsychology is a relatively new field of psychology and medicine, and attempts to pinpoint the physiological and neurological mechanisms that contribute to and/or create psychological temperaments and disorders. Understanding how the nervous system operates in a manner that influences consciousness, and understanding the many different factors that can have an effect on the nervous system, constitute the primary research questions that the field of biopsychology is concerned with; the ways in which the physiological workings of the body and mind affect the psychological perspectives, attitudes, and functions of an individual are of direct and explicit interest to researchers in this field. Developing such understandings can lead to better diagnostic indicators for physiological disorders and symptoms as well as producing better understandings of and treatments for many psychological issues and disorders, improving knowledge and practice in both physical medicine and often less-concrete psychological undertakings through the careful and rigorous examination of their common elements, influences, and mutual interactions.

This paper examines a broad array of literature in order to develop a better understanding of the interactions that occur between the human immune system and the nervous system, and the relationships that these many complex and multidirectional interactions have on biopsychology. Beginning with an overview of the immune system, followed by one of the nervous system, the broad interactions between these two systems are then presented, with several specific examples of interactions explored and analyzed as examples.

Following this examination of the ways in which the nervous and immune systems interact within the human body, the ultimate implications of these interactions in the field of biopsychology are examined and detailed. Though many of these implications and the overall biopsychological context of the phenomena and mechanisms discussed are apparent throughout the examination of current literature contained herein, this explicit discussion of biopsychology and its influence by the interactions between the nervous and immune systems is useful for its collation and coordination of the data and conclusions encountered in a broader review of current literature. By progressing from independent overviews of specifics aspects of the research question to a cohesive and comprehensive analysis of the query and resultant information as a whole, it is hoped that this paper will provide insight into the development and implications of the biopsychological perspective as it is applied practically and theoretically.

The Immune System

Researchers and practitioners have noted that it is fundamentally wrong to consider the immune system as having developed with the "purpose" of protecting the body from disease and the effects of various pathogens, but they also acknowledge the practical benefit of approaching a broad understanding of the system with this purpose in mind (Hofmeyr 2000). That is, though the immune system did not evolve as and discrete system with the purpose of protecting the organism as a whole from disease, this is a useful understanding of the immune system's current functioning, and one that makes an examination of its specific mechanisms simpler.

The immune system also does not consist of a discrete or concrete set of organs and functions; though some elements of the immune system are wholly and solely devoted to maintaining basic health in the body, especially in the face of various pathogens, many parts of the immune system are more directly related to other systems in the body (Hartford 2001). The major fluid systems in the body, i.e. The blood and lymph systems, are especially essential elements of the immune system that also serve larger purposes in the body (Hartford 2001). Both of these systems, and the fluids that they transport, assist in delivering nutrients to the various parts of the body as well as clearing away pathogens and delivering cells that act specifically as parts of the typical immune response (Hartford 2001). Because of the importance of both lymph and blood flow throughout the body as a part of the immune system, the heart, lungs, and certain other major organs of the cardiovascular and lymph systems have a large impact on the functioning of the immune system, and vice versa.

This multi-system nature of the immune system will be of greater importance in later discussions of the implications of immune system functioning and nervous system interaction, yet for the purposes of providing a basic understanding of immune system functioning it is more effective to understand the constituent parts of the immune system as elements belonging more specifically to the immune system. In this way, the basic architecture and separate functions of the immune system can be better understood at their level of functionality, before broader interactions and influences are examined and explained.

The first line of defense in the design of the immune system is the innate immune response, which consists of broad mechanisms that provide for a general defense against any undesirable elements within the body, including external pathogens and unwanted or unnecessary cells and cell detritus in the blood system and collected in the body's lymph (Hartford 2001; Dugdale 2008). The skin and mucus secretions at skin openings provide physical protection against the entrance of outside pathogens; once pathogens have found entrance, phagocytes chemically attract, engulf, and digest foreign bodies, reducing them to harmless waste that is then washed out of the body through the excretory system (Dugdale 2008; Hofmeyr 2000). These cells develop in the bone marrow and usually reach maturity in the bloodstream, and remain generally consistent in structure and function throughout the human life cycle, though numbers are often reduced in old age (Hofmeyr 2000).

The other major component of the immune system in this view is the adaptive immune response, which is developed as the body encounters specific pathogens. Macrophages engulf foreign antigens, and eventually display certain marker proteins from these invaders; this sensitizes T-cells produced by the lymphatic system and causes them to recognize the surface proteins during subsequent invasions, particularly attuning these cells to specific antigens and thus facilitating their faster destruction in the body (Hartford 2001). These cells divide in a way that retains this "memory" of antigens, and allows immune systems to become more refined and effective as exposure continues (Hartford 2001; Hofmeyr 2000).

An interesting view of the immune system with particular implications for the current review and collation of information is provided by the field of computer science. The immune system makes many series of continual trade-offs, distributing resources in a way that necessarily leaves certain vulnerabilities in the system as a whole while providing greater comprehensiveness in coverage and protection when necessary (Hofmeyr 1997). This makes the immune system an adaptive and continually evolving and self-improving system; with little outside direction it is capable of assessing changing needs, and altering itself not only in particular instances but even in some of its general responses in order to provide greater long-term efficacy for the task of protecting the human organism from disease (Hofmeyr 1997). This view of the immune system as a contained and self-informing system is not entirely accurate, but it is a very useful perspective for our purposes herein.

The Nervous System

The nervous system is much more simply explained than the immune system, at least in a superficial sense, though its effects and ramifications throughout the body are at times highly complex and entirely pervasive. With the brain as the primary source of direct instruction to other organs and systems, and the primary receiver of information from other areas of the body, the nervous system provides communication throughout the body. It is through the functioning of the nervous system that external and internal elements and changes can be responded to in both conscious and unconscious manners in order to (generally) maintain health and homeostasis.

Like the immune system, the nervous system is in a constant state of evolution, development, and reaction throughout life (Michigan 2002). Certain things occur on a conscious or from-conscious level -- the nervous system is involved in transmitting the images of words from the page to the brain where they are deciphered as one purposefully reads, and the muscles controlling the hand and fingers are fires as one turns the page -- and other functions are carried out wholly subconsciously, such as the actually focusing of the eyes and the control of the pupil size based on distance and light, respectively. The full array of bodily functions, from the continued beating of one's heart to the contraction of muscles in the digestive tract and all reaction to -- and indeed notice of -- sensory input, all depend on the proper and continued functioning of the nervous system. This means that disruptions to the nervous system can be hugely influential in the functioning of other bodily systems and functions.

Also like the immune system, though along very different lines, the basic architecture of the nervous system is divided into two parts. The central nervous system is made up of the brain and the spinal cord -- a bundle of nerves running through the spinal column; these two organs are responsible for originating, coordinating, and disseminating most communications throughout the body (Ophardt 2003). Specific chemical messengers, called neurotransmitters, travel between nerve cells in the brain in a cascade action that produces electrical current and triggers other nearby neurons in a highly specific manner, producing the (generally) desired actions and adjustments in the body and its functions (Ophardt 2003).

The nerves running from the central nervous system, i.e. The spinal cord, to the many organs and muscles of the body, constitutes the second part of the nervous system's basic architecture, and is known as the peripheral nervous system (Michigan 2002). While there are different types of cells in the central nervous system, particularly in the brain, the peripheral nervous system is composed only of nerves -- bundles of neurons, which are used only for the transmission of electric impulses through certain chemical chain reactions and cascade effects (Farabee 2001; Ophardt 2003). The central nervous system contains both neurons and specialized glial cells that insulate and protect neurons in the brain; some similar functions are provided by the myelin sheaths that surround neurons in the peripheral nervous system (Farabee 2001). These myelin sheaths not only protect the nerve cells, but they also serve as electronic insulators, increasing the speed of transmission of the signals sent both towards and away from the brain throughout the nervous system (Michigan 2002; Farabee 2001).

Given the nervous systems spread and relative simplicity, it is fairly easy to see how issue sin the nervous system would have major impacts on the functioning of other organ systems, including the immune system. On the other hand, as the immune system operates largely via chemical messengers in the blood and lymph systems, bypassing much of the communication network that is the nervous system, the interactions between these two essential organ systems in the human body are not entirely obvious or straightforward. An examination of the specifics of these interactions makes it clear how intertwined their workings truly are.

Key Interactions Between the Nervous and Immune Systems

There are many direct and indirect ways in which he workings of the nervous system can affect those of the immune system and vice versa. Some of these interactions result in specific disorders, diseases, or adverse symptoms developing, and are generally undesirable yet serve to advance medical knowledge and science as they are better understood. Other interactions are actually directly supportive of the functionality of one or the other or even both systems. Regardless of the purposefulness of the interactions that occur or the ultimately positive or negative effects of that interaction, most of the influence that the nervous and immune systems wield over each other come from crossovers in the communications networks for the two systems that are not really as discrete as they initially appear.

One of the ways in which these systems interact, it has been found, is in the partial regulation of T-cell presence and activity by the nervous system. A specific peptide -- one of many types of chemical messengers -- that has long been known to stimulate neuronal activity and serve as a regulator for neuron survival, also mediates the survival of Th1 and Th2 cells, two different types of T-cells with varying functions (UCSF 2001). Blocking receptors for this peptide results in a disproportionate amount of Th1, which redistributes the immune system's resources in a way that makes it fight pathogenic infection much harder, while leaving it more vulnerable to parasitic organisms and certain other health issues (UCSF 2001). This interaction is already being heavily explored as a method of treating certain infections and autoimmune disorders (UCSF 2001).

Such a reordering of the immune system's resources can occur on a much more extensive and profound level due to certain other issues affecting the nervous system, including conscious though uncontrollable emotional issues. Studies have revealed that certain stressors, especially major catastrophic incidents, can lead to major overall drops in the number of T-cells within an organism, and to the overall functionality and efficiency of the immune system (Shomon 2010). Stress can cause the release of adrenal hormones, which shift the body's energy to immediate usefulness at the expense of systems such as the immune system; the nervous system effectively slows all immediately unnecessary processes (Shomon 2010). More intriguing still is the fact that certain macrophages and lymphocytes that roam the body in search of antigens have actually been found to secret certain neuropeptides, activating both other immune cells and cells within the nervous system to create further signals for immune activity, instigating a self-responsive neural and immune response to specific situations (Shomon 2010).

The interactions between these two systems can also occur in the opposite direction, with immune responses having an effect on the workings of the nervous system. The secretion of certain cytokines by immune system cells, for instance, has been found to activate the secretion of neural hormones and messengers in the hypothalamus, pituitary, and adrenal glands, thus stimulating specific neuronal activity based on the fact that an infection has been encountered (Dunn 2000). Just as issues that directly affect the nervous system affect other functions and systems indirectly, an immune response changes the way in which all of the functions of the body are coordinated.

These interactions are but a few of the many different ways in which the nervous systems and the immune systems of the human body interact with each other. These interactions ultimately all take place on molecular and chemical levels, with communication between the nervous and immune systems more extensive than previously thought due to the presence and secretion of many different chemical messengers by both systems that have direct and apparently purposeful effects on the other system (Dunn 2000; Shomon 2010). These molecular interactions are responsible for large scale changes in both physiology and temperament, making the interactions between the nervous and immune systems a matter of great importance not simple in direct physical medicine but also in psychology.

Implications for Biopsychology

What this means, in essence, is that there is a significant biopsychological element to the interactions that occur between the nervous and immune systems. The workings of the body necessarily affect certain psychological outcomes, with this relationship becoming more clear as the causes originating in the body become more extreme. The influence of the immune system on the nervous system, and vice versa, demonstrated the degree to which the mental/nervous workings of a person are related to their health, and even more specifically to their bodies' attempts at retaining health. Though the direct purpose for many of the biophysical impacts that the nervous and immune systems have is unknown, these impacts can have both positive and negative psychological outcomes overall.