Validación de hipótesis a través de Chi 2

During the last few decades, much knowledge has been gained with regard to the biochemistry and the psychophysiology of stress. The two systems that are primarily responsible for the stress response are the sympathetic-adrenal medullary system (SAM) and the hypo- thalamic-pituitary-adrenocortical system (HPAC) (Girdano, Everly, and Dusek, 1997). Because of their central role in understanding the stress phenomenon and how pain can bring about significant bio- chemical changes, these two systems and their functions will be briefly discussed in this section.

The Sympathetic-Adrenal Medullary System (SAM)

The autonomic nervous system (ANS) is that branch of the periph- eral nervous system that is responsible for regulating the functions of all the visceral systems in the body (e.g., the cardiovascular system, the respiratory system, the gastrointestinal system, and the excretory system), as well as the smooth muscles. The ANS operates beyond conscious awareness and as a result was referred to as the involuntary nervous system in years past. With the advent of applied psycho- physiology, namely biofeedback, it is possible to gain some con- scious control over the activity of this branch of the nervous system.

The ANS is composed of two subsystems, the sympathetic ner- vous system (SNS) and the parasympathetic nervous system (PNS). Whereas the SNS is generally responsible for increasing the activities of various organs, such as increasing the heart rate and constricting blood vessels (for the most part), the PNS reduces their activities, such as lowering the respiratory rate, decreasing the heart rate, stimu- lating digestion, and allowing bodily repair to take place.

The sympathetic nervous system has a catabolic function, that is utilizing resources to increase energy expenditure. On the other hand, the function of the parasympathetic nervous system is to reduce en- ergy expenditure and to replenish the bodily resources. The sympa- thetic nervous system is activated during a stress response, such as when a certain source of threat is perceived, and the parasympathetic nervous system is activated during the regeneration response.

The scientific interest in the impact of the sympathetic activation in stressful situations may be traced back to the observations of the prominent physiologist Walter B. Cannon (1932), who introduced the concept of the fight-or-flight response. Since Cannon’s early studies of the fight-or-flight response, a large body of evidence has suggested that the sympathetic activity plays a major role in the stress response. The sympathetic-adrenal medulla (SAM) axis of the stress response func- tions in the following fashion. When a person encounters a threaten- ing and/or stressful situation, the SNS stimulates the adrenal medulla, the inner layer of the adrenal glands which are located on top of the kidneys, and hormones such as adrenaline and noradrenaline are se- creted (Hassett, 1978). These hormones are collectively referred to as catecholamines.

It has been documented that overactivation of the sympathetic- adreno-medullary system may result in a chain of reactions that could eventually result in physical and psychological complications. For example, excessive catecholamine secretion is believed to cause many of the illnesses associated with stress such as hypertension, in- creased cardiac output, disorders of the digestive tract such as indi- gestion and irritable bowel syndrome, constriction of peripheral (arms, hands, legs, and feet) blood vessels, and dilation of blood ves- sels within the internal organs (Selye, 1984). The constriction of pe- ripheral blood vessels has also been implicated in conditions such as Raynaud’s disease, in which sufferers experience extremely cold hands and feet even to the point that their hands actually turn blue. This extremely painful condition is especially aggravated by pro- longed exposure to stress. Many fibromyalgia patients often complain of similar symptoms, although they may not meet the specific criteria for the diagnosis of Raynaud’s disease.

Prolonged activation of the sympathetic adreno-medullary system due to stress and pain may also result in a condition known as dysautonomia which results in fluctuations and even at times an abrupt drop in blood pressure. Sudden dizziness and fatigue are some of the most common symptoms of this condition. Problems with de- pression and sleep disorders may also be attributed to states of dys- function and depletion in this system. That is why certain antidepres- sants (for example, Effexor) are used to help some of the symptoms of chronic pain because they help to replenish and make more available the needed levels of noradrenaline in the brain.

The Hypothalamic Pituitary-Adrenocortical System (HPAC)

Another system which plays an important role in the stress re- sponse is the hypothalamic pituitary-adrenocortical system (HPAC). This system begins with the hypothalamus, a major regulatory mech- anism in the brain which closely interacts with the master hormonal regulator, the pituitary gland, located at the base of the brain. The hy- pothalamus interacts with the pituitary gland via the production of the corticotropin releasing factor (CRF). Once a stressful stimulus (e.g., physical, psychological, environmental) is perceived and CRF is released, the pituitary gland stimulates the outer layer of the adre-

nal gland (the adrenal cortex) through the secretion of the adreno- corticotrophic hormone (ACTH). As a result of the stimulation of the adrenal cortex, specialized hormones known as glucocorticoids (such as cortisol and corticosterone) are poured into the bloodstream. Cortisol is primarily involved in the metabolic function through the process of gluconeogenesis, which provides the body with the needed source of energy. Cortisol also plays an important role in reducing in- flammation and inhibiting fluid loss. Prolonged secretion of cortisol may result in structural damage (tissue degeneration), muscle wast- ing, and suppression of the body’s immune system (Selye, 1982). Some studies have shown that the secretion of cortisol appeared to be especially high among people who were struggling with emotional stress and felt ineffective in managing their situation (Schneiderman and Tapp, 1985).

A depletion of cortisol may result in adrenal insufficiency. Symp- toms include fatigue, weakness, diabetic-like symptoms, and im- mune dysfunction. Indeed, one of the most common symptoms of cortisol insufficiency is debilitating fatigue, followed by joint pain, muscle pain, swollen glands, allergic responses, and finally distur- bances in mood and sleep (Baxter and Tyrell, 1981). Griep, Boersma, and de Kloet (1993), in their study of patients with primary fibro- myalgia, concluded that these patients suffered from adrenal insuffi- ciency which may be due to exposure to prolonged stress. The authors also suggested that the reduced cortisol levels may explain changes in aerobic capacity and the consequent impairment in mus- cle activity.

The other hormone produced by the adrenal cortex is aldosterone. Aldosterone affects the availability of certain minerals which are cru- cial for proper heart and muscle functioning. This mineralocorticoid is responsible for intercellular retention of calcium, sodium, and wa- ter, as well as the excretion of intercellular potassium and magne- sium. It is important to note that many fibromyalgia and chronic fatigue patients are found to be deficient in magnesium, which plays an important role in metabolic functions (Cox, Campbell, and Dowson, 1991; Eisinger et al., 1994). In chronic exposure to stress, the reten- tion of additional sodium may result in edema, bloating, and signifi- cant changes in the blood pressure.

A number of studies have suggested that during the experience of constant, unabating stress, such as in chronic conditions, the activi- ties of the adrenals can become chaotic and quite problematic. For example, a person’s neurochemical system may begin to respond in a haphazard, unnecessary fashion to a minor stressor that may be quite harmless but is perceived as threatening. Again, such inappropriate stress responses are especially seen in those who feel helpless and “victims” of a chronic condition. An increase in a sense of mastery over the situation appears to gradually rectify this problem.

In summary, both the SAM and the HPAC axes play important functions in the stress response. Prolonged activation of the two sys- tems appears to be responsible for potentially deleterious effects that can even become life threatening (Cohen et al., 1986). Chronic condi- tions, such as chronic pain, if not managed properly can in time bring about a breakdown in various body systems. I can easily recall at least a dozen chronic pain patients who reported that they always had low blood pressure only to realize that after a few years of grappling with pain, “all of a sudden,” they were diagnosed with hypertension. There are also those who “suddenly” discover that they have diabetes or a bleeding ulcer.

Again, it is important to note that it is not pain that causes these conditions, but prolonged stress in addition to some hereditary vul- nerability. Since stress inevitably tends to increase the body’s rate of wear and tear, dormant conditions that are often genetically linked can become visible in time—often surprising the person by the sud- den appearance of unexpected symptoms.

Therefore, stress reduction and management play important roles in treating patients who are suffering from chronic pain and other chronic conditions. In the next chapter we will review several tech- niques that purport to accomplish this task. Once patients have an ad- equate knowledge of such approaches, they can then begin incorporat- ing them into their daily activities.