Porth's Essentials of Pathophysiology, 4e

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Integrative Body Functions

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reported decline in ANS and cardiovascular responsive- ness to stress associated with advancing age. 39 Aging is also associated with impaired activation and proliferation of T and B lymphocytes, as well as poorer natural killer cell response to stimulatory cytokines. 40 Gender. Within the last decade, primarily because females have been included in basic science and clinical investi- gations, differences between the sexes in cardiovascular, respiratory, endocrine, renal, and neurophysiologic func- tion have been found, and it has been hypothesized that sex hormones are the basis of these biologic differences. Technological advances in cellular and molecular biology have made it clear, however, that there are fundamental differences in the locale and regulation of individual genes in the male and female genome that can account at a very basic level for differences in physiologic function and disease manifestation. 41 These differences have general implications for the prevention, diagnosis, and treatment of disease and specific implications for our understanding of the sex-based differences in response to life’s stressors. Given the nature of sex-based differences, it is not sur- prising that there are differences in the physiologic stress response in both the HPA axis and the ANS. For example, the male hypothalamus produces more CRF and more ACTH than the premenopausal female hypothalamus, in response to psychological stressors (e.g., public speak- ing). 42 However, secretion of arginine vasopressin (AVP), a hormone that has cardiovascular and renal effects and potentiates the release of ACTH, is greater in the female. Premenopausal women also tend to have a lower activa- tion of the SNS than men in response to stressors. The phase of menstruation (luteal vs. follicular), as well as menopausal status, can alter these responses and need to be considered when studying these responses. 42 These sex- based differences in activation of the stress response may partially explain differences in susceptibility to diseases in which the stress response may play a causal role. These research results are not definitive, but they are intriguing and may serve as a foundation for further research. Health Status. Physical and mental health status deter- mine physiologic and psychological reserves, and they are strong determinants of one’s ability to adapt. For example, persons with heart disease are less able to adjust to stressors that require recruitment of cardiovascular responses. Severe emotional stress often produces disrup- tion of physiologic function and limits the ability to make appropriate choices related to long-term adaptive needs. Professionals who have worked with acutely ill persons have witnessed that the will to live often has a profound influence on survival during life-threatening illnesses. Nutrition. There are 50 to 60 essential nutrients, includ- ing minerals, lipids, certain fatty acids, vitamins, and spe- cific amino acids. Deficiencies or excesses of any of these nutrients can alter a person’s health status and impair the ability to adapt. The importance of nutrition to enzyme function, immune response, and wound healing is well known. On a worldwide basis, malnutrition may be one of the most common causes of immunodeficiency.

Among problems associated with dietary excess are obesity and alcohol abuse. Obesity is a common problem. It predisposes an individual to a number of health prob- lems, including atherosclerosis and hypertension. Alcohol is commonly used in excess. It acutely affects brain func- tion, and with long-term use, can seriously impair func- tion of the liver, brain, and other vital structures. Sleep–Wake Cycles. Sleep is considered to be a restor- ative function, in which energy is restored and tissues are regenerated. 43 Sleep occurs in a cyclical manner, alternating with periods of wakefulness and increased energy use. Biologic rhythms play an important role in adaptation to stress, development of illness, and response to medical treatment. Many rhythms such as rest and activity, work and leisure, and eating and drinking oscillate with a frequency similar to that of the 24-hour light–dark solar day. The term circadian, from the Latin circa (“about”) and dies (“day”), is used to describe these 24-hour diurnal rhythms. Sleep disorders and alterations in the sleep–wake cycle have been shown to alter immune function, the normal circadian pattern of hormone secretion, and physical and psychological functioning. 44 The two most com- mon manifestations of an alteration in the sleep–wake cycle are insomnia and sleep deprivation or increased somnolence. In some persons, stress may produce sleep disorders; in others, sleep disorders may lead to stress. Acute stress and environmental disturbances, loss of a loved one, recovery from surgery, and pain are common causes of transient and short-term insomnia. Air travel and jet lag constitute additional causes of altered sleep– wake cycles, as does shift work. Hardiness. Studies by social psychologists have focused on individuals’ emotional reactions to stressful situations and use of coping mechanisms in order to determine characteristics that help some people remain healthy despite being challenged by high levels of stressors. For example, the concept of hardiness describes a personality characteristic that includes a sense of having control over the environment, a sense of having a purpose in life, and an ability to conceptualize stressors as a challenge rather than a threat. 45 Lower levels of hardiness have been linked with greater reaction to stress, including suppressed pro- inflammatory cytokines (IL-12), increased anti-inflamma- tory cytokines (IL-4, IL-10), and lower neuropeptide-Y levels. Individuals with higher levels of psychological har- diness demonstrated more moderate and healthy immune and neuroendocrine responses to stress. 46 Psychosocial Factors. Several studies have related social factors and life events to illness. Scientific inter- est in the social environment as a cause of stress has gradually broadened to include the social environment as a resource that modulates the relationship between stress and health. Presumably, persons who can mobi- lize strong supportive resources from within their social relationships are better able to withstand the negative effects of stress on their health. Studies suggest that social support has direct and indirect positive effects on