Stress and Adaptation: Key Concepts

Stress and Adaptation

• Stress is a widely discussed topic affecting health, economics, politics, business, and education.
• The physiological response to stress can contribute to physical, mental, and societal challenges.
• Walter Cannon used the word stress in relation to the "fight-or-flight" response.
• Hans Selye defined stress as an orchestrated set of bodily responses to any form of noxious stimulus.

Homeostasis

• Homeostasis is the maintenance of a stable internal environment.
• Claude Bernard described the importance of a stable internal environment, or milieu intérieur.
• Walter Bradford Cannon proposed homeostasis is achieved through coordinated physiological processes that oppose change.
• Homeostatic control systems regulate cellular function, control life processes, and integrate functions of different organ systems.
• These systems involve a sensor, an integrator, and effector(s) to reverse change.
• Early negative experiences can impact adult health, increasing risks for depression, suicide, and other issues.
• Actively creating a feeling of balance and considering the future can help manage stress.

Key Points: Homeostasis

• Homeostasis is the purposeful maintenance of a stable internal environment.
• Physiologic control systems operate by negative feedback mechanisms.
• Negative feedback mechanisms involve a sensor, integrator, and effector system.
• Most control systems function under negative feedback mechanisms to maintain stability.
• Physiologic and psychological adaptation maintains constancy of the internal environment.

Stress and Adaptation

• Stress can contribute directly to disease or exacerbate behaviors that increase disease risk.
• Hans Selye described stress as a state manifested by a specific syndrome in response to intense systemic demand.
• Selye described the general adaptation syndrome (GAS) with three stages: alarm, resistance, and exhaustion.
• Stressors can be endogenous (within the body) or exogenous (outside the body).
• Two factors determine the stress response: properties of the stressor and conditioning of the person.
• Eustress is mild, brief, and controllable stress that can be positive, while distress is severe, protracted, and uncontrolled.

Neuroendocrine Responses

• The stress response is influenced by the nervous and endocrine systems.
• Chronic stress can override dynamic regulation critical to homeostasis, leading to a lack of system sensitivity.
• Allostatic load describes the cumulative effects of chronic stress on health.
• The central nervous system (CNS) integrates the stress response.
• The cerebral cortex, limbic system, thalamus, hypothalamus, pituitary gland, and reticular activating system (RAS) are involved.
• The locus coeruleus (LC) in the brain stem is a central integrating site for the autonomic nervous system (ANS) response.
• Corticotropin-releasing factor (CRF) is central to the endocrine response.
• Glucocorticoid hormones (e.g., cortisol) mediate the stress response and maintain blood glucose levels.
• Angiotensin II enhances CRF formation and release and stimulates norepinephrine release.
• Other hormones, including growth hormone, thyroid hormone, and reproductive hormones, are responsive to stressful stimuli.
• Stress affects the hypothalamic–pituitary–gonadal (HPG) axis, leading to ovulatory dysfunction and decreased sperm quality.
• Antidiuretic hormone (ADH) increases water retention and vasoconstriction.
• Serotonin plays a role in the stress response.
• Oxytocin reduces stress-related physiological consequences.

Immune Responses

• The stress response involves endocrine–immune interactions.
• Immune cells can penetrate the blood–brain barrier and secrete cytokines that influence the stress response.
• Hormones and neuropeptides can alter the function of immune cells.
• Cortisol suppresses immune function.
• Cytokines activate the HPA axis.
• The sympathetic nervous system and catecholamines regulate immune function.
• Stress hormones can change the quality of the immune response, stimulating different subtypes of T lymphocyte helper cells.

Key Points: Stress and Adaptation

• Stress involves activation of the neuroendocrine and immune systems (general adaptation syndrome).
• Hormones and neurotransmitters alert the person to a threat, enhance cardiovascular and metabolic activity, and focus energy.
• Adaptation is the ability to respond to challenges and return to a balanced state.
• Adaptation is influenced by learning, physiologic reserve, time, genetics, age, health status, nutrition, sleep–wake cycles, and psychosocial factors.

Coping and Adaptation to Stress

• Adaptation is the ability to respond to a range of environments and stressors.
• Humans have alternative mechanisms for adapting and controlling their environment.
• The response to psychological disturbances may be inappropriate and sustained compared to physiological disturbances.
• Coping strategies manage threats to physiological and psychological homeostasis.

Factors Affecting the Ability to Adapt

• Adaptation involves creating a new balance between the stressor and the ability to deal with it.
• Physiologic reserve is the ability of body systems to increase function when needed.
• Anatomic reserve is provided by paired organs.
• Adaptation is more efficient when changes occur gradually.
• Genetics can ensure adequate function of systems essential to adaptation.
• The capacity to adapt decreases at extremes of age.
• Sex hormones and fundamental genetic differences influence stress responses.
• Health status determines physiological and psychological reserves.
• Nutrition affects health status and the ability to adapt.
• Circadian rhythms play a role in adaptation, illness, and treatment response.
• Hardiness (control, challenge, and commitment) allows resilience through stress.
• Psychosocial factors and strong social support enhance the ability to withstand negative effects of stress.

Stress Response Stages

• Alarm Stage: Activation of the sympathetic nervous system and the HPA axis.
• Resistance Stage: The body selecting the most effective defenses.
• Exhaustion Stage: Physiologic resources are depleted and signs of systemic damage appear.

Disorders of the Stress Response

• The stress response is meant to be acute and time limited; the chronicity of the response is disruptive.
• Stressors can be acute time limited, chronic intermittent, or chronic sustained.
• Chronic exposure to a stressor can fatigue the system and impair its effectiveness.

Effects of Acute Stress

• Reactions to acute stress involve the ANS (fight-or-flight response).
• Acute stress can be detrimental for those with limited coping abilities or preexisting conditions.
• It can redirect attention from health-promoting behaviors and interrupt adherence to medication regimens.

Effects of Chronic Stress

• Chronicity and excessive activation can result from chronic illnesses and lead to long-term health problems.
• Stress is linked to cardiovascular, gastrointestinal, immune, and neurologic diseases, as well as mental health disorders.

Posttraumatic Stress Disorder (PTSD)

• PTSD is caused by chronic activation of the stress response due to a significant traumatic event.
• It involves intrusion, avoidance, alteration in cognition and mood, and alteration in arousal and reactivity.
• People with PTSD may experience flashbacks, emotional numbing, depression, and hyperarousal.
• Physiologic changes include increased norepinephrine and activity of α2-adrenergic receptors.
• There are alterations in neural systems in the amygdala and hippocampus.
• Those with PTSD demonstrate decreased cortisol levels and increased sensitivity of cortisol receptors.
• Early treatment offers the best chance for recovery.
• Risk factors include traumatic events in childhood, extreme fear, lack of support, and loss.

Treatment and Research of Stress Disorders

• Treatment should help people avoid risky coping behaviors and provide alternative stress-reducing strategies.
• Nonpharmacologic methods include relaxation techniques, guided imagery, music therapy, massage, and biofeedback.
• Relaxation involves decreasing sympathetic system activity and musculoskeletal tension.
• Imagery uses mental images to reduce anxiety and stress.
• Deep breathing reduces stress, negative affect, and anxiety.
• Music therapy uses selected music to ameliorate anxiety or stress, reduce pain, and facilitate emotional expression.
• Biofeedback involves electronic monitoring of physiological responses to stress with immediate feedback.
• Cognitive behavioral therapy replaces negative behaviors with positive coping strategies.
• Research in stress requires careful interpretation due to individual differences.

Key Points

• Stress in itself is neither negative nor deleterious to health.
• The stress response is designed to be time limited and protective.
• Chronic activation of the response can be damaging to health.
• Treatment of stress should be aimed at helping people avoid coping behaviors that can adversely affect their health and providing them with other ways to reduce stress.
• Nonpharmacologic methods include relaxation techniques, guided imagery, music therapy, massage techniques, and biofeedback.

Geriatric Considerations

• An interpreter may be helpful when bilingual people use their home language when stressed.
• Caregiver stress contributes to abuse of older adults.
• Role fulfillment is key to stress management in the aging adult.
• Stress is twice as common in people aged 50 to 65 than those aged 65 to 80 years.

Pediatric Considerations

• Stress in children can be due to normal developmental issues or atypical events.
• Resilience (coping skills to effectively deal with stress) will help the child to achieve balance.
• Infants deal with stress by sucking.
• Comfort measures such as rocking, stroking, cuddling, and holding the child can reduce stress.