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.