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ORIGIN & TERMINOLOGY
• Stress is a word derived from the Latin word stringere, meaning to draw tight .
• The term stress was first employed in a biological context by Hans Selye in the 1930s.
• He explained stress as an inappropriate physiological response to any demand.
• In his usage stress refers to a condition and stressor to the stimulus causing it.
• Now, the most commonly accepted definition of stress (mainly attributed to Richard S Lazarus) is that stress is a condition or feeling experienced when a person perceives that demands exceed the personal and social resources the individual is able to mobilize.
• Stress occurs when the demand is greater than the resource
S = D > R
“To understand the stress response, we must process a fundamental knowledge not only of psychology but of physiology as well.”
—George Everly
A systems model of the human stress response
The Anatomy and Physiology of the Human Stress Response, G.S. Everly and J.M. Lating, A Clinical Guide to the Treatment of the Human Stress Response,© Springer Science and Business Media New York 2013
TYPES OF STRESSORS
EXTERNAL
INTERNAL
INTERNAL STRESSORSLIFESTYLE CHOICES
NEGATIVE SELF TALK
MIND TRAPS
PERSONALITY TRAITS
EXTERNAL STRESSORS
PHYSICAL ENVIRONMENT
SOCIAL INTERACTION
MAJOR LIFE EVENTS
ORGANISATIONAL
DAILY HASSLES
Cognitive–Affective Domain
• Cognitive appraisal refers to the process of cognitive interpretation, that is, the meanings that we assign to the world as it unfolds before us.
• Affective integration refers to the blending and coloring of felt emotion into the cognitive interpretation.
• The resultant cognitive–affective complex represents how the stressors are ultimately perceived.
• In effect, this critical integrated perception represents the determination of whether psychosocial stimuli become psychosocial stressors or not.
• Appraisal is a function of any existing biological predispositions, personality patterns, learning history, and available coping resources. Once appraisal is made, efferent impulses project so as to potentiate the stimulation of two major effector systems:
1. Impulses project back to the limbic system, especially the hippocampus , for the experience of stimulus-specific felt emotion and the potential to trigger visceral effector mechanisms.
2. Impulses similarly project to the areas of the neocortex concerned with neuromuscular behavior where, through pyramidal and extrapyramidal systems, muscle tone (tension) is increased and the intention to act can be potentially translated to actual overt motor activity.
“Men are disturbed not by things, but by the views which they take of them” – Epictetus (5th century)
“It is not what happens to you that matters, but how you take it” – Hans Selye 1950s
“Stressors, like beauty, lie in the eye of the beholder” - Everly, Davy, Smith, Lating, and Nucifora (2011)
Neurological Triggering Mechanisms
• The next step in the model is the neurological triggering mechanisms
• Linked through ventral and dorsal adrenergic as well as serotonergic projections (among others), this complex appears to consist of the LC, the hippocampus, the septal–hippocampal–amygdaloid complexes, and the anterior and posterior hypothalamic nuclei
• These structures give rise to the multiaxial stress response
Physiological Systems Involved in the Stress Response
• Neural axis• Neuroendocrine axis• Endocrinal axis• Immune system
The Neural Axis
• Three neural axis comprise the neural stress response:
(1) the sympathetic nervous system,
(2) the parasympathetic nervous system, and,
(3) the neuromuscular nervous system.
• These neural pathways are the first of all stress response axes to become activated during stress arousal.
AUTONOMIC NERVOUS SYSTEMSympathetic Parasympathetic
The effects of activation via the parasympathetic system are inhibition, slowing, and “restorative” functions—a “trophotropic” response
The effects of neural activation via the sympathetic system are those of generalized arousal within the end an “ergotropic” response.
The “Fight-or-Flight” Response: The Neuroendocrine Axis
Dorsomedial amygdalar complex
Lateral and posterior hypothalamic regions
Thoracic spinal cord
Celiac ganglion
Adrenal medulla
STRESS
Sympathetic ANS
Increase Serum Glucose
Liver LiverGlycogen Glucose
Increase plasma fatty
acids available for
energy
Endorphin Release Decreased PAIN
Endocrine Axis
• The most chronic and prolonged somatic responses to stress are the result of the endocrine axis.
• Four endocrine axes associated with the stress response:1. The adrenal cortical axis.2. The somatotropic axis.3. The thyroid axis.4. The posterior pituitary axis.
• These axes require greater intensity stimulation to activate
Adrenocorticotropic Hormone
Corticotropin Releasing Hormone
Glucocortoid
Increase Energy Available
Reduce InflammationReduce HistaminesReduce immunity
ACTH axis
HPA and SAM work together to control stress response
SAM
Sympathetic Adrenal Medullary System
HPA
Hypothalamic
-Pituitary
-Adrenal - axis
• Behaviorally, the HPAC system appears to be activated when active coping is not possible; thus, it has been called the “passive coping” system.
• Considering the HPAC system with respect to the SAM:
1. Effort without distress → activation of the SAM system
2. Distress without effort → activation of the HPAC system
3. Effort with distress → activation of both SAM and HPAC
The Somatotropic Axis
• The septal–hippocampal complex the median eminence of the hypothalamus release somatotropin-releasing factor (SRF) stimulates the anterior pituitary.
• The anterior pituitary responds to the SRF by releasing growth hormone.
• The role of growth hormone in stress is somewhat less clearly understood.
The Thyroid Axis
• Median eminence of the hypothalamus release thyrotropin-releasing factor (TRF) anterior pituitary TSH.
• TSH stimulates the thyroid gland to release : triiodothyronine (T3) and thyroxine (T4).
• In humans, psychosocial stimuli have generally led to an increase in thyroidal activity.
• Thyroid hormones increases general metabolism, heart rate, heart contractility, peripheral vascular resistance, and the sensitivity of some tissues to catecholamines.
The Posterior Pituitary Axis
• Stimulation of hypothalamic nuclei results in the release of the hormones vasopressin and oxytocin from posterior pituitary into the systemic circulation.
• ADH result in water retention.
• Role of oxytocin in the human stress response is currently unclear but may be involved in psychogenic labor contractions and premature birth, as well as the stress response, particularly for women
Others
• Various investigations have shown that both luteinizing hormone, and testosterone have been shown to be responsive to the presentation of various stressors.
• The hormone prolactin has clearly shown responsiveness to psychosocial stimulation as well.
• Melatonin and serotonin are not stress hormones, yet there decreased levels are associated with depression.
Temporal relationship
between primary stress axes
The “General Adaptation Syndrome”• Hans Seyle ( 1956 ) proposed an integrative model for the stress response, known as the “General Adaptation Syndrome” (GAS).
The GAS is a tri-phasic phenomenon which involves “alarm”, ”resistance” and “exhaustion” phase
CHRONIC STRESS
PSYCHONEUROIMMUNOLOGY
• Recent research has shown that immune system is a key player in stress physiology.
• Psychoneuroimmunology is the study of the bidirectional interactions between brain, behaviour, and the immune system.
• The immune system is regulated by neural input from sensory, sympathetic and parasympathetic nerves, as well as by circulating hormones, of which the glucocorticoids are among the most prominent
• Lymphocytes, monocytes and NK cells are all reduced in number in blood and increased in number in tissues, such as the skin, as a result of acute stress
• Chronic stress causes decrement in memory T cell responses to latent virus antigens and to vaccines, in terms of antigen-induced T-cell proliferation and T-cell–mediated killing of virally transformed B lymphocytes
• The term target-organ activation refers to the phenomenon in which the neural, neuroendocrine, and endocrine constituents of the stress response
1) activate,
2) increase, or
3) inhibit normal activation, or
4) catabolize some organ system in the human body
• Potential target-organ systems the CVS, the GIS, the skin, the immune system, the brain and its mental status.
WARNING SIGNS AND SYMPTOMS OF STRESS
COPING
• Coping is expending conscious effort to solve personal and interpersonal problems, and seeking to master, minimize or tolerate stress or conflict.
• Adaptive or maladaptive.
• Adaptive coping strategies reduce stress while at the same time promoting long-term health (e.g., exercise, relaxation, proper nutrition).
• Maladaptive coping strategies, on the other hand, do indeed reduce stress in the short term but serve to erode health in the long term (alcohol/drug abuse, cigarette smoking, interpersonal withdrawal).
RECENT ADVANCES
• Bruce McEwen coined term Allostatic load for stress• Some salient features of McEwen’s research:1. The hippocampus and amygdala together form conscious memories
of emotional events2. The hippocampus is highly sensitive to stress hormone cortisol,
which aids in memory formation of stress3. The hippocampus region is rich in receptor sites for glucocorticoids4. The amygdala is responsible for the emotional content of memory,
particularly fear5. Repeated excessive exposure to cortisol accelerates the aging
process of the hippocampus and may, in fact, damage or shrink brain cells. Moreover, chronic stress may affect memory and learning process
The neurobiology of stress: from serendipity to clinical relevance Bruce S. McEwen, Brain Research 886 (2000) 172–189
The neurobiology of stress: from serendipity to clinical relevance Bruce S. McEwen, Brain Research 886 (2000) 172–189
SUMMARY
The Anatomy and Physiology of the Human Stress Response, G.S. Everly and J.M. Lating, A Clinical Guide to the Treatment of the Human Stress Response,© Springer Science and Business Media New York 2013
References
• Physiology and Neurobiology of Stress and Adaptation: Central Role of the Brain.. Physiol Rev 87: 873–904, 2007
• The Anatomy and Physiology of the Human Stress Response, G.S. Everly and J.M. Lating, A Clinical Guide to the Treatment of the Human Stress Response,© Springer Science and Business Media New York 2013
• The neurobiology of stress: from serendipity to clinical relevance Bruce S. McEwen, Brain Research 886 (2000) 172–189
• Physiology of stress. Jones Bartlett publishers pg no. 35-48
