Protective and Damaging Effects of Stress Mediators (Stress and the Immune System) Chapter Four - PowerPoint PPT Presentation

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Protective and Damaging Effects of Stress Mediators (Stress and the Immune System) Chapter Four

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Title: Protective and Damaging Effects of Stress Mediators (Stress and the Immune System) Chapter Four


1
Protective and Damaging Effects of Stress
Mediators(Stress and the Immune System)Chapter
Four
  • Caitlin Cleary
  • June 13, 2007

http//www.kf6nvr.net/blog/archives/images/computi
ng_stress.jpg
2
Psychoneuroimmunology
  • Scientific field investigating the link between
    bidirectional communications among the nervous
    system, endocrine and immune systems
  • What are the implications of these linkages for
    physical and mental health?
  • - Stress!!!

3
What is stress?
  • A specific response by the body to a stimulus
    that disturbs or interferes with normal
    physiological equilibrium/homeostasis
  • Stressors can be real, imagined, internal or
    external
  • Physical/environmental
  • Natural disasters
  • Major life changes (good and bad)
  • Hassles/day-to-day aggravations
  • Personality related

4
Stress - cross talk between CNS and immune system
  • The brain is the master controller of the
    nervous, endocrine, and immune system
  • However, the brain is also a target for these
    systems
  • Subject to both protection and damage

5
New Terms
  • Allostasis superordinate system by which
    stability is achieved through change
  • Primary mediators HPA axis, catecholamines, and
    cytokines
  • When set homeostatic points are out of
    boundaries, it is referred to as allostatic
    states (ex. hypertension, cytokines increasing
    risk for autoimmune/inflammatory disorder)
  • Allostatic load and allostatic overload the
    cumulative wear and tear on the regulatory
    systems of the brain and body from the cumulative
    result of an allostatic state

6
Peripheral Limbs of the Stress System Part One
HPA axis hypothalamic-pituitary-adrenal axis
which regulates body processes including
digestion, immune system, mood/sexuality, energy
usage Regulates hormone levels and maintains
homeostasis
http//cti.itc.virginia.edu/psyc220/kalat/JK367.f
ig12.6.HPA_axis.jpg
7
Peripheral Limbs of the Stress System Part Two,
Autonomic Nervous System
  • Involuntary activities that maintain homeostasis
    i.e., cardiovascular, respiratory, and
    digestive functions, etc.
  • Sympathetic and Parasympathetic branches that
    work complementary to each other

http//www.buteyko.co.nz/asthma/facts/images/nervo
us.jpg
8
Normal Stress Response
Prey sees a predator The event initiates stress
response The prey is able to escape
predation Stress response dissipates and body
returns to homeostasis Fight or Flight or Tend
and Befriend
9
Complicated Stress Interactions
10
Stress induces change for adaptation
  • Behavioral/Psychological (changes to eating,
    sleeping patterns, mood, etc.)
  • Physiological (increased blood pressure, heart
    rate, dry throat, etc.)
  • Immunological (suppression of immune system)

11
The General Adaptation Syndrome
  • Hans Selye (1936)/ Cannon (1932) the general
    adaptation syndrome, a classic, stereotyped
    theory of stress
  • Alarm reaction adrenal medulla releases
    epinephrine, and the adrenal cortex produces
    glucocorticoids, promoting adaptation and
    restoring homeostasis (allostasis)
  • Resistance defense and adaptation are optimal
    (allostatic load)
  • Exhaustion persistence of stress response
    which may lead to illness or death (allostatic
    overload)

12
Chronic Stress Effects
  • Consistently elevated cortisol and catecholamine
    levels (Stress response chronically activated)
  • Non immune related Diabetes, insomnia,
    myocardial infarction
  • Stressful events predispose to disease and immune
    deregulation infection, cancer, autoimmune
    diseases (ms)
  • Impaired learning atrophy in hippocampus
  • Depression (resulting from altered immune
    function)

13
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14
Non-immune related allostatic overload
  • Glucocorticoids regulate behaviors that control
    energy input and expenditure
  • - energy conversion serves the body well in the
    short term
  • - elevated insulin levels (glucose uptake) and
    glucocorticoids promotes deposition of body fat
    and the formation of atherosclerotic plaques in
    the coronary arteries in the long term

15
Immune related allostatic overload
  • These glucocorticoids can modulate the immune
    system by lowering the Th1 response and
    increasing the Th2 response (diminishing cell
    mediated immune response)
  • Cortisol, a specific glucocorticoid, and
    catecholamines can cause changes in
    proliferation, cytokine secretion, antibody
    production, cellular trafficking, and cytolytic
    processes
  • It has been shown that adding CRH in vivo causes
    NK cell cytotoxicity to go down
  • Clinical administration of glucocorticoids, such
    as cortisol, cause eosinophil and lymphocyte
    numbers to decrease
  • Products of the Immune system also can react with
    the HPA axis. IL-1, a cytokine produced by the
    immune system to mediate inflammation, causes
    ACTH release indirectly by increasing CRH

16
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