Transcript Chapter_010.ppt

Chapter 10
Stress and Disease
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Stress
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A person experiences stress when a demand
exceeds a person’s coping abilities, resulting
in reactions such as disturbances of
cognition, emotion, and behavior that can
adversely affect well-being
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Dr. Hans Selye
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Worked to discover a new sex hormone
Injected ovarian extracts into rats
Witnessed:
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Enlargement of the adrenal cortex
Thymic atrophy
Development of bleeding ulcers in the stomach
and duodenal lining
Dr. Selye witnessed these changes with many
agents. He called these stimuli “stressors.”
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General Adaptation Syndrome
(a Nonspecific Response)
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Selye termed this general response the
general adaptation syndrome (GAS)
Three stages
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Alarm stage
• Arousal of body defenses
 Stage of resistance or adaptation
• Mobilization contributes to fight or flight
 Stage of exhaustion
• Progressive breakdown of compensatory mechanisms
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GAS Activation
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Alarm stage
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Resistance stage
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Stressor triggers the hypothalamic-pituitaryadrenal (HPA) axis
• Activates sympathetic nervous system
Begins with the actions of adrenal hormones
• Cortisol, epinephrine, norepinephrine
Exhaustion stage
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Occurs only if stress continues and adaptation is
not successful
• Onset of disease
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Psychologic Mediators
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Reactive response
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Anticipatory response
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To psychologic stressors
Anticipating a disruption in homeostasis
Conditional response
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Associating a stimuli with danger
Posttraumatic stress disorder (PTSD)
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Stressors
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Anything that demands a response in order to
maintain homeostasis
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Noxious
• Pain, cold, trauma, hunger, electric shock
Not noxious
• Life events (wedding)
• Excitement
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Stress and Disease
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Can precipitate disease
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Cardiac
Can worsen existing disease
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Irritable bowel disease
Asthma
Autoimmune diseases
HIV progression
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Psychoneuroimmunologic
Mediators
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Interactions of consciousness, the brain and
spinal cord, and the body’s defense
mechanisms
Corticotropin-releasing hormone (CRH) is
released from the hypothalamus
CRH also released peripherally at
inflammatory sites
Immune modulation by psychosocial
stressors leads directly to health outcomes
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Stress Response
(Neural Recognition)
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Central Stress Response
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Catecholamines
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Released from chromaffin cells of the adrenal
medulla
• Large amounts of epinephrine; small amounts of
norepinephrine
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α-adrenergic receptors
• α1 and α2
β-adrenergic receptors
• β1 and β2
Mimic direct sympathetic stimulation
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Central Stress Response
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Cortisol (hydrocortisone)
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Activated by adrenocorticotropic hormone (ACTH)
Stimulates gluconeogenesis
Elevates the blood glucose level
Protein anabolic effect in the liver; catabolic effect in
other tissues
Lipolytic in some areas of the body, lipogenic in others
Powerful anti-inflammatory or immunosuppressive
agent
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Emerging Research
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Glucocorticoids, insulin, inflammation
Link to obesity
Link to Type 2 diabetes
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Stress and Immunity
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T helper 1 to T helper 2 shift (Th1 to Th2)
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Decrease in cellular immunity
Increase in humoral immunity
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Central Stress Response
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Psychoneuroimmunology
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Interaction of factors
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Psychologic
Neurologic
Immunologic
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Stress-Induced Hormone
Alterations
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Female reproductive system
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Cortisol exerts inhibiting effects by suppressing
the release of luteinizing hormone, estradiol, and
progesterone
Stress suppresses hypothalamic gonadotropinreleasing hormone
Estrogen stimulates the HPA axis
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Stress-Induced Hormone
Alterations
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Endorphins and enkephalins
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Proteins found in the brain that have pain-relieving
capabilities
In a number of conditions, individuals not only
experience insensitivity to pain but also increased
feelings of excitement, positive well-being, and
euphoria
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Stress-Induced Hormone
Alterations
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Growth hormone (somatotropin)
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Produced by anterior pituitary, lymphocytes, and
mononuclear phagocytic cells
Affects protein, lipid, and carbohydrate metabolism
and counters the effects of insulin
Enhances immune function
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Stress-Induced Hormone
Alterations
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Prolactin
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Released from the anterior pituitary
Needed for lactation and breast development
Prolactin levels in the plasma increase as a result
of stressful stimuli
Oxytocin
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Produced by the hypothalamus
Produced during orgasm in both sexes
May promote reduced anxiety
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Stress-Induced Hormone
Alterations
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Testosterone
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Secreted by Leydig cells
Regulates male secondary sex characteristics and
libido
Testosterone levels decrease due to stressful
stimuli
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Stress, Personality,
Coping, and Illness
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A stressor for one person may not be a
stressor for another
Psychologic distress
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Coping
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General state of unpleasant arousal after life
events that manifests as physiologic, emotional,
cognitive, and behavior changes
Managing stressful demands and challenges that
are appraised as taxing or exceeding the
resources of the person
Link to coronary heart disease
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Stress, Personality, Coping, and
Illness
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Aging and Stress
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Stress-age syndrome
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Excitability changes in the limbic system and
hypothalamus
 Increased catecholamines, ADH, ACTH, and cortisol
 Decreased testosterone, thyroxine, and other
hormones
 Alterations of opioid peptides
 Immunodepression
 Alterations in lipoproteins
 Hypercoagulation of the blood
 Free radical damage of cells
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