STRESS
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STRESS. What is stress?. Physical stressors Illness Surgery Cold Heat Hunger Competitive athletics Fighting Fleeing . Psychological stressors Any new experience (potentially) Anticipation of something previously experienced as unpleasant

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STRESS

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STRESS


What is stress?


  • Physical stressors

  • Illness

  • Surgery

  • Cold

  • Heat

  • Hunger

  • Competitive athletics

  • Fighting

  • Fleeing


  • Psychological stressors

  • Any new experience (potentially)

  • Anticipation of something previously experienced as unpleasant

  • Situations in which rules are changed or previous behavior no

  • longer effective

  • Fighting or observing others fighting

  • Crowding

  • Acute situations: airplane flight, exam, new situations,

  • competitive athletics, workdays vs weekends

  • Chronic life situations (divorce, death in the family, illness in the family)

  • Note: Context matters


Fight or run away?

image from: naturescrusaders.wordpress.com


Dominance versus submission

image at: www.flickr.com/photos/chrisgcom/2245593489


Stress and performance in competitive sports

image at: www.transfersnowboard.com/features/7343011


  • Physiological responses to stress

  • Increased rate and contractility of the heart

  • Alterations in blood flow distribution

  • Increased gluconeogenesis (synthesis of glucose)

  • Mobilization of amino acids (used to synthesize glucose)

  • Increased muscle contractility and decreased fatiguability

  • Increased learning and memory


Stress

Hypothalamus

Sympathetic nervous system CRH

Epinephrine/norepinephrine ACTH

cortisol


Location of adrenal glands

image at: www.aurorahealthcare.org/yourhealth/healthgat


  • Effects of epinephrine

  • Increased heart rate and contractility

  • Effects on arteriolar smooth muscle

  • Widens pupil and flattens lens (far vision)

  • Decreases GI motility

  • Promotes glucose synthesis

  • Increases central nervous system activity

  • Decreases fatigue of skeletal muscle


Context matters


Psychological stress: exams

image at: www.engineering.unl.edu/.../Summer07/05.shtml


The Limbic SystemSite where emotional stimuli, is integrated, and behavioral and physiologic responses are initiated

http://cwx.prenhall.com/bookbind/pubbooks/morris5/medialib/images/F02_09.jpg


Diurnal variations in plasma cortisol

http://junior.britannica.com/eb/art/print?id=1588&articleTypeId=1


growth of

adrenal cortex


  • Hans Selye: General Adaptation Response

  • Chronic exposure of rats to noxious stimuli (cold, restraint, surgery):

    • Enlarged adrenal glands

    • Atrophy of lymphoid structures

    • Gastric ulcers and bleeding

Note: similar responses were observed with many diverse

stimuli, including psychological stress


  • Effects of cortisol

  • Increased plasma glucose

  • Increased contractility of skeletal and cardiac muscle

  • Inhibits bone growth

  • Inhibits protein synthesis, accelerates protein degradation

  • -inhibits collagen formation, easy bruising

  • Required for maintenance of blood pressure

  • CNS effects on learning and other responses

  • Increases gastric secretions

  • Modulates inflammatory and immune responses


  • Hans Selye: General Adaptation Response

  • Chronic exposure of rats to noxious stimuli (cold, restraint, surgery):

    • Enlarged adrenal glands

    • Atrophy of lymphoid structures

    • Gastric ulcers and bleeding

Note: similar responses were observed with many diverse

stimuli, including psychological stress


  • Some conditions in which corticosteroids are useful

  • Allergic disorders (asthma, atopic dermatitis)

  • Gastrointestinal disorders (Crohn’s disease, ulcerative colitis)

  • Arthritis

  • Skin irritations


Typical course of prednisone treatment (oral corticosteroid)

Why is it necessary to “taper off”

Day 6

Day 5

Day 4

Day 3

Day 2

Day 1

image at: www.healthcentral.com/asthma/h/how-long-does-...


growth of

adrenal cortex


Differences between physical and psychological stressors


  • Effects of chronic stress

  • GI system: worsens ulcers

  • Immune system: immunosuppression (increased autoimmune

  • diseases, increased infections)

  • Endocrine system: type II diabetes

  • Growth: retards growth in children, induces weight and bone

  • loss in adults

  • Cardiovascular system:

    • Hypertension

    • Atherosclerosis

    • Sudden cardiac death


Psychological stress increases susceptibility to the common cold

From: Cohen SC et al, New England Journal of Medicine 325:606-612, 1991


  • Effects of chronic stress

  • GI system: worsens ulcers

  • Immune system: immunosuppression (increased autoimmune

  • diseases, increased infections)

  • Endocrine system: type II diabetes

  • Growth: retards growth in children, induces weight and bone

  • loss in adults

  • Cardiovascular system:

    • Hypertension

    • Atherosclerosis

    • Sudden cardiac death


Stress promotes type II diabetes

From: Mooy J et al, Diabetes Care, 23:1443, 2005


  • Effects of chronic stress

  • GI system: worsens ulcers

  • Immune system: immunosuppression (increased autoimmune

  • diseases, increased infections)

  • Endocrine system: type II diabetes

  • Growth: retards growth in children, induces weight and bone

  • loss in adults

  • Cardiovascular system:

    • Hypertension

    • Atherosclerosis

    • Sudden cardiac death


Daily numbers of Deaths Listed by the Department of Coroner of Los Angeles County from January 10 through 23, 1991, 1992, 1993, and 1994

Emotional stress can trigger cardiac events in at risk individuals: Earthquake occurred early in the morning of Jan 17, 1994 in Los Angeles

Leor, J. et al. N Engl J Med 1996;334:413-419


US National Mortality Data

from 1973 to 1998

From: BMJ 2001;323:1443-1446

The number “4” and the word

“death” are pronounced similarly

in Chinese and Japanese and “4”

is considered to be unlucky


Weighing risk versus reward while experiencing a stressor

Image at: www.canada.com/.../1186256/story.html


Balloon analogue risk task

the image at: psycnet.apa.org/index.cfm?fa=fulltext.printAr...


Lighthall N, et al PLoS One, Volume 4, issue 7, 2009


Males

Stress→  testosterone

Females

Stress→  oxytocin


Stress

  • heart rate

  • cortisol

Control treatment

Block oxytocin receptors in the brain

Stress

  •  heart rate

  •   cortisol

Conclusion: Oxytocin reduces the cardiovascular responses to stress

Wysol, A et al, J Physiol Pharmacol, 59(Suppl 5):117-132, 2008


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