Sapolsky, Chapter 1: Why Don’t Zebras Get Ulcers?


I.     Awake at 2:30 am: You’re afraid of cancer, heart attack, ulcer—not leprosy, dysentery or liver flukes!

       A.       Different diseases than a century ago. (1900: pneumonia, tuberculosis, flu, childbirth)

       B.    Now we fall apart slowly.  Personality, stressors, social support influence our health.

II.    What do you find stressful? 

       A.       Humans: traffic, family relationships, money worries

       B.       Zebras and lions:  acute physical stressors: escaping predators and finding food

       C.       Chronic stressors: drought, famine, parasites

       D.       Psychological and social stressors  (stressors purely in our heads)

       E.    Our bodies’ stress response is great for dealing with acute physical stressors, but can be disastrous if

              activated all the time. 

III.        Physiological stress response

       A.       Homeostasis—there is a single optimum level for any measure in your body, and mechanisms to

maintain that level.

       B.       Allostasis—different circumstances demand different set points (sleep vs. bungee-jumping).

       C.       Stressor: anything that throws your body out of allostatic balance

1.       Injury, illness, heat, cold

2.       Anticipation of bad things, empathy with others in bad situation, financial worries, relationships

       D.    Stress response: body’s attempt to restore balance

IV. Hans Selye  (insightful and in some ways inept)

       A.       Ovarian extract—what did it do? 

               1.       Inject rats every day—rats got ulcers, enlarged adrenal glands, & shrunken immune tissues

               2.        So did control rats!

               3.       So did others subjected to cold, heat, forced exercise, or surgical procedures. 

       B.       Stress!

       C.        General Adaptation Syndrome

1.       Response to a wide array of stressors

2.     It can make you sick.

3.       Rapid mobilization of energy from storage sites and inhibition of further storage.

       a.       Glucose, amino acids, and fats pour out from liver, muscles, and fat cells.

       b.       Increase in heart rate, breathing, & blood pressure: rapidly transport oxygen and fuels.

       c.        Tornado—not a time to repaint the kitchen!

4.        Inhibit digestion, growth, reproduction, immunity, and pain perception.

5.       Memory and sensory detection improve.

V.    Walter Cannon

       A.    Fight or flight syndrome—positive response to stressors.

VI.  Selye: General Adaptation Syndrome—3 stages

       A.    Alarm stage: initial response.

       B.       Resistance stage: reattainment of allostatic balance

       C.       Exhaustion stage: resources are depleted (every day is an emergency)

               1.       Not just that the body “runs out of bullets.”

               2.       Spending so much on bullets depletes the rest of the system.

VII. The stress response itself can become damaging.  (penny-wise and dollar-foolish)

       A.    You will never store surplus energy, fatigue more rapidly, increase chance of a form of diabetes.

       B.       Chronically active cardiovascular system—increased blood pressure, heart disease, and strokes.

       C.    Stress dwarfism

       D.       Reproductive disorders (irregular menstrual cycles, decreased sperm counts, decreased libido)

       E.        Immune suppression

       F.    Some neurons in brain (hippocampus) are destroyed.

VII. 2 elephants on a seesaw: enormous energy wasted; hard to fix one thing without unbalancing the rest; hard to get off.

IX.   Problems with turning on the stress response

       A.       Addison’s disease—can’t secrete glucocorticoids: stressà decreased blood pressure and shock.

       B.    Shy-Drager syndrome—impaired secretion of epinephrine and norepinephrine: hard even to stand up.

X.    Problems with turning off the stress response: increased risk of getting diseases that make you sick.

       A. Individual differences, chance for intervention.