STRESS

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STRESS

• April 12, 2006

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What is stress?

• Stress is one of those terms that we use to
  shield us from our ignorances. We would be better
  off without it. It survives because it is a
  convenient term to indicate the general topic
  under discussion. Attempts to provide such a
  vague concept with a precise physiological
  definition engender confusion and
  misunderstanding.
• - (Rushen, 1986)

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Stressor ? Stress Response

• Stressor any environmental stimulus that
  disrupts homeostasis and causes the stress
  response
• - Examples a tiger running toward you, a
  difficult and important exam, imagined events
• Stress response a suite of physiological and
  behavioral responses to a stressor that help to
  restore homeostasis

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Stressors

• 1. Crises/Catastrophes
• September 11, 2001
• Natural disasters
• War
• PTSD
• 2. Major Life Events
• 3. Microstressors
• Corridors vs. Suites

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The stress response fight-or-flight

• 2-step physiological stress response
• Sympathetic nervous system
• Quick response system, within seconds
• Release of epinephrine (adrenaline)

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The stress response fight-or-flight

• 2. HPA Axis (hypothalamic-pituitary-adrenal axis)
  
• Slower response system, minutes to hours
• Release of cortisol

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HPA Axis
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Consequences of the stress response

• Immediate effects
• Increased heart rate
• Increased oxygen intake
• Increased blood glucose levels
• Increased blood flow to muscles
• Increased alertness
• Inhibition of digestion, immune system
• Release of endorphins
• Dilation of pupils

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General Adaptation Syndrome

• Three stages
• Alarm stage
• - Emergency reaction (fight-or-flight)
• Resistance stage
• - Coping and fighting
• Exhaustion stage
• - Termination of stress response and onset of
  stress pathology (more accurate is prolonged
  activation of stress response)

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Gender Differences

• Men fight-or-flight
• Women tend-and-befriend

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Consequences of the stress response

• Is stress a good or bad thing?
• Short-term versus long-term consequences
• In general, stress is beneficial in the
  short-term or at mild levels, but can cause major
  long-term problems if stress is chronic

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Stress and health

• Chronic stress related to several health
  problems
• Heart disease
• Diabetes
• Ulcers
• Growth problems
• Compromised immune system

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Stress and the cardiovascular system

• Increased heart rate (blood moves faster and with
  more force)
• Constriction of major arteries (like a garden
  hose) ? increased blood pressure
• Blood delivered with great speed to muscles, but
  blood flow decreased to digestive system, kidneys
  and skin
• Kidneys conserve water

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Stress and cardiovascular system

• Short-term consequences
• Facilitates fight-or-flight response
• Adaptive for the survival of the species
• Long-term consequences
• If stress is chronic, individual can develop
  heart disease

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Stress and heart disease

• How does chronic stress ? heart disease?
• Blood vessels more to prone to damage due to
  increased blood pressure
• Damage to blood vessel inner lining
  causesplaques to build up (atherosclerosis)
  clogging of the arteries
• Once system is damaged, more vulnerable to acute
  stressors

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Stress response and metabolism

• Stress response ? more energy!
• Breaks down stored fat to use for energy
• Stops fat from being stored by decreasing insulin
  levels (hormone used in fat storage)
• Gluconeogenesis liver makes new glucose

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Stress and metabolism

• Short-term consequences
• Facilitates fight-or-flight response
• Adaptive for the survival of the species
• Long-term consequences
• If stress is chronic, individual may have
  problems with diabetes through increased blood
  sugar levels

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Stress response and digestive system

• Digestion is shut down
• Decreased saliva secretion
• Decreased enzyme secretion in stomach
• Blood flow to stomach and gut decreased

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Stress and digestion

• Short-term consequences
• Facilitates fight-or-flight response
• Adaptive for the survival of the species
• Long-term consequences
• If stress is chronic, individual may develop
  ulcers

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Chronic stress and ulcers

• Ulcer hole in the wall of an organ
• Chronic stress inhibits digestion and the
  secretion of stomach fluids
• Stomach lining becomes thinner/weaker
• When stress is over, acids released during normal
  digestion put strain on stomach lining

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Stress response and growth

• Cortisol blocks the secretion of growth hormone

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Stress response and growth

• Short-term consequences
• Facilitates fight-or-flight response
• Adaptive for the survival of the species
• Long-term consequences
• If stress is chronic, individual may develop
  stress dwarfism or simply decreased growth

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Stress response and the immune system

• 1st few minutes immune system is enhanced
• After about an hour of stress immune system
  returns to normal
• Chronic stress suppresses immune system
  functioning

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Stress response and immune system

• Short-term consequences
• Facilitates fight-or-flight response
• Adaptive for the survival of the species
• Long-term consequences
• If stress is chronic, individual is more prone to
  infection via immune system suppression

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Stress response and cancer

• Stress may lead to worse survival rates
• Fighting spirit leads to better survival rates

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Stress and health

• Chronic stress related to several health
  problems
• Heart disease
• Diabetes
• Ulcers
• Growth problems
• Immune system suppression
• Lower survival rates with cancer

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Stress and memory

• Does stress enhance or inhibit memory?
• Yerkes-Dodson Law of optimal arousal (1908)

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Stress and memory

• Short-term or mild stress response helps memory
• High levels of stress or chronic stress impair
  memory

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Mild stress and memory

• Subjects read one of two stories
• Control story unexciting story
• Emotional story boy gets hits by a car
• Subjects remember details of emotional story
  better than control story
• If you give drug to block sympathetic nervous
  system activation (propanolol), then no
  difference in memory

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Stress and memory

• Short-term, mild stress increases glucose
  delivery to brain
• High levels of stress or continued stress
  suppress glucose delivery to hippocampus
• Exposure to stress over several weeks can cause
  neuronal atrophy in the hippocampus

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Psychological stressors

• What event characteristics lead to smaller or
  larger stress responses?
• Perceptions of Control
• Self-efficacy
• Predictability
• Rats and shocks
• Optimism/Hope
• Self-serving bias
• Social support (if you have friends present)

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Personality and stress response

• What personality characteristics make individuals
  more or less vulnerable to stressors?
• Type A vs. Type B
• Neuroticism (high vs. low reactors)
• Challenge vs. threat
• Take-charge vs. passive
• Social affiliation
• Low vs. high SES