PSY 241 Lecture 21

  1. What is stress?
    Any circumstance that upsets homeostatic balance, mainly to increase energy consumption

    • 1. Provokes elevated arousal
    • 2. Stressful stimuli is aversive (hurtful)
    • 3. Element of control ameliorates (betters) effects of stress
  2. Stress Response
    • Combination of physiological and behavioral responses to reestablish homeostasis
    • Nonspecific - many different stressors elicit similar stress response
  3. 3 Stages of Stress Response
    • Alarm Reaction
    • Adaption Stage
    • Exhaustion Stage
  4. Alarm Reaction
    "Fight or Flight" prepares body for action

    • 2 endocrine systems:
    • Epinephrine & Hypothalamic Pituitary Adrenal axis (HPA) response
  5. Adaption Stage
    Reestablishes physiological balance
  6. Exhaustion Stage
    Prolonged or frequent stress causes susceptibility
  7. Stress Response: Epinephrine
    • During Alarm Reaction, hypothalamus activates Sympathetic Nervous System
    • Adrenal Medulla releases epinephrine (adrenaline) and norepinephrine (noradrenaline)

    • Boost heart rate, breathing, increase glucose levels
    • Epinephrine directs blood flow to muscles; away from digestive system
  8. Stress Response HPA
    • Hypothalams activates hypothalamic-pituitary-adrenal axis (HPA axis) to release corticotropin-releasing hormone (CRH)
    • CRH activates anterior pituitary gland to release adrenocorticotropin hormone (ACTH)
    • ACTH enters blood stream and activates adrenal cortex to release glucocoticoids (Cortisine in rodents; cortisol in humans)
  9. Vasopressin
    • Increases blood pressure
    • Makes delivery of energy to muscles more efficient

    Ex: Helps zebra outrun lion
  10. Prolactin
    Suppress reproduction temporarily
  11. Endorphins and enkephalins
    Provide relief from pain

    Ex: If animal is bitten, it will not feel pain and continue running
  12. Adaptive Effects of the Stress Response
    • Increase immediate availability of energy
    • Increased oxtgen intake
    • Decreased bloodd flow to area not necessary for movement
    • Inhibition of processes not related to immediate survival (digestion, growth, immune function and reproduction)
    • Decreased pain perception
    • Enhancement of sensory function and memory
  13. Pathological Effects of Stress
    • Stress response is meant to: 
    • allow individuals to cope with immediate stress
    • deactivate immediately after stressor subsides (e.g. zebra running away from lion)

    • Prolonged stress
    • jeopardize health and survival
    • contribute to disease onset and progression
  14. Prenatal Stress
    • Reduced birth weights
    • Experience developmental delays
    • Display attentional deficits
    • Increase incidence of schizophrenia as adults

    • Exposure to glucocorticoids
    • Low birth weight
    • hypertension
    • ischemic heart diseas
  15. Neonatal Stress
    • Stress immunization
    • Brief separation of Rat pups evokes stress response
    • Maternal tactile and feeding cues suppress elevated concentrations of corticoterone
    • Epigenic regulation
  16. Stress immunization
    Mild stress early in life makes individual better able to handle stress later in life
  17. Epigenic Regulation
    Change in gene expression to environmental effects
  18. Stress and Male Reproductive Dysfunction
    • Stress inhibits testosterone production resulting in reduced sexual motivation and performance
    • Glucocorticoid have been shown to inhibit testosterone secretion and suppress spermatogenesis

    • Epinephrine interferes with reproductive function
    • SNS and PSNS act together to generate penile erection
    • Stress can cause erectile dysfunction by preventing parasympathetic activity in the penis
    • Stress can cause premature ejaculation by activating rapid activation of sympathetic input to penis
  19. Stress and Female Reproductive Dysfunction
    • Stress can result in cessation of menstrual cycles and interrupt pregnancy or lactation
    • Fasting increases blood glucocorticoid concentrations and is considered a stressor and causes problems with fertility
    • Suppression of reproductive function to balance energy is controlled by mechanisms that overlap with those that control food intake
  20. Stress and Social Behavior
    • Socially dominant animals:
    • low levels of glucocorticoids

    • Lower ranked animals:
    • high levels of glucocorticoids
    • harassed by higher ranked animals
    • died at young age
    • enlarged adrenal glands
    • gastric ulcers
    • atrophy in CA1 region of hippocampus
  21. The rewarding properties of cocaine mediated by ____________.
    The rewarding properties of cocaine mediated by dopamine.
  22. Cocaine increases extracellular in ____________.
    Cocaine increases extracellular in Nucleus Accumbens (NAcc).
  23. What do glucocorticoids do?
    • Increase dopamine release
    • Decrease dopamine metabolism
    • Modify binding of dopamine to postsynaptic receptors
  24. Controlling the situation
    Rats able to press lever to reduce shocks showed less glucocorticoid levels than rat that could not reduce shocks
  25. Predictability
    Rats given warning signals prior to shock have lower glucocorticoid levels than rats given no signals
  26. Displacement behavior
    • Enaging in a hobby
    • Moderate exercise
Card Set
PSY 241 Lecture 21
arturo zavala psychobiology stress