Hormones and Stress

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  • M Women and men differ not only in physical attributes and reproductive function but also in the way in which they solve intellectual problems. It is cool to say that men and women are equally potential regardless of the type of the tasks, but it is not true. Let’s see how different they are.
  • The authors suggest that the magnitude of stress responses to emotional arousing events affect the storage of emotional memories. Norepinephrine and Cort released in response to emotional provoking stimuli modulate the output of the amygdala There are a lot of data to support this theory: The amygdala has a very high density of adrenoceptor Levels of Norepinephrine in the amygdala go up as footshock intensity goes up Drugs that increase Cort or Norepinephrine in the hippocampus and amygdala enhance memory. Drugs that block Norepinephrine in the amygdala ( muscimol) impair memory So McGaugh feels that the sympathetic nervous system is responsible for memory consolation of fearful memories.
  • Hormones and Stress

    1. 1. Hormones and Stress
    2. 2. Hormones Classifying Hormones by Structure Steroid Hormones  Fat-soluble chemical messenger synthesized from cholesterol  Examples: gonadal (sex) hormones, thyroid Peptide Hormones  Chemical messenger synthesized by cellular DNA that acts to affect the target cell’s physiology  Examples: insulin, growth hormone
    3. 3. Hormones Classifying Hormones by Function Hormones that maintain homeostasis  State of internal metabolic balance and regulation of physiological systems in an organism Gonadal (sex) hormones  Control reproductive functions and sexual appearance and identity Stress hormones (e.g., glucocorticoids)  Secreted in times of stress (fight or flight); important in protein and carbohydrate metabolism
    4. 4. Hormones Hierarchical Control Four Levels Hypothalamus Pituitary Gland Target Endocrine Glands Target Organs and Tissues
    5. 5. Hormones Hierarchical Control Hormones affect almost every neuron in the brain Hormones Neurons Genes Proteins
    6. 6. Hormones Homeostatic Hormones Homeostasis of intracellular and extracellular environments are essential to life Diabetus mellitus  Caused by a failure of the pancreas to secrete enough (or any) insulin  Hyperglycemia: High blood-glucose levels; cells are not using glucose and therefore are not able to function properly  Hypoglycemia: Low blood-glucose levels
    7. 7. Hormones Gonadal Hormones Sex hormones begin to affect us before we are born and continue to affect us throughout our life Organizational Hypothesis  Proposal that actions of hormones during development alter tissue differentiation  Example: Testosterone masculinizes the brain
    8. 8. Biological effects of sex hormones organizational effects: permanent structural changes elicited by sex hormones during critical period of embryonic / fetal life activational effects: reversible effects of sex hormones (e.g. estrus)
    9. 9. Steroid Hormones Act Through Gene Expression hormone Hormone receptor hormone Hormone receptor Gene products Synthesizes transcription factor mRNA
    10. 10. Hormones Gonadal Hormones Sex hormones contribute to brain differences:  Male brain is slightly larger than female after correcting for body size  Right hemisphere is larger than the left hemisphere in men  Female brains have higher rates of cerebral blood flow and glucose utilization  Parts of the corpus callosum are larger in women  Language areas of the brain are somewhat larger in women
    11. 11. Copyright © 2004 Allyn and Bacon
    12. 12. Neural Control of Sexual Behavior  Brain Mechanisms  Sexually dimorphic nucleus (SDN):  A nucleus in the preoptic area that is much larger in males than in females; first observed in rats; plays a role in male sexual behavior.  Periaqueductal gray matter (PAG):  The region of the midbrain that surrounds the cerebral aqueduct; plays an essential role in various species-typical behaviors, including female sexual behavior.
    13. 13. Copyright © 2004 Allyn and Bacon
    14. 14. Hormones Gonadal Hormones Sex hormones contribute to differences in cognitive performance:  Men tend to excel on spatial tasks whereas women tend to excel on verbal tasks  Performance of women differs during the course of menstruation  Low female sex hormones: Better spatial performance  High female sex hormones: Better verbal performance  Differences between pre- and postmenopause, and during various stages of pregnancy
    15. 15. Gender differences in brain structure & function  less lateralization of cerebral hemispheres in women (in men, left more concerned with verbal skills, right with visual-spatial function)  larger fiber tracts in female corpus callosum  “sexually dimorphic nucleus” present in hypothalamus (also: INAH 3) Males > FemalesFemales > Males
    16. 16. Difference in Solving Intellectual Problems • Boys and girls different way of developing brains. • Difference between boys and girls lies in patterns of ability rather than in overall level of intelligence (IQ).
    17. 17. * ** Townsend et al. 2004
    18. 18. Hormonal Control of Sexual Behavior of Laboratory Animals  Males  Oxytocin:  A hormone secreted by the posterior pituitary gland; causes contraction of the smooth muscle of the milk ducts, the uterus, and the male ejaculatory system.  Prolactin:  A hormone of the anterior pituitary gland, necessary for production of milk; has an inhibitory effect on male sexual behavior.
    19. 19. Copyright © 2004 Allyn and Bacon
    20. 20.  Hormonal Control of Sexual Behavior  Hormonal Control of Female Reproductive Cycles  Corpus luteum:  A cluster of cells that develops from the ovarian follicle after ovulation; secretes estradiol and progesterone.  Progesterone:  A steroid hormone produced by the ovary that maintains the endometrial lining of the uterus during the later part of the menstrual cycle and during pregnancy.
    21. 21. Organizational Effects of Androgens on Behavior: Masculinization and Defeminization  Effects of Pheromones  Pheromone:  A chemical released by one animal that affects the behavior or physiology of another animal; usually smelled or tasted.  Lee-Boot effect:  The slowing and eventual cessation of estrous cycles in groups of female animals that are housed together; caused by a pheromone in the animals urine.
    22. 22. Organizational Effects of Androgens on Behavior: Masculinization and Defeminization  Effects of Pheromones  Whitten effect:  The synchronization of the menstrual or estrous cycle of a group of females, which occurs only in the presence of a pheromone in a male’s urine.  Vandenbergh effect:  The earlier onset of puberty seen in female animals that are housed with males; caused by a pheromone in the male’s urine.
    23. 23. Hormones Stress Hormones Stressor  A stimulus that challenges the body’s homeostasis and triggers arousal Stress Response  The physiological and behavioral arousal and any attempt to reduce the stress  Two sequences  Fast-acting: Activation of sympathetic nervous system; “fight-or-flight” response  Slow-acting: Activation of parasympathetic nervous system; “rest-and-digest” response
    24. 24. Stress Disorders  Stress:  A general, imprecise term that can refer either to a stress response or to a stressor (stressful situation).  Stressor:  A stimulus (or situation) that produces a stress response.
    25. 25. Stress Disorders  Fight-or-flight response:  A species-typical response preparatory to fighting or fleeing; thought to be responsible for some of the deleterious effects of stressful situations on health.
    26. 26. Stress Disorders  Physiology of Stress  Glucocorticoid:  One of a group of hormones of the adrenal cortex that are important in protein and carbohydrate metabolism, secreted especially in times of stress.
    27. 27. Stress Disorders  Physiology of Stress  Corticotropin-releasing hormone (CRH):  A hypothalamic hormone that stimulates the anterior pituitary gland to secrete ACTH.  Adrenocorticotropic hormone (ACTH):  A hormone released by the anterior pituitary gland in response to CRH; stimulates the adrenal cortex to produce glucocorticoids.
    28. 28. Copyright © 2004 Allyn and Bacon
    29. 29. CRF and the Hypothalamus
    30. 30. PVN CRH Anterior Pituitary Glucocorticiods Adrenal CTX ACTH Target Organs
    31. 31. PVN CRH Anterior Pituitary Glucocorticiods Adrenal CTX ACTH Systemic effects: Fight or flight responses ↑BP ↑HR ↑O2 ↑Blood sugar LH Lateral horn Adrenal medulla Epi/NE
    32. 32. Functions BASAL LEVELS (Proactive) Circadian rhythm Mood Sleep Sensory perception Learning ELAVATED LEVELS (Reactive) Stress Reponses
    33. 33. CRH Feedback Rapid pvn Intermediate Cort (pvn/pituitary) Delayed Higher brain areas
    34. 34. PVN CRH Anterior Pituitary Glucocorticiod Adrenal CTX ACTH Hippocampus CRH CORT SeptumBNST Somatostatin BRAKE INHIBIT CRH Release Receptors -
    35. 35. PVN CRH Anterior Pituitary Glucocorticiods Adrenal CTX ACTH
    36. 36. CRF Receptor types
    37. 37. CRF Receptor types TYPE 1 (MR)  High affinity  Binds CORT and aldosterone  Stabilizes excitability  Stress Sensitivity TYPE 2 (GR)  Low affinity  Binds only CORT  Suppresses excitability  Recovery from stress
    38. 38. CRF receptor distribution
    39. 39. CRF cellular effects
    40. 40. CRF cellular effects
    41. 41. Chronic Stress Both Receptors down regulated Enlarged Adrenal gland Reduced neuronal activity Reduced neurogenesis Reduced metabolic activity Inhibited Glucose uptake
    42. 42. Chronic Stress and Hypothalamic integration
    43. 43. Stress and Depression Hypothesis Depression is predicated by deregulation of the HPA axis
    44. 44. PVN CRH Anterior Pituitary Glucocorticiod Adrenal CTX ACTH Hippocampus CRH CORT SeptumBNST Somatostatin BRAKE INHIBIT CRH Release Receptors -
    45. 45. Stress and Depression Hypothesis
    46. 46. Stress and Depression Hypothesis  After depression treatment Cort secretion returns to normal  Cushing Disease- always depressed  High CORT and CRH disregulates 5ht, causing Learned Helplessness  Symptomology matches CRH functions  Dexamethasone Test
    47. 47. Stress and Depression Hypothesis CRH/Depression leads to behavioral symptoms and inability to learn new coping strategies Therapy or SSRI Drug treatment allows for the brake to become functional again Prozac—BDNF ---ROS-neurogenesis Therapeutic lag = Mrna CORT rebalancing
    48. 48. PVN CRH Anterior Pituitary Glucocorticiod Adrenal CTX ACTH Hippocampus AMYGDALA NE CORT Receptors Memory Storage NE
    49. 49. Stress Disorders  Psychoneuroimmunology  Psychoneuroimmunology:  The branch of neuroscience involved with interactions between environmental stimuli, the nervous system, and the immune system.  Antigen:  A protein present on a microorganism that permits the immune system to recognize the microorganism as an invader.
    50. 50. Stress Disorders  Psychoneuroimmunology  Antibody:  A protein produced by a cell of the immune system that recognizes antigens present on invading microorganisms.  B-lymphocyte:  A white blood cell that originates in the bone marrow; part of the immune system.
    51. 51. Stress Disorders  Psychoneuroimmunology  Immunoglobulin:  An antibody released by B-lymphocytes that bind with antigens and help to destroy invading microorganisms.  T-lymphocytes:  A white blood cell that originates in the thymus gland; part of the immune system.
    52. 52. Stress Disorders  Psychoneuroimmunology  Cytokine:  A category of chemicals released by certain white blood cells when they detect the presence of an invading microorganism; causes other white blood cells to proliferate and mount an attack against the invader.
    53. 53. Hormones Ending a Stress Response Normally, stress responses are brief Stress responses are turned on and off in the brain Sapolsky (2003)  Hippocampus is involved in turning off the stress response  Too much cortisol will damage neurons in the hippocampus  Vicious cycle involving prolonged stress, cortisol levels, and hippocampal functioning
    54. 54. Hormones Ending a Stress Response Posttraumatic Stress Disorder  Syndrome characterized by physiological arousal symptoms related to recurring memories and dreams related to a traumatic event – for months or years after the event

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