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Biological Basis of Gender

Biological Basis of Gender. PSYC101 Prof. Gregg Fall, 2007. Background: Sociobiology. Evolution suited men to struggle for power & run society; women to raise babies & nurture Men evolved to spread sperm widely; seek physically attractive & healthy partners

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Biological Basis of Gender

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  1. Biological Basis of Gender PSYC101 Prof. Gregg Fall, 2007

  2. Background: Sociobiology • Evolution suited men to struggle for power & run society; women to raise babies & nurture • Men evolved to spread sperm widely; seek physically attractive & healthy partners • Women evolved to nest; seek provider-protectors  Don’t mess with biology  Socialization should affirm biology

  3. Background:Cultural Determinism • Great cultural variation in gender roles shows plasticity of human nature • Our gender roles are cultural constructions: masculinity & femininity are performances • Socialization should be non-gender based, or encourage androgyny

  4. Psychology Research:“Sex Typing” of Behavior • Individual differences: • Prominent & rigid gender schemas vs. • “a-schematic” or “androgynous” • Historical change from 1940s: • From rigid toward flexible • or: from clear toward ambiguous

  5. Essentialists vs. Constructivists • Essentialism: • Gender differences are biological • Advocates of difference • Constructvism: • Gender differences are cultural • Advocates of sameness

  6. Difference vs. Sameness Advocates of difference: • Innate differences need parental & cultural support • Guide male / female complementarity Advocates of sameness: • Raise girls & boys same • Allow temperaments to be expressed

  7. Biological Bases of Gender • John Money: Sexual Signatures • John Pinel: Biopsychology • Colapinto: Joan / John Case?

  8. Components of Gender 1. Gender identity 2. Gender role behaviors 3. Sexual orientation

  9. Key Processes • Hormonal influences on bodies & brains • Neuro-endocrine axis: hypothalamus – pituitary – gonads • Critical stages: “gates” • Non-normal development

  10. Adam Principle • Default development of both XY and XX: female! • Something must be added – mostly androgens – to get a “male.”

  11. Non-“normal” development • Johns Hopkins Gender Clinic (J. Money) • Intersexes (hermaphrodites) • homosexuals • transvestites • transexuals • Genetics & hormones not in synch • genetic males + no androgens (insensitivity) • genetic females + androgens (adrenogenital)

  12. Three Cases • Joan / John case: raised as a girl • Chose to become boy • Biology or rearing? • 12 yr old XX adreno-genital raised as boy • Chose to become girl • 11 yr old XX adreno-genital raised as girl • Chose to become boy

  13. John Money’s Theory • Role behaviors  mainly nature • Sex orientation  mainly nature • Gender identity  mainly nurture • Identity “Gate” remains open until language, then closes

  14. Mystery Why does gender identity sometimes develop contrary to nature & rearing?

  15. Neuro-endocrinologyofGender Development

  16. “Adam Principle” • “Nature’s impulse is to create a female” • “Default” development – no androgens  female body and brain (estrogens required at puberty)

  17. Brain Basics

  18. Neuron Basics About 100 billion of ’em About 100 trillion connections

  19. Neuron

  20. Axon Button

  21. Resting Potential-70 mvsodium, chlorine & potassium move across cell membrane, through ion channels

  22. “Firing” of Neuron Neurotransmitter binds to protein on dendrite, and either… Fast: opens ion channel (Na+ ions flow in), triggering shift in potential or… Slow: triggers series of reactions that may open ion channels -- and also change cell metabolism and/or gene expression.

  23. Potassium channels open restores - charge Sodium channels open charge becomes + “Firing” of Neuron

  24. “Firing” of Neuron

  25. Neuron“Firing”:neuro-transmitterrelease

  26. Psychoactive Drugs • Chlorpromazine: anti-schizophrenic, blocks dopamine receptors • Valium: blocks one type of GABA receptor, causing increased GABA binding at others • Prozac: anti-depressant, blocks re-uptake of serotonin (prolonging its action in synapse)

  27. Biology of Gender Development • Controlled by neuro-hormonal feedback system • Hypothalamus -- pituitary gland – testes • Critical stages in development • Non-normal development

  28. Hormones • Androgen:any substance that promotes development or function of male reproductive system (mainly synthesized by testes, but small amounts synthesized by adrenal gland and by ovaries) • Estrogen & progestins: substances that stimulate the maturation or function of female reproductive system (mainly synthesized by ovaries, but small amounts synthesized by adrenal gland and testes)

  29. Hormones • Everyone has both androgens & estrogens • Males: mainly androgens • Females: mainly estrogens • Estrogen may play imp’t role in male development • Androgen may play imp’t role in female development

  30. Anatomy Hypothalamus Pituitary Gonad axis

  31. Gonads • Testes in men • Ovaries in women

  32. Primary glands

  33. Pituitary Gland • “Master gland” • Produces hormones that regulate synthesis and release of other hormones from thyroid, adrenal gland, testes & ovaries, etc. • Gonadotropins: cause testes or ovaries to produce and release androgens and estrogens

  34. Pituitary Gland

  35. Pituitary • Cyclical release of gonadotropins in females • Menstrual cycle • Sexual activity in animals • Steady release of gonadotropins in males

  36. Pituitary • Sexually dimorphic? • 1952 study: cycling female rat pituitary transplanted into male stops cycling; steady-state male rat pituitary transplanted into female begins cycling • Pituitary not sexually dimorphic

  37. Origin of Sexual Dimorphism? • Animals that breed seasonally influenced by light • Birds taken across equator reverse seasons of breeding • Whatever controls pituitary influenced by optical information  Hypothalamus?

  38. Hypothalamus • Composed of various nuclei, which produce different releasing and inhibiting hormones • Regulate 4 F’s: feeding, fighting, fleeing & mating • Also: body temperature, thirst, sleep, stress response

  39. Hypothalamus

  40. Hypothalamus

  41. Hypothalamus • Electrical stimulation and lesions in hypothalamus affect pituitary’s production & release of hormones • 1960s: thyrotropin-releasing hormone identified in pig hypothalamus – influences pituitary function • Thyrotropin-releasing hormone produced in hypothalamus, transported to pituitary

  42. Hypothalamus Might the hypothalamus be sexually di-morphic?

  43. Hypothalamus • 1970s: gonadotropin releasing hormone identified in hypothalamus • Causes pituitary to release gonadotropins • Evidence for sexual dimorphism

  44. Hypothalamus – • pituitary • connections • Neurohormonal • nerve cells

  45. Hypothalamus – Pituitary2. capillary portal system

  46. Hypothalamus - Pituitary • 9 neurohormones secreted or transported from hypothalamus to pituitary by nerve cells and capillary system • Control release of sexual hormones, growth hormones (from thyroid), endorphins, and others.

  47. Hypothalamus – PituitaryGonadotrohpins • FSH: Follicle-stimulating hormone sperm production in men mature germ cells in women • LH: Lutinizing hormone release of androgens from testes release of estrogens from ovaries

  48. Feedback System • Hypothalamus – pituitary – gonads • Hormones released in pulses relatively large doses over minutes several times a day • Hormone levels fluctuate during day • “Gonadostat” adjusting hormones in hyhpothalamus

  49. Feedback circuit: Hypothalamus Pituitary Gonads

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