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Chapter Ten

Chapter Ten. Sexual Behavior. CHAPTER 10 SEXUAL BEHAVIOR. Sexual Development. Sexual chromosome abnormalities Turner syndrome (XO) Normal female external genitalia but ovaries develop abnormally Normal intelligence, deficits in spatial relationships and memory Klinefelter syndrome (XXY)

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Chapter Ten

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  1. Chapter Ten Sexual Behavior

  2. CHAPTER 10SEXUAL BEHAVIOR

  3. Sexual Development • Sexual chromosome abnormalities • Turner syndrome (XO) • Normal female external genitalia but ovaries develop abnormally • Normal intelligence, deficits in spatial relationships and memory • Klinefelter syndrome (XXY) • Male with reduced fertility • Require hormone treatment at puberty to develop secondary sex characteristics and inhibit female characteristics • Normal intelligence but social awkwardness, delayed or reduced verbal skills • XYY • Subtle physical and behavioral correlates • Controversial association with antisocial behavior

  4. Figure 10.2 The Human Genome

  5. Figure 10.3 Turner Syndrome

  6. Sexual Development • Three Stages of Prenatal Development • The Development of Gonads • Sex determining region of Y chromosome expressed at 6 weeks gestation • Differentiation of Internal Organs • Wolffian system develops into seminal vesicles • Müllerian sytem develops into uterus, upper vagina, and fallopian tubes • Androgen insensitivity syndrome (AIS) • XY genotype, but female appearance and gender identity • disrupts normal development of the Wolffian system

  7. Figure 10.4 Differentiation of Gonads and External Genitals

  8. Figure 10.5 Androgen Insensitivity Syndrome

  9. Sexual Development • Three Stages of Prenatal Development • Development of External Genitalia • No hormonal activity required for development of female genitalia • 5-alpha-dihydrotestosterone needed for development of male genitalia • Congenital adrenal hyperplasia (CAH) – genetic females exposed prenatally to excess androgens, leads to masculinized genitalia

  10. Figure 10.6 Congenital Adrenal Hyperplasia (CAH) Masculinizes Genetic Female

  11. Sexual Development • Development at Puberty • Secondary sex characteristics • Gonadotropin-releasing hormone (GnRH) released by the hypothalamus • Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) have different effects in males and females • 5-alpha-reductase deficiency and maturation of external genitalia

  12. Figure 10.7 Female Age at Puberty

  13. Figure 10.8 5-Alpha-Reductase Deficiency Changes External Appearance at Puberty

  14. Hormones and Sexual Behavior • Regulation of Sex Hormones by the Hypothalamus and Pituitary Gland • Hypothalamus exerts control over release of sex hormones, through release of gonadotropin-releasing hormone (GnRH) • Melatonin inhibits release of GnRH • GnRH travels to anterior pituitary, which releases gonadotropins, LH, and FSH

  15. Figure 10.9 The Synthesis of Human Sex Hormones

  16. Figure 10.10 Hypothalamic Control of the Pituitary Gland

  17. Hormones and Sexual Behavior • The Menstrual Cycle and Female Fertility • Stable and predictable fluctuation in events controlled by LH and FSH • Ovulation about 2 weeks after the first day of the last menstruation • Correlations Between Mood, Menstruation, and Childbirth • Premenstrual syndrome • Premenstrual dysphoric disorder • Postpartum depression • Female Contraception • Oral contraceptives interfere with ovulation • Use of uninterrupted cycles of birth control to reduce frequency of menstruation is now standard medical practice

  18. Figure 10.11 The Human Menstrual Cycle

  19. Hormones and Sexual Behavior • Sex Hormones and Female Behavior • Sexual Interest in Human Females • Report slightly more interest around ovulation • Testosterone has greatest impact on women’s sexuality • Estrogens and Cognition • Best scores on spatial abilities tests when testosterone levels high and worst when estrogen levels are high • Best scores on verbal abilities and manual dexterity tests when estrogen levels are high

  20. Figure 10.12 Sex Influences Cognition

  21. Hormones and Sexual Behavior • Sex Hormones and Male Behavior • Androgens and Competition • Testosterone levels increase in anticipation of competition • Androgens and Sexual Interest • If in normal range, young men’s testosterone levels don’t predict sexual frequency • Married men have lower testosterone than single or recently divorced men • Androgens and Cognitive Behavior • Spatial abilities advantage may be related to testosterone • Male Contraceptives

  22. Hormones and Sexual Behavior • Anabolic Steroids • Synthetic versions of testosterone that build tissue • Build strength and muscle mass and improve recovery time following muscle damage • Significant side effects • Acne • Enlargement of clitoris or penis • Lower voice • Unusual hair loss or growth • Psychological disturbances • Larger breasts in males • High blood pressure and kidney disease

  23. Sex Differences in the Nervous System • Differences in the brains and nervous systems of males and females • Sexually dimorphic structures • Sexually dimorphic nucleus of the preoptic area • Interstitial nuclei of the anterior hypothalamus • Hypothalamus, thalamus, white matter • Spinal cords of mammals • Masculinization of the brain • Aromatization masculinizes brains of many animals • Testosterone is transformed into estradiol producing masculinization • Androgens play a greater role in the masculinization of the human brain

  24. Figure 10.14 The SDN-POA of the Hypothalamus is Sexually Dimorphic

  25. Sexual Orientation • Hormones, Sexual Behavior, and Sexual Orientation • Early exposure to androgens influences adult sexual behavior • Development of structures not involved in sexual behavior often reflect the influence of prenatal hormone exposure • Otoaccoustic emissions of lesbian and bisexual women • Comparative size of ring and index finger of gay men

  26. Sexual Orientation • Brain Structure and Sexual Orientation • LeVay – INAH-3 different between heterosexual and homosexual men? • Two to three times larger in heterosexual men than homosexual men • Interpretation of findings limited: • INAH-3 is too small to observe in living participants , studied autopsied brains • Homosexual men identified by diagnosis of AIDS • No one knows effect of AIDS on brain • Genes and Sexual Orientation • Unknown whether direct effect on orientation or indirect effect on prenatal androgen environment

  27. Figure 10.16 INAH-3 Size Correlates with Sexual Orientation

  28. Attraction • The Importance of Symmetry • Degree of similarity of one side of face or body to the other • The Beauty of Fertility and a Good Immune System • Preference for younger features on female • Preference for masculine men (testosterone-related facial features) for casual sexual encounter, less masculine men for long-term partner • Smell preference may indicate preference for an immune system different from our own

  29. Figure 10.17 Beautiful Female Faces Are Symmetrical and Youthful

  30. Romantic Love, Sexual Desire, and Parenting • Sexually dimorphic pituitary hormones • Oxytocin • Vasopressin • Gender-specific mating pressures • Men pressured to be promiscuous • Women pressured to be selective

  31. Figure 10.18 Brain Activity and Love

  32. Sexual Dysfunction and Treatment • Masters and Johnson estimated half of couples experienced some sexual problem • Many sexual dysfunctions are psychological in origin • Erectile dysfunction can be treated by enhancing activity of NO

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