1. Chapter Ten
Sexual Behavior

2. CHAPTER 10 SEXUAL BEHAVIOR

3. Sexual chromosome abnormalities
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. Three Stages of Prenatal Development
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. Three Stages of Prenatal Development
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. Development at Puberty
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. 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. 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. The Importance of Symmetry
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