TED TALKS Mary Roach Orgasm Chapter 10 Sexual Behavior OUTLINE Sexual Development Hormonal Effects on the Brain and Behavior Sexual Orientation Attraction Sex Determination Genetic sex determined at the time of fertilization Depends on whether the sperm that fertilizes the egg carries an X or Y sex chromosome XX Females XY Males Sex Determination Genetic sex determined at the time of fertilization Depends on whether the sperm that fertilizes the egg carries an X or Y sex chromosome XX Females XY Males Sex chromosome abnormalities Turner Syndrome XO Klinefelter syndrome XXY XYY Sex Determination Genetic sex determined at the time of fertilization Depends on whether the sperm that fertilizes the egg carries an X or Y sex chromosome XX Females XY Males Sex chromosome abnormalities Turner Syndrome XO Klinefelter syndrome XXY XYY Sex Determination Genetic sex determined at the time of fertilization Depends on whether the sperm that fertilizes the egg carries an X or Y sex chromosome XX Females XY Males Sex chromosome abnormalities Turner Syndrome XO Klinefelter syndrome XXY XYY Richard Speck Development of Gonads Gonads internal organs Females ovaries Males testes Have two functions 1 to produce eggs or sperm 2 to secrete hormones 6 weeks after conception gonads are undifferentiated Sex determining region of the Y chromosome or SRY gene Testis determining factor protein Gonads develop into testes Without SRY gonads become ovaries Differentiation of the Internal Organs All embryos have precursors to male and female internal organs Wolffian system develops into seminal vesicles vas deferens prostate M llerian sytem develops into uterus upper vagina and fallopian tubes Differentiation of the Internal Organs All embryos have precursors to male and female internal organs Wolffian system develops into seminal vesicles vas deferens prostate M llerian sytem develops into uterus upper vagina and fallopian tubes During 3rd month males testes secrete two hormones Testosterone a type of androgen masculinizing effect promotes development of Wolffian system Anti M llerian hormone defeminizing effect prevents Mullerian system from developing Differentiation of the Internal Organs All embryos have precursors to male and female internal organs Wolffian system develops into seminal vesicles vas deferens prostate M llerian sytem develops into uterus upper vagina and fallopian tubes During 3rd month males testes secrete two hormones Testosterone a type of androgen masculinizing effect promotes development of Wolffian system Anti M llerian hormone defeminizing effect prevents Mullerian system from developing Ovaries not active during fetal development M llerian system develops in the absence of hormones Testosterone in Males Androgen Insensitivity Syndrome AIS Abnormal androgen receptors disrupt normal development of the Wolffian system though testosterone and anti Mullerian hormone are released in normal manner Anti Mullerian hormone prevents development of female Mullerian system Development of Male Genitalia Females labia clitoris and outer vagina No hormonal activity required for development of female genitalia Males scrotum and testes 5 alpha dihydrotestosterone needed for development of male genitalia loss results in ambiguous external genitalia Converted from testosterone by the enzyme 5 alpha reductase 5 Alpha Reductase Deficiency At puberty unconverted testosterone produces male secondary sex characteristics Testosterone in Females Congenital Adrenal Hyperplasia CAH Adrenal glands release elevated levels of androgen Males few observable effects Females exposed to excessive androgen born with ambiguous external genitalia Mokgadi Caster Semenya Masculinized Female Athletes Hormonal Control of Development Hormones Sexual Development Organizational Hormonal effects on the differentiation and development of the sex organs brain and behavior in early development Permanent Sensitive Period Activational Effect of a hormone that occurs in the fully developed organism beginning at time of puberty Sexual Development Puberty Sexual maturation and the development of secondary sex characteristics Hypothalamus releases Gonadotropin releasing hormone GnRH Stimulates production of the follicle stimulating hormone FSH and luteinizing hormone LH from the pituitary Secretion of sex hormones from the gonads Secondary Sex Characteristics In males testosterone stimulates Muscular development Maturation of external genitalia Facial hair Enlargement of larynx deeper voice Hairline on the head baldness In females estradiol stimulates Breast growth Maturation of external genitalia and uterus Changes in deposition of body fat Menstrual cycle Female Age at Puberty Possible Causes Increasing rates of obesity Increased exposure to estrogen like compounds Menstrual Cycle Pituitary increases FSH Follicles develop ovum Estrogen stimulates LH release LH initiates ovulation Estradiol uterine wall Corpus luteum progesterone Hormonal decrease Menstruation Menstrual Cycle Pituitary increases FSH Follicles develop ovum Estrogen stimulates LH release LH initiates ovulation Estradiol uterine wall Corpus luteum progesterone Hormonal decrease Menstruation