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Janelle Leboutillier

PSYB64: Introduction to Physiological Psychology Lecture 7: Sexual Behaviour (Chapter 10) Overview 1. Sexual Development 2. Hormones & Sexual Behaviour 3. Sex Differences in Nervous System 4. Sexual Orientation 5. Attraction 6. Sexual Dysfunctions The Human Genome (Figure 10.2)  Twenty-three pairs of chromosomes are found in the nuclei of all human body cells except red blood cells (which have no DNA) and sperm and egg cells (which contain only one copy from each pair of chromosomes). Differentiation of Gonads and External Genitals (Figure 10.4)  During the first six weeks after conception, the primordial gonads are undifferentiated.  Subsequently, testis-determining factor encoded by the SRY gene on the Y chromosome will begin to turn the undifferentiated gonads into testes in males  The testes begin to release androgens, causing the external genitalia to develop into a penis and scrotum.  Alternate genes guide the development of female gonads into ovaries.  In the absence of androgens, the female external genitalia develop into clitoris, labia, and vagina. Sexual Development  Sexual chromosome abnormalities o Turner syndrome (XO)  Approx. 2 in 2500 live births o Klinefelter syndrome (XXY)  Approx. 1.79 out of 1000 male births o XYY  Approx. 1 out of 1000 male births Sexual Development  Sexual chromosome abnormalities  Turner syndrome (XO) o Normal female external genitalia but ovaries develop abnormally o Normal intelligence, deficits in spatial relationships and memory  Klinefelter syndrome (XXY) o Male with reduced fertility o Require hormone treatment at puberty to develop secondary sex characteristics and inhibit female characteristics o Normal intelligence but social awkwardness, delayed or reduced verbal skills  XYY o Subtle physical and behavioral correlates o Controversial association with antisocial behavior VIDEO LINK: Gender Development: Social Influences = Do social influences play a role? YES! Hormones and Sexual Behavior  YOU ARE NOT RESPONSIBLE FOR PAGES 294 to 300 EXCEPT TO THE EXTENT WE COVER THIS CONTENT IN LECTURE Female Age at Puberty  1820s = age 15 years; 2000 = age 12.5 years  Researchers are suggesting that obesity may play a role, food additives, etc. for earlier periods The Synthesis of Human Sex Hormones (Figure 10.9)  Aromatization is the only step necessary to turn testosterone into estradiol  Sex hormones are steroids derived from cholesterol  There are several chemical reactions, indicated by the broken arrows, that take place in the development of progesterone from cholesterol and testosterone from progesterone  However, there is only one step, aromatization, that is necessary to turn testosterone into estradiol. Hypothalamic Control of the Pituitary Gland (Figure 10.10)  By secreting GnRH, the hypothalamus stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by the anterior pituitary gland  In males, LH signals the testes to produce testosterone  Both testosterone and FSH are necessary for producing mature sperm  In females, LH and FSH control the menstrual cycle Sex and Senses  3YmQ1d0&feature=channel_page  In fruit flies, male and females have a genetic predisposition to sense the world in different ways  Sense organs that look the same do not necessarily behave the same  Need to follow-up in humans Typical Hormone Levels  Testosterone o Males 300-900 nanograms/dl of blood o Women less than 100 nanograms/dl blood  Estrogen o Males less than 50 picograms/ml blood o Females 100-400 picograms/ml blood Hormones and Sexual Behaviour  Sex Hormones and Female Behavior o Sexual Interest in Human Females  Report slightly more interest around ovulation  Testosterone has greatest impact on women’s sexuality o 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  HRT influences cognitive function Sex Influences Cognition (Figure 10.12)  Women generally have a slight advantage in verbal tasks such as naming objects that have the same color and listing words that begin with a particular letter  Men have a slight advantage in spatial tasks, such as this figure rotation task  When asked whether the two shapes are the same, males respond somewhat faster than females Hormones and Sexual Behavior  Sex Hormones and Male Behavior o Androgens and Competition  Testosterone levels increase in anticipation of competition o 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 o Androgens and Cognitive Behavior  Spatial abilities advantage may be related to testosterone Male Monkeys’ Preference of Toys   Research by Kim Wallen, a psychologist shows that toy preference may be influenced by biology Feminizing Effect of Pollution  Scientific communication!  Recent claims have been made regarding possible feminizing effects of environmental toxins DDT and PCB  Concerns based on converging support from independent and reliable source  Polluted Lake Gators o Lower reproduction rates o Greater expression of female traits in both genders o Can be explained by greater ratios of E.T in both genders o Others have shown: PCB's that pollute lake can act on Estrogen o Unclear: If feminizing effect is direct 1 of toxin or indirect effect mediate by an increase in E itself or other indirect effect? Effect of Sex Hormones on Neutral Circuitry  Estradiol can stimulate an increase of the number of synaptic contact  These changes in neuronal circuitry may underlie difference in learning and memory over the estrous cycle Hormones and Sexual Behavior:  Anabolic Steroids o Synthetic versions of testosterone that build tissue o Build strength and muscle mass and improve recovery time following muscle damage o 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 VIDEO LINK: Effects of Hormones and the Environment on the Brain   Nature of nurture debate Sex Differences in the Nervous System  Differences in the brains and nervous systems of males and females o Sexually dimorphic structures o Masculinization of the brain EXTREME SEXUAL DIMORPHISM IN THE BLANKET OCTOPUS. THE FEMALE IS 40,000 TIMES LARGER THAN THE MALE. HE COULD FIT IN HER EYE. Sex Differences in the Nervous System  Sexually dimorphic structures o Sexually dimorphic nucleus of the preoptic area (hunger, thirst, regulation) o Interstitial nuclei of the anterior hypothalamus o Hypothalamus, thalamus, white matter o Spinal cords of mammals The SDN-POA of the Hypothalamus is Sexually Dimorphic (Figure 10.14)  The SDN-POA, which is believed to be involved with sexual behavior, is much larger in male rats than in female rats  This difference probably results from the male rats’ exposure to androgens shortly after birth. Sex Differences in the Nervous System  Masculinization of the brain o Aromatization masculinizes brains of many animals  Testosterone is transformed into estradiol producing masculinization o Androgens play a greater role in the masculinization of the human brain Sexual Orientation
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