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Canada (161,368)
Psychology (9,685)
PSYB64H3 (201)
Chapter 10

all chapters notes for the final (chapters 10,11,12,14,15) - very detailed!

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Janelle Leboutillier

Chapter 10 Sexual Behaviour Sexual Development Aristotle argued that the sex of a child was the result of the temperature of semen at the time of conception. Hot semen resulted in males, and cool semen resulted in females. We understand today that an individuals genetic sex begins with sex chromosomes inherited from two parents mothers provide an X chromosome while the fathers determine the offsprings sex by providing either another X (producing a female) or an Y chromosome (producing a male). Sex Chromosome Abnormalities When a child receives only a single X chromosome (XO) instead of the usual pair (XX or XY) the result is Turner Syndrome and from this syndrome, we have learned that a single X chromosome carries sufficient genetic material to produce an individual who is quite normal in many ways. Individuals with Turner syndrome have normal female external genitalia, but the ovaries develop abnormally. Klinefelter syndrome is one the most common genetic abnormalities and features an XXY genotype. These individuals are male, but they usually experience reduced fertility and require hormone treatment at puberty to promote the development of secondary male sex characteristics. Like turner syndrome, klinefelter syndrome is associated with normal intelligence that may be marked by mild cognitive difficulties and social awkwardness. Klinefelter syndrome might affect brain lateralization or the localization of specific functions such as language in one hemisphere or the other. The relationship between the XXY genotype and a higher likelihood of antisocial behaviour has been the subject of considerable debate but further analysis suggests that criminal and antisocial behaviour was more closely associated with lower intelligence than with atypical genotype. Abnormalities due to a third sex chromosome appear to have relatively mild effects. Three stages of prenatal development The development of gonads until the sixth week after conception, both female and male foetuses have identical primordial gonads that have the capacity to develop into either ovaries, or testes. At about sex weeks, a gene on the short arm on the Y chromosome known as the sex-determining region of the Y chromosome (SRY) is expressed in male embryos. Testis-determining factor, the protein encoded by the SRY gene, switches on additional genes that cause the primordial to develop into testes. Differentiation of the internal organs until about the third month of development, both male and female foetuses posses a male Wolffian system and a female Mullerian system. In males, the Wolffian system develop in to the seminal vesicles, the vas deferens, and the prostate while the mullerian system in females will develop the uterus, the upper portion of the vagina, and the fallopian tubes. During the third month, the males testes secretes testosterone and anti-mullerian hormone and testosterone promotes the development of the wolffian system and the anti-mullerian hormone initiates the degeneration of the mullerian system. Androgen insensitivity syndrome (AIS) disrupts the normal development of the Wolffian system in males and will have an XY genotype and normal testes. The testes still release androgens and anti-mullerian hormone but it is the lack of functional androgen receptors that prevents the www.notesolution.comdevelopment of the wolffian system. However, the anti-mullerian hormone still works and the result is a shallow vagina, no ovaries, fallopian tubes, or uterus and although they are infertile, their external appearance is quite typically female. Individuals with AIS are genetic males but typically have female appearance and strong female gender identities. Development of External Genitalia no hormonal activity is required to develop female external genitalia. A particular androgen, 5-alpha-dihydrotestosterone must be recognized by receptor sites for the male external genitalia to develop normally. Congenital adrenal hyperplasia (CAH) is a recessive heritable condition in which the fetuss adrenal glands release elevated levels of androgens and males with CAH does not show anything abnormal but females are born with ambiguous external genitalia. Important to remember that most females with CAH are heterosexual and that majority of bisexual and lesbian women do not have CAH. Development at Puberty Secondary sex characteristics such as facial hair and deeper voices for males and wider hips and breast development for females are caused at puberty by additional hormonal events. Accumulation of enough body fat to support reproduction might serve as a signal for puberty and when body fat is abnormally low, puberty is delayed. At the onset of puberty, gonadotropin-releasing hormone (GnRH) is released by the hypothalamus and initiates the release of two gonadotropic hormones by the anterior pituitary gland, FSH and LH. In response to stimulation by FSH and LH, the testes begin to produce addition testosterone and the ovaries produce estradiol. 5 alpha reductase deficiency is a rare condition in which a child is born with ambiguous genitalia but develops male secondary sex characteristics at pubery and are raised as females. Sex Differences in the Nervous System Sexually dimorphic is displaying structural differences between the sexes. The sexually dimorphic nucleus of the preoptic area (SDN-POA) located in the hypothalamus is much larger in male rats than in female ones. Human beings do not have SDN POA but might have an equivalent. Interstitial nuclei of the anterior hypothalamus (INAH), or INAH, INAH -2, INAH -3, are about twice as large in males as in females and seems that these areas participate in sexual behaviour and that INAH-3 might be the human form of SDN POA. Seems that masculinisation of the human brain is not as dependent on aromatizatino as in rodents and some other mammals and appears that androgens appear to play a direct role in the masculinisation of the human brain that is not depend on aromatization into estradiol. Sexual Orientation Hormones, sexual behaviour, and sexual orientation Early exposure to androgens influences adult sexual behaviour. The high levels of prenatal androgens typical of males have an impact on the development of the inner ear which produces tiny sounds known as otoacoustic emissions and these emissions are stronger in women than men. Another possible indicator of prenatal exposure to androgens, and the results influence on sexual orientation, is the 2D:4D ratio. Men www.notesolution.com
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