Reproductive Behaviors Textbook PDF

Chapter 10 Type textbook Tags BIOPSYCH Due Date @December 16, 2024 Status Done Reproductive behaviours Module 10.1 Sex and hormones evolutionary interpretations of m...

Chapter 10 Type textbook Tags BIOPSYCH Due Date @December 16, 2024 Status Done Reproductive behaviours Module 10.1 Sex and hormones evolutionary interpretations of male-female differences sexual selection : genes that increase an individual’s probability of mating, or probable number of surviving offspring, will also spread in the population interest in multiple mates differences in jealousy men said they would be more upset if their partner became sexually intimate with another man than if she became emotionally intimate with him women reported that they would be more upset if their partner became emotionally intimate with another woman than if he had sex with her mate preferences tendency for females to prefer good providers genes in sexual development female : XX, male : XY turner syndrome : XO pattern, an X chromosome and no second sex chromosome or just part of a second X chromosome result is a typtical feminine appearance, and almost always self identification as female, but ovaries that secrete less than average amounts of sex hormones Chapter 10 1  klinefelter syndrome : XXX pattern, or less commonly XXYY or XXXY appearance is masculine, but most individuals are infertile learning difficulties are common, especially with language and problem solving, and mental health problems are elevated organising effects of sex hormones both male and female have Müllerian ducts (precursors to female internal structures) and Wolffian ducts (precursors to male internal structures) biological males SRY gene (Sex-determining Region on the Y chromosome) causes those undifferentiated gonads to develop into testes testes produce androgens that increase the growth of testes, causing them to produce still more androgens androgens cause the Wolffian ducts to develop into seminal vesicles (structures that store semen) and the vas deferens (a duct from the testis into the penis) the testes also produce Müllerian-inhibiting hormone (MIH) that causes the Müllerian ducts to degenerate testes produce more androgens the estrogenes biological females the gonads develop into ovaries instead of testes (no SRY gene) the Wolffian ducts degenerate, and the Müllerian ducts mature into oviducts, uterus, and the upper vagina ovaries produce more estrogens than androgens progesterone prepares the uterus for the implantation of a fertilised ovum and promotes the maintenance of pregnancy androgens and estrogens are steroid hormones containing four carbon rings androgens include testosterone estrogens include estradiol Chapter 10 2  steriods exert their effects in three ways bind to receptors on the membrane they enter cells and activate certain proteins bind to chromosomes to activate inactivate certain genes organising effects are long-lasting during a sensitive period in early development, which is the first trimester of pregnancy for humans, sex hormones determine whether the body develops female or male genital high level of testosterone causes the external genitals to develop the male pattern, and a low level leads to the female pattern estradiol is essential for proper development of a female’s uterus and other internal organs, but it has little effect on the external genitals they alter certain aspects of brain development produce additional organizing effects at puberty activating effects are temporary, continuing only while a hormone is present sex drive, mood changes while pregnancy... sex differences in the brain female hypothalamus generates a cyclic pattern of hormone release stronger connections between the two hemispheres tend to age more slowly male hypothalamus releases hormone more steadily have more connections within each hemisphere the metabolic rate in the brain declines more rapidly brain differences in rats in early development Chapter 10 3  testosterone enter cells of hypothalamus, enzyme converts it to estradiol, exerts masculinising effects in the medial preoptic area, both testerone and its conversion to estradiol increase the porduction of prostaglandin, leads to an increase in microglia, dendritic spines and synapses anteroventral periventricular nucleus of the preoptic area : estradiol and testosterone combine to increase cell death in males, leaving this area larger in females in part of the ventromedial hypothalamus : estradiol activates an enzyme called PI3 kinase that increases gluta- mate release, and thereby causes postsynaptic neurons to increase their dendritic branching in the arcuate nucleus and the anteroventral periventricular nucleus : estradiol increases GABA production, which acts on astrocytes to decrease dendritic spines in humans testosterone acts on the hypothalamus directly instead of by conversion to estradiol but the final mechanism in terms of prostaglandins, PI3 kinase, and so forth appear to be the same as in rodents sex differences in play girls who had been exposed to higher testosterone levels in prenatal life showed slightly elevated preferences for boys’ toys activating effects of sex hormones at any time of life, sex hormones (such as testosterone and estradiol) excert activating effects and thus temporarily alter behaviour bidirectional influence : sex hormonal secretion → influence sexual behavior directly+ certian behaviours → influence hormonal secretion next to sex hormones, the pituitary hormone oxytocin is also important for reproductive behaviour stimulates contractions of the uterus during giving birth Chapter 10 4  stimulates the mammary gland to release milk sexual pleasure releases oxytocin, especially during orgasm, and leads to relaxation, calmness, and lack of anxiety after an orgasm males testosterone that is essential for male sexual arousal acts partly by increasing touch sensitivity in the penis also binds to receptors that increase responses in parts of the hypothalamus MPOA in the hypothalamus and other areas are thus primed to release dopamine dopamine release is strong during sexual activity and even more dopamine leads to that the male copulate (paaren) moderate concentrations of dopamine → stimulation of receptors D1 and D5 → erection of penis + sexually receptive postures in females higher concentration of dopamine → stimulation of type D2 receptor → orgasm high levels of testosterone, men is sexually aroused and drive to seek sexual partners decreases in testosterone levels, decreases in male’s sexual activity not cause for impotence : inability to have an erection (impaired blood circulation) females the hypothalamus, pituitary and ovaries interact to produce the menstrual cycle: periodic variation in hormones and fertility over the course of about 28 day after menstruation, the anterior pituitary releases follicle-stimulating hormone (FSH), which promotes the growth of a follicle in the ovary the follicle nutures the ovum and produces several types of estrogen, including estradiol Chapter 10 5  toward the middle of the cycle, the follicle builds up more and more receptors to FSH. the follicle produces increasing amounts of estradiol → increases release of FSH and a surge in the release of luteinizing hormone (LH) from the anterior pituitary. FSH and LH combine to cause the follicle to release an ovum the remnant of the follicle releases the hormone progesterone, prepares uterus for the implantation of a fertilized ovum during pregnancy, estradiol and progesterone levels continue to increase consequence of high estradiol and progesterone levels during pregnancy is fluctuating activity at the serotonin 3 (5HT3) receptor, which is responsible for nausea birth control interfers with usual feedback cycle between ovaries and pituitary widely used, combination pill : containing estrogen and progesterone, prevents the surge of FSH and LH that would otherwise release an ovum also prevents an ovum from implanting in the uterus and thickens the mucus of the cervix, making it harder for a sperm to reach the ovum sexual desire correlated strongly with changes in levels of estradiol, not testosterone initiating sexual activity does increase during the preovulatory period (the days of her menstrual cycle when estradiol levels are highest) parental behaviour (mammal) after delivering the young, mother increases secretion of oxytocin and prolactin, which promote milk production and several aspects of maternal behaviour late in pregnancy, sensitivity to estradiol increases in the brain areas important for maternal behavior and attention to the young, including the medial preoptic area and anterior hypothalamus and nucleus accumbens in humans - pregnancy leads to decreased gray matter volume in several brain areas (result of pruning the most ineffective synapses) Chapter 10 6  males with highest vasopressin levels show the highest level of sexual fidelity to their mates in humans, growth of several brain areas in pregnancy; especially for reward & motivation growth correlates with individual amount of positive emotions towards baby men with less testosterone & higher prolactin levels -> spend more time with caring for children testosterone levels often decline for fathers after birth human parental behaviour more experience-dependent (more than hormone- dependant) Module 10.2 Variations in sexual behaviour gender identity and gender differentiated behaviours gender identity : what we consider ourselves to be intersex people common cause of an intermediate sexual anatomy is congenital adrenal hyperplasia (CAH), meaning overdevelopment of the adrenal gland if a fetus has a genetic limitation in the ability to produce cortisol, the pituitary fails to receive the usual feedback signal, and it continues secreting more ACTH, stimulating the adrenal gland beyond the usual level the extra ACTH causes the adrenal gland to secrete extra testoster- one, which has little effect on male development, but partly masculinizes the external genitals of a female interests and preferences of girls with CAH girls played more with boys’ toys (but less than most boys) also performed slightly better in spatial & mechanical skills than most girls in adulthood more physical aggression, less interest in infants & choose more male-dominated occupations testicular feminisation Chapter 10 7  someone with XY chromosome has deficiency in receptor for androgens, circulating androgens have little or no effect this condition, known as androgen insensitivity or testicular feminization, produces an anatomy ranging from a smaller than average penis to an external appearance of a typical female discrepancies of sexual appearance when genetic males fail to produce 5a-reducatase 2 -> testosterone not converted into dihydrotestosterone (important for masculinizing the external genitals at birth they appear to be female at puberty: sharp increase of testosterone levels -> growth of a penis & scrotum then often developed male gender identity biological predisposition often stronger influence than family’s ways of rearing the child wrong to force child to become female/male through surgery & hormonal treatments issues of gender assignment and rearing sexual orientation whereas most men discover their sexual orientation early, many women are slower behavioural and anatomical differences people who differ in sexual orientation also tend to differ in many behaviors not directly connected to sex gay men are more likely than average to choose female-typical careers such as florist or hair stylist genetics monozygotic twins are more likely to have the same sexual orientation an evolutionary question Chapter 10 8  genes for same-sex orientation are maintained by kin selection. that is, those who do not have children themselves might do a better than average job of helping their siblings rear children sexual orientation relates to epigenetics rather than changes in DNA sequence genes that produce same-sex orientation might produce advantages for their relatives, increasing their probability of reproducing prenatal influences possible that sexual orientation depends on hormone levels during a sensitive period of brain development prenatal stress and alcohol may alter brain development through several routes stress releases endorphins, which can antagonize the effects of testosterone on the hypothalamus stress also elevates levels of certain adrenal hormones that decrease testosterone release brain anatomy third interstitial nucleus of the anterior hypothalamus (INAH-3) : which is generally more than twice as large in heterosexual men as in women INAH-3 nucleus of homosexual men was intermediate between those of heterosexual men and heterosexual women transgender people those who affirm that they were “born in the wrong body” that although their anatomy appears male or female, they clearly identify with the other gender two areas that are most likely to match the experienced gender are the INAH-3 nucleus, which corrrelates with sexual orientation, and one extension of the amygdala that pertains to sexual behaviour but not to sexual orientation Chapter 10 9