Neuro Reading Summary Quiz 1 Semester 2, 23

Freberg 326-361 Turner syndrome- I laving the paternal X was, however, associated with better visuospatial abilities Klinefelter syndrome is a genetic condition that affects males. It is caused by an extra X chromosome, resulting in a 47/XXY genotype instead of the typical 46/XY genotype. T...

Freberg 326-361 Turner syndrome- I laving the paternal X was, however, associated with better visuospatial abilities Klinefelter syndrome is a genetic condition that affects males. It is caused by an extra X chromosome, resulting in a 47/XXY genotype instead of the typical 46/XY genotype. This extra chromosome can cause differences in sexual development and fertility. Individuals with Klinefelter syndrome are typically male in appearance but may experience reduced fertility and require hormone treatment during puberty to develop secondary male sex characteristics such as facial hair, a deeper voice, and external genitalia. They may also require treatment to inhibit female characteristics such as breast development. Klinefelter syndrome is the most common genetic abnormality related to sex chromosomes, occurring in about 1.79 out of 1,000 male births. 47,XYY is a genetic condition that occurs in about 1 out of 1,000 male births. It is characterized by an extra Y chromosome, resulting in a 47,XYY genotype instead of the typical 46,XY genotype. The physical and behavioral effects of this condition are typically subtle and do not usually prompt parents to seek genetic analysis. Boys with 47,XYY tend to be taller and leaner than average, may suffer from acne, and have a slightly increased risk for minor physical abnormalities such as those affecting the eye, elbow, and chest. Average IQ scores for individuals with 47,XYY are slightly below the average for males with typical 46,XY genotypes. The development of the gonads: is the first step in the development of male and female reproductive structures. Up until the sixth week after conception, both male and female embryos have identical primordial gonads that have the capacity to develop into either ovaries (the female gonads) or testes (the male gonads). During this time, a gene called SRY on the Y chromosome begins to turn the undifferentiated gonads into testes in males. The testes then begin to release hormones called androgens, which cause the external genitalia to develop into a penis and scrotum. In females, without the presence of SRY gene, ovaries will develop instead of testes. If there is a problem with this process, it can lead to intersex conditions where elements of both male and female development occur in the same fetus. These conditions can be caused by genetic mutations or hormonal imbalances during fetal development. Key Definitions: X Chromosome: One of two types of sex chromosomes; individuals with 2 will usually develop into females Y chromosomes: One of two types of sex chromosomes; individuals with a Y chromosome will usually develop into makes. Karyotype: A profile of chromosome number and appearance in the nucleus of a cell as seen under a light microscope. Turner Syndrome: A condition caused by an XO genotype, Individuals with Turner syndrome have normal female external appearance and genitalia but are usually Infertile due to abnormally developing ovaries. This condition is also associated with short stature, skin folds In the neck, and difficulty with spatial relations tasks. Mosaic karyotype a condition where an individual has two or more groups of cells with different numbers or arrangements of chromosomes. This can happen when there are errors during cell division. In terms of sexual development, having a mosaic karyotype can cause differences in the development of male or female characteristics due to variations in sex chromosome number and appearance. Klinefelter syndrome: A condition in males caused by an XX Y genotype, characterized by frequent problems with fertility, secondary sex characteristics and verbal skills. Secondary sex characteristics: are physical features that develop during puberty and distinguish males from females. These characteristics are not directly related to reproduction but are associated with sexual maturity and attraction. In males, secondary sex characteristics include facial hair, a deeper voice, increased muscle mass, and the development of external genitalia. In females, secondary sex characteristics include breast development, wider hips, and the growth of pubic and underarm hair. The development of secondary sex characteristics is largely driven by hormonal changes during puberty. Gonads: The internal organs, ovaries in females and testes in males, that produce reproductive cells (eggs and sperm) and secrete sex hormones External genitalia: the external sexual organs, including the penis and scrotum in males and the labia, clitoris and lower third of the vagina in females. Intersex: a condition in which elements of both male and female development occur in the same fetus Ovaries: female gonads; the source of ova and sex hormones Testes: Male gonads; source of sperm and sex hormones Sex determining region of the Y chromosome (SRY) a gene located on the short arm of the Y chromosome that encodes for testis-determining factor. Testis determining factor: A protein encoded by the SRY gene on the Y chromosomes that turns the primordial gonads into testes. Wolffish system: The internal system that develops into seminal vesicles, vas deferred and the prostate gland in males. Mullerian system: The internal system that develops into a uterus, fallopian tubes and the upper two thirds of the vagina in the absence of anti- Mullerian hormone. Testosterone: an androgen produced primarily in the testes Anti-Mullerian hormone: A hormones secreted by fetal testes that causes the degeneration of the Mullerian system Androgen: A steroid hormone that develops and maintains typically masculine characteristics. Androgen insensitivity syndrome: (AIS): A condition in which a genetic male fetus lacks functional androgen receptors which leads to the development of female external genitalia and typically female gender identity and sexual behavior. Gender Identity: The sense of being male or female, independent of genetic sex or physical appearance. 5- Alpha- dihydrotestoterone: An androgen secreted by the testes that masculinizes the external genitalia. Congenital adrenal hyperplasia (CAH) a condition in which a fetus is exposed to higher-than- normal androgens, resulting in masculinization of external genitalia and some cognitive behaviors in affected females. Secondary sex characteristics: Characteristics related to sex that appear at puppetry, including seeping voice and facial hair growth in males and widening hips and breathe development in females. The differentiation of the internal organs is the second step in the development of male and female reproductive structures. Until about the third month of development in humans, both male and female embryos possess a male Wolffian system and a female Müllerian system. The differentiation of the internal organs follows the development of the gonads. In males, the Wolffian system will develop into the seminal vesicles, vas deferens, and prostate. In females, the Müllerian system will develop into the uterus, upper portion of vagina, and fallopian tubes. During the third month following conception, in males, testes begin to secrete two hormones called testosterone and anti- Müllerian hormone. Testosterone promotes further development of male reproductive structures such as penis and scrotum while anti-Müllerian hormone causes regression of Müllerian ducts which would otherwise develop into female reproductive structures. Androgen insensitivity syndrome (AIS) is a condition that affects the normal development of the Wolffian system in males. It is caused by a defective gene that produces abnormal androgen receptors, which makes the fetus's tissues blind to the presence of androgens. Individuals with AIS have an XY genotype, normal testes that remain undescended within the abdomen, and female external genitalia. The severity of AIS can vary widely from person to person. Because 1hc Miillerian S)•slcm is responsible for the upper two thirds of the vagina and the female internal organs, the result is a shallow vagina and no ovaries, fallopian tubes, or uterus. Although adult individuals with Al$ are infertile, their external appearance is quite typically female. The development of the external genitalia follows the differentiation of the gonads during the sixth week after conception. In males, the external genitalia include the penis and scrotum, while in females, they include the labia, clitoris, and outer part of the vagina. The appearance of external genitalia is an important psychological "sign" of sex, and ambiguity of genitalia at birth can cause significant stress for parents. Healthcare providers typically use a scale called Prader scale to assess the relative masculinization of external genitalia. At the onset of puberty, gonadotropin-releasing hormone (GnRH) is released by the hypothalamus. This hormone initiates the release of two hormones by the anterior pituitary gland, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Both males and females release these same hormones, but with different effects. In response to stimulation by FSH and LH, the testes begin to produce additional testosterone, and the ovaries produce estradiol. The testes also produce small amounts of estrogens, including estradiol, and the ovaries produce small amounts of androgens, including testosterone. The age at which puberty begins can vary widely between individuals but typically occurs between 8-13 years in girls and 9-14 years in boys. The timing of puberty is influenced by a variety of factors such as genetics, nutrition, physical activity level, and environmental factors. Early or late onset of puberty can have implications for physical development as well as psychological well- being. Sex reassignment can alleviate gender dysphoria , but it also carries risks of suicide and psychological disorders. Tr e a t m e n t g u i d e l i n e s h a v e b e e n d e v e l o p e d b y t h e A m e r i c a n Psychiatric Association to address gender dysphoria. The guidelines emphasize appropriate diagnosis, evaluation of any coexisting psychological problems, psychotherapy to address discrimination and stereotyping, provision of complete education for the individual regarding medical and psychological options, evaluation for possible hormonal or surgical treatment, and education of family members and the community. It is recommended that therapists with specialization and experience in this area provide treatment, using evidence-based practice that combines professional expertise with the goals of the patient or client. Key terms: Estrogen: A steroid hormone that develops and maintains typically female characteristics Estradiol: An estrogen hormone synthesized primarily in the ovaries Gonadotropin-releasing hormone (GnRh) A hormone released by the hypothalamus that stimulates the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) by the anterior pituitary gland. Follicle-stimulating hormone (FSH) A hormone released by the anterior pituitary that stimulates the development of eggs in the ovaries and sperm in the testes. Luteinizing hormone (LH) A hormone released by the anterior pituitary that signals the male testes to produce testosterone and that regulates the menstrual cycle in females. 5-alpha-reductase deficiency A rare condition in which a child is born with ambiguous genitalia but develops male secondary sex characteristics at puberty. Gender Dysphoria: distress that may accompany the i congruence between one’s experienced or expressed gender and one’s assigned gender Review questions: 1. What processes must occur in order to develop male and female gonads, internal organs and external genitalia ? In order to develop male and female gonads, internal organs, and external genitalia, a complex series of processes must occur during embryonic development. These processes involve the differentiation of the gonads into testes or ovaries, the development of internal reproductive structures such as the uterus and fallopian tubes in females or the vas deferens and seminal vesicles in males, and the formation of external genitalia such as the penis or clitoris. 2. What different pathways can occur in sexual development: Sexual development can follow different pathways depending on a variety of factors. For example, genetic sex (XX or XY) determines whether the gonads will develop into testes or ovaries. However, hormonal factors also play a critical role in sexual differentiation. In some cases, genetic mutations or variations in hormone levels can lead to differences in sexual development that result in intersex conditions such as androgen insensitivity syndrome or congenital adrenal hyperplasia. In addition to these biological factors, social and environmental factors can also influence sexual development. For example, exposure to certain chemicals or drugs during pregnancy may affect fetal hormone levels and contribute to differences in sexual development. Cultural norms and expectations may also shape gender identity and expression. Overall, sexual development is a complex process that involves multiple biological and environmental factors interacting over time. Key definitions: Organization: The permanent effects of sex hormones on body structures Activation: reversible effects of sex hormones on body structures and functions. Otoacoustic emissions: sounds emitted by the cochlea of the inner ear that show sex differences. Sexually dimorphic nucleus of the pre optic area (SDN-POA) A nucleus in the pre optic area of the hypothalamus that is larger in male rats than female rats. Interstitial nuclei of the anterior hypothalamus: A collection of four small nuclei in the anterior hypothalamus, two of which (INAH-2 and INAH-3) appear to be sexually dimorphic. The size of INAH-3 might be associated with male sexual orientation. Human equivalent Spinal nucleus of the bulbocavernosus: Motor neurons in the spinal cord that innervate the male rat’s bulbocavernosus muscles in the penis Transsexuality: having a gender identity that is inconsistent with biological sex Sex hormones = steroids. Synthesized= cholesterol in the gonads and in lesser amounts in the adrenal glands, brain, bone and fat cells. Females= produce 10% of androgens that males produce Organization during development: During prenatal and early postnatal development, sex hormones organize circuits in the brain that differ according to sex. This process is called sexual differentiation. The organization of these circuits produces permanent changes in biological structures, which can affect behavior and other aspects of development. For example, the size and structure of certain brain regions may differ between males and females due to differences in the levels of sex hormones during development. After sexual differentiation has occurred, these circuits are then activated by the sex hormones at the onset of puberty and throughout adulthood. This process is called sexual maturation. Activation by hormones is reversible, although the effects of activation are constrained by the organizational effects that occurred earlier. For example, if a male is castrated before puberty, he will not develop typical male secondary sexual characteristics such as facial hair growth or a deep voice, even if he receives testosterone replacement therapy later in life. Markers of Development: Researchers have attempted to identify "markers" that are correlated with prenatal exposure to hormones. For example, testosterone levels in both maternal blood and in amniotic fluid are correlated with sex-typical behavior in offspring. In one study, researchers measured the levels of testosterone in amniotic fluid obtained during routine amniocentesis procedures from pregnant women. They then followed up with the children born to these women and found that higher levels of prenatal testosterone were associated with more male-typical play behavior in girls and more female-typical play behavior in boys. However, ethical constraints certainly preclude the artificial manipulation of the prenatal hormonal environment in humans. Therefore, researchers must rely on natural variations in hormone levels and other indirect measures to investigate the possible influences of the prenatal hormonal environment on outcomes in typical individuals. Otoacoustic emissions are sounds that are produced by the cochlea of the inner ear. These sounds can be measured using a sensitive microphone placed in the ear canal. Research has shown that there are sex differences in otoacoustic emissions, with females producing louder and more frequent emissions than males. These differences appear early in life and may be due to the amount of prenatal testosterone exposure experienced by an individual SDN-POA: Castration or injection of older animals does not change the siie of the SDN-POA, indicating that this structure responds to early hormonal organization. Sex Differences in Behavior and Cognition: Interaction between social and biological factors. Play Behavior: Playing with female toys vs males toys = socialization Biology evidence for play behavior= CAH (girls with 25% more androgen than typically developing girls play with more boy orientated toys than girls, against their socialization cues but still lower than boys. CAH stands for Congenital Adrenal Hyperplasia, which is a genetic disorder that affects the adrenal glands. Boys with CAH are exposed to higher levels of androgens than typically developing boys, but because prenatal androgens are very high in both cases, this seems to have little behavioral effect. However, girls with CAH show differences in play behavior compared to typically developing girls. Time spent with girls' toys is lower in girls with CAH than typically developing girls, but both are much higher than boys. Time spent with boys' toys is higher in girls with CAH and typically developing unaffected girls, but is still lower than in boys. The PSAI score results from subtracting scores for girl-typical items from boy-typical items on a 24-item, standardized measure. Higher scores reflect more male-typical behavior. Gender Identity: Transsexuality is more common in biological males than females, and individuals with congenital adrenal hyperplasia (CAH) are more likely to express a wish to live as the opposite gender. 8% of woman with CAH wish to be men. Tr a n s s e x u a l i t y m a y o c c u r d u e t o t h e p r e n a t a l t i m i n g o f h o r m o n e i n f l u e n c e s o n t h e r e p r o d u c t i v e s y s t e m a n d o n t h e b r a i n . Personality: Early Organisation of the nervous system might influence personality as well as socialization. Research suggests that both boys and girls with high levels of prenatal testosterone exposure show reduced empathy compared to those with lower levels of exposure. Additionally, females with congenital adrenal hyperplasia (CAH) show decreased empathy relative to typically developing girls. Adult Hormone Levels and Cognition: Te s t o s t e r o n e h a s b e e n f o u n d t o b o o s t s p a t i a l p e r f o r m a n c e i n b o t h m e n a n d w o m e n , w h i l e v e r b a l p e r f o r m a n c e w a s enhanced by testosterone in men and by estrogens in women. 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, on the other hand, have a slight advantage in visuospatial tasks, such as figure rotation tasks. CAH individuals show a mix in strength suggesting that the organising role of prenatal hormones plays less of a part. The differences could be environmental, epigenetic due to activation rather than Organization. Sexual Dimorphism in the brain: to display structural differences between the sexes The book discusses sexual dimorphism in the brain, which refers to structural differences between the brains of males and females. While social factors are important in gender differences, researchers have also observed differences in the brains and nervous systems of males and females. Exposure to prenatal androgens masculinizes the brain as well as the internal and external reproductive systems. Masculinizing a brain or nervous system means identifying features that are sexually dimorphic, which display structural differences between the sexes. Masculinizing the brain would result in the male pattern in any sexually dimorphic feature. Sex differences and psychological disorders: two-thirds of adults with major depressive disorder are female, while three-quarters of individuals with autism spectrum disorder, attention deficit hyperactivity disorder, and Tourette's syndrome are male. Sexual orientation: Sexual orientation refers to a stable pattern of attraction to members of a particular sex. Approximately 1.8 percent of adult males and 1.5 percent of adult females identify themselves as gay or lesbian, and 0.4 percent of men and 0.9 percent of women describe themselves as bisexual. However, sexual orientation is not synonymous with sexual behavior, as many people engage in same-sex behavior and fantasy while maintaining a strong heterosexual orientation. The section also notes that sexual orientation is associated with possible genetic and prenatal hormonal influences, leading to structural differences in the brain. Hormones and sexual orientation: relationship between prenatal hormone exposure and sexual orientation. Research suggests that exposure to prenatal androgens masculinizes the brain as well as the internal and external reproductive systems, leading to structural differences in the brain that may influence sexual orientation. For example, studies have found that women with congenital adrenal hyperplasia (CAH), a condition that results in high levels of prenatal androgens, are more likely to report same-sex attraction than women without CAH. However, the relationship between hormones and sexual orientation is complex and not fully understood. The section notes that while prenatal hormone levels seem to have a significant impact on sexual development, they do not explain all of the observed differences in sexual orientation between individuals. Brain structure ands sexual orientation: INAH-3 is a region of the hypothalamus that has been found to be sexually dimorphic, meaning that it differs in size between males and females. Studies have also found that INAH-3 differs in size between heterosexual and homosexual men, with homosexual men having a smaller INAH-3 than heterosexual men. However, the differences observed are smaller and show greater overlap than the differences observed between men and women. These findings suggest that while INAH-3 may be related to sexual orientation, it is not a definitive marker of sexual orientation and other factors may also play a role. Genes and sexual orientation: research suggests that genetics may have a direct or indirect effect on sexual orientation. For example, studies have found that the chances of a homosexual male twin having a homosexual brother are 20 to 25 percent for fraternal twins and about 50 percent for identical twins. Sexual orientation and cognition: discusses whether sexual orientation is related to variations in cognitive performance. One study mentioned in the section used mental rotation tasks to assess visuospatial skills and found that men consistently performed better than women, regardless of sexual orientation. When taking sexual orientation into account, heterosexual men outperformed homosexual men, with bisexual men scoring between these two groups. Homosexual and bisexual women scored at about equal levels, and both groups outperformed heterosexual women. These findings suggest that there may be some differences in cognitive performance based on sexual orientation. The point is that homosexual men did not see themselves as very feminine nor did homosexual women see themselves as very masculine, which would be required to support the gender inversion approach. Biological influences on adult sexual Behavior: The activation of Behavior by hormones is important in sexual Behavior, beginning at puberty and extends through the remainder of the lifespan. The regulation of sex hormones: The hypothalamus exerts the most immediate control over the endocrine system. Manages the release of sex hormones through the secretion of GnRH. Melatonin normally inhibits the release of GnRH, and light in turn inhibits melatonin, which is secreted primarily at night. Light, therefore, increases GnRH release b)' reducing the inhibition normally produced by melatonin. Key terms: Follicle: one of several clusters of cells in the ovary, each of which contains an egg Ovum: a female reproductive cell, or egg Ovulation: the process of releasing a mature egg from the ovary Corpus Luteum: a yellow mass of cell in the ovary formed by a ruptured follicle that has released an egg Progesterone: a hormone produced in the corpus luteum that prevents the development of additional follicles and promotes the growth of the uterine lining. The menstrual cycle represents a very stable and predictable fluctuation in events controlled by Lh and FSH . 1. On the first day of menstruation, the anterior pituitary gland increases secretion of FSH. 2. When this hormone circulates to the ovaries, they respond by developing follicles, small clusters of cells that each contain an egg cell, or ovum . 3. One follicle begins to develop more rapidly than the others, and it releases estrogens that inhibit the growth of competing follicles. **If more than one follicle matures, and the ova are fertilized, fraternal (nonidentical) twins will develop. prescribed fertility drugs stimulate the development of follicles and ova and subsequently promote multiple births. 4. Estrogens from the follicle also provide feedback to the hypothalamus and pituitary gland, which respond by sharply Increasing release of LH. 5. Increased LH levels Initiate the release of the ovum, or ovulation, about two weeks after the first day of the last menstruation. 6. Estradiol released by the ovaries signals the uterus to thicken in anticipation of a fertilized embryo. 7. After the release of the ovum, the ruptured follicle is now called the corpus luteum, which means "yellow body." The corpus luteum releases estradiol and a new hormone, progesterone. 8. Progesterone promotes pregnancy (gestation) by preventing the development of additional follicles and by further developing the lining of the uterus. 9. If fertilization does not take place, the corpus luteum stops producing estradiol and progesterone. When levels of these hormones drop, the uterine lining cannot be maintained, menstration will start, and the entire cycle will repeat. Mood, menstruation and childbirth: 5-8% of women experience premenstrual syndrome in response to shifts in the hormones that regulate the menstrual cycle. Premenstrual syndrome is characterized by physical symptoms of bloating and breast enlargement and tenderness as well as psychological symptoms of depression and irritability. Severe cases of premenstrual mood changes are diagnosed as premenstrual dysphoric disorder (PMDD). Women with PMDD experience more depression, changes in appetite (consuming more calories total and more calories from fat), and impaired cognitive performance than women who do not suffer from this disorder. These symptoms are consistent with a hypothesis linking serotonin dysfunction with PMDD, leading to the current treatment of medication with selectiveserotonin rcuptakc inhibitors (SSRis) Within one year of the delivery of a baby, approximately 10to 15percent of women experience postpartum depression as hormones shift from the pregnant state back to normal monthly cycles . Postpartum depression appears to be quite mild in the vast majority of cases. Mothers at highest risk for postpartum depression are younger than 20 years of age, unmarried, less educated, and of lower socioeconomic status. -A history of being physically abused or using tobacco during the last three months of pregnancy also increases risk. -Cases of postpartum depression can be detected in nearly 90 percent of patients as the third trimester of pregnancy by evaluating sensitivity to estrogen signalling. This predictive ability might lead to additional support for women judged to be at risk for this condition. Key terms: Premenstrual syndrome: a condition in which some women experience physical and psychological symptoms immediate prior to the onset of menstruation. Premenstrual dysphoric disorder (PMDD): A condition in which premenstrual mood changes are usually severe. Postpartum depression: A condition in which mothers who have recently given birth experience feelings of depression die to their rapidly changing hormonal environment. Female Contraception: • Breastfeeding exclusively without water, juice, solid foods, or formula and not menstruating leads to a 1 to 6 percent chance of becoming pregnant. • Breastfeeding suppresses GnRH, which interferes with the pulse of LH associated with follicle growth and ovulation. —Oral contraceptives work by providing synthetic hormones that interfere with normal ovulation . There are two types of commonly used oral contraceptives: the combination pill, which contains estrogen and progestin and prevents the maturation of follicles and ovulation, and the progestin-only pill, which prevents the thinning of cervical mucus that typically accompanies ovulation. Both types of pills also prevent fertilized eggs from implanting in the lining of the uterus. • and reduce a woman's testosterone levels, which are related to a woman's sexual desire. • Medroxyprogesterone acetate (MPA or Depo-Provera contraceptive injection) suppresses ovulation and is administered by injection at three-month intervals. Long-term use can cause bone density loss. • Emergency contraception can be administered within 72 hours of intercourse using the "morning after" pill, copper-bearing intrauterine wires, or mifepristone (RU-486) to interrupt pregnancies up to nine weeks following conception by blocking the action of progesterone. • Elsimar Coutinho, the Brazilian physician who developed Depo- Provera, argues that the number of lifetime menstrual cycles for the average woman has increased from 100 a century ago to over 400 today, and it is not the pregnancy that provides the protective benefit but the lack of ovulation, menstruation, and high estrogen levels associated with the menstrual cycle. The use of uninterrupted cycles of birth control pills to reduce the frequency of menstruation has become an accepted medical practice to counteract the harm of greater estrogen exposure. Male Contraception: Pharmaceutical companies have been slow to invest in male contraception due to the belief that there is little market demand and concerns about side effects, despite a desire among some men to have more control over reproductive decisions. Ancient use of marijuana has been shown to reduce fertility in men, but it is not recommended. Currently, condoms, withdrawal, and vasectomies are the only methods of contraception available to men. However, there are ongoing investigations into new options for male contraception, including progestin-based birth control pills, devices that physically block the movement of sperm, gels that damage sperm, pills that reduce vitamin A levels, and medications that block ejaculation without impacting the viability of sperm or affecting orgasm. Hormones and adult sexual Behavior: Hormones play a significant role in determining the timing and frequency of sexual behavior in females that undergo estrus. However, human females, who do not display estrus, show receptivity throughout the menstrual cycle, and their sexual activity is under little if any control of the hormones involved with ovulation. Women's testosterone levels have the most significant impact on their sexual activity, and adrenal disease can have negative impacts on sexual behavior. Women with higher testosterone levels demonstrate increased sexual interest and a greater preference for "masculinity" in faces, voices, and behavioral displays. Male sexual frequency varies across cultures and depends on a variety of factors including relational satisfaction, mental and physical health, and individual importance placed on sex. Testosterone levels do not strongly predict sexual frequency in young males, but in older men, testosterone levels are more closely correlated with sexual frequency. Significant reductions in testosterone levels can lead to changes in male sexual behavior. Men in long-term marriages have lower testosterone levels compared to single men or men near divorce. This may be due to lower levels of competition with other men for mates or that men with lower testosterone are more successful in maintaining stable relationships. Testosterone levels increase in both male and female athletes in anticipation of competition, and following a competition, testosterone levels increase in winners and decrease in losers. Observing a competition also influences testosterone levels, with men supporting the winning team experiencing an increase and those supporting the losing team experiencing a decrease. Key terms: Estrus: a regularly occurring period of sexual desire and fertility in some mammals. Major Histocompatabilit y complex MHC gene: a gene that encodes out immune systems ability to recognise intruders; might account for preferences for body odour. Oxytocin: A hormone, release by the posterior pituitary gland, that stimulates uterine contractions, releases milk, and participates in social boding, including romantic love and parenting Behavior. Elements of physical attractiveness: The concept of physical attractiveness is a complex one that has long been of interest to both scientists and the general public. Attraction is often associated with pleasure and reward, as demonstrated by studies using brain imaging techniques that show activation of the brain's pleasure and reward centers when viewing images of physically attractive people. These reward centers, such as the nucleus accumbens, are also associated with addictive behaviors, suggesting that attraction may have addictive qualities. Physical attractiveness is often defined by cultural standards, but research has found that preferences for beauty exist even in very young infants. One possible factor influencing these preferences is body symmetry, which is the degree of similarity between the two sides of the face or body. Highly symmetrical bodies are generally healthier, and some researchers believe that we are programmed to select healthy mates. As a result, we view symmetry as attractive and beautiful. Beyond symmetry, research has found that men and women have different preferences for physical features in their partners. Women tend to prefer more masculine-looking men for short-term sexual relationships, as these features may indicate good genes and an excellent immune system. However, women associate negative traits, such as dominance and unfaithfulness, with highly masculine features, and so may prefer less masculine-looking men for long-term relationships. In terms of smell, studies have found that people may be attracted to particular scents based on aspects of their immune system. For example, women have been found to be more attracted to the sweat of men whose immune system is genetically dissimilar to their own, potentially indicating a higher chance of producing offspring with strong immune systems. These preferences may be influenced by past experiences, as people tend to prefer scents associated with past or current romantic partners. Romantic love and sexual desire: The experience of romantic love and sexual desire is important and confusing for adolescents and young adults. The fMRI literature suggests that sexual desire and love belong on a continuum. Romantic love produces characteristic patterns of activity in the human brain, with increased activity in areas associated with reward when viewing photographs of a lover, and less activity in areas associated with negative emotions and social judgment. Oxytocin and vasopressin, two pituitary hormones, influence bonding associated with romantic love. Oxytocin enhances bonding and is released during orgasm, childbirth, and breastfeeding. Women's oxytocin levels increase in response to physical intimacy with their partners, and couples with higher oxytocin levels report greater intimacy and support. Oxytocin supplied in a nasal spray improves positive communication during arguments. Reduced levels of oxytocin might account for the reduced sociability associated with autism spectrum disorder, particularly in males. Reproduction and Parenting: Evolutionary psychologists argue that the primary goal of sexual behavior is the production of offspring who will survive and reproduce. Different reproductive pressures act on males and females, leading to different sexual behaviors. Males are more promiscuous as they can produce many offspring over their lifespan, while females are highly selective because the costs of reproduction are high. Monogamy can be advantageous for males if it increases the survival rate of offspring, and for females if it provides the protection and benefits offered by a father. Research on voles suggests that mating patterns and reproductive strategies may be biological in origin, with differences in hormone receptor densities in the brain contributing to monogamous versus promiscuous behavior. Oxytocin and vasopressin are two hormones that help parents achieve a balance between caretaking and aggression designed to protect their young. Oxytocin levels during pregnancy and following childbirth predict maternal bonding behaviors, and oxytocin levels in young adults are correlated with their reports of bonding to their parents. Sexual Dysfunction and its treatment: According to sex therapists Masters and Johnson, up to half of all American couples experience some type of sexual problem, many of which are psychological in origin, but in some cases, they are biological. Sexual dysfunction in both men and women can be associated with type 2 diabetes due to circulatory and neurological problems, which is becoming more common due to increasing obesity. The frequent use of antidepressants is also increasing rates of sexual dysfunction in both men and women. Common forms of female sexual dysfunction include reduced sexual desire and orgasm problems, which can be alleviated by treatments that increase testosterone levels. A common type of sexual dysfunction in men is erectile dysfunction, which occurs when a man is unable to achieve an erection sufficient for satisfactory sexual activity. Approximately 30 million men in the United States experience some degree of erectile dysfunc- tion, including about half the men between the ages of 40 and 70 years. Erections occur as a result of either direct stimulation or cognitive factors. Parasympathetic neurons in the sacral spinal cord respond lo both mechanoreceptors in the genitals (direct stimulation) and descending input from the brain (cognitive factors). These parasympathetic neurons release acetylcholine (Ach) and nitric oxide (NO) into the spongy erectile tissues of the penis, which subsequently fill with blood. Medications used to treat erectile dysfunction promote erection by enhancing the effects of NO on the erectile tissues.