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Chapter 6 Sexual Arousal and Response Hormones • Steroid hormones – Commonly referred to as “male sex hormones” and “female sex hormones,” although both sexes produce both types of hormones. – Testosterone: the major androgen, or male sex hormone • Produced in the testes (men), adrenal glands (men and women), & ovaries (women). • Men typically produce 20-40X more testosterone than women. – Estrogen: the major female sex hormones • produced by ovaries & testes. • Testes produce much smaller quantities of estrogens than ovaries. • Neuropeptide hormones – Oxytocin--often called the “love hormone;” seems to influence erotic and emotional attraction to one another. Hormones in male sexual behavior • Testosterone linked to male sexual desire (libido) – Less linked to functioning; a man w/low testosterone level can be fully capable of erection and orgasm but might have little interest in sex. • Evidence 1) Research on men who have undergone castration shows significant reduction in sexual desire and activity. 2) Androgen-blocking drugs (antiandrogens) • Have been used to try and treat sex offenders, and are used to treat some medical conditions, such as prostate cancer. • Depo-provera (medroxyprogesterone acetate, MPA) has been shown to reduce sexual desire and activity in men and women. 3) Hypogonadism: endocrine disorder causing testosterone deficiency in males; also causes major reduction in sexual desire that can be treated with testosterone replacement. Hormones in female sexual behavior • Testosterone linked to female sexual desire (libido) • Evidence 1) Testosterone-replacement therapy enhances sexual desire and arousal in post-menopausal women and other women with low levels of testosterone 2) In women with normal testosterone levels, supplemental testosterone caused a significant increase in genital responsiveness within hours. 3) Women with a history of low sex drive and inhibited arousal positively responded to testosterone administration. 4)Comparisons of women w/history of healthy sex drive and women w/history of low libido showed that women in the low-libido group had lower testosterone levels. Hormones in female sexual behavior, (cont.) • Estrogens: role in female sexual behavior is still unclear. – Contribute to general sense of well-being – Help maintain thickness & elasticity of vaginal lining – Contribute to vaginal lubrication – However, there are contradictory findings about whether administration of estrogen increases or decreases libido in women. How much testosterone is necessary for normal sexual functioning? • Levels of free testosterone are much lower in women than men. – This does not mean that women have lower or weaker sex drives. – Rather, women‟s body cells are more sensitive to testosterone than a man‟s body cells are. • Testosterone levels decline w/age in both sexes. Testosterone replacement therapy • Use of testosterone supplements to treat a deficiency in testosterone. – Relatively common to treat sexual difficulties in men. – Women have a harder time receiving TRT, although testosterone deficiency is a fairly common experience during menopause. – There are some negative side effects, and long-term effects of TRT aren‟t yet known. • Can stimulate growth of prostate cancer cells, if present. • Some concerns about cardiovascular problems in men. • Little research done on TRT in women. • More long-term studies are needed. Oxytocin in male & female sexual behavior • Oxytocin: a neuropeptide (a short string of 9 amino acids produced in the hypothalamus in both sexes). • Stimulates release of milk during breast-feeding; thought to facilitate mother-child bonding • Released during physical intimacy/touch – Increases skin sensitivity to touch – High levels are associated w/orgasm – Levels remain high after orgasm; thought to contribute to emotional and erotic bonding of sexual partners • Research suggests oxytocin is important for facilitating social attachments and development of feelings of love. • Stress lowers oxytocin secretion. Funny ad . . . oxytocin spray! The brain and sexual arousal • Sexual arousal can occur w/o any sensory stimulation, through thoughts and fantasy alone. • Stimuli that people find arousing is greatly influenced by cultural conditioning. – Features that are considered attractive vary from one culture to another. – In many cultures, bare female breasts are not viewed as erotic stimuli, as they are in the U.S. – Foreplay leading to arousal varies considerably in different cultures. • Ex: in a survey of 190 cultures, mouth kissing was only practiced in 21. Anatomical regions of the brain involved in sexual arousal & response cerebral cortex: thinking center Limbic system: of the brain associated w/emotion & motivation; also includes the “pleasure center” Limbic system • Associated with emotion, motivation, and memory • Includes several brain structures – Hypothalamus, hippocampus, amygdala, cingulate gyrus • 1950s study: rats implanted w/electrodes in regions of limbic system that could be activated by a lever. – Rats pressed lever over and over, in preference to eating or drinking, eventually dying of exhaustion. • Limbic stimulation in people (done for therapeutic purposes) : patients reported intense sexual pleasure. • Damage to certain parts of the hypothalamus seems to dramatically reduce sexual behavior of both males and females in several species. Neurotransmitters and sexual arousal • Dopamine – Released in the “pleasure center” of the limbic system. – Facilitates sexual arousal and response. – Testosterone stimulates dopamine release in both males and females. • Oxytocin (already discussed) • Serotonin – Inhibits sexual activity – inhibits release of dopamine. – Antidepressants called SSRIs increase serotonin levels in the brain--side effects often include decreased libido and diminished sexual response. Sexual arousal: the role of the senses • Touch is the dominant "sexual sense” – Primary erogenous zones: areas of the body that contain dense concentrations of nerve endings. • Includes genitals, buttocks, anus, perineum, breasts, inner thighs, armpits, navel, neck, ear lobes, mouth. • Varies from one person to another. – Secondary erogenous zones: areas of the body that have become erotically sensitive through learning and experience. • Virtually any other region of the body--depends on personal erotic experiences. Sexual arousal: the role of the senses • Vision: usually next important sense in arousal. – Early research supported the idea that males are more aroused by visual stimuli than females. • Reflects many social influences: – Was considered culturally inappropriate for women to view pornography. – Most pornography was made to appeal exclusively to men; some women found themes/ideas offensive. – Today, pornography and erotica is available that appeals to many women. – Studies using physiological recording devices while subjects viewed pornography showed equal physiological signs of arousal in women and men. – When arousal was assessed by self-reporting, women are less inclined to report being sexually aroused by visual erotica. Sexual arousal: the role of the senses • Smell: highly influenced by a person‟s sexual history and social conditioning. – In some cultures, the smell of genital secretions are considered a sexual stimulant. • Use as a „perfume‟ by some women in Europe. – U.S.: near obsession w/masking any natural body odor • Difficult to study effect of natural odors on desire when they are so heavily masked by frequent bathing, deodorants, perfumes, and antiperspirants. – Even so, many report being aroused by the smell of their partner, or by people to whom they are attracted. – Pheromones: odors produced by the body that relate to reproductive functions (e.g. fertility). • Very important in sexual response and arousal in many animals. • Research still not clear on how important they are in humans. Sexual arousal: the role of the senses • Taste: seems to play a minor role in arousal. • Hearing: highly variable. – Some people find words, erotic conversation, moans, etc. to be very arousing – Others prefer more silent sex. • Different people receive different cultural messages about whether it is “okay” to talk or make noise during sex. Aphrodisiacs • Definition: substances that allegedly arouse sexual desire and increase the capacity for sexual activity. • Foods: Almost none of these substances actually work! – Many that resemble a penis: bananas, asparagus, cucumbers, ground-up horns of animals such as rhinoceros and reindeer (origin of the term horny) • Drugs: (see table) – Alcohol, amphetamines, barbiturates, cocaine, LSD, marijuana, amyl nitrite, L-dopa – Not one actually qualifies as a sexual stimulant – Some lower inhibitions, some can hinder the ability to think clearly and make conscious decisions. – Some can have dangerous side effects. Table 6.2 List of alleged aphrodisiacs Aphrodisiacs, (cont): yohimbine – Crystalline alkaloid derived from the bark of the yohimbe tree that grows in West Africa. • Aphrodisiac effects: – In rats, yohimbine extracts induced sexual arousal and activity – Positively affected sexual desire and performance in men w/erectile disorders – Increased sexual arousal in postmenopausal women who reported below-normal levels of sexual desire. • Concerns: – However, side effects are common, such as heart palpitations, sweating, anxiety, nausea, insomnia (like a stimulant). The appropriate dose for each person is difficult to determine. – Can‟t be taken by anyone w/medical problems such as heart problems, high b.p., liver problems, diabetes, or anyone taking a number of different medications. Anaphrodisiacs • Definition: substances that inhibit sexual behavior – Birth control pills (progesterone-containing) • Reduce sexual desire by lowering testosterone levels – Opiates, tranquilizers, sedatives • Reduce sexual interest, activity, and function – Nicotine • Reduces sexual interest and function by constricting blood vessels and by reducing blood testosterone levels. – Blood pressure medicine, drugs that treat heart disease • Inhibit erection and ejaculation, reduce orgasm intensity, reduce sexual interest – Antidepressants • Decreased desire, erectile disorder, delayed or absent orgasm – Anticonvulsant and antipsychotic drugs Models of sexual response: Masters & Johnson four-phase model excitement plateau orgasm resolution Female sexual response cycle Male sexual response cycle 3 patterns identified 1 pattern identified 6-A Discussion question: Do you believe that men and women differ in the importance they attach to experiencing orgasm during sexual sharing? Why or why not? Masters & Johnson four-phase model of sexual response: excitement plateau orgasm resolution • Remember: – There‟s lots of individual variation. – Model focuses only on physiology, not the entire personal experience of sexual response. – Too-literal interpretation of the plateau stage • Still a lot happening, even though it‟s described as a “leveling-off” Two fundamental physiological responses to effective sexual stimulation • Vasocongestion: engorgement of blood vessels in particular body parts in response to sexual arousal. • Myotonia: muscle tension Masters & Johnson's four phases • Excitement • Plateau Let‟s examine the changes that occur in the internal & external • Orgasm anatomy of men & women at each stage… • Resolution Changes in external & internal male anatomy during sexual response Excitement phase: • engorgement of penis and testes (vasocongestion) • increase in muscle tension • increased heart rate and blood pressure Changes in external & internal male anatomy during sexual response Plateau phase: • engorgement and elevation of testes increases. • further increase in muscle tension, heart rate and b.p. • Cowper‟s gland secretions may occur. Changes in external & internal male anatomy during sexual response Emission phase of orgasm: • contractions of internal structures • both internal and external urethral sphincters contract • result: seminal fluid pools in urethral bulb (see chapter 5) Changes in external & internal male anatomy during sexual response Expulsion phase of orgasm: • contractions of muscles at base of penis and in penile urethra • external urethral sphincter relaxes • result: expulsion of semen (see chapter 5) Changes in external & internal male anatomy during sexual response Resolution phase: • sexual anatomy returns to the nonexcited state • Refractory period (in men): time following orgasm in the male during which he cannot experience another orgasm. (see chapter 5) Changes in external female anatomy during sexual response Excitement phase: • engorgement of clitoris, labia minora, vagina, and nipples (vasocongestion); produces vaginal lubrication. • increase in muscle tension • increased heart rate and blood pressure Unaroused state Excitement phase Changes in internal female anatomy during sexual response Excitement phase: • vaginal lubrication begins (due to vasocongestion) • clitoris engorges with blood • uterus elevates • increase in muscle tension, heart rate, and b.p. Unaroused state Excitement phase Changes in external female anatomy during sexual response Plateau phase: • further increase in muscle tension, heart rate and b.p. • labia minora deepen in color • clitoris withdraws under its hood Changes in internal female anatomy during sexual response Plateau phase: • further increase in muscle tension, heart rate and b.p. • orgasmic platform forms • clitoris withdraws under its hood • uterus becomes fully elevated Changes in external female anatomy during sexual response Orgasm phase: • orgasmic platform (outer 1/3 of vagina) contracts rhythmically 3-15 times • clitoris remains retracted under hood Changes in internal female anatomy during sexual response Orgasm phase: • uterine contractions (in addition to contractions of orgasmic platform) Changes in external female anatomy during sexual response Resolution phase: • clitoris descends and engorgement subsides • labia return to unaroused size and color Changes in internal female anatomy during sexual response Resolution phase: • uterus descends to unaroused position • vagina shortens and narrows back to unaroused state Changes in the breasts during sexual response (summarizes figures) Historical misinformation about female orgasm • Sigmund Freud (early 1900s) – Developed theory of the “vaginal” vs. “clitoral” orgasm that led to misguided thinking about female sexual response for years – Theory stemmed from erroneous assumption that the clitoris was a “stunted penis,” so all erotic sensations from the clitoris were expressions of “masculine” rather than “feminine” sexuality-- therefore undesirable in a woman. – During adolescence, female was supposed to transfer her erotic center from her clitoris to her vagina--otherwise, she needed psychotherapy. • During Freud‟s time, surgical removal of the clitoris was actually recommended for little girls who masturbated to help them later attain “vaginal” orgasms. • Cultural remnants still persist--women often feel uncomfortable asking partners for clitoral stimulation or stimulating clitoris herself b/c they believe they “should” experience orgasm from vaginal stimulation alone. The “G” spot: what is it? • Stands for Grafenberg spot – From Ernest Grafenberg, a gynecologist who first publicized G spot in the 1950s. • Area of erotic sensitivity located along the anterior (front) wall of the vagina. • Some women are able to experience orgasm and possibly ejaculation from G spot stimulation. – G spot tissue is similar to male prostate; therefore, fluid may be similar to prostatic component of semen. • Supported by research that showed presence of enzyme in female ejaculate characteristic of prostate secretions • Note: orgasm from G spot stimulation is same as orgasm from clitoral stimulation, though intensity may vary depending on the method of stimulation. The “G” spot: exploring • After becoming aroused . . . • Partner inserts two fingers, presses or taps firmly against anterior vaginal wall – Initial sensation may feel slightly uncomfortable, need to urinate, or pleasurable. – After a minute or more of stimulation, sensations usually become more pleasurable, and area may begin to swell. • Many toys available to help • Sexual exploration is always a good thing, but important not to treat the G-spot as a new sexual achievement to be relentlessly pursued. Aging and the sexual response cycle • Women: (note: changes in sexual response vary considerably among women) – Some women report reduced desire – Reduced vasocongestion response, causing less and slower vaginal lubrication – Women who have more frequent sex (1-2 times weekly) lubricated more readily – Vaginal and urethral tissue loses some elasticity and becomes drier – Length and width of vagina decrease, reduced expansive ability of inner vagina during arousal. – Number of orgasmic contractions is often reduced. – More rapid resolution Aging and the sexual response cycle • Men: (note: changes in sexual response vary considerably among men) – Longer time to develop an erection • i.e. several minutes of stimulation vs. 8-10 seconds – Erection may be less firm. • Complete penile erection is often not obtained until late in the plateau phase, just before orgasm. • On the plus side, older men are often more able to sustain the plateau phase longer, enhancing pleasure for both partners. – Some men report reduced intensity of orgasm • Reduced number of contractions, force of ejaculation is reduced, less semen produced. – More rapid resolution – Refractory period between orgasm and next excitement phase gradually lengthens (could be hours to days) Sexual response: some differences between the sexes * There are many more similarities than differences in sexual response btwn. men and women. Greater variability in female response Male refractory period Multiple orgasms – Some women can have >1 orgasm separated by brief periods of time (maybe only a few seconds) – All women are theoretically physiologically capable of experiencing multiple orgasms, though only about 15% of women report regularly having multiple orgasms – Some men can also experience multiple orgasms • These men report that withholding ejaculation is important for experiencing multiple orgasms--ejaculation often triggers refractory period.
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