2Hormones Steroid hormones Neuropeptide 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 hormoneProduced 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 hormonesproduced by ovaries & testes.Testes produce much smaller quantities of estrogens than ovaries.Neuropeptide hormonesOxytocin--often called the “love hormone;” seems to influence erotic and emotional attraction to one another.Produced in the brain by the hypothalamus.
3Hormones 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.Evidence1) 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.
4Hormones in female sexual behavior Testosterone linked to female sexual desire (libido)Evidence1) Testosterone-replacement therapy enhances sexual desire and arousal in post-menopausal women and other women with low levels of testosterone2) 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.
5Hormones in female sexual behavior, (cont.) Estrogens: role in female sexual behavior is still unclear.Contribute to general sense of well-beingHelp maintain thickness & elasticity of vaginal liningContribute to vaginal lubricationHowever, there are contradictory findings about whether administration of estrogen increases or decreases libido in women.
6How 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.
7Testosterone 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.
8Oxytocin in male & female sexual behavior Oxytocin: a neuropeptide (a short string of amino acids produced in the hypothalamus in both sexes).Stimulates release of milk during breast-feeding; thought to facilitate mother-child bondingReleased during physical intimacy/touchIncreases skin sensitivity to touchHigh levels are associated w/orgasmLevels remain high after orgasm; thought to contribute to emotional and erotic bonding of sexual partnersResearch suggests oxytocin is important for facilitating social attachments and development of feelings of love.Stress lowers oxytocin secretion.
10The 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.
11Anatomical regions of the brain involved in sexual arousal & response cerebral cortex: thinking center of the brainLimbic system: associated w/emotion &motivation;also includesthe “pleasurecenter”
12Limbic system Associated with emotion, motivation, and memory Includes several brain structuresHypothalamus, hippocampus, amygdala, cingulate gyrus1950s 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.
13Neurotransmitters and sexual arousal DopamineReleased 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)SerotoninInhibits sexual activityinhibits release of dopamine.Antidepressants called SSRIs increase serotonin levels in the brain--side effects often include decreased libido and diminished sexual response.(selective serotonin reuptake inhibitors)
14Sexual 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.
15Sexual 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.
16Sexual 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 odorDifficult 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.
17Sexual 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 arousingOthers prefer more silent sex.Different people receive different cultural messages about whether it is “okay” to talk or make noise during sex.
18AphrodisiacsDefinition: substances that allegedly arouse sexual desire and increase the capacity for sexual activity.Foods: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-dopaNot one actually qualifies as a sexual stimulantSome lower inhibitions, some can hinder the ability to think clearly and make conscious decisions.Some can have dangerous side effects.Almost none of these substances actually work!
20Aphrodisiacs, (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 activityPositively affected sexual desire and performance in men w/erectile disordersIncreased 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.
21Anaphrodisiacs Definition: substances that inhibit sexual behavior Birth control pills (progesterone-containing)Reduce sexual desire by lowering testosterone levelsOpiates, tranquilizers, sedativesReduce sexual interest, activity, and functionNicotineReduces sexual interest and function by constricting blood vessels and by reducing blood testosterone levels.Blood pressure medicine, drugs that treat heart diseaseInhibit erection and ejaculation, reduce orgasm intensity, reduce sexual interestAntidepressantsDecreased desire, erectile disorder, delayed or absent orgasmAnticonvulsant and antipsychotic drugs
22Models of sexual response: Masters & Johnson four-phase model excitement plateau orgasm resolutionFemale sexual response cycle3 patterns identifiedMale sexual response cycle1 pattern identified
236-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?
24Masters & Johnson four-phase model of sexual response: excitement plateau orgasm resolutionRemember: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 stageStill a lot happening, even though it’s described as a “leveling-off”NOTE: Kaplan has Desire as first phase
25Two fundamental physiological responses to effective sexual stimulation Vasocongestion: engorgement of blood vessels in particular body parts in response to sexual arousal.Myotonia: muscle tension
26Masters & Johnson's four phases ExcitementPlateauOrgasmResolutionLet’s examine the changes that occur in the internal & external anatomy of men & women at each stage…
27Changes in external & internal male anatomy during sexual response Excitement phase:• engorgement of penis (cavernous and spongy bodies) and testes (vasocongestion)• increase in muscle tension• increased heart rate and blood pressure
28Changes 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 glandsecretions mayoccur.
29Changes 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)
30Changes 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)
31Changes 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 themale during which he cannot experience another orgasm.(see chapter 5)
32Changes 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 pressureUnaroused stateExcitement phase
33Changes 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 stateExcitement phase
34Changes 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
35Changes 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
36Changes in external female anatomy during sexual response Orgasm phase:• orgasmic platform (outer 1/3 of vagina) contractsrhythmically 3-15 times• clitoris remains retracted under hood
37Changes in internal female anatomy during sexual response Orgasm phase:• uterine contractions (in addition tocontractions of orgasmic platform)
38Changes in external female anatomy during sexual response Resolution phase:• clitoris descends and engorgement subsides• labia return to unaroused size and color
39Changes in internal female anatomy during sexual response Resolution phase:• uterus descends to unaroused position• vagina shortens and narrows back to unaroused state
42Historical 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 yearsTheory 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.
43The “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 secretionsNote: orgasm from G spot stimulation is same as orgasm from clitoral stimulation, though intensity may vary depending on the method of stimulation.
44The “G” spot: exploring After becoming aroused . . .Partner inserts two fingers, presses or taps firmly against anterior vaginal wallInitial 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 helpSexual exploration is always a good thing, but important not to treat the G-spot as a new sexual achievement to be relentlessly pursued.
45Aging and the sexual response cycle Women: (note: changes in sexual response vary considerably among women)Some women report reduced desireReduced vasocongestion response, causing less and slower vaginal lubricationWomen who have more frequent sex (1-2 times weekly) lubricated more readilyVaginal and urethral tissue loses some elasticity and becomes drierLength and width of vagina decrease, reduced expansive ability of inner vagina during arousal.Number of orgasmic contractions is often reduced.More rapid resolution
46Aging and the sexual response cycle Men: (note: changes in sexual response vary considerably among men)Longer time to develop an erectioni.e. several minutes of stimulation vs secondsErection 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 orgasmReduced number of contractions, force of ejaculation is reduced, less semen produced.More rapid resolutionRefractory period between orgasm and next excitement phase gradually lengthens (could be hours to days)
47Sexual 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 orgasmsSome 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 orgasmsSome men can also experience multiple orgasmsThese men report that withholding ejaculation is important for experiencing multiple orgasms--ejaculation often triggers refractory period.