Chapter 6 Sexual Arousal and Response The Brain

Chapter 6 Sexual Arousal and Response

The Brain and Sexual Arousal • Cerebral cortex (mental events) – Reasoning, language, and imagination • Limbic system and sexual behavior • Hypothalamus • Neurotransmitters – Dopamine facilitates sexual arousal – Serotonin inhibits sexual arousal

The Limbic System and Sexual Behavior

The Brain and Sexual Response • Chemical Connection – Oxytocin – Phenylethylamine/Dopamine – Endorphins – Adrenaline – Testosterone – Prolactin – Serotonin

The Brain and Sexual Response • Oxytocin – During sex (but drops off quicker in men after orgasm) – Contractions • Phenylethylamine – Causes release of dopamine – Reward center & focus – Found in chocolate • Endorphins – ACH & DA – Euphoria, sleepiness • Adrenaline – Heart racing – Causes refractory period in men

The Brain and Sexual Response • Testosterone – Fuels sex drive – Rush of confidence after sex (esp for men) • Prolactin – Rises sharply after orgasm – Disengages the mind after sex • Serotonin – Released after orgasm – Mood enhancer

The Senses and Sexual Arousal • All sensory systems can contribute to arousal • Touch is the dominant “sexual sense” – Primary erogenous zones – Secondary erogenous zones • Vision usually next in dominance – Visual stimuli • Men self-report higher arousal than women • Women and men have similar physiological responses

Other Senses and Sexual Arousal • Smell may arouse or offend – Pheromones • Taste plays a minor role • Hearing plays a variable role

Aphrodisiacs • Substances believed to arouse sexual desire or increase capacity for sexual activity – Foods – Drugs and alcohol • No clear evidence of genuine aphrodisiac qualities – Role of expectations

Anaphrodisiacs • Inhibits sexual behavior – – Drugs (e. g. opiates, tranquilizers) Antihypertensives, antidepressants & antipsychotics Birth control pills Nicotine • Constricts blood flow • Possibly reduces circulating testosterone

The Role of Hormones in Sexual Behavior • Steroid hormones – Androgens (including testosterone) • Produced by testes, adrenal glands, and ovaries – Estrogens • Produced by ovaries and testes – Women and men produce both types • Neuropeptide hormones – Oxytocin

Sex Hormones in Male Sexual Behavior • Testosterone – – Linked to sexual desire and genital sensitivity Castration leads to reduced sexual desire Antiandrogen drugs Hypogonadism

Sex Hormones in Female Sexual Behavior • Estrogens – Overall link between estrogen and female sexual behavior is unclear – Estrogen Therapy (ET) • Testosterone – Role as major libido hormone in females

How Much Testosterone Is Necessary? • Two forms of testosterone (free and bound) – Free testosterone linked to libido – Although women have less free testosterone, their cells are more sensitive to it than men’s • Too much testosterone is linked to adverse effects • Testosterone levels decrease with age – Fairly rapid decrease for women at menopause; more gradual decline for men • Testosterone Replacement Therapy

Oxytocin and Sexual Behavior • Secreted during cuddling and physical intimacy – Increased skin sensitivity – High levels associated with orgasmic release for women and men – For women, stimulates contractions of uterine wall during orgasm

Sexual Response

Sexual Response • Master’s and Johnson’s Four Phases – – Excitement Plateau Orgasm Resolution

Sexual Response • Master’s and Johnson’s Four Phase Model – Phases of physiological responses – Two basic physiological processes • Vasocongestion • Myotonia

Sexual Response Cycle

Female Sexual Response

Male Sexual Response

Orgasm • Shortest phase of sexual response cycle – Men and women’s subjective descriptions of orgasm are similar, but there are many differences between their experiences.

Sex Differences in Sexual Response University of Minnesota Medical School – Two studies in 80’s • Orgasm begins as a series of 6 - 15 regular contractions of high intensity occurring over about 20 -30 seconds. There are individual differences (but no gender differences) in what occurs after this series of regular contractions. For some men and women, these regular contractions are the primary orgasmic experience. These Type I orgasms are the most frequent. Other men and women, however, may continue to experience irregular contractions for another 30 - 90 seconds, so called Type II orgasms. A relatively few people have mixed patterns of regular and irregular contractions. • Two things are important about these data. One is that the individual differences were reliable: people who had Type I orgasms on one occasion were more likely to have Type I orgasms on subsequent occasions, and similarly for Type II. The other important conclusion is that not only were there no gender differences, but the same types of individual differences occurred in males and females. Some women and some men are Type I climaxers and some are Type II.

Sex Differences in Sexual Response • Greater variability in female response; male refractory period • Men’s orgasms may be shorter than women’s • Studies show that it takes 15 to 40 minutes for the average woman to reach orgasm and 2 minutes for men • 75 percent of men reach orgasm consistently in their sex lives, while just 50 percent of women could say the same • Women can experience multiple orgasms according to M & J; Kinsey found 15% of men can too • While only 64 percent of women reached orgasm during their last sexual experience, 85 percent of men believed that they gave their partner an orgasm

Locating the G-Spot

Aging & Sexual Response Cycle Older women • Response cycle continues, but with decreased intensity • Excitement: – Vaginal lubrication begins more slowly, reduced amount • Plateau: – decreased vagina flexibility • Orgasm: – number of uterine contractions decrease • Resolution: – occurs more rapidly

Aging and the Sexual Response Cycle Older men • Response cycle continues, with changes in intensity and duration of response • Excitement: – lengthened time to erection • Plateau: – able to sustain plateau phase longer • Orgasm: – reduced muscular contractions and force of ejaculation • Resolution: – occurs more rapidly – refractory period lengthens

Age-Related Changes in the Sexual Response Cycle