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Chp 6 Sexual Arousal _ Response - Laney College


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									   Chapter 6

Sexual Arousal and
• Steroid hormones
  – Commonly referred to as “male sex hormones” and “female
    sex hormones,” although both sexes produce both types of
  – 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,

• Estrogens: role in female sexual behavior is still
   –   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
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 &
                                also includes
                                 the “pleasure
                   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
    • 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
         – 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
  – 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
  – 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.
• 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
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.
• 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
   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
   – Initial sensation may feel                          slightly
     uncomfortable, need                            to urinate, or
   – After a minute or more of                       stimulation,
     sensations usually                      become more
     pleasurable, and                        area may begin to
• 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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