This document summarizes key points about hormones and the brain in relation to sexual arousal and response. It discusses how testosterone and estrogen influence male and female libido. The limbic system and neurotransmitters like dopamine and oxytocin facilitate sexual arousal. Visual, tactile, and olfactory senses can stimulate arousal depending on cultural conditioning. The document also describes Masters and Johnson's four phase model of sexual response and changes in male and female anatomy that occur during each phase. It addresses historical misconceptions about female sexuality and explores the purported "G-spot".

1. Chapter 6
Sexual Arousal and
Response

2. 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.
– Produced in the brain by the hypothalamus.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. Funny ad . . . oxytocin spray!

10. 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.

11. Anatomical regions of the brain involved
in sexual arousal & response
cerebral cortex:
thinking center
of the brain
Limbic system:
associated
w/emotion &
motivation;
also includes
the “pleasure
center”

12. 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.

13. 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.
– (selective serotonin reuptake inhibitors)

14. 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.

15. 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.

16. 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.

17. 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.

18. Aphrodisiacs
• Definition: 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-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.
Almost none of these substances actually work!

19. Table 6.2
List of
alleged
aphrodisiacs

20. 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.

21. 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

22. Models of sexual response:
Masters & Johnson four-phase model
 excitement  plateau  orgasm  resolution
Female sexual response cycle
3 patterns identified
Male sexual response cycle
1 pattern identified

23. 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?

24. 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”
– NOTE: Kaplan has Desire as first phase

25. 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

26. Masters & Johnson's four phases
• Excitement
• Plateau
• Orgasm
• Resolution
Let’s examine the changes that
occur in the internal & external
anatomy of men & women at
each stage…

27. Changes 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

28. 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.

29. 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)

30. 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)

31. 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)

32. 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

33. 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

34. 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

35. 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

36. 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

37. Changes in internal female anatomy
during sexual response
Orgasm phase:
• uterine contractions (in addition to
contractions of orgasmic platform)

38. Changes in external female anatomy
during sexual response
Resolution phase:
• clitoris descends and engorgement subsides
• labia return to unaroused size and color

39. Changes in internal female anatomy
during sexual response
Resolution phase:
• uterus descends to unaroused position
• vagina shortens and narrows back to unaroused state

40. Changes in the breasts during
sexual response

41. (summarizes figures)

42. 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.

43. 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.

44. 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.

45. 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

46. 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)

47. 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.