Sexual arousal - a summary of chapter 8 of Understanding human sexuality by Hyde and DeLamater

Sexology
Chapter 8
Sexual arousal

Satisfying sexual expression contributes to good physical and mental health.

The sexual response cycle

Sexual response typically progresses in thee stages, according to the Masters and Johnson’s model

• Excitement
• Orgasm
• Resolution

Physiological processes that occur during these stages are

• Vasocongestion:
  An accumulation of blood in the blood vessels of a region of the body, especially the genitals; a swelling or erection results.
• Myotonia
  Muscle contraction
  Not only in the genitals, but also throughout the body.

Excitement

Excitement: the first stage of sexual response, during which erection in males and vaginal lubrication in females occur.
The basic physiological process that occurs during excitement is vasocongestion.

Erection may be produced by

• Direct physical stimulation of the genitals
• Stimulation of other parts of the body
• Erotic thoughts or sensory images

Erection occurs rapidly, although it may take place more slowly as a result of a number of factors

• Age
• Intake of alcohol
• Fatigue

As the man gets closer to orgasm, a few drops of fluid, secreted by the Cowper’s gland, appear at the tip of the penis.
They may contain active sperm.

In men, the skin of the scrotum thickens, the scortal sac tenses, and the scrotum is pulled up and closer to the body.

For an erection to occur, several arteries must dilate, allowing a strong flow of blood into the corpora. They dilate because the smooth muscle surrounding the arteries relaxes.
At the same time, the veins carrying blood away from the penis are compressed, restricting the outgoing blood flow.
Multiple neurotransmitters are involved in this process

• Nitric oxide (NO)
• Dopamine

Vasoconstriction makes an erection go away.

• Epinephrine
• Norepinephrine

An important response of females in the excitement phase is lubrication of the vagina.
Results from vasocongestion.
During excitement, the capillaries in the walls of the vagina dilate and blood flow through them increases.
Vagina lubrication results when fluids seep through the semipermeable membranes of the vaginal walls, producing lubrication as a result of vasocongestion in the tissues surrounding the vagina.
Lubrication begins 10 to 30 seconds after the onset of arousing stimuli.
Can be affected by

• Age
• Alcohol
• Fatigue

Orgasmic platform: a tightening of the entrance to the vagina caused by contractions of the bulbospongiosus muscle (which covers the vestibular bulbs) that occur during the excitement stage of sexual response.

During the excitement phaser, the glans of the clitoris (the tip) swells.
This results form engorgement of its corpora cavernosa.
The crura of the clitoris also swell.
The vestibular bulbs, which lie along the wall of the vagina, are erectile and swell.
Relaxation of the smooth muscle surrounding the arteries supplying the glans and crura of the clitoris and the verstibular bulbs occurs, allowing a great deal of blood flow to the region.

• Nitric oxide is a key neurotransmitter involved in the process.
• Estrogen helps the vasodilation

During excitement the nipples become erect.
This results from contractions of the muscle fibres surrounding the nipple.
The breast swell and enlarge somewhat in the late part of the excitement phase.

During excitement the inner lips swell and open up

The vagina shows change during excitement.

• In the unaroused state the walls of the vagina lie against each other
• During excitement, the upper two-thirds of the vagina expands dramatically in a ballooning response.
  This ballooning helps accommodate the entrance of the penis
  • As part of the ballooning, the cervix and uterus pull up

During excitement, a ‘sex flush’ may appear on the skin of both men and women.
Pulse rate, breathing rate, and blood pressure also increase in both men and women.
Late in the excitement phase, the processes of vasocongestion and myotonia continue to build until there is sufficient tension for orgasm.

Orgasm

Orgasm: an intense sensation that occurs at the peak of sexual arousal and is followed by release of sexual tensions.

In males

• Orgasm consist of a series of rhythmic contractions of the pelivic organs at 0.8 second intervals.
• Male orgasms occurs in two stages
  • The preliminary stage
    The vas, seminal vesicles, and prostate contract, fording the ejaculate into a bulb at the base of the urethra
    Ejactulatory inevitability (coming). It cannot be stopped once the man has reached this point
• The urethral bulb and the penis itself contract rhythmically, forcing the semen through the urethra and out the opening at the tip of the penis

In both males and females, pulse rate, blood pressure, and breathing rate increase sharply during orgasm.
Muscles contract throughout the body.

The process of orgasm in females is basically similar to that of males .
It is a series of rhythmic muscular contractions of the orgasmic platform.
Generally occur at about 0.8 second intervals.
There may be three or four in a mild orgasm or as many as a dozen in a very intense, prolonged orgasm.
The uterus also contracts rhythmically.

Resolution

Resolution: the body returns to the unaroused state.

Orgasm triggers a massive release of muscular tension and of blood from the engorged blood vessels.
Resolution represent a reversal of the processes that build up during the excitement phase.

Women

• In the 5 to 10 seconds after the end of the orgasm, the clitoris returns to its normal position, although it takes longer for it to shrink to its normal size.
• The orgasmic platform relaxes and begins to shrink.
• The ballooning of the vagina diminishes and the uterus shrinks.
• The resolution phase generally takes 15 to 30 minutes, but it may take longer in women who have not had an orgasm.

In both men and women, resolution brings a gradual return of pulse rate, blood pressure, and breathing rate to the unaroused levels.

Men

• Detumescence: the loss of erection in he penis
  Happens in two stages
  • The first occurs rapidly but leaves the penis still enlarged
    Results from an emptying of the corpora cavernosa
  • The second stage occurs more slowly
    Results from the slower emptying of the corpus spongiosum and the glans

Refractory period: the period following orgasm during which the male cannot be sexually aroused.
Vary greatly from one men to the next.
Become longer as men grow older.

Women do not have a refreactory period.

More on women’s orgasms

Some people believe that women have two kinds of orgasm

• Clitoral orgasm
  Freud’s term for orgasm in females resulting form stimulation of the clitoris
• Vaginal orgasm
  Freud’s term for orgasm in females resulting from stimulation of the vagina in heterosexual intercourse.

According to research, there is no difference between clitoral and vaginal orgasms.

• All female orgasms are physiologically the same, regardless of the site of stimulation
• Clitoral stimulation is almost always involved in producing orgasm, even during vaginal intercourse.

Women can have multiple orgasms within a short period of time.
Multiple orgasms do not differ physiologically from single orgasms.
Multiply orgasmic men exist.

Other models of sexual response

Criticisms of Masters and Johnson’s model

• It ignores the cognitive and subjective aspects of sexual response
• How research participants were selected and how this process may have created a self-fulfilling prophecy for the outcome
  To participate in the research, participants were required to have a history of orgasm both through masturbation and through coitus.
  • Everyone whose pattern of sexual response did not include orgasm, and therefore did not fit the model, was excluded from research

Kaplan’s Triphasic model

Sexual response as having three relatively independent stages, or components

• Sexual desire
  Can occur either
  • Spontaneously, motivating the person toward sexual activity and excitement
  • Excitement can come first, activating desire
• Vasocongestion of the genitals
• The reflex muscular contractions of the orgasm phase

Justifications for Kaplan’s approach

• The two physiological components are controlled by different parts of the nervous system
• The two components involve different anatomical structures
• Vasocongestion and orgasm differ in their susceptibility to being disturbed by injury, drugs or age.
• The reflex of ejaculation in the male can be brought under voluntary control by most men, but the erection reflex generally not
• Impairment of the vasocongestion response or the orgasm response produces different sexual disorders.

The sexual excitation-inhibition model

Dual control model: a model that holds that sexual response is controlled both by

• Sexual excitation
• Sexual inhibition

According to the model, propensities toward sexual excitation and sexual inhibition vary widely from one person to the next.
Most people fall in the moderate range on both and function well.
At the extremes, problems can occur.

Although both excitation and inhibition have biological bases, early learning and culture are critical factors because they determine which stimuli the individual will find to be sexualy exciting or wil set of sexual inhibition.

Why inhibition?

• Sexual activity in some situations could be dangerous
• Sometimes the environment is not conductive to reproduction, and it is better to wait for a better day or a better season
• Excessive sexual behaviour in men, perhaps with ejaculations several times a day, would reduce fertility.

Emotion and arousal

No one has proposed a formal model of emotion and arousal.
Positive emotions show a strong positive association with sexual arousal.
The same goes for negative emotions.

Neural and hormonal bases of arousal

The brain, the spinal cord, and sex

Spinal reflexes

Several components of sexual behaviour are controlled by spinal cord reflexes
A reflex has three basic components

• Receptors
• Transmitters
• Effectors

Erection

The penis has lots of receptor neurons, and tactile stimulation of the penis or nearby neurons produces a neural signal that is transmitted to an erection centre in the lowest part of the spinal cord.
This centre sends out a message via the pathetic division of the autonomic nervous system to the muscles around the walls of the arteries in the penis.
The response is vasocongestion.

Besides tactile stimulation of the genitals, other conditions may also produce erection.

Ejaculation

There are two ejaculation centres and they are located higher in the spinal cord.
Both the sympathetic and parasympathetic divisions of the nervous system are involved.
The response is muscular.
In the ejaculation reflex, the penis responds to stimulation by sending a message to the ejaculation center.

The three main problems of ejaculation are

• Premature ejaculation
• Male orgasmic disorder
  Delayed ejaculation
• Retrograde ejaculation
  A condition in which orgasm in the male is not accompanied by an external ejaculation; instead, the ejaculate goes into the urinary bladder.

Reflexes in women

Sensory input to the clitoris travels along the dorsal nerve of the clitoris and continues within thepudendal nerve to a reflex centre in the sacral potion of the spinal cord.
Neural circuits for orgasm in women are very similar to those for orgasm and ejaculation in men.

Female ejaculation occurs in some women.
Gräfenberg spot (G-spot): a small region on the front wall of the vagina, emptying into the urethra, and responsible for female ejaculation.

Brain control of sexual response

Sexual responses may be brought under voluntary control and may be initiated by purely psychological forces.
Environmental factors may also affect a person’s sexual response.

Distinct brain regions and networks are associated with desire/interest, arousal, orgasm, and the refractory period.

Brain-imaging researchers think about

• An anticipatory phase
  Includes sexual interest, desire and the beginnings of arousal
• A consummatory phase
  Involves sexual activity and orgasm
• A post-orgasmic period

Anticipatory phase

Sexual interest network

• Nucleus accumbens
• Amygdala
• Anterior cingulate cortex
• Hypothalamus

These are part of the limbic system.
Erection is not associated with activity in these regions.
The activation of the sexual interest network is automatic.

Consummatory phase: brain activity during sexual activity

Genital stimulation creates activity in the motor cortex.
There is activity in the somatosensory cortex as we respond to the feel of the stimulation.
There is reduced activity in the amygdala.

Orgasm

Decreased activity in the prefrontal cortex.
Increased activity in the orbitofrontal cortex.

Resolution and post-orgasmic refractory period

De-arousal neural network

• Septal area
• Temporal lobe
• Amygdala

Neurochemical influences on sexual response

Distinctive neurochemicals are involved in sexual excitation and sexual inhibition

• Excitement and arousal
  Dopamines
  Melanocortins
  Oxytocin
  Norepinephrine
  • The activation of these neurochemicals also blocks the action of inhibitiory processes
• Inhibitory
  Opioids
  Endocannabinoids

Androgens, estrogen and progestin faciliate or prime the brain to respond to sexual incentives by binding to specific hormone receptor complexes, which in turn lead to the synthesis of these neurochemicals.

Hormones and sex

Organizing versus activating effects

Organizing effects of hormones: effects of sex hormones early in development, resulting in a permanent change in the brain or reproductive system.
Activating effects of hormones: effects of sex hormones in adulthood, resulting in the activation of behaviours, especially sexual behaviours and aggressive behaviours.

It seems, that males and females initially have capacities for both male and female behaviours.
If testosterone is present early in development, the capacity for exhibiting female behaviours is suppressed.
But, in humans it is more under control of the brain.

Testosterone and sexual desire

Testosterone has effects on sexual desire in humans.
Testosterone seems to have an activating effect in maintaining sexual desire in men.
At puberty, testosterone affects sexual motivation directly.

Androgens are also related to sexual desire in women.

Sexual behaviour also affects testosterone levels.
The effects are bidirectional.

Sex offenders – castration or incarceration?

Physical castration: surgical removal of the testes. Also known as bilateral orchiectomy.
Chemical castration: injections of a drug that sharply reduces the levels of testosterone in the body.

The low level of testosterone is a sharply reduced sex drive and the virtual elimination of sexual behaviour.
However, the effects in humans are not so clear.

Pheromones

Pheromones: biochemicals secreted outside the body that are important in communication between animals and that may serve as sex attractants.

The sense of smell is essential for pheromone effects to occur.
The vomeronasla organ (VNO).
Activation of the VNO activates cells in the hypothalamus.
The VNO is a kind of second olfactory pathway.
The VNO functions in addition to the main sense of smell.

Human pheromones exist and may play an important role in sexuality.
It may be the ‘body chemistry’ that attracts people to each other.

• The VNO consists of just a few neurons in humans and seems to be non-functional
• But, when humans smell pheromones, a region of the hypothalamus is activated, as is the amygdala.
  • Humans have cells in the lining of the nose that contain pheromone receptors
• Humans do secrete pheromones
• Research provides indications that pheromones may play a role in human sexuality

Menstrual synchrony: the convergence, over several months, of the dates of onset of menstrual periods among women who are in close contact with each other.
This phenomenon is thought to be be due to pheromones produced by the women.

The smell of pheromones does not necessarily have ot be consciously perceived in order to have an effect.

Sexual techniques

Erogenous zone

Erogenous zones: areas of the body that are particularly sensitive to sexual stimulatoin.
One’s person’s erogenous zones can be quite different from another’s.

One-person sex

Autoeroticism: sexual self-stimulation.

Masturbation

Masturbation: stimulation of one’s won genitals with the hand or with some object.
Very common sexual behaviour.

The techniques used by males and females in masturbation are interesting in part because they provide information to their partners concerning the best techniques to use in lovemaking.

Fantasy

Sexual fantasy: sexual thoughts or images that alter the person’s emotions or physiological state.
The themes of sexual fantasies reported by men and women are similar

• Taking part in fellatio or cunnilingus
• Having sex in an unusual place
• Sex in a romantic place
• Being masturbated by my partner
• Having sex with someone I know who is not my spouse

Some fantasies show gender differences in preferences

• Men are more likely to fantasize about
  • Being masturbated by an unknown person
  • Having anal sex
  • Having interracial sex
  • Having sex with someone much younger (but legal) than they are
• Women are more likely to have fantasized about having same-gender sex

Sexual fantasies can have a variety of functions

• Enhancing self-esteem and attractiveness
• Increasing the person’s own sexual arousal
• Facilitating orgasm
• Mentally rehearse future possibilities

Vibrators and other sex toys

Both male and female artificial genitals can be purchases.
Dildo: a rubber or plastic cylinder, often shaped like a penis.
And sex oils.

Two-person sex

Kissing

Two basic approaches

• Simple kissing
• Deep kissing

There are endless variations and plenty of regions.

Touching

Enjoying touching and being touched is essential to sexual pleasure.
The regions that are exciting vary a great deal from one person to the next and depend on hwo the person is feeling at the moment.

One of the best ways to find out how to use your hands in stimulating the genitals of another person is to find out how that person masturbates.

One of the things that make hand stimulation most effective is for the man’s partner to have a playful delight in, and appreciation of, the man’s penis.

Generally it is best, to begin with gentle, light stroking of the inside of the thighs and the inner and outer lips, moving to light stroking of the clitoris.
As she becomes more aroused, the stimulation of the clitoris can become firmer.
Moisture makes the stimulation more comfortable and sensuous.

The other senses

Vision, smell and hearing can contribute.

Perhaps the biggest visual turn-on comes simply form looking at your body and your partner’s.
Odours can be turn-ons or turn-offs.
Many people respond with arousal to specific musical stimuli, probably reflecting classical conditioning.

Fantasy during two-person sex

Fantasies can be done solo or can heighten the experience of sex with another person.
Fantasies are one way to introduce some variety and excitement without violating an agreement to be faithful to the other person.

Genital-genital stimulation: positions of intercourse

Coitus: sexual intercourse; insertion of the penis into the vagina.

There are an infinite number of positions of intercourse.
There are a few basic positions

• Face-to-face position
  Whether the couple face each other
• Rear-entry position
  Whether one partner faces the other’s back
• Whether one partner is on top of the other
  Or the couple are side by side.

Variations

• The man-on-top position
  • The best position for ensuring conception
  • The couple may feel better able to express their love or to communicate
  • Does not work well if the women is in the advanced stages of pregnancy or if she or the man is extremely obese
  • Not a good position if the man wants to control is ejaculation
• Woman-on-top
  • Provides as lot of clitoral stimulation
  • The woman can control the kind of stimulation she gets
  • A good position for the man who wants to delay his ejaculation
• Rear-entry position
• Side-to-side position
  • Either face-to-face or rear-entry
  • Is good for prolonged intercourse or if one or both of the partners is tired
  • Good for pregnant and obese people

Other variations

There are many possibilities.

Mouth-genital stimulation

Two kinds of mouth-genital stimulation

• Cunnilingus: mouth stimulation of the female genitals
• Fellatio: mouth stimulation of the male genitals

Cautions

• Both can transmit some sexually transmitted infections.
• Some women enjoy having their partner blow air forcefully into the vagina
  The is not dangerous under normal circumstances, but when used on pregnant woman can cause death, damage to the placenta, and embolism

Sixty-nining: simultaneous mouth-genital stimulation.

Anal intercourse

Anal intercourse: insertion of the penis into the partner’s rectum.
Somewhat more difficult than coitus, because the rectum has not natural lubrication and because it is surrounded by fairly tight muscles.
The man should begin with moistening the partner’s anus and his penis.
The more the partner can relax, the less uncomfortable it is.

Some health risks are associated with anal intercourse

• It can cause damage or injury to the tissue of the rectal lining and anal sphincter.
• Can lead to infections with various organisms.
• HIV can be transmitted

The penis should never be inserted into the vagina after anal intercourse unless it has been washed thoroughly.
The rectum contains bacteria that do not belong in the vagina.

Anilingus: mouth stimulation of the partner’s anus.

Techniques of lesbians and gays

Interfemoral intercourse: a sexual technique used by gay men in which one man moves his penis between the thighs of the other.
Tribadism: a sexual technique used by lesbians in which one women lies on top of another and moves rhythmically in order to produce sexual pleasure, particularly clitoral stimulation.

Aphrodisiacs

Is there a good aphrodisiac?

Aphrodisiac: a substance that increases sexual desire.
There is no known substance that works well as an aphrodisiac.

Anaphrodisiacs

Anaphrodisiacs: a substance that decreases sexual desire.

Exceptional sex

• Being fully present and focused
• Connection, merger, being in synch
• Deep intimacy
• Extraordinary communication
• Authenticity, being genuine, uninhibited
• Exploration, interpersonal risk-taking, fun