1. PHYSIOLOGY OF THE SEXUAL RESPONSE
Masters and Johnson: four phases
Excitation:
Vasocongestion: pelvic area receives more blood in general, in particular to genitals.
Males:
penile erection
scrotal sac thickens, elevates

2. PHYSIOLOGY OF THE SEXUAL RESPONSE
Excitation (Cont’d)
Females:
vaginal lubrication
glans clitoris enlarges (similar to penile erection)
nipples erect (myotonia: muscle contraction)
breasts enlarge (vasocongestion
inner lips of vulva swell and open, change in colour (darker)
upper 2/3rds of vagina balloons
cervix and uterus stand up: tenting effect
angle of cervical opening more receptive to sperm

5. PHYSIOLOGY OF THE SEXUAL RESPONSE
Excitation (Cont’d)
Both Sexes:
sex flush (can happen later)
heart rate, respiration rate gradually increase
generalized myotonia

6. PHYSIOLOGY OF THE SEXUAL RESPONSE
Plateau:
Both males and females continue vasocongestion to max
Heart rate, respiration rate and blood pressure continue to increase
Copious perspiration
Increased myotonia

7. PHYSIOLOGY OF THE SEXUAL RESPONSE
Plateau (Cont’d)
Females:
orgasmic platform: outer third of vagina thickens, swells: condition sine qua non: without it, no orgasm
tenting complete
clitoris erect

8. PHYSIOLOGY OF THE SEXUAL RESPONSE
Plateau (Cont’d)
Males:
Cowper’s glands secrete fluid through tip of penis. WARNING: may contain live sperm!
scrotum even higher and testicles bigger

9. PHYSIOLOGY OF THE SEXUAL RESPONSE
Orgasmic:
Males: Two stages:
contraction of seminal vesicles, vas and prostate
contraction of urethra and penis: ejaculation

10. PHYSIOLOGY OF THE SEXUAL RESPONSE
Orgasmic:
Females:
contractions of orgasmic platform
contractions of uterus
several orgasms possible if stimulation continues
oxytocin

11. PHYSIOLOGY OF THE SEXUAL RESPONSE
Orgasmic:
Both:
very high heart rate, blood pressure and breathing
intense myotonia

12. PHYSIOLOGY OF THE SEXUAL RESPONSE
Health Benefits Associated With Orgasm
General Health
An orgasm at least once or twice per week appears to strength the immune system’s ability to resist flu and other viruses
Pain Relief
Some women find that an orgasm’s release of hormones and muscle contractions help relieve the pain of menstrual cramps and raise pain tolerance in general.

13. PHYSIOLOGY OF THE SEXUAL RESPONSE
Health Benefits Associated With Orgasm (Cont’d)
Lower Cancer Rate
Men who have more than five ejaculations per week during their 20s have a significantly lower rate of prostate cancer later in life
Mood Enhancement
Orgasms increase estrogen and endorphins, which tend to improve mood and ward off depression in women

14. PHYSIOLOGY OF THE SEXUAL RESPONSE
Health Benefits Associated With Orgasm
Greater Feelings of Intimacy
The hormone oxytocin, which may play a role in feelings of love and intimacy, increases fivefold at orgasm
Better Sleep
The neurotransmitter dopamine, released during orgasm, triggers a stress-reducing, sleep-inducing response that may last up to two hours

15. PHYSIOLOGY OF THE SEXUAL RESPONSE
Emotional Changes During Orgasm:
Based on EEG, MRI and PET scans done in the lab while subjects having an orgasm.
General emotional response:
coded in limbic association area, especially prefrontal cortex and cingulate gyrus.
Pleasure:
coded in basal forebrain, especially ventral tegmental area and its dopaminergic stimulation of the reward centres of the septal nuclei and the nucleus accumbens.
Euphoria:
probably by assymetric cortical activation
The proportion and intensity of each varies with each orgasm.
So: orgasms differ

16. PHYSIOLOGY OF THE SEXUAL RESPONSE
Resolution:
Return to normal, muscles relax, breathing etc. back to normal, blood back to circulation from genitals.
Males
refractory period
EACH PHASE MUST BE FULLY COMPLETED IN ORDER TO REACH THE NEXT ONE

18. PHYSIOLOGY OF THE SEXUAL RESPONSE
SOME GENDER DIFFERENCES:
Excitation: women slower:
cultural expectations, socialization
pregnancy
IT IS VERY IMPORTANT FOR MALE PARTNER TO MAKE SURE SHE IS READY FOR PLATEAU STAGE

19. PHYSIOLOGY OF THE SEXUAL RESPONSE
SOME GENDER DIFFERENCES (cont’d)
Plateau:
without orgasmic platform women can’t have orgasm.
Orgasm:
multiples for many women. Some women cannot go through resolution without several orgasms, vasocongestion persists. Thoughtful male partners go last. Some men report more than one orgasm, usually dry ones (no ejac.) and only one wet one.
Three types of female orgasm have been identified by some researchers:
from clitoral stimulation, via pudendal nerve
from G-spot stimulation, via pelvic nerve
a blend of both
Resolution:
women have no refractory period

20. PHYSIOLOGY OF THE SEXUAL RESPONSE
SOME GENDER DIFFERENCES (cont’d)
“Pleasure centers”: (for arousal and orgasm)
Both:
genital area
Women (and some men):
nipples, breasts, G-spot
Men:
prostate
Many body areas can be:
ears, back of knees, neck, feet, abdomen, thighs, inside of elbows, scalp

21. PHYSIOLOGY OF THE SEXUAL RESPONSE
SOME GENDER DIFFERENCES (cont’d)
Retrograde Ejaculation:
Two separate valves or sphincters, one to let urine into urethra, and another to let semen into urethra. When one is open, the other closes. In some cases, the semen valve is closed and the urinary valve that opens to the bladder is open. Semen flows into bladder. No ill effects.
Is there female ejaculation? Mixed evidence.
Skene’s glands or paraurethral glands: on the urethra. Could be supplying ejaculatory fluid.

22. PHYSIOLOGY OF THE SEXUAL RESPONSE
Female Ejaculation: Fact or Fiction?
anecdotal reports available for a couple of centuries or more
some women were said to have a copious release of fluid that was not urine during orgasm
research is very inconclusive, only case histories
chemical analysis of fluid: in some studies, found to be identical to urine, in other studies found to be very similar to prostatic fluid

23. PHYSIOLOGY OF THE SEXUAL RESPONSE
Female Ejaculation: Fact or Fiction?
the female equivalent of the prostate, developed from the same embryonic tissue, are the Skene’s or paraurethral glands, lining the outside of the urethra, with some ducts found going into the urethra
it is possible that, due to small differences during prenatal development, some women have hyperdeveloped Skene’s glands that produce a fluid similar to prstatic fluid, while many women do not have this capacity.

25. PHYSIOLOGY OF THE SEXUAL RESPONSE
Each phase shows age changes.
Excitation:
Men:
fastest years, then slow decline
Middle Age:
very noticeable, need direct stimulation
Old Age:
need lots of direct stimulation
Women:
slower in teens, early 20s
faster 30’s on
Plateau:
capacity for longer with age
same, but never a big problem

26. PHYSIOLOGY OF THE SEXUAL RESPONSE
Orgasmic:
Men:
intensity lessens from mid- to late 20s
Middle Age:
really noticeable
ejaculate less volume, less forceful
Resolution:
Refractory period increases

27. PHYSIOLOGY OF THE SEXUAL RESPONSE
Resolution:
Men:
longer refractory periods, 24 hrs. midlife, longer in old age.
Women:
no refractory periods ever.

28.
Females
Intensity of Response
Males
Age

30. PHYSIOLOGY OF THE SEXUAL RESPONSE
Cognitive models:
Kaplan’s triphasic model:
sexual desire
vasocongestion
muscular contraction
Walen and Roth’s model:
emphasis on perception and evaluation, 8 steps, necessary for the arousal cycle to be completed

31. NEUROPHYSIOLOGY OF THE SEXUAL RESPONSE
Neural and hormonal involvement in sexual responses:
Parasympathetic:
arousal
Sympathetic:
orgasm
Spinal reflexes:
erection and ejaculation
Erection:
sacral cord responds to stimulation, sends message via parasympathetic to relax penile arteries: more blood flows to penis. Also, message to brain, awareness (not if spine severed above sacrum)
Ejaculation:
higher in spinal cord, message to sympathetic that causes muscle contractions. Also, message to brain, awareness, possibility of control

32. PHYSIOLOGY OF THE SEXUAL RESPONSE
Women’s Neural Mechanisms:
Not yet well known
Controversy surrounding G-spot and female ejaculation.
One recent study found that sexual sensations can be transmitted to the brain via the vagus nerve, which is normally used for digestive processes.

33. PHYSIOLOGY OF THE SEXUAL RESPONSE
Higher Centres:
limbic system: septal region of the amygdala

34. PHYSIOLOGY OF THE SEXUAL RESPONSE
Experiments using electrical stimulation:
Erection centers found in the limbic system, both in monkeys and humans.
In addition to the experiment mentioned in the text (Heath, 1972), there have been others where male volunteers were wired and had control of the electric charge. They would have spent hours at it if allowed!

35. PHYSIOLOGY OF THE SEXUAL RESPONSE
Hormonal Influences on Sex:
Hormone:
substance produced by endocrine glands (internal secretion) which affect specific organs via the blood stream
Exocrine Gland:
substance produced by a gland that goes to the ‘outside’, e.g., sweat, tears
Most Studied Sex Hormone:
testosterone
produced by testes, ovaries and adrenal glands
important for sexual desire in both sexes

36. PHYSIOLOGY OF THE SEXUAL RESPONSE
Hormonal Influences on Sex (Cont’d):
Women have 1/10th the amount but are ten times more sensitive to it.
More testosterone in a normal person will not increase desire or response.
Most testosterone is ‘bound’, not available in this regard, ‘free’ testosterone is 2-5%.
Oxytocin, produced by the pituitary, important for female orgasm.

37. Chemistry of Attraction
DHEA (dehydroepiandrosterone): secreted by adrenal glands, weak androgen. Pro-hormone. Most sex hormones and pheromones derived from it. Same amount for males and females in bloodstream.
Pheromones: sexual signals for both sexes. Sensed by the vomeronasal organ.
Oxytocin: released by the pituitary when touching or being touched by loved ones, even not in a couple relationship. Important for attachment, also involved in parental behaviours.

38. Chemistry of Attraction
PEA (phenylethylamine): called “the molecule of love”, produce euphoria, amphetamine-like substance produced in brain capillaries and in catecholaminergic terminals. Low PEA levels associated with depression (some depressions successfully treated with PEA). Some people become addicted to the PEA “high” and change partners frequently to get it, it is more abundant early in a relationship. Or believe real love has died.

39. Chemistry of Attraction
Estrogen: makes women sexually attractive and receptive. Skin, lips, hair, fatty padding (curves), breasts, hips.
Testosterone: increases sex drive in both sexes, too much is counterproductive.
Endorphins: produced in the brain, released in response to touch and sex, produce positive feelings.
Progesterone: testosterone antagonist, lowers sex drive (in the pill as well), mild sedative, calming effect.

40. Chemistry of Attraction
Serotonin: neurotransmitter. At low levels intensifies sex drive, at high levels decreases it. Antidepressants elevate serotonin, decrease sex drive.
Dopamine: neurotransmitter associated with all pleasures, increases sex drive, promotes action.
Prolactin: decreases sex drive, especially in men (Couvade).

41. Chemistry of Attraction
Vasopressin: hormone produced by the pituitary, antidiuretic (water retention), increases blood volume and blood pressure, identified as the “monogamy molecule”, modulates testosterone, levels extremes of feelings, increases focus in lovemaking.
All these substances fluctuate in a 24 hr. cycle, also with age and environmental events.
The “high” of early love is short-lived (6-30 months). Cultural belief in passionate love forever not realistic.
But long-term couples experience periodic re-awakening of passion, (vacation, children away, etc.)

42. PHYSIOLOGY OF THE SEXUAL RESPONSE
Hormonal Influences on Sex (Cont’d):
Hormones are NOT directly responsible for human sexual behaviour, as they are in most animals.
Psycho-social context and culture are the most important determinants.
In real life, people in good relationships say that sex is better than in casual situations.

43. PHYSIOLOGY OF THE SEXUAL RESPONSE
Hormonal Influences on Sex (Cont’d):
Pheromones:
In animals, substances that act as sexual attractants, olfactory perception. Very important for sex.
In humans, there is a vomeronasal organ, located in the nose, that picks up pheromones, found in sweat and genital secretions.
Pheromones involved in menstrual synchrony.
What could be the effect of perfumes, deodorants,etc.?

44. PHYSIOLOGY OF THE SEXUAL RESPONSE
Anatomy and physiology of sex only give us an idea of how our biological equipment tends to work, but it does not give us an understanding of human sexual behaviour. Knowing car mechanics does not make you a good driver!
In order to get this, we need to explore our psychology, our communication styles, our culture/s, our interpersonal skills, etc.