PHYSIOLOGY OF THE SEXUAL RESPONSE

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 16-20 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: • Men: • capacity for longer with age • Women: • 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, itis 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.