PHYSIOLOGY OF THE SEXUAL RESPONSE

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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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Excitation (Contd)
• 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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Excitation (Contd)
• Both Sexes
• sex flush (can happen later)
• heart rate, respiration rate gradually increase
• generalized myotonia

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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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Plateau (Contd)
• Females
• orgasmic platform outer third of vagina
  thickens, swells condition sine qua non without
  it, no orgasm
• tenting complete
• clitoris erect

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Plateau (Contd)
• Males
• Cowpers glands secrete fluid through tip of
  penis. WARNING may contain live sperm!
• scrotum even higher and testicles bigger

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Orgasmic
• Males Two stages
• contraction of seminal vesicles, vas and prostate
• contraction of urethra and penis ejaculation

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Orgasmic
• Females
• contractions of orgasmic platform
• contractions of uterus
• several orgasms possible if stimulation continues
• oxytocin

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Orgasmic
• Both
• very high heart rate, blood pressure and
  breathing
• intense myotonia

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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 systems ability to resist
  flu and other viruses
• Pain Relief
• Some women find that an orgasms release of
  hormones and muscle contractions help relieve the
  pain of menstrual cramps and raise pain tolerance
  in general.

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Health Benefits Associated With Orgasm (Contd)
• 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

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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

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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

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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

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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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• SOME GENDER DIFFERENCES (contd)
• Plateau
• without orgasmic platform women cant 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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• SOME GENDER DIFFERENCES (contd)
• 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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• SOME GENDER DIFFERENCES (contd)
• 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.
• Skenes glands or paraurethral glands on the
  urethra. Could be supplying ejaculatory fluid.

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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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Female Ejaculation Fact or Fiction?
• the female equivalent of the prostate, developed
  from the same embryonic tissue, are the Skenes
  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 Skenes glands that produce a
  fluid similar to prstatic fluid, while many women
  do not have this capacity.

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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 30s on
• Plateau
• Men
• capacity for longer with age
• Women
• same, but never a big problem

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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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Resolution
• Men
• longer refractory periods, 24 hrs. midlife,
  longer in old age.
• Women
• no refractory periods ever.

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20 30 40 50 60 70 80
Females
Intensity of Response
Males
Age
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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Cognitive models
• Kaplans triphasic model
• sexual desire
• vasocongestion
• muscular contraction
• Walen and Roths model
• emphasis on perception and evaluation, 8 steps,
  necessary for the arousal cycle to be completed

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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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Womens 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.

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Higher Centres
• limbic system septal region of the amygdala

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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!

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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

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Hormonal Influences on Sex (Contd)
• 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.

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• 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.

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• 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.

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• 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.

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• 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).

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• 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.)

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Hormonal Influences on Sex (Contd)
• 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.

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PHYSIOLOGY OF THE SEXUAL RESPONSE

• Hormonal Influences on Sex (Contd)
• 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.?

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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.