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HUMAN REPRODUCTION BIOLOGY 269

HUMAN REPRODUCTION BIOLOGY 269. Previous lectures: discussed how anatomy & physiology of the human reproductive system are evolutionarily adapted for specific reproductive strategies. Human sexual responses are also the product of adaptation. Includes Emotions Behaviors

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HUMAN REPRODUCTION BIOLOGY 269

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  1. HUMAN REPRODUCTIONBIOLOGY 269

  2. Previous lectures: discussed how anatomy & physiology of the human reproductive system are evolutionarily adapted for specific reproductive strategies. Human sexual responses are also the product of adaptation. • Includes • Emotions • Behaviors • Biochemical changes • Physiological changes • Feelings of pleasure / satisfaction • … (many others) Clearly, human sexuality and sexual responses are a lot more complex than simply getting a penis into a vagina for the deposition of semen.

  3. Humans, like all animals, send and receive many sexual signals indicating availability, willingness, health, stage of arousal, etc. These allow us to communicate before, during, and after sexual intercourse and coordinate our sexual responses. Some are conscious, others are not: Visual signals: Changes in Changes in Flushing of Changes in Physical signals: Standing Verbal signals: Changes in Changes in Changes in Odors:

  4. 1960s: Masters & Johnson defined four “stages of human sexual response” during sexual intercourse for both men and women :

  5. Both physiologic and cultural reasons: men and women tend to be sexually aroused in different ways Men tend to be quickly aroused by signals which indicate They are not particularly selective, and typically do not view arousal within Women tend to be aroused more slowly by signals which indicate They are more selective and view arousal more ? Female Equivalent ?

  6. “The male paradigm is simple: erection and release. Women’s satisfactions and drives are more complex, organized as much around the health of the relationship as the majesty that is orgasm.” Dr. John Bancroft Kinsey Institute Newsweek, 2000

  7. Male Sexual Response 1. Soliciting: (Minutes to hours)Primarily visual and verbal “I am available” “I am healthy” “I am interested in you” “I am sexually aroused” Eyes and pupils get larger, direct eye contact “Masculine” posture, stands closer, touches Lowering of volume, pitch, and rhythm of voice Conversation to convince woman of masculinity, health, interest, availability, etc.

  8. Male Sexual Response 2. Excitement: (Minutes to hours) Usually during foreplayIncreased blood flow to skin = flushing Increased respiration and vocalization Increased sweating Secretion of pheromones from armpits, genitals, anal region Erection of penis Elevation of testes Increased secretion of fluids by seminal vesicles and prostate Pituitary increases oxytocin secretion, causing feelings of pleasure and “drive”

  9. Male Sexual Response 3. Plateau: (Minutes) Intercourse beginsSweating, flushing, increased respiration, vocalization continue Heart rate and blood pressure rise Swelling of glans of penis Full elevation of testes Lubrication of urethra by bulbourethral (Cowper’s) glands Leakage of sperm and fluid from seminal vesicles & prostate into ejaculatory duct Secretion of oxytocin from pituitary increases, thus increased pleasure and “drive”

  10. Male Sexual Response 4. Orgasm: (Seconds to a minute or two)Heart rate, blood pressure, respiration very high Contraction of sphincter (valves) between bladder and urethra prevents urination Contraction of sphincter in anus prevents defecation Ejaculation occurs in two phases: Emission: Contraction of ductus deferens, seminal vesicles, and prostate force semen into urethra Expulsion: Contraction of muscles surrounding urethra eject semen from urethra Secretion of oxytocin from pituitary very high & brain produces many other “pleasure” chemicals; thus strong feelings of pleasure and satisfaction.

  11. Male Sexual Response 5. Resolution: (Minutes)Heart rate, blood pressure, respiration return to normal Sweating and flushing decrease but may not completely disappear Testes descend to normal position into scrotum Penis softens, eventually becomes flacid Sphincters of bladder and anus relax Oxytocin secretion from pituitary decreases slowly (minutes/hours)

  12. Male Sexual Response 6. Refractory period: (Minutes to hours)General body relaxation, drowsiness Lower parts of ductus deferens move sperm toward ampulla Seminal vesicles and prostate begin replacing fluids Erection or ejaculation not possible Can also enter refractory period from excitement or plateau periods if orgasm does not occur If proper stimuli still present, men typically re-enter excitement phase after refractory period

  13. Female Sexual Response 1. Soliciting: (Minutes to hours)Primarily visual and verbal, includes physical signals and odors “I am available” “I am healthy” “I am interested in you” “I am sexually aroused” Eyes and pupils get larger, direct eye contact “Feminine” posture, exposes more of body, stands closer, touches Lowering of volume, pitch, and rhythm of voice Conversation to convince man of femininity, health, interest, availability, etc. Odors from pheromones and vaginal lubrication

  14. Female Sexual Response 2. Excitement: (Minutes to hours) Usually during foreplayIncreased blood flow to skin = flushing Increased respiration and vocalization Increased sweating Secretion of pheromones from armpits, genitals, anal region Erection of clitoris and nipples Swelling of vagina and of labia Elevation of uterus begins Lubrication of vagina begins (mostly distal part) Pituitary increases oxytocin secretion, causing feelings of pleasure and “drive”

  15. Female Sexual Response 3. Plateau: (Minutes to hour) Intercourse beginsSweating, flushing, increased respiration, vocalization continue Heart rate and blood pressure rise Swelling of vagina and of labia continue Erection of clitoris more pronounced Elevation of uterus continues, swelling of uterus Lubrication of vagina and vestibule by vestibular (Bartholin’s) glands Pituitary increases oxytocin secretion, causing feelings of pleasure and “drive”

  16. Female Sexual Response 4. Orgasm: (Seconds to a minute or two)Heart rate, blood pressure, respiration very high Contraction of sphincters (valves) between bladder and urethra prevents urination Contraction of sphincter in anus prevents defecation Rhythmic contractions of vagina Rhythmic contractions of uterus, primarily cervix Contractions of muscles surrounding vagina to “grasp” penis Secretion of oxytocin by pituitary very high (more than in men) while brain produces many other “pleasure” chemicals; thus strong feelings of pleasure and satisfaction.

  17. Female Sexual Response 5. Resolution: (Seconds to minutes)Heart rate, blood pressure, respiration return to normal Sweating and flushing decrease but may not completely disappear Uterus returns to normal position Swelling of uterus, vagina, and labia decreases Clitoris softens Sphincters of bladder and anus relax Muscles surrounding vaginal opening relax Oxytocin secretion from pituitary decreases more slowly than in men (minutes/hours), thus period of pleasure/satisfaction lasts much longer

  18. Female Sexual Response Refractory period generally does not occur in women If proper stimuli still present, woman may re-enter at excitement, plateau, or orgasm phases. Thus, multiple orgasms possible X

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