1. No category

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
 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.
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:
1960s: Masters & Johnson defined four “stages of human
sexual response” during sexual intercourse for both men and
women :
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 ?
“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
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.
Male Sexual Response
2. Excitement: (Minutes to hours) Usually during foreplay
Increased 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”
Male Sexual Response
3. Plateau: (Minutes) Intercourse begins
Sweating, 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”
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.
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)
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
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
Female Sexual Response
2. Excitement: (Minutes to hours) Usually during foreplay
Increased 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”
Female Sexual Response
3. Plateau: (Minutes to hour) Intercourse begins
Sweating, 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”
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.
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
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