SAPOLSKY Ch' 7 SEX AND REPRODUCTION

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SAPOLSKY Ch. 7SEX AND REPRODUCTION
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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Sexual attraction
• Appetitive behaviors
• Copulation
• Refractory phase

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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Sexual attraction
• Attractivity
• Role of estrogen in females
• Coordinates fertility and attractiveness
• Sex skin swelling in some primates

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Sexual swellings of female baboons
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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Sexual attraction
• Pheromones
• Chemicals released by an animal that influence
  the behavior (especially sexual behavior) of
  other members of its species.

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Atlas moth, Attacus atlas
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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Sexual attraction
• Males
• Size, strength, territory, nest, money, lack of
  physical imperfections
• Womens menstrual cycle may affect their
  preference for more masculine faces.

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SURVIVAL OF THE SPECIES REQUIRES REPRODUCTIVE
SUCCESS. NEANDERTHALS FAILED!
MANY ANIMALS ADVERTISE REPRODUCTIVE STATUS WITH
COLOR
MALE VERVET MONKEY
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• Sexual attraction
• Males
• Counterintuitive antlers, peacock tails, dark
  manes, bright colors
• May signify that males are so fit they can
  overcome their disadvantages

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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Appetitive behaviors (motivation)
• Proceptivity in females
• Hopping, darting, ear-wiggling in rats
• Eye contact and proximity
• Role of menstrual cycle in women (small effect)
• Timing of most copulation is determined by female.

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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Appetitive behaviors
• Males
• Birds elaborate songs and/or nests
• Proximity to female

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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Copulation
• Receptivity in females
• Rats a few hours every 4 or 5 days
• Lordosis necessary for copulation
• Rats spontaneous ovulators but need patterned
  stimuli to induce luteal phase/pregnancy
• Monkeys social variables

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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Copulation
• Males mounts, intromissions, ejaculation
• Great variability among and within species re.
  stimulation needed for ejaculation
• Dogs begin to ejaculate as soon as intromission
  is achieved.
• Rats 7-10 brief intromissions before ejaculation

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4 STAGES OF REPRODUCTIVE BEHAVIOR

• Refractory phase
• Ultrasonic song in male rats
• Sleep EEG
• Coolidge effect (male will copulate with new
  female)
• Pair bonding in prairie voles

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Neural circuitry in females

• Receptivity
• Lordosis posture necessary for copulation in
  most mammals

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Neural circuitry in female rats

• Ventromedial nucleus
• Has estrogen receptors
• Sends output to midbrain ? brain stem ? spinal
  cord

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Neural circuitry in male rats

• Medial preoptic area (MPOA)
• Major integrative site
• Has androgen and estrogen receptors
• Receives input from vomeronasal organ, medial
  amygdala, and genitals
• Sends output to midbrain ? brain stem ? spinal
  cord
• Can initiate erection, ejaculation, as can
  several lower structures

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Effects of stress on gonadal hormones

• Endorphins enkephalins shut down GnRH (LHRH)
  from hypothalamus ? drastic decrease in LH FSH
  from anterior pit. ? testes, ovaries close for
  lunch.
• Highly trained athletes reach puberty later
  women have menstrual irregularities.
• Same for opiate addicts.
• Too much or too little exercise can be bad.

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Effect of stress on erections

• Parasymp. system (PNS) ? blood flow to penis.
• Nitric oxide (NO) ? vasodilation
• Viagra prolongs NOs effects.
• Balance between SNS PNS
• SNS ? heart rate, breathing, getting ready for
  ejaculation
• PNS ? maintain erection, also moves sperm to
  seminal vesicle
• Finally, SNS takes over and ? ejaculation

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Effect of stress on erections

• Stress, via SNS, can either ? premature
  ejaculation or lack of erection altogether.
• Erectile dysfunction is a stressor in itself.
• Test psychogenic vs. physiological dysfunction
  with a roll of stamps at night.

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Our friend the hyena

• Females are dominant have a penis.

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Our friend the hyena

• Females have high levels of androstenedione, an
  androgen.
• Made in ovaries.
• Androstenedione both masculinizes the genitals
  and ? aggressiveness.
• Males and subordinate females get erections to
  show submission!!
• Especially when they are stressed.

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Females lengthened cycles and amenorrhea

• Stress decreases conversion of adrenal androgens
  to estrogen in fat tissue .
• Therefore, there is less estrogen.
• Same thing if you starve voluntarily
• Anorexia nervosa ? amennorhea
• Avg. pregnancy costs 50,000 calories.
• Nursing costs 1000 calories/day
• You need some fat to provide calories.

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Females lengthened cycles and amenorrhea

• Endorphins enkephalins also decrease GnRH
  release.
• Prolactin glucocorticoids block pituitary
  sensitivity to GnRH.
• Glucocorticoids decrease sensitivity of ovaries
  (and testes) to FSH LH.
• Prolactin breast feeding contraceptive
• Nursing has to be frequent

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Females disruption of libido

• Both estrogen and adrenal androgens contribute to
  libido.
• Both are decreased by stress.

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Stress and the success of high-tech fertilization

• Artificial fertilization and in vitro
  fertilization have a high failure rate.
• Due, in part, to stress of the procedure.

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Miscarriage, psychogenic abortions, and preterm
labor

• Miscarriage in wild animals when new male takes
  over
• The male would kill the previous offspring.
• Female has odor-based mechanism that ?
  miscarriage. (Bruce-Parkes effect)
• However, such miscarriages in humans are rare,
  unless severe and repeated activation of SNS
  shuts down blood flow to uterus.

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Reproduction during extreme stress

• The amazing thing is how resistant to stress
  reproduction is.
• Even in Nazi death camps, almost half the women
  continued to menstruate.

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Summary

• All steroids are closely related (derived from
  cholesterol) P ? T ? E or DHT.
• GnRH (from hypothalamus) ? ant. pit. (AP)
• FSH LH (from AP) ? ovaries or testes
• FSH stimulates follicles to produce E and nurture
  ova.
• FSH stimulates testes to produce sperm.

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Summary

• LH stimulates Leyden cells in male to ? T
• LH surge in females ? ovulation
• After ovulation, LH stimulates thecal cells in
  corpus luteum to ? P, most of which is released
  without conversion to T and E
• P builds up endometrium.

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Summary

• Menstrual cycle FSH ? egg (oocyte) E
• High E ? positive feedback on GnRH ? LH surge.
• LH breaks gap junctions that have kept oocytes
  from 1st meiotic division ? ovulation.
• Oocyte has 2nd meiotic division only if
  fertilized by a sperm.
• LH also causes follicle to ? corpus luteum ? P ?
  increase vascularization of endometrium.
• If no fertilization high EP ? neg feedback?
  decreased EP ? endometrial lining sloughs off.

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Summary

• Sexual behavior 4 components
• Attractivity
• Proceptivity
• Copulation
• Refractory period

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Summary

• Main control area for female sexual behavior is
  ventromedial nucleus of hypothalamus
• Main control area for male sexual behavior is
  medial preoptic area, at front of hypothalamus

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Summary Stress effects on reproduction

• Endorphins enkephalins decrease GnRH from
  hypothalamus
• PRL decreases ant. pit. response to GnRH
• Therefore less FSH and LH
• GCs decrease responsiveness of ovaries and testes
  to FSH LH
• Therefore hormone production and gamete
  production are impaired.

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Summary

• SNS overactivity inhibits erections
• Erections are caused by parasympathetic sys
• Nitric oxide (NO) ? vasodilation
• Viagra increases duration of NOs effects
• In females starvation or excessive exercise ?
  decrease of body fat ? decrease in E production
  in fat ? delays puberty, can cause amenorrhea.