HORMONES AND SEXUAL BEHAVIOR

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HORMONES AND SEXUAL BEHAVIOR
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Hormonal communication
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Principles of hormonal action

• Frequently act in a gradual fashion.
• Often take days to act or to wear off.
• Change frequency or intensity of behavior.
• Not a switch.
• Reciprocal effect
• Behavior can affect hormone release.

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Principles of Action

• Multiple effects on multiple targets.
• Estrogen?brain (mult.), uterus, bone, fat
• Chemical structure similar across species
• Require receptor to mediate effect
• Frequently genomically mediated
• Some fast membrane effects
• Pulsatile secretion

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Pulsatile release
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Types of Hormones

• Steroid hormones
• Lipid molecules, derived from cholesterol
• Gonads (testes, ovaries, adrenals)
• Protein peptide hormones
• Amino acid chain, large or relatively small
• Brain, pituitary, many organs/glands

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Classes of sex steroids

• Androgens
• Estrogens
• Progestins/progestogens
• Corticosteroids

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Structures synthetic pathways for sex steroids
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Structures synthetic pathways for sex steroids
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Steroids influence gene expression
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Synthesis and release of oxytocin
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GnRH control of gonadotropin secretion
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Mode of action of protein and peptide hormones
such as GnRH
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Influence of gonadotropins on the testis
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Estrogen production
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A 28-day menstrual cycle
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Hormonal basis of the menstrual cycle
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Menstrual cycle
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Hormones and the menstrual cycle

• Background
• Female fetus Oogonia proliferate ? 4-5 M _at_ 5
  months gestation.
• Mitosis stops, prophase of meiosis begins.
• Replication and lining up of chromosomes
• Girl is born with 2M primary oocytes

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Asexual Reproduction - mitosis
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Sexual reproduction Meiosis prophase
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Sexual reproduction Meiosis I
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Sexual reproduction Meiosis II
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Hormones the menstrual cycle

• Follicular phase
• FSH ? 1 or 2 follicles develop.
• Early negative feedback by E ? decreases FSH
• But, granulosa cells are multiplying increasing
  their FSH receptors ? hi E levels for 2 days
• Something magic happens! Positive feedback ? LH
  (and FSH) surge.

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Hormonal basis of the menstrual cycle
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Stages of follicular development
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Hormones and the menstrual cycle

• Follicular phase (cont.)
• For 12 40 yrs, granulosa cells nourish oocyte,
  prevent 1st meiotic div.
• Via gap junctions
• LH blocks gap junctions primary oocyte divides
  ? secondary oocyte polar body
• Follicle ruptures and secondary oocyte is
  released into abdom. cav., swept up by cilia and
  muscular contractions into fallopian tubes, where
  fertilization can occur.
• Still no 2nd meiotic division unless fertilized.

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Hormones the menstrual cycle

• Luteal phase (After ovulation)
• LH maintains corpus luteum (remnant of follicle)
  ? Progesterone
• P ? further thickening of endometrium dense,
  protein-rich secretion
• Cervical mucus ? thick, impenetrable

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Secondary oocyte w/ zona pellucida cumulus cells
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Hormones the menstrual cycle

• If fertilization conceptus implants and begins
  to secrete hCG (takes the place of LH in
  maintaining corpus luteum).
• 12-14 days necessary to let conceptus implant
  and start secreting hCG.

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Hormones the menstrual cycle

• If no fertilization E P ? negative feedback ?
  GnRH decreases ? corpus luteum degenerates
• E P fall ? endometrium breaks down ?
  menstruation

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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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