06-female%20sb - Neuroendocrinology of female copulatory...

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Neuroendocrinology of female copulatory behavior
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Very little research prior to ~1900 compared with work on male copulatory behavior. Why? 1. No economic incentive to remove ovaries 2. Ovariectomy (spaying) more difficult than castrating males 3. Sexism a. Scientists were overwhelmingly male and more interested in what made themselves tick b. Female copulatory behavior thought to be less complex than male behavior c. Females regarded as passive with males doing the interesting parts
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Unlike males, sub-primate female mammals are willing to mate only at selected times. In sub-primate mammals, the occurrence of female sexual behavior is tightly controlled by the fluctuations in ovarian hormone levels and is limited to the time around ovulation. In many primates, sexual activity is at least partially ‘liberated’ from levels of ovarian hormones.
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Etymology of the word ‘estrous’: New Latin, from Latin oestrus - gadfly, frenzy, from Greek oistros Humans and most other primates have menstrual cycles. ‘Lower’ mammalian species have estrous cycles. Estrus : noun. Estrous : adjective. Oestrus, oestrous, oestrogen, etc : British
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Behaviorally , the difference between estrous and menstrual cycles is: Animals with estrous cycles only mate for a limited period around the time of ovulation. Animals with menstrual cycles will mate at all stages of the cycle – but there are changes in the female’s interest in mating.
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The menstrual cycle. Stages of the menstrual cycle: Follicular stage. Periovulatory stage. (peri = around) Luteal stage. Menses.
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LH /FSH Ovary Uterus Immediately after menses, pituitary FSH and LH stimulate the growth of one Graafian follicle which secretes increasing amounts of estradiol and keeps FSH and LH levels in check via negative feedback. This is the follicular stage of the cycle. { menses
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LH /FSH Ovary Uterus Eventually the rising levels of estradiol feed back on the hypothalamus and pituitary to evoke a LH surge – positive feedback . The LH surge acts on the mature follicle to cause ovulation – it is called the periovulatory stage (around ovulation).
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LH /FSH Ovary Uterus The ovulatory LH surge also transforms the follicle into a corpus luteum (yellow body) which produces estradiol and progesterone and supports the maintenance of the uterine lining in preparation for the implantation of a blastocyst. This is the luteal stage of the cycle.
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LH /FSH Ovary Uterus If the ovum isn’t fertilized, the corpus luteum eventually degenerates, and estradiol and progesterone levels plummet. Without hormonal support, the uterine lining sloughs off, and menses occurs.
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The hamster (mouse, rat) estrous cycle.
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estradiol LH progesterone estrous behavior ovulation light dark On day one of the hamster estrous cycle, reproductive hormone are quite low, although a fresh set of Graafian follicles starts to develop.
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  • Spring '08
  • GeorgeWade

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