BI 230 - L7-8(Female sexual behavior I&II)

Exam 2 starting @ “Interspecies variation in the female reproductive cycle“

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What are 3 characteristics that distinct human females from other female mammals?

• no stereotypical mating position

  • in comparison to female mice who stereotypically display lordosis in estrus

• NO estrous cycle

• NO breeding season

  • can mate anytime year-round

Typical length in days of the human menstruation cycle?

(about) 28

What are the 2 types of female reproductive cycles in mammals?

• spontaneous ovulation

  • where a female's ova are released without the need for copulation

• induced ovulation

  • where ovulation is stimulated by copulation

In humans, what is menstruation? When does it occur?

• shedding of the uterine endometrium that occurs each cycle

• occurs when blood concentrations of estrogens and progesterone is low

• endometrial tissue no longer supported by steroid hormones

In some mammalian species besides humans (ex: dogs), what is menstruation? When does it occur?

• discharge of blood from the vagina

• occurs prior to estrus

• results from estrus induced stimulation of the uterine wall, which causes rapid growth of the endometrium and many tears in the supporting blood vessels

Why are there so many kinds of reproductive cycles?

• from an ecological perspective, each species’ pattern can be seen as an adaptation for increasing its reproductive success

  • increases probability that mating will occur when female is fertile

  • increases probability that offspring will be produced and will survive

Why do female prairie voles display IRREGULAR estrus cycles?

• behavior estrus is induced by the presence of fertile male conspecific or his urine

• behavioral influence on reproductive cycle → if females don’t engage in anogenital investigation, she WON’T enter estrus

  • females houses with related males (ex: father or brothers) don’t engage in this behavior and WON’T enter estrus

1. Urine detected via the VNO → signal sent to accessory olfactory bulb

2. triggers the release of GnRH → anterior pituitary releases FSH and LH (occurs within 1 hr of exposure)

3. ovulation is induced and occurs ~12 hrs after mating

Social and environmental effects on reproductive cycle

• Lee-Boot effect

• Whitten effect

• Bruce effect

• Vandenbergh effect

3 factors that adversely affect ovarian cycles

• lack of proper nutrients

• stress

  • stressful life events in women have been found to impact the reproductive cycle

  • one study found that perimenopausal women on death row were not experiencing any menstrual cycles

• illness

  • chemical messengers called cytokines (released by activated macrophages) are how the immune system affects neuroendocrine processes in the hypothalamus and pituitary

  • administration of one such cytokine causes female rats to reduce their receptivity and proceptivity

How do birth control pills work?

• combination pills work by keeping estrogen and progesterone concentration at a stable level

  • suppresses the secretion of LH and FSH by the pituitary

  • no ovulation occurs because follicles don’t mature

  • thickens the mucus of the cervix (progestin has this effect) which makes it a more effective barrier for sperm

  • thins uterine lining which makes it less likely to support a pregnancy

• mini pills work by delivering a low dose of progestin

  • thickens the mucus of the cervix (progestin has this effect) which makes it a more effective barrier for sperm

  • thins uterine lining which makes it less likely to support pregnancy

  • may suppress ovulation, but this effect is more variable

Ovulatory vs. uterine cycle

Ovulatory

1. follicular phase (days 1-14)

2. ovulation (day 14)

3. luteal phase (days 14-28)

Uterine

1. menstrual phase (days 1-5)

2. proliferative phase (days 6-14)

3. secretory phase (days 14-28)

Hormone fluctuations across ovarian cycle: what