Study Guide PSB2000 1 Organizing and activating effects of hormones 11 1 1 Know the 3 classes of sex steroid hormones and their synthesis pathway Know examples of each class ie testosterone is an androgen o Androgens testosterone DHT typically male hormones o Estrogens estradiol female hormones o Progestins progesterone another predominantly female hormone Synthesis Pathways start with a cholesterol base then goes through 4 enzymatic steps turns into Progesterone then Progesterone goes through 3 enzymatic steps and turns into Testosterone Estrogen 2 Know the differences between organizational and activational effects of hormones What are some examples of each type of effect in men and in women Organizing effects o Occur during a sensitive period of development in rats this period is the first day of birth in humans it is the second or third month in utero o Determines whether the brain and body of fetus will develop in a male pattern or female pattern of development o Organizing effects of hormones influence patterns of spatial reasoning males more likely than females to orient by directions such as North South whereas women are more likely to rely on landmarks Activating effect o Occur at any point in life typically later in life when a hormone temporarily activates a response o Effects last as long as hormone is present o Includes menstrual cycle in women sexual excitement in men and women 3 What is the chromosomal difference between males and females o Female has XX Male has XY What is the region of the Y chromosome that is important for male development and how why does that trigger male development o SRY sex determining region of the Y chromosome o SRY gene male development no SRY gene female development o The SRY gene causes the primitive gonads to develop into testes the sperm producing organs Study Guide PSB2000 2 The developing testes produce the hormone testosterone an androgen which increases the growth of the testes and causes them to produce more testosterone Testosterone causes the primitive Wolffian ducts which are precursors to other male reproductive structures to develop into seminal vesicles and the vas deferens Mullerian inhibiting hormone is released and causes degeneration of the Mullerian ducts precursors to the females oviducts uterus and upper vagina The result of all the testosterone induced changes is the development of a penis and scrotum Because typical females aren t exposed to high levels of testosterone their gonads develop into ovaries and the Wolffian ducts degenerate What does it mean that the default development pattern is female o Female is default pathway no hormonal signal needed Males need signal to override female plan o Male gonad secretes two hormones Anti Mullerian hormone causing regression of Mullerian ducts androgens testosterone promoting development of Wolffian ducts o Development of male or female reproductive tracts Default is female presence of the SRY gene signals male development makes testes determining factor Internal reproductive structures based on circulating Testosterone levels 4 How can a male be feminized demasculinized or a female masculinized o Individuals sex is determined by the presence or absence of the Y chromosome o We can alter the pattern of development by altering testosterone during critical period Feminization demasculinization of a genetic male o The default development pattern is female so without androgens or the ability to respond to androgens androgen receptors the individual develops as a female o Things that can block androgen activity Castration Lack of androgen receptors Drugs that block effects of testosterone including marijuana alcohol haloperidol and cocaine o To a much lesser extent estrogens including environmental estrogens plastics water because of hormonal birth control more female urine with hormones going into environment can alter the male pattern of development o Prostate gland which stores sperm and releases it during intercourse is especially vulnerable Study Guide PSB2000 3 5 Understand how hormones affect sexual behavior and know some evidence for those effects in rats and in humans o In terms of sexual behavior hormones change activity in some brain regions and change sensitivity of penis vagina and cervix o T and probably E can decrease pain and anxiety o Decreases in T and E associated with memory problems o E stimulates growth of dendritic spines in hippocampus o E increases production of dopamine and serotonin receptors in nucleus accumbens PFC olfactory cortex other cortical regions o In rats women only give men attention for sex during the fertile time menstrual cycle 6 In what pattern do testosterone levels change in males Do they also fluctuate in females If so in what pattern Men o Sexual excitement is highest in men when testosterone is highest 18 25 o Testosterone highest in men during noon hours lowest at night o Higher levels of T levels more partner seeking even if married o Decrease in T decrease sexual activity o Viagra works by prolonging effects of nitric oxide NO o N O is important is sexual behavior and increases blood flow to penis o T increases the release of Nitric Oxide Females o Hypothalamus was made early on to release hormones in a specific way o Testosterone is at its highest when women is periovulatory 7 What hormones are involved in the menstrual cycle o Menstrual cycle depends on 4 hormones luteinizing follicle stimulating estrogen and progesterone o Those hormones need to be released in certain way activation effect What are hormone levels low medium high when a woman is periovulatory o Certain changes when periovulatory around time of ovulation Estrogen is high Testosterone is as high as it ever gets in females Progesterone is getting ready to get high You do not need to know any details of the menstrual cycle beyond these questions However if is always good to have such knowledge of how the body functions What changes in behavior do we see during the periovulatory phase More likely to initiate sexual behavior Study Guide PSB2000 4 Find erotica more pleasant and arousing Prefer more masculine looking men and men who seem athletic competitive etc Lap dancers earn most tips because they feel sexier and release pheromones 8 What are some examples of differences in the hypothalamus between males and females o Region in hypothalamus is much larger in males than in females o Study shows that this region is larger in males because of higher levels of
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