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37 Cards in this Set
- Front
- Back
What is reproductive cycle called in primates? other animals?
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primates: menstrual cycle
other: estrous cycles - controlled by hormones secreted by pituitary glands and ovaries |
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describe a sexual encounter between two rats
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-female if receptive arches back (lordosis) and may entice male with sniffing and nuzzling .
-female also hops around and wiggles ears. -male will mount several times and intromit on most ocassions but will only ejaculate after 8-15 intromissions. - after a refractory period male will return to copulate again (responds more quickly to a new female) |
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What will happen when a male rat encounters a female with ovaries removed?
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Males will ignore females whose ovaries have been removed but injections of estradiol and progesterone will increase her attractiveness. Ovariectomised rats are not sexually receptive but it can be produced by administering estradiol followed by progesterone t mimic natural hormone release
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Describe androgens and behavioural defeminization
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- Androgens are male sex steroid hormones which stimulate the development of the male sex organs.
- Main androgen is testosterone - Androgens have a defeminizing effect; they inhibit the later development of anatomical or behavioural female characteristics - If a rodent brain is NOT exposed to androgens at a critical time during development (shortly after birth), and treated with estradiol and progesterone as an adult, the rat will engage in female sexual behaviour. - If a male rat is castrated after birth and given injections of estradiol and progesterone as an adult, it will respond to the presence of another male by assuming lordosis, i.e. it acts as if it were a female. |
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an animal which has not been exposed to androgens at birth (nonandrgenized) but then given female sex hormones as an adult will _______
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express female behaviour
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An animal that is nonandregenized at birth but then given androgens will _______
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show NO sexual behaviours at all.
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in order for a male rat to be male he must :
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have testes and must produce/be given testosterone early after birth
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if a rat is androgenized at birth and then given female sex hormones as an adult then he will______
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show no sexual behaviour
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if rat is androgenized and this is followed by more testosterone as adult he will_____
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of course show male sexual behaviour
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Define Pheromones
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chemicals that carry messages from one animal to another. in humans found in urine, vaginal secretion, saliva, tears
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Give the three examples of pheromones cycles
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1) Lee-boot effect: Groups of female rats when housed together show slowing down of their estrous cycle
2) Whitten Effect: Exposure to male odour (or urine) will begin the cycle again and the cycles will synchronise. 3) Vandenbergh effect: A female rat will show accelerated puberty if she is exposed to male odour (urine) ****castrated male has no effect! |
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The Bruce Effect
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If a recently impregnated mouse encounters a male mouse other than the one she mated, the pregnancy will fail.
- This effect is caused by a substance in the ‘intact’ male urine which tells the women's body to stop. - Thus, a male mouse is able to prevent the birth of infants carrying another male’s genes and subsequently impregnate the female himself. ** important evolutionary advantage |
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The Vomeronasal Organ
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-mediates the effects pheromones have on repro cycle
- projects to olfactory bulb (removing bulb disrupts lee-boot, whitten, bruce and vandenbergh cycles) |
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The VNO neurons respond when/to.... What happens when we delete a pheromone receptor from VNO in females?
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- respond only when a mouse actively investigates the mouth or anogenital region or another mouse.
-- responds to non-volatile compounds found in urine - deleting a pheromone receptor from the VNO causes male sexual behaviour in females |
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Medial Nucleus of Amygdala (receives axons from, projects to, role, lesions of this area cause...)
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- receives axons from olfactory bulbs, part of system that mediates effects of pheromones
- amygdala projects to preoptic area and ventromedial hypothalamic nuclei (arousal!) - lesions to this region abolish sexual behaviour in males |
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in humans, women who spend more time in male company have...
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shorter cycles
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androstadienone
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compound in human sweat which increases alertness and positive mood in females and decreases positive mood in males
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social explanation for sexual orientation
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there is no evidence of childhood affecting it
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biological explanation speculations for homosexuality
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- hetero and homosexual men have same levels of sex steroids
- male homosexual brains are neither masculinized nor defeminized - female homosexual brains are masculinized and defeminized |
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What role does Congenital Adrenal Hyperplesia CAH play in sex orientation?
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adrenal glands here secreteabnormal amounts od androgen prenatally which causes prenatal ,asculinization. therefore boys born with CAH develop as boys. Girls born with CAH are born with enlarged clitoris and labia fused together
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Androgen insensitivity syndrome
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males with this develop as females with female genetalia but also with testes and without a uterus or fallopian tubes
- lack of androgen from testes (once removed) prevents masculinization and most are just raised as girls with no reports of sexuality towards women |
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name two brain structures which appear to be associated with a man's sexual orientation
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suprachiasmatic nucleus (SCN) of the hypothalamus, and the anterior commissure
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Bed nucleus of the stria terminals (BNST)
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larger in males than females, small in male transexuals (same size as a females) but normal male size in male homosexuals
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pair bonding in voles
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praire voles are monogamous, meadow voles promiscuous
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Vasopressin receptors; vasopressin receptor blockers
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-in ventral forebrain- high levels of them associated with monogamous animals more than polygamous ones
-blockers disrupt the formation of pair bonds - * if you inject a modified virus containing the vasopressin gene into a ventral forebrain of polygamous male, will make him manogamous!! |
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oxytocin and pair bonding in humans
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mating stimulates oxytocin release, and injecting it will facilitate pair bonding. Oxytocin causes relaxation, calmness, and trust
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Describe the meaning of the phase “Nature’s impulse is to create a female”
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if a rodent’s brain is not exposed to androgens during a
critical period of development, the animal will engage in female sexual behavior as an adult (if the animal is then given estradiol and progesterone). behavioural defeminization prevents the rat from exhibiting female behaviour and behavioural masculinization promotes male behaviour |
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Non-classical CAH
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Girls born with NCAH show normal female genitalia at birth and do not show signs of increased androgen levels until late childhood or adolescence.
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main differences between estrous cycle mammals and menstral cycle mammals
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the shedding of the lining, also mating on estrous cycles is linked to ovulation whereas most primates can mate at anytime
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ovarian follicles
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- small spheres of epithelial cells surrounding each ovum which releases estradiol
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ovulation
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LH causes the ovarian follicle to rupture, releasing the ovum. the ruptured follicle becomes a CORPUS LUTEUM which produces estradiol and PROGESTERONE (maintains uterine lining)
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What happened in the armpit compound study?
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took compounds from armpit of females and dissolved in alcohol and rubbed on lip of other females and they synched cycles
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AND, EST
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AND= pheromone produced by males, increases level of attractiveness of male to female.
EST= pheromone produced by females |
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two peptides in brain related to monogamy
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vasopressin (plays a more important role in males) and oxytocin (more in females)
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Parturition
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giving birth
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describe maternal behaviour examples
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- make nests
- facilitate the birth process - lick pups urine to transfer nutrients -many mother rats will accept any pup given even if it is not her own - maternal behaviour is affected by hormones but not controlled by them - even virgin rats will exhibit motherly behaviour if pups are placed wight them |
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3 hormones that influence maternal behaviour; female nest building is facilitated by...
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progesterone, estradiol and prolactin (hormone necessary for milk production too); progesterone
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