Hormonal Control of Development and Behaviour

Question 1

initial gender difference when born

Answer 1

girl babies like to look at people, vs boys looking at things

Question 2

Major glands in neuroendocrine system

Answer 2

pineal
hypothalamus - controls release of hormones by anterior and posterior pituitary
pituitary
adrenal
pancreas
ovary
testis

Question 3

anterior pituitary

Answer 3

master gland

controls endocrine system

controlled mostly by things released by hypothalamus into blood

hypothalamus connection to anterior pituitary is through capillaries

hormones work much slower than neurons

organs have receptors that only respond to certain hormones

Question 4

posterior pituitary

Answer 4

mostly controlled by neurons

thought of as an extension of hypothalamus

hypothalamus produces posterior pituitary hormones and directly controls their secretion ie oxytocin

Question 5

brain to body tissues

Answer 5

brain sends neural signals

hypothalamus releases gonadotropin-releasing hormone

goes through hypothalamic portal system

reaches anterior pituitary which releases gonadotropin

goes through general circulation to the gonads

gonads release estrogens, androgens and progestins

these reach body tissues which give either positive or negative feedback that influences subsequent release of hormones

behaviour is influenced by gonadal hormone acting on brain

Question 6

gender differences in brain

Answer 6

men’s brains 15% larger than womens’ (as they are bigger creatures)

womens’ hemispheres share more functions than men - females can compensate better to damage to one side of brain as hemispheres share more function

different size in medial preoptic area of hypothalamus (in charge of sexual behaviour) - Rhees et al 1990 = male vs female rats where some female rats given injection of testosterone shortly after birth, critical period for injection is 18th day of gestation to 5 days after birth for more sexually dimorphic nuclei to develop

more sexually dimorphic nuclei in medial preoptic area in male than females (due to testosterone?)

De Jonge et al 1989 = lesions of sexually dimorphic nuclei decreases masculine behaviour

Question 7

causes of gender differences in our brain

Answer 7

masculinising of brain is caused by estradiol (females ovaries don’t produce estradiol until puberty - the placenta protects them from their mothers’ estrogen)

aromatisation (change chemical structure slightly) of testosterone (only in males, cannot cross blood-brain barrier) produces estradiol

blocking aromatisation blocks masculinisation

human females protected from mothers’ estradiol by placenta

Question 8

sexual maturation

Answer 8

puberty initiated when hypothalamus secretes gonadoptropin-releasing hormones which stimulate release of gonadotropic hormones by anterior pituitary gland

Question 9

what is an activational effect of estradiol

Answer 9

ie growth of uterine lining during the menstrual cycle

Question 10

development of an ovary or a testes

Answer 10

6 weeks after conception, primordial gonads of XX and XY individuals are identical

primordial gonad has cortex (looks like casing) and medulla (looks like bits and bots inside cortex)

if no Y chromosome present, cortex of primordial gonad develops into ovary

under influence of Y chromosome, medulla or primordial gonad develops into testis

Question 11

development of wolfian or mullerian system

Answer 11

at week 6, under influence of testicular testosterone, wolfian system develops and Mullerian-inhibiting substance causes mullerian system to degenerate

in absence of testosterone, mullerian system develops into female reproductive duct and wolfian system fails to develop

Question 12

how does external genitalia develop

Answer 12

conversion of testosterone to dihydrotestosterone leads to differentiation of external genitalia

Question 13

gender differences in monkeys

Answer 13

Alexander and Hines 2002
vervet monkeys like gender specific toys ie dolls and cars

Question 14

what is an organisational effect of testosterone

Answer 14

rats given testosterone and estradiol+progesterone treatment in diff combos of immediately after birth or when rat is fully grown

activational effect (treatment given when female rat is fully grown) of estradiol and progesterone can result in nonandrogenised animal

Defeminisation occurs when testosterone given immediately to female rat after birth then estradiol and progesterone when rat is fully grown

masculinisation can occur when testosterone given both immediately after birth and when male rat is fully grown

Question 15

what is angroden insensitivity syndrome

Answer 15

XY persons

insensitive to testosterone so wolfian system doesn’t develop

external genitalia not sensitive to dihydrotestosterone so external develops as female genitalia

sensitive to anti-mullerian hormone so mullerian system doesn’t develop either

no internal reproductive system

Question 16

what is congenital adrenal hyperplasia

Answer 16

overactivity of adrenal gland (producing testosterone)

increase in testosterone levels is noticeable in females - ie hyperandrogenised athletes ie Caster Semenya

Question 17

what is turner’s syndrome

Answer 17

abnormal sex chromosomes

XO chromosome

no ovaries (or weakly functioning ovaries) nor testes

normal female internal sex organs and external genitalia

Question 18

what is persistent mullerian duct syndrome

Answer 18

caused by failure to produce anti-mullerian hormone OR absence of receptors for anti-mullerian hormone

both sets of internal sex organs, male and female, develop

presence of additional female sex organs usually interfere with normal functioning of male sex organs

Question 19

what is 5a-reductase deficiency

Answer 19

two enzymes impair differentiation of external genitalia

only form penis at about 12 years old when hypothalamus releases gonadotropin-releasing hormones to initiate puberty (secondary gender differentiation)

high proportion of male population from dominican republic suffer from 5a-reductase deficiency

Question 20

list of hormonal disorders

Answer 20

androgen insensitivity disorder

congenital adrenal hydroplasia

turner’s syndrome

persistent mullerian duct syndrome

5a-reductase deficiency

Question 21

what are behavioural differences due to stress

Answer 21

maternal stress causes cortisol release

medial preoptic area (MPA) of brain is reduced in male rats born to stressed mothers - less likely to display male sexual behaviour

LaPlante et al = children exposed in utero to high levels of objective stress (Canadian ice storm) had lower Full Scale IQs, verbal IQs, and language abilities compared to children exposed to low or moderate levels of objective prenatal maternal stress

Question 22

what are behavioural differences causing female aggression

Answer 22

Vom Saal and Bronson = being next to male fetus increases female blood levels of testosterone, females positioned between two male feotuses in womb are more prone to inter-female aggressiveness

Question 23

Van de Poll et al

Answer 23

1988
testosterone increases interfemale aggression in rats

Question 24

hormonal control of male sexual behaviour

Answer 24

reduction in testosterone levels leads to reduction in sexual behaviour

thinking about sex increases testosterone levels - making a beard grow faster

castration might cause slow decline in sexual activity

androgens produced by adrenal gland, prostate gland and fat tissue

oxytocin (hormone released by pituitary gland) responsible for refractory period (recovery phase after orgasm) - when oxytocin levels increase, calmness and wellbeing are reported

oxytocin increases memory for faces but not nonsocial stimuli in men and women

Question 25

neuronal control of sexual behaviour in males

Answer 25

androgens exert activational effects on neurons in medial preoptic area and associated brain regions if male rodent is castrated in adulthood, its sexual behaviour stops BUT can be reinstated by implanting some testosterone into MPA or in central tegmental field and medial amygdala (their axons project to the MPA and they contain high concentration of androgen receptors in male rat brain) desruction of MPA abolishes sexual behaviour prenatal stress reduces size of sexually dimorphic nucleus, decreasing sexual behaviour mating causes production of Fos protein the nucleus paragigantocellularis normally inhibits mating behaviour and is inhibited by medial preoptic area

Question 26

hormonal control of female sexual behaviour

Answer 26

Morries et al = 1987 - day to day fluctuations in ovarian hormones showed little correlation with sexual activity Matteo and Rissman 1984 = study of lesbian couples found significant increase in activity during synchronised ovulation allyn and bacon 2004 found women initiated sex a decent amount in follicular, peaking in ovulatory, then dropping drastically in midluteal and increasing slowly in premenstrual phase testosterone released from adrenal gland in females is highest just prior to ovulation Sherwin 1985 = studies on hormone replacement in women following hysterectomy found injection of testosterone not estradiol increased sexual motivation

Question 27

neuronal control of female sexual behaviour

Answer 27

same process as males but instead of medial preoptic area, it is the ventromedial nucleus of hypothalamus that destruction of abolishes sexual behaviour etc electrical stimulation of ventromedial nucleus facilitates female sexual behaviour

Question 28

pheromones effect

Answer 28

pheromones (Chemicals released by one animal affecting behaviour of another) McClintock = woman attending all female college synchronise Cowley and Brookshank = exposure to sweat increases social interactions wyart = women exposed to androstadienone found in men's sweat raises attention and mood whilst it increases drowsiness in men Savic 2001 = activated preoptic area in women but not men - estrogenic chemical had similar result for men Singh and Bronstad 2001 = males reported sweaty t-shirts from female in fertile cycle more pleasant major histocompatibility complex-dependent mate preferences in humans = females prefer t-shirt smells of males with different immune systems to themselves - major histocompatibility complex binds short self or foreign peptides and presents them, on cell surface, to T-lumphocytes

Question 29

hormonal control of sexual orientation overview

Answer 29

no differences in levels of testosterone in homosexual and heterosexual males 30% female homosexuals have elevated testosterone levels

Question 30

prenatal effects on sexual orientation

Answer 30

30 women with congenital adrenal hyperplasia reported 4x homosexuality incidence Money and Ehrhardt = cases of androgen insensitivity don't indicate sexual interest in women Anderson et al = maternal stress in rats leads to reduced exposure to androgens, reduced sexual behaviour in males and reduced preoptic area of hypothalamus LeVay 1991 = preoptic area is smaller in human females than males, and smaller in homosexual men

Question 31

hormonal control of maternal behaviour

Answer 31

prolactin - stimulates nest building in females progesterone eostrodial ovariectomised virgin female rats given these three hormones, the time taken to sensitise maternal behaviour is drastically reduced pregnant rats won't care for foster pups til their own are born no evidence of organisational effect like testosterone with sexual behaviour

Question 32

neural control of maternal behaviour

Answer 32

Numan 1974 lesions of medial preoptic area in rats disrupted nest building and pup care increased oxytocin levels facilitates maternal behaviour and positive parent-infant bond formation Van Leengoed et al = reduced maternal behaviour in animals treated with oxytocin antagonist fMRI study - mothers looking at infant pictures shows brain regions involved in reinforcement and those with oxytocin receptors increase activity - amygdala etc had decreased activity

Question 33

control of paternal behaviour in animals

Answer 33

relationship between monogamy and levels of vasopressin and oxytocin - both released by posterior pituitary gland and by neurons in brain as neurotransmitters - in males, vasopressin appears to play more important role prairie voles are monogamous, meadow voles are promiscuous no sexual dimorphism in MPA of prairie voles Kirkpatric et al = neural activation in MPA when male prairie voles exposed to pups monogamous voles have higher V1a vasopressin receptor levels in ventral forebrain than polygamous voles