sexual differentiation

Question 1

What happens at the gonadal level?

Answer 1

At 6-7 weeks, thick rige of protokidney skin develops into gonads

• If SRY gene (Sex-determining Region on the Y chromosome, Berta et al, 1990) activates, testes form
• If SRY gene not activated, ovaries form
• If SRY transposed onto X chromasome, XX indiv (female) will develop male gonads/genetalia

Question 2

What happens at the morphological level?

Answer 2

Until 6 weeks, embryos have both wolffian and mullerian systems
Mullerian duct system: Female acessory sex organ develops into ovaries, phalopian tubes, uterus and cervix
Wolffian duct dydtem: Male acessory sex organ develops into vas deferens, seminal vesticle

Question 3

How is development of gonads determined and what happens after? (Hormonal level)

Answer 3

Hormones determine development.
Mullerian system stays if no hormones are released, overies dont produce much hormones, which promotes development in female direction, causing Wolffian system to die out
Wolffian system releases Mullerian Inhibitor Hormone (MIH), promoting development in male direction, causing Mullerian system to die out

Question 4

When do males show peaks in androgen production?

Answer 4

10-18 weeks of genstation
2-6 months after birth - no idea why
puberty

Question 5

What does the enzyme aromatase do?

Answer 5

Aromatisation - converts testosterone to estradiol (estrogen) in females

Question 6

What are the varieties of hormones like?

Answer 6

Males: vary during the day, not day to day
Females: vary from day to day, when in their cycle

Question 7

What are testosterone and estrogen/progestorone regulated by?

Answer 7

T: negative feedback loop from hypothalamus(GnRH releasing) and pitary(FSH and LH releasing)
E/P: positive feedback loop right before ovulation in prep for pregnancy, negative feedback loop during most of cycle when no pregnancy from hypothalamus(GnRH prducing), pituritary (FSH and LH releasing) and ovary (estrogen and progestorone releasing)

Question 8

Davidson 1966

Answer 8

Castrating male rats stops mounting behaviour, T replacement therapy resotres mounting behaviour.
Suggests mounting behaviour is controlled by T levels

Question 9

Phoenix, Goy, Gerall, & Young, 1959

Answer 9

Steroid hormones permanently organise nervous system at a point during development. As adults, those steroid hormones activate, modulate or inhibit adult typical fe/male behaviours.

Question 10

Phoenix et al., 1959

Answer 10

Preg guinea pigs given high or low levels of T to affect offsprings development.
When adult, offspirng spayed/neutered and given E or T to observe mating behaviour.
Before birth T-treated females less likely to display lordosis position, more likely to display mounting behaviour when treated with T as adults

Question 11

Grady et al., 1965

Answer 11

Exposing rats to androgens before 10 days old causes masculinization and defeminization of behaviour,
not exposing them to androgens causes demasculization and feminization of behaviour.
There are sensitive periods for organisational effects

Supports Phoenix et al 1959

Question 12

Gorski, 1993

Answer 12

Many behavioural effects are dependant on aromatisation

Question 13

Van Goozen et al, 1995

Answer 13

Administered androgens to f2m and deprieved in m2f humans

f2m: increase in aggression proneness, spacial ability increased, deteriorating effect on verbal fluency tasks
m2f: anger and aggression proneness, spatial ability decreased, verbal fluency improved.

Supports: Davidson 1966; Gorski, 1993

Question 14

Hart & Eckstein, 1997

Answer 14

Sexually dimorphic behavioural patterns reduced or eliminated in males by castration
Not all males undergo a change in behaviour following castration
Experience and age at time of castration does not predict which males will be altered by castration

Does not support Davidson 1966;