Neuroscience of sex Flashcards
Sex
refers to a set of biological attributes in humans and animals.
Gender
refers to the socially constructed roles, behaviours, expressions and identities of girls, women, boys, men, and gender diverse people.
Who was Anton von Leeuwenhoek?
examined sperm and drew what he thought he saw…
What determines the sex of the child?
the last of 23 pairs of chromosomes determines sex of the child.the
females
XX
Males
XY
Y chromosome
not responsible for everything – it does control the development of glands producing male sex hormones.
Sry
single gene called Sry on the Y chromosome produces testis -determining factor, which causes the formation of testicles.
What is the default for humans?
default for humans is female if they don’t have SRY gene
organization
permanent, influence brain and sex organ development. Effects occur during the early development of an animal.
activation
effect of a hormone on a fully developed (adult) organism. Occurs later in life, after development of sex organs.
Levels of sexual
Genes: XY or XX
Gonads: Testes or Ovaries
Internal Sex Organs: Wolffian System, Vas Deferens, Prostate or Mullerian System, Fallopian Tubes, Uterus
External Genitalia: Penis, Scrotum or Clitoris, Labia
Secondary Sex Traits: Body & Facial Hair, Muscle Mass or Body Hair, Breasts
T.D.F =
testes determining factor
Internal sex organs
Precursor of female internal sex organs (Mullerian system)
Precursor of male internal sex organs (Wolffian system)
1 promoted & 1 goes away
The fight to be male!
sexual dimorphism becomes apparent ≈60 days after conception.
testosterone stimulates differentiation.
presence of hormones (HORMONES ANTIMULLERIAN AND ANDROGEN) will lead to development of internal sex organs that eventually leads to male sex organs
absence of hormones will lead to development of female organs.
b/c
default setting is female
antiMullerian hormones
prevents female development
androgen
stimulates Wolffian system for male development
Androgen insensitivity syndrome
(an XY female) – lack of androgen receptors.
- can’t have children
external genitalia are female but internal female organs fail to develop (antiMullerian hormone still functions).
Persistent Mullerian duct syndrome
(genetic males) – both male and female internal sex organs develop (failure to produce antiMullerian hormone or receptors).
- causes female precursor to die away
- in this case, there’s a failure so both internal systems will develop
Congenital adrenal hyperplasia
– exposure of female fetus to androgens (can produce an enlarged clitoris, fused labia and tomboyish behaviour).
CAH
Hydroxylase deficient congenital adrenal hyperplasmia. The patient was GENETICALLY FEMALE (XX), PHENOTYPICALLY & BEHAVIOURALLY MALE, & presented only as a problem of infertility with ‘ABSENT TESTES.’ Note short statue due to premature epiphyseal fusion.
- looks & acts male, but don’t have testicles
Turner’s syndrome — monosomy
- 23rd pair of chromosomes isn’t a pair, it’s a single
(X0) - only 1 X chromosome
- fetus still develops into a female (the default setting hypothesis - evidence of that!)
- characterized by undeveloped ovaries but otherwise normal female sex organs & genitalia
- infertile
- short of stature, webbed neck
Klinefelter syndrome
trisomy
XXY Males: testes do not develop as normal (remain small), which leads to infertility. Extra X comes from father just over ½ the time.
1/500 males
- extra chromosome on 23rd pair
XYY
- “Super Male”
- tend to be more physically active as children.
- somewhat delayed emotional maturity.
- sexual development is normal.
- 1/1000 males
- everything of a male stereotypically exaggerated
XXX
- “Super Female”
- quiet and passive as infants.
- delayed development in motor function, speech, and maturation.
- normal physical sexual development.
- normal-to-slightly diminished fertility.
- 1/1000 females
- everything of a female stereotypically exaggerated
Sexual maturation
sex hormones
- estradiol (from ovaries).
- testosterone, androgen (from testes).
- a little of the opposite sex hormone is produced by each sex.
other effects of gonadal steroids
- halt skeletal growth. (after puberty, done growing by enlarge)
- estradiol (during puberty)
- androgens (during puberty)
