3 - BRAIN DEVELOPMENT Flashcards

1
Q

statement:

brain requires hormones to develop in male-typical form

(rodents)

A

-

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2
Q

what hormone is required to masculinise the brain?

A

estrogens (female sex hormone)

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3
Q

experimental (behavioural) evidence of how estrogens affect brain development (rodents)

A
  • treating new-born female rats with estrogens will cause them to show male-typical sexual behaviour as adults
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4
Q

what does SDN-POA stand for?

A

sexually dimorphic nucleus of the preoptic area of the hypothalamus

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5
Q

problem with the hormonal influence on brain development (rodents)

+

what solves it?

A

problem: all rat embryos are exposed to maternal estrogens
- so why do not all rats show male-typical sexual behaviour? (large SDN-POA)
- how do brains then develop differently?
solution: aromatisation hypothesis

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6
Q

what is the aromatisation hypothesis?

rodents

A
  • the mother’s estrogen is inactivated (by a-fetoprotein)
  • but androgens (produced by newly developed testes of male rat embryo) can enter the brain
  • in the brain - aromatase converts androgens to estrogens
  • this then masculinises the brain
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7
Q

human brain development

A
  • male and female brain assumed to develop differently (assumed to be similar as in rats)
  • no influence of maternal estrogens as they can’t cross the placenta
  • thought maybe aromatisation?
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8
Q

evidence supporting the aromatisation hypothesis in humans

A
  • synthetic estrogens can cross the placenta (given to support pregnancy if women has has previous complications)
  • daughters may then show male-specific behaviour?
  • but male-specific behaviour in humans is not clear in humans
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9
Q

which type of developmental disorder is used as evidence against the aromatisation hypothesis in humans

A

androgen-insensitive XY individuals

  • normal levels of androgens
  • normal levels of aromatase
  • normal estrogen receptors in brain
  • should develop ‘male-typical’ brains
  • but show ‘female typical’ behavioural patterns instead
  • could be because they don’t have working androgen receptors so androgens cannot convert into estrogens, so therefore the brain isn’t masculinised
  • therefore androgen receptors play a role in human male brain development (not clear what a human male brain even is)
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10
Q

are differences between males and females categorical or gradual?

A

gradual!

no clear categorical differences between them

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