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Chapter 11:
Reproductive Behaviors
Hormones
1.
We all know what these are, we talk about
them all the time – in reference to what?
2.
The technical definition
3.
There are two types:
1.
2.
Protein hormones – amino acid chains
Steroid hormones – carbon rings
Steroid Hormones
1.
2.
3.
Androgens
Estrogens
Both are present in both sexes, but
differences in activation exist
Control of Steroid Release


We’ve got two main structures involved in
the control of steroid hormones
Those hormones go work on other endocrine
glands in the system

Gonadotropins  Gonads
What do hormones do?
Hormones have two general effects in the
body:

1.
Organize
2.
Activate
a)
b)
primary sex characteristics
secondary sex characteristics
Nature’s Default…
1.
We all start off with the potential to develop
into a boy or a girl
2.
Activation of a certain region on the Y
chromosome (sex-determining region), will
cause:
1.
2.
3.
The female system (Mullerian) to degenerate
The gonads to develop into testes
The male system (Wolffian) to develop
Sexualization of the Brain
1.
During development, it isn’t just the
reproductive system that is sexualized, made
female or male
2.
The hypothalamus is also ‘turned into’ a boy
or a girl hypothalamus

Sexually dimorphic nucleus
Mating Behavior
1.
Why do some species have multiple partners and
others just one?

Where do humans fall on this continuum?
2.
The evolutionary perspective
3.
However it isn’t just about spreading genes…
Issues in Reproduction
1.
2.
3.
4.
Difference between genetic sex and gender identity
Intersexes
Accidents
Androgen insensitivity
Sexual Orientation
There are a number of biological factors that
may influence our sexual orientation:

1.
2.
3.
Brain differences between homosexuals and
heterosexuals
Genetic influence
Exposure to atypical prenatal hormones