neurobiology of sex and sex differences chapter 12

gonadal hormones definition + examples

hormones that shape brain early so that they can eventually trigger normal reproductive behaviors. examples: testosterone and estradiol

why are sex differences established so early

evolutionary basis (need for reproductive strategies)

why is there gender variability

complexity of cordial/brain processing

evolutionary advantage (optimize adaptation)

reproductive behavior steps

attracting a mate → exchanging gametes → nurturing offspring

how many chromosomes

23 pairs (22 autosomes and 1 sex chromosome)

androgen definition and what it releases

it’s a gonadal steroid (made in testes) that releases testosterone

estrogen definition and what it releases

it’s a gonadal steroid (made in ovaries) that releases estradiol

what is a gene

unit of heredity that determines characteristics

Sry gene definition

sex determining region of y chromosome that directs the formation of testes

Sry activated

male

Sry unactivated

female

sexual differentiation

if someone will have a male or female body

wolffian ducts

develop into male reproductive organs. in males, müllerian systems shrinks (a little)

müllerian ducts

develop into female reproductive organs. most of wolffian system degenerates (none)

when does sexual differentiation happen/ steroids have effect

during a sensitive period in early development

What does OAH stand for and what is it

Organization/ Activation hypothesis was based on the work of William Young. describes 2 sensitive periods for gonadal steroid influences

organization sensitive period

(gestation) testosterone secretion → start of masculinization. ends when females aren’t sensitive to androgens anymore

activational sensitive period

(puberty) gonadal hormones surge and activate brain networks

rat sex

lordosis by female + male mounting = intromission (7-9)

what does it take to masculizine the body, brain and behavior during gestation

one steroid signal (testosterone)

no androgen means

feminine behavior

what does full masculinity require

testosterone during development and adulthood

what happens if you castrate a male and inject it with estradiol (rat version of estrogen) in adulthood?

produces feminine reproductive behaviors

if you inject a female rat with testosterone during the sensitive period and also again during adulthood?

it will mount instead of showing lordosis (masculine behavior)

what do androgen and estrogen (steroids) also mediate in neurobiology

aspects of neural development such as cell survival/cell death in brain structures (that produce sex specific reproductive behaviors)

sexual dimorphism

marked sex differences in someone’s outward appearance. also occurs IN brain

what is POA

pre optic area

SDN-POA

sexually dimorphic nucleus of the POA (lesions disrupt ovulatory/copulatory behaviors)

SDN-POA and relation to OAH?

SDN-POA conforms to the organizational piece of the hypothesis

how does testosterone alter the SDN-POA

it makes it larger, which is why male’s are bigger

why is the sensitive period so important

changes made during this period can cause much bigger changes later on. you can’t get huge changes by injecting anything during adulthood

key CNS structures

1. SDN-POA

2. AVPV-POA

3. pBST

4. SNB

CNS structures important for gonadal steroid effects are usually _____ in males than females

larger

are there different neural circuits for male and female reproductive behavior?

prolly not

differences in male and female structure networks

differentially weighted (differences in synapse number/density, dendritic structures, functional differences in properties)

hippocampus and amygdala differences in males/females