sex differences

which gene initiates testes development

SRY gene on the Y chromosome produces the androgens

which hormones masculinise the brain

testosterone and oestradiol

gonadal hormones

hormones produced by reproductive organs (gonads)

function of gonadal hormones

to regulate sexual development, control reproduction and maintain secondary sexual traits

sexually dimorphic nucleus

cluster of neurons in the hypothalamu which exhibit sex differences in INAH-3, cortical thickness, white matter and brain size

wolffian duct system

presence of Y chromosome and testosterone which maintains and develops the male reproductive system

mullerian duct system

absence of testosterone and presence of oestrogen for female system

2 duct systems determining the formation of the reproductive system during embryonic development

1. wolffian ]

2. mullerian

presence of AMH

causes the mullerian ducts to degenerate and eliminatees female reproductive potential

absence of AMH

allows mullerian ducts to develop, only testes develop AMH

role of DHT

essential in developing external male genitalia

DHT formation

enzyme 5-alpha reductase converts testosterone into DHT and strongly targets androgen receptors

deficiency in 5-alpha reductase

leads to ambiguous genitalia or underdeveloped external male genitalia

2 conditions affecting sex differences

1. androgen insensitivity syndrome (AIS)

2. congenital adrenal hyperplasia (CAH)

androgen insensitivity syndrome

XY male unresponsive to androgens (testosterone + DHT) due to mutations on the androgen receptor gene

congenital adrenal hyperplasia

XX female dont produce AMH so internal reproductive organs are normal but their excess androgen exposure makes their external genitalia masculinised

hypothalamus (INAH-3) nucleus size

smaller in homosexual men, more similar to female

SDN and rams

SDN was smaller in male-oriented rams, more similar to female

2D:4D finger ratio

ring finger longer than index linke to higher prenatal androgen exposure

male-to-female neurobiology

show feminised cortical thickness and connectivity in certain areas

female-to-male neurobiology

masculinised basal ganglia structures and white matter tracts

t-shirt pheromone study

men rated women’s t-shirts smell sexier when worn in fertile phase

suppression of testosterone levels

reduces sexual motivation but shows increase in anticipation of sex

sexual initation

long-term couple study found women initiate sex more during ovulation

3 stage process of physioloigical response to sexual arousal

1. PNS initiates genital vasodilation

2. blood vessels lining the genitals release nitric oxide

3. NO stimulates enzyme to increase cyclic GMP levels

what does GMP do

causes vasodilation

myotonia orgasm

involuntary muscle spasms

GnRH

gonadotropin releasing hormone

testosterone receptors

reduce the release of GnRH from the hypothalamus and of LH and FSH in the anterior pituitary gland

reduction of LH

seizure of testosterone production in the testes

reduction in FSH

arrest in sperm development, reducing fertility in the anabolic steroid takers

anabolic steroids

mimic testosterone by binding to testosterone receptors and triggering feedback inhibition

hypothalamus function

releases GnRH to start testosterone production

GnRH function

stimulates pituitary gland to release LH and FSH

LH

stimulates tesosterone production in the testes

FSH

stimulates sperm production in testes

2 types of hormone behaviours

1. organisational

2. activational

organisational hormone behaviour

effect remains after the hormone has been removed. often occurs during a sensitive period

activational hormone behaviour

effect is irreversible, depending on presence or absence of the hormone

3 parts of the hypothalamo-pituitary-gonadal axis

1. hypothalamus

2. pituitary gland

3. gonads

what does the hypothalamus release in HPG axis

GnRH

what does the pituitary gland release in HPG axis

gonadotropins

FSH in females

causes follicles to open

LH in females

induces ovulation and formation of corpus cutem

why do anabolic steroids lead to lower amounts of testosterone

as the pituitary makes less LH and FSH so the hypothalamus produces less GnRH

how does oestradoil make women fertile

it causes FSH and LH to release and trigger the ovum to go into the tubes

5-alpha reductase

an enzyme which turns testoesterone (internal gentials) into DHT (external)

which hormone is important for male internal genitalia

testosterone

which hormone is important for male external genitalia

DHT

what releases cortisol

adrenal cortex

21-hydroxylase enzyme function

final step to make cortisol

deficiency of 21-hydroxylase enzyme

means the adrenal cortex will release testosterone instead

how is 21-hydroxylase enzyme deficiency treated

external/ replacement cortisol

who are better at spatial mental rotation tasks

men

whos brains are 10% larger

men

who has more grey matter

women

who has larger white matter volume and subcortical structures

men

fraternal birth order effect

the more older brothers they have the more like they are gay

maternal immune hypothesis

suggests mums create antibodies toward the male foetus with more boys they have and this makes further boys gay

appetitive behaviour

behaviour of finding and obtaining a sexual partner

consummatory behaviour

the sex act itself

conspecifics

of the same species

4 stages of aoursal

1. excitement

2. plateau

3. orgasm

4. resolution

2 things ED are maybe caused by

1. stress due to SNS activation

2. vasoconstriction