sex differences Flashcards
what is meant by organisational effects of hormones?
effects on tissue differentiation and development
permanent
what is meant by activational effects of hormones?
effects occuring in fully developed organisms
may depend on prior exposure to organisational effects of hormones
transient (temporary)
what is meant by ‘sexual dismorphisms’?
differences in anatomy, physiology and behvaiour between males and females
what does sexual differentiation depend on?
organisational effects of hormones during development
what do diploid human cells contain?
46 chromosomes (23 matched pairs)
- 22 pairs of autosomes (common between males and females)
- 1 pair of sex chromosomes
example of haploid cell, what does it mean?
how are offspring created from it?
gametes (sex cells) are haploid due to meosis cell division meaning there is just one copy of each chromosome
gametes (egg and sperm) fuse to create diploid offspring
males = XY
female = XX
where is dna located?
in the nucleus of every cell in body except from RBC (anucleate)
what is sex determined by?
genes and specifically which sperm cell fertilises the egg as have X and Y sperm and egg is only X
so X sperm will be female
Y sperm will make male
what does SRY stand for and what is it?
sex-determing region Y which marks the beginning of sexual differentiation into male so also known as testis determining factor (TDF) gene
describe gonadal sex differentiation?
before and after 6 weeks?
undifferentiated ‘primordial’ gonads in foetus (the same)
after 6 weeks of conception:
XX - no SRY gene so no SRY protein produced so gonad develops into ovary ‘default sex’
XY - SRY gene so SRY protein produced so gonad develops into testis
what happens after 6 weeks to female gonads?
ovary doesn’t produce significant amounts of steroid horones during embryonic development
so each part of body develops according to its own intrisic programme ‘default setting as no homrone altering this set of events’
absense of AMH and testosterone means walffian ducts regress and ovaries etc. develop
what happens after 6 weeks to male gonads?
various androgens (steroid hormone) including testosterone - which masculinise other tissues including brain
anti-Mullerian hormone AMH (protein hormone) - masculinises internal genitalia and regress mullerian ducts so testes etc. develop
describe testosterone?
steroid hormone - fat soluble and passes through cell membrane
primary androgen
synthesised by leydig cells in testes
which cells produce AMH?
sertoli cells
describe external gonads in foetus after 6 weeks?
presense of testosterone to DHT - more potent form of testosterone (governs changes in external genitalia)
no testosterone so no DHT (have converting enzyme but nothing to convert)
what is the sex-determining cascade for females?
genotypic sex: XX and no SRY gene
gonadal sex: ovaries
phenotypic sex: feminisation (default)
what is the sex-determining cascade for males?
genotypic sex: XY and SRY gene - SRY protein to…
gonadal sex: testes - AMH and androgens (masculinising hormones) to…
phenotypic sex: masculinisation
what do genotypic and gonadal sex determine?
genotypic - gonadal
gonadal - phenotypic
what is meant by masculinsation/de-feminisation?
and examples?
Effect of hormone present early in development promotes later development of anatomical or behavioural characteristics typical of males
AMH = internal genitalia and development of Walffian ducts
DHT = external genitalia
testosterone = rest of body including brain
what are the further organisational effects of hormones at puberty?
anterior pituitary releases growth hormone,
gonadotropic hormone (surge in testosterone and stimulation of hormones for menstrual cycle)
and adrenocorticotropic hormone
development of secondary sexual characteristics
what is meant by primary sexual characteristics?
already present at birth
describe some female and male-typical behaviours in animals?
female - nursing, suckling, looking after young
male - agression, competition, teritorial scent marking, specific mating techniques
describe some female and male-typical behaviours in humans?
females - much lower same sex homicides
males - much higher same sex homicide rates and peaks into 20-30 (fits idea of aggression)
- majority of victims and offenders are young men
describe 2 examples of brain masculinisation studies?
female guinea pigs treated with testosterone when pregnant produce defeminised/masculinised daughters with male-typical behaviours
female rhesus monkeys given testosterone as newborns show male-typical behaviours as adults e.g mounting females and preference for female partners
describe 2 examples of sexually dimorphic brain structures?
song control region in zebra finches much larger in males and gets bigger in females if given testosterone when hatchlings
nuclues of pre-optic area (in hypothalamus) in rats smaller when males castrated at birth and bigger when females given testosterone but no effects in adulthood
what are the sex differences in the human brain?
male brains 10-15% heaver and heavier relative to body size
difference there at birth despite equal body weights
describe sex differences in human brian lateralisation?
female brains less strongly lateralised with respect to various functions than male brains
anatomical lateraliation of cerebral hemispheres moe marked in males
describe sex differences in connection between hemispheres?
between men?
between sexes?
parts of corpus-callsoum bigger in right than left handed men (no difference in women)
posterior portion more bulbous in women than men
