sex differences

Question 1

what is meant by organisational effects of hormones?

Answer 1

effects on tissue differentiation and development

permanent

Question 2

what is meant by activational effects of hormones?

Answer 2

effects occuring in fully developed organisms
may depend on prior exposure to organisational effects of hormones

transient (temporary)

Question 3

what is meant by ‘sexual dismorphisms’?

Answer 3

differences in anatomy, physiology and behvaiour between males and females

Question 4

what does sexual differentiation depend on?

Answer 4

organisational effects of hormones during development

Question 5

what do diploid human cells contain?

Answer 5

46 chromosomes (23 matched pairs)

• 22 pairs of autosomes (common between males and females)
• 1 pair of sex chromosomes

Question 6

example of haploid cell, what does it mean?

how are offspring created from it?

Answer 6

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

Question 7

where is dna located?

Answer 7

in the nucleus of every cell in body except from RBC (anucleate)

Question 8

what is sex determined by?

Answer 8

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

Question 9

what does SRY stand for and what is it?

Answer 9

sex-determing region Y which marks the beginning of sexual differentiation into male so also known as testis determining factor (TDF) gene

Question 10

describe gonadal sex differentiation?

before and after 6 weeks?

Answer 10

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

Question 11

what happens after 6 weeks to female gonads?

Answer 11

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

Question 12

what happens after 6 weeks to male gonads?

Answer 12

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

Question 13

describe testosterone?

Answer 13

steroid hormone - fat soluble and passes through cell membrane

primary androgen

synthesised by leydig cells in testes

Question 14

which cells produce AMH?

Answer 14

sertoli cells

Question 15

describe external gonads in foetus after 6 weeks?

Answer 15

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)

Question 16

what is the sex-determining cascade for females?

Answer 16

genotypic sex: XX and no SRY gene

gonadal sex: ovaries

phenotypic sex: feminisation (default)

Question 17

what is the sex-determining cascade for males?

Answer 17

genotypic sex: XY and SRY gene - SRY protein to…

gonadal sex: testes - AMH and androgens (masculinising hormones) to…

phenotypic sex: masculinisation

Question 18

what do genotypic and gonadal sex determine?

Answer 18

genotypic - gonadal

gonadal - phenotypic

Question 19

what is meant by masculinsation/de-feminisation?

and examples?

Answer 19

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

Question 20

what are the further organisational effects of hormones at puberty?

Answer 20

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

Question 21

what is meant by primary sexual characteristics?

Answer 21

already present at birth

Question 22

describe some female and male-typical behaviours in animals?

Answer 22

female - nursing, suckling, looking after young

male - agression, competition, teritorial scent marking, specific mating techniques

Question 23

describe some female and male-typical behaviours in humans?

Answer 23

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

Question 24

describe 2 examples of brain masculinisation studies?

Answer 24

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

Question 25

describe 2 examples of sexually dimorphic brain structures?

Answer 25

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

Question 26

what are the sex differences in the human brain?

Answer 26

male brains 10-15% heaver and heavier relative to body size

difference there at birth despite equal body weights

Question 27

describe sex differences in human brian lateralisation?

Answer 27

female brains less strongly lateralised with respect to various functions than male brains

anatomical lateraliation of cerebral hemispheres moe marked in males

Question 28

describe sex differences in connection between hemispheres?

between men?
between sexes?

Answer 28

parts of corpus-callsoum bigger in right than left handed men (no difference in women)

posterior portion more bulbous in women than men