topic 1 - sex differences Flashcards
(38 cards)
what are the two principle cells of the nervous system?
Glia and Neurones
what are the two forms of communication of neurones?
within cells/ electrical
between cells / chemical
What are the two types of receptor molecules?
EPSP = excitatory post synaptic potential / makes a neurone MORE likely to fire an action potential
IPSP = inhibitory post synaptic potential / makes a neurone LESS likely to fire an action potential
whats the difference between neurotransmitters and hormones?
neurotransmitters
- one neurone to another
- local action
hormones
- bloodstream
- global action
what is the role of the SRY gene?
located on the Y chromosome. turns the foetal gonad into testis (testis-determining factor) in its absence, the gonad becomes an ovary
what are the two types of hormones produced by the early testis?
1) anti-mullerian hormone = defeminising
2) androgen = testosterone
what is the mullerian system?
- the precursor for female internal sex organs
- anti-mullerian hormones removes the mullerian system
what is the wolffian system?
- the precursor for male internal sex organs
- maintained by androgens allowing it to develop into the male internal sex organs
what is the role of dihydrotestosterone (DHT)?
made by testes and is required to turn external organs male. dependent on gonads turning into either testi or ovary
describe hormonal control of development of the male sex organs
the XY genes determines whether the primordial gonads develop into testes. in XY males this means that anti-mullerian hormones are released causing the mullerian system to wither away. Androgens such as testosterone are also released allowing the wolffian system and male internal sex organs to develop. the testes which develop release dihydrotestosterone allowing the male external sex organs to develop.
describe hormonal control of development of the female sex organs
SRY gene not present therefore the primordial gonads develop into ovaries. the mullerian system develops into the female internal sex organs. the wolffian system withers away due to lack of androgens. female external organs develop due to the lack of dihydrotestostrone released
what is persistent mullerian duct syndrome?
male external genitalia, with testes, male and female internal genitalia
what are the two types of hormone action?
- organisational: effect remains after hormone has been removed
- activational: effect is reversible depending on presence or absence of hormone
GnRH and puberty
during the pre-pubertal period sex hormone levels are low.
- KNDy neurones are inhibited by GABA preventing the activity of GnRH
- GnRH is involved with the onset of puberty
- during the post-pubertal period GABA is not inhibiting KNDy and GnRH pulses increase
- when GnRH neurones are activated by the KNDy neurones, GnRH pulses released into the pituitary glands/blood
- causes gonadotropin to be released to the gonads
what are the two types of gonadotropins?
Follicle stimulating hormone (FSH) = in males = sperm production, in females = causes follicles to ripen
- luteinising hormone (LH) = in males = testosterone production, female = induce ovulation and formation of corpus luteum
describe the hypothalamus - pituitary - gonadal axis
anterior pituitary releases gonadotropin –> gonads release oestrogens, androgens and progestins –> circles back to anterior pituitary creasing positive and negative feedback which influences subsequent release of hormones –> gonadal hormones act on the brain –> brain releases signals –> hypothalamus releases gonadotropin releasing factors –> anterior pituitary releases gonadotropin
effect of anabolic steroids on testosterone levels
- testosterone aimed to be kept at neutral level
- anabolic steroids act like testosterone and therefore the hypothalamus produces less GnRH and the testes make lower amounts of testosterone
describe the menstrual cycle
- similar to the HPG axis but different
- feedback system
- slower than the HPG axis so the different stages are easier to see
1) response to increase in FSH, ovarian follicles grow round eggs
2) follicles release oestrogens
3) oestrogens stimulate hypothalamus to increase release of LH and FSH from anterior pituitary
4) LH surge causes one follicle to release ovum
5) follicle develops into corpus luteum due to LH, releases progesterone which prepares lining of uterus
6) ovum moves down fallopian tubes. if ovum not fertilised progesterone and estradol (oestrogen) levels drop = period
what is androgen insensitivity syndrome?
- 46, XY individuals develop anatomically as female, but without internal female genitalia - gonads develop as testes
- due to androgen receptors not working properly meaning testosterone cannot do its job
- puberty is typically late, sometimes helped with hormone supplements
- often raised female and typically identify as women
- 46 XX individuals only lack pubic hair
what is 5a-reductase deficiency?
- deficiency in enzyme which turns testosterone in DHT
- crucial for prenatal external genital development
- 46, XY children born with female external genitalia but male internal genitalia
- at puberty high levs of testosterone mimic DHT leading to development of external male genitalia
- after puberty mostly identify as men
what is congenital adrenal hyperplasia?
- HPA axis
- 21-hydroxylase deficiency
- vulnerable to symptoms caused by low cortisol
- low cortisol can lead to adrenal glands releasing more testosterone
- negative feedback mechanism by giving external cortisol suppresses HPA axis - lower testosterone
- causes high levels of testosterone in girls and ambiguous external genitalia
- often treated once diagnosed, often at birth in female so is treated quickly
some 46 XX children assigned male at birth
mice and sec differences through genetics
there are four core genotypes
1) XX = ovaries, typical female mouse
2) XYsry = testes, typical male mouse
3) XY minus SRY gene = produces ovaries but develop everything else male
4) XX plus SRY = produces testes and testosterone but female
researching sex differences in humans
- no experimental manipulations possible
- info instead gathered through
–> congenital adrenal hyperplasia in 46 XX individuals
–> complete androgen insensitivity in 46 XY individuals and hormone treatment in transgender individuals
behavioural differences between sexes examp 1
- idea that boys and girls tend to have different toy preferences
- congenital adrenal hyperplasia XX individuals have more masculine toy preferences (should have female)
- complete androgen insensitivity syndrome individuals typically have feminine toy preferences
- not all culture/nurture?
