Lecture 18: Sex Difference Flashcards
What is biological sex
differences due to sex chromosomes (XX vs. XY) and the cascade of developmental changes that follow in the vast majority of people
What are the three exceptions to biological sex?
- People with other genotypes (e.g. Turner syndrome XO or Kinefelter syndrome XXY)
- People with XX/XY genoytype but atypical development, often due to mutations
- People who have undergone medical procedures to alter sex/ gender phenotype
What is sexual dimophism?
differences between sexes in anatomy, physiology, psychology and behaviour
How has the castration of young male chickens helped with our knowledge of testosterone?
For instance, castration of young male chickens removes their typical crowing behaviour and castration of male calves leads to docile oxen. Therefore the involvement of the testes during development of typical male development is quite well documented.
How have eunuchs in ancient history helped with our knowledge of testosterone?
Eunuchs terrible practice used in ancient world to control behaviours in humans.
During development only and effect is not related to amount of testosterone
Minimal amount enough to reinstate male-typical sexual behaviour.
What are organisational effects?
Effects of tissue differentiation and development
- permanent
What are activational effects?
Effects that occur in fully developed organism; may depend on prior exposure to organisational effects of hormones
- transient
What is the genetic basis of sex differentiation?
Sex is genetically determined
Diploid human cells contain 46 chromosomes (23 matched pairs):
- 22 pairs of autosomes
- 1 pair of sex chromosomes
How is biological sex determined?
Randomly by the type of male’s gametes (sperm cells)
What are gametes?
They are haploid: just one copy of each chromosone
What do gametes create when fused?
Diploid (parents) offspring
What is Gonadal sex differentiation?
During early embryonic development
- ovary does not produce significant amounts of steroid hormones during embryonic development
- each part of the body develops according to its own intrinsic programme
- Testis start to produce hormones: androgens (incl. testosterone) and AMH
- Called ‘regression’ factor because of defeminisation process – causes Mullerian ducts to regress
What do genotypic sex determine?
Gonadal sex
What does gonadal sex determine?
Phenotypic sex
What do differential exposure to sex steroids during critical periods of development cause?
Sexual differentiation of the body, brain and behaviour
What are the sex differences in homicide rates?
- Men’s severe violence to men much more frequent than women’s severe violence to women
- Most victims and offenders are young men
- This pattern is stable across cultures and over time
- This suggests involvement of testosterone in male-male aggressive behaviour, although the evidence is not so convincing for human populations (e.g. influence of environment, social aspects)
What is the Mammalian oestrous cycle?
Cyclic patterns of gonadotropin secretion (FSH, LH), present only in females, prompted by surge in GnRH (from hypothalamus) above tonic levels
What is pro-oestrus?
Follicular development and ovulation
What is Oestrus?
Receptive period during which fertilisation is most likely to lead to pregnancy
What is Beall and Tracy (2013) study?
- N = 124 normally ovulating women, aged 17–47 (undergrad + community samples)
- asked on-line what colour shirt they were wearing
- classified as high fertility or low fertility based on reported time since last period
What is premenstrual dysphoric disorder?
- Affects 3-8% menstruating women
- Occurs within one week before period starts (luteal phase)
- Symptoms
- Mood swings, depression, anxiety, irritability
- Difficulty concentrating
- Sleep problems
- Physical symptoms
- Treatment based on hormone therapy, antidepressants, surgery.
What did Masters and Johnson (1966) say about reproductive behaviour in humans?
- Detailed lab observations of physiology and behaviour during intercourse
- 4 stages of physiological response to sexual stimulation : excitement, plateau, orgasm , resolution
- Similarities between males and females
What is the song control region in zebra finches?
- 5–6 times larger in males than in females
- gets bigger in females given testosterone as hatchlings
What is the rat hypothalamus: sexually dimorphic nucleus or pre-optic area?
- smaller in males castrated at birth
- bigger in females given testosterone at birth
- no effect of castration/testosterone treatment in adulthood
