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PSY1202 Introduction to biological psychology > Sex differences > Flashcards

Sex differences Flashcards

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1
Q

types of hormone action

A

organisational

activational

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2
Q

organisation effects

A

effects on tissue differentiation and
development

Permanent – long lasting

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3
Q

activational effects

A

effects that occur in fully developed organism; may depend on prior exposure to organisational effects of hormones

Transient – short term effects

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4
Q

sexual differentiation

A

Development of sexual dimorphisms
- differences in anatomy, physiology and behaviour between males and females

Sexual differentiation in mammals depends on organisational effects of hormones during development

  • 2D-4D ratio
  • Facial width to height
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5
Q

genetic basis of sex differentiation

A

Sex is genetically determined – due to genotype

Diploid human cells contain 46 chromosomes (23 matched pairs):

  • 22 pairs of autosomes – don’t determine sex differences – common between genders
  • 1 pair of sex chromosomes
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6
Q

gametes

A

are haploid: just one copy of each chromosome

fuse to create diploid offspring

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7
Q

what is sex determined by?

A

the male’s gametes (sperm)

SRY (sex-determining region Y) gene a.k.a. testis determining factor (TDF) gene

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8
Q

gonadal sex differentiation

A

during early embryonic development

  • no SRY gene –> no protein = ovaries
  • gene –> protein = testis

sets off chain of events that (usually) results in male v female indvs

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9
Q

ovary in development

A

ovary does not produce significant amounts of steroid hormones during embryonic development

each part of the body develops according to its own intrinsic programme

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10
Q

testis in development

A

various androgens, incl. testosterone –> masculinises many other tissues, incl. brain

anti-Müllerian hormone (AMH) –> masculinises internal genitalia (a.k.a. Müllerian regression factor)

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11
Q

testosterone

A

steroid hormone
- fat-soluble, passes readily through cell membrane

primary androgen

synthesised by Leydig cells in testes

Sertoli cells produce AMH

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12
Q

what does testosterone lead to?

A

dihydrotestosterone (DHT)

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13
Q

phenotypic sex differentiation

A

Genotypic sex determines gonadal sex

Gonadal sex determines phenotypic sex

Differential exposure to sex steroids during critical periods of development (e.g. foetal development, puberty) causes

  • sexual differentiation of the body
  • sexual differentiation of the brain and behaviour

These are permanent effects – organisational effects – may then affect how we respond behaviourally to hormones later in development

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14
Q

masculinisation and de-feminisation

A

Effect of hormone present early in development promotes later development of anatomical or behavioural characteristics typical of males

AMH –> internal genitalia

DHT –> external genitalia

testosterone –> rest of body (inc. brain)

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15
Q

puberty

A

Further organisational effects of hormones at puberty:

  • anterior pituitary releases growth hormone, gonadotropic hormone and adrenocorticotropic hormone
  • leads to development of secondary sexual characteristics (not present at birth)
  • Primary sexual characteristics = present at birth
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16
Q

sex differences in behaviour

A

homicide rates

  • men kill men much more frequently than women kill women
  • most victims and offenders are young men
  • this pattern is stable across cultures and over time
17
Q

brain masculinisation

A

Female guinea pigs treated with testosterone when pregnant produce de-feminised, masculinised daughters with male-typical behaviour

Female rhesus macaques given testosterone as new-borns show male-typical behaviour as adults:

  • pursuit and mounting of other females
  • pelvic thrusting
  • post-ejaculatory behaviours
  • preference for female partners
18
Q

sexually dimorphic brain structures

A

Song control region in zebra finches

  • 5–6 times larger in males than in females
  • gets bigger in females given testosterone as hatchlings – organisational effect

Rat hypothalamus: sexually dimorphic nucleus of pre-optic area (SDN-POA) – function not definitively known

  • smaller in males castrated at birth
  • bigger in females given testosterone at birth
  • no effect of castration/testosterone treatment in adulthood
  • Organisational effect of testosterone
19
Q

brain size in humans

A

On average male brains are 120–160 g (10–15%) heavier

Also heavier relative to body size – men on average weigh more

Difference present at birth despite equal body weights

What does it mean?

  • are female brains more “efficient”?
  • is bigger necessarily better?
  • is the extra weight due to extra neurons or supporting cells, or water?
  • is there a correlation between brain weight & performance in specific domains?
20
Q

brain lateralisation

A

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

Anatomical lateralisation of the cerebral hemispheres appears to be more marked in males

Subtle differences but statistically significant

21
Q

connection between hemispheres

A

Parts of corpus callosum are bigger in right-handed than left-handed men; no such pattern for women

Posterior portion (splenium) perhaps more bulbous in women than men

Subtle differences

22
Q

reproductive behaviour can be divided into 4 stages

A

Sexual attraction

appetitive behaviour

copulation

postcopulatory behaviour, inc parental behaviours in some species

23
Q

gonadal steroids activates sexual behaviour

A

Alterations in circulating gonadal steroids after sexual behaviour in male and female mammals

24
Q

Androgens act on a neural system for male reproductive behaviour and oestrogens and progesterone regulate a lordosis circuit that spans from brain to muscle

A

In the female rat, a steroid-sensitive lordosis circuit extends from the ventromedial hypothalamus (VMH) to the spinal cord, via the periaque-ductal gray and medullary reticular formation

In male rat, neurons of medial preoptic area (mPOA) exert descending control of sexual behaviour, integrating inputs from the media amygdala and vomeronasal organ (VNO)

Projections, via ventral midbrain and brainstem nuclei, terminate on motor neurons involved in copulation

25
Q

diversity

A

Human copulatory behaviour varied

Most men show single copulatory pattern; women show much more varied sexual responses

Classic model of sexuality

Modern models

Male and female sexuality overlap, and both are heavily influenced by sociocultural factors

26
Q

for many vertebrates, parental care determines offspring survival

A

Parental behaviour crucial aspect of reproduction and significantly influenced by hormones

Brain mechanisms for parental behaviour show considerable overlap with mechanisms implicated in sexual behaviour

27
Q

gonadal hormones direct sexual differentiation of the body

A

In birds and mammals, genetic sex determines whether testes/ovaries develop, and hormonal secretions from the gonads determine whether the rest of the body, inc the brain, developed in a feminine/masculine fashion

In presence of testicular secretions, a male develops; in the absence, a female develops

28
Q

dysfunctional androgen receptors can block male masculinisation

A

People can be classified on the basis of their sex chromosomes, genitalia/gender they identify with

Options within each of these categories complex and sometimes overlap, so attempts to classify all indvs into just 2 gender groups oversimplify real situation

29
Q

Gonadal hormones direct sexual differentiation of the brain and behaviour

A

Brains of vertebrates masculinised by presence of testicular steroids during early development

Such organisational effects pf steroids permanently alter the structure and function of brain and therefore permanently alter the behaviour of the indv

30
Q

The spinal cord in mammals

A

gonadal steroids have been shown to alter characteristics such as neuronal survival, structure and synaptic connections

31
Q

do foetal hormones masculinise human behaviours in adulthood?

A

Several regions of human brain sexually dimorphic

Don’t know whether dimorphisms general by foetal steroid levels/sex differences in early social env

32
Q

what determines a person’s sexual orientation?

A

Although no perfect animal model of sexual orientation has been developed, all research indicates sexual orientation determined early in life and esp. in men, not a matter of indv choice

33
Q

what is the hallmark of human sexual behaviour?

A

diversity

34
Q

what does the classic model of sexuality emphasise?

A

4 stages:

  1. Increasing excitement
  2. Plateau
  3. Orgasm
  4. Resolution
35
Q

what do modern models of sexuality empahsise?

A

identify emotional factors and desire as crucial aspects of female sexuality, whereas male sexuality may involve feelings of power

PSY1202 Introduction to biological psychology (23 decks)

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