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Brain & Behaviour > Lecture 15 - Sex > Flashcards

Lecture 15 - Sex Flashcards

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1
Q

‘Sex’ and ‘gender’ are often used interchangeably, despite having different meanings:

A

Sex refers to a set of biological attributes in humans and animals.

Gender refers to the socially constructed roles, behaviours, expressions and identities of girls, women, boys, men, and gender diverse people.

We’ll be talking about sex because that is what Neuroscience has been studying. Although, it has taken 100s of years for them to realize that research should include both sexes.

But…”Genetic Variants Linked to Disparity Between a Person’s Internal Gender and Their External Sex”

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2
Q

Sex

A

refers to a set of biological attributes in humans and animals.

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3
Q

Gender

A

refers to the socially constructed roles, behaviours, expressions and identities of girls, women, boys, men, and gender diverse people.

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4
Q

Anton von Leeuwenhoek, early microscopist

A

Examined sperm and drew what he thought he saw…

His perception of spermatozoa in 1685 - thought it was a baby curled up

Meanwhile, 400 years later…clearly not the case

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5
Q

Chromosomes

A

the last of 23 pairs of chromosomes determines sex of the child.

females – XX males – XY.

Y chromosome not responsible for everything – it does control the development of glands producing male sex hormones.

single gene called Sry on the Y chromosome produces testis -determining factor, which causes the formation of testicles.

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6
Q

Y chromosome not responsible for everything – it does control…

A

control the development of glands producing male sex hormones.

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7
Q

Single gene called ____ on the Y chromosome produces ___________, which causes the formation of testicles.

A

Sry

testis -determining factor

(default is female)

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8
Q

Organization vs. Activation

Effects of Hormones

A

organization – permanent, influence brain and sex organ development. Effects occur during the early development of an animal.

activation – effect of a hormone on a fully developed (adult) organism. Occurs later in life, after development of sex organs.

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9
Q

Levels of Differentiation

A

Genes: XY or XX

Gonads: Testes or Ovaries

Internal Sex Organs: Wolffian System, Vas Deferens, Prostate or Mullerian System, Fallopian Tubes, Uterus

External Genitalia: Penis, Scrotum or Clitoris, Labia

Secondary Sex Traits: Body & Facial Hair, Muscle Mass or Body Hair, Breasts

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10
Q

T.D.F =

A

testes determining factor

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11
Q

Internal sex organs

A

Precursor of female internal sex organs (Mullerian system)

Precursor of male internal sex organs (Wolffian system)

1 promoted & 1 goes away

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12
Q

The fight to be male!

A

sexual dimorphism becomes apparent ≈60 days after conception.

testosterone stimulates differentiation.

presence of hormones (HORMONES ANTIMULLERIAN AND ANDROGEN) will lead to development of internal sex organs that eventually leads to male sex organs (ANTIMULLERIAN PREVENTS FEMALE DEVELOPMENT AND ANDROGEN STIMULATES WOLFFIAN SYSTEM FOR MALE DEVELOPMENT).

absence of hormones will lead to development of female organs.
b/c
default setting is female.

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13
Q

Genetic disorders of differentiation

A

Androgen insensitivity syndrome

Persistent Mullerian duct syndrome

Congenital adrenal hyperplasia

CAH

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14
Q

Androgen insensitivity syndrome

A

(an XY female) – lack of androgen receptors.
therefore, should’ve developed as a male but lack receptors that would masculinarize them (b/c theirs no androgen receptors they dev. as the default; female)

1/20,000 females

Jamie Lee Curtis? - can’t have children, dev. as female

external genitalia are female but internal female organs fail to develop (antiMullerian hormone still functions).

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15
Q

Persistent Mullerian duct syndrome

A

(genetic males) – both male and female internal sex organs develop (failure to produce antiMullerian hormone or receptors).

  • causes female precursor to die away
  • in this case, there’s a failure so both internal systems will develop
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16
Q

Congenital adrenal hyperplasia

A

– exposure of female fetus to androgens (can produce an enlarged clitoris, fused labia and tomboyish behaviour).

1/21,500 females

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17
Q

CAH

A

Hydroxylase deficient congenital adrenal hyperplasmia. The patient was GENETICALLY FEMALE (XX), PHENOTYPICALLY & BEHAVIOURALLY MALE, & presented only as a problem of infertility with ‘ABSENT TESTES.’ Note short statue due to premature epiphyseal fusion.
- looks & acts male, but don’t have testicles

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18
Q

Turner’s syndrome — monosomy

A

1/2500 females

  • 23rd pair of chromosomes isn’t a pair, it’s a single

(X0) - only 1 X chromosome

  • fetus still develops into a female (the default setting hypothesis - evidence of that!)
  • characterized by undeveloped ovaries but otherwise normal female sex organs & genitalia
  • infertile
  • short of stature, webbed neck
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19
Q

Klinefelter syndrome — trisomy

A

XXY Males: testes do not develop as normal (remain small), which leads to infertility. Extra X comes from father just over ½ the time.

1/500 males

  • extra chromosome on 23rd pair
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20
Q

XYY

A
  • “Super Male”
  • tend to be more physically active as children.
  • somewhat delayed emotional maturity.
  • sexual development is normal.
  • 1/1000 males
  • everything of a male stereotypically exaggerated
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21
Q

XXX

A
  • “Super Female”
  • quiet and passive as infants.
  • delayed development in motor function, speech, and maturation.
  • normal physical sexual development.
  • normal-to-slightly diminished fertility.
  • 1/1000 females
  • everything of a female stereotypically exaggerated
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22
Q

Sexual maturation

A

sex hormones

  • estradiol (from ovaries).
  • testosterone, androgen (from testes).
  • a little of the opposite sex hormone is produced by each sex.

other effects of gonadal steroids

  • halt skeletal growth. (after puberty, done growing by enlarge)
  • estradiol (during puberty)
  • androgens (during puberty)
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23
Q

Estradiol

A

promotes growth of breasts, widening of hips and maturation of genatalia. (during puberty)

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24
Q

Androgens

A

facial and pubic hair, lower voice, alter hairline of head, stimulate muscle and genital growth. (during puberty)

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25
Q

Why Sex?

A

sex is not necessary for reproduction.

for ex:
fission: reproduction by simple cell division (unicellular organisms).

parthenogenesis: reproduction by multicellular duplication (‘cloning’).

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26
Q

Fission:

A

reproduction by simple cell division (unicellular organisms).

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27
Q

Parthenogenesis:

A

reproduction by multicellular duplication (‘cloning’).

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28
Q

The Argument Against Sex

A

biologically, the purpose of an individual is to propel a copy of its genes into the next generation.

with asexual reproduction, 100% of one’s genes are propagated.

with sexual reproduction, 50% of one’s genes are propagated.

sex is dangerous and expensive.
- maybe picked wrong mate - have a genetic disorder you didn’t realize & hurts chances of offspring surviving & chances of your genetic material propagating & continuing

29
Q

Arguments in favour of sex (imagine)

A

imagine two cars - one has an engine and no gearbox and the other has a gearbox and no engine.

how do we get a functioning car? The two deficient cars could mate.

hopefully, some offspring will have both an engine and a gearbox.

plausible, but not much evidence: one approach is to look for higher rates of sexual reproduction where mutation rates are higher (tropics and high altitude –> more UV).

30
Q

Arguments in favour of sex

A

sometimes a trait that is adaptive for one generation is NOT for the next.

sexual reproduction could promote rapid change in traits through reshuffling of genes.

one likely requirement for rapidly changing adaptation has to do with developing resistance to parasites.

parasites like bacteria can adapt very rapidly compared to us because they have short life-spans.

31
Q

Arguments in favour of sex (ex)

A

EXAMPLE:
Penicillin was introduced in 1943.
by 1946, 16% of staph strains were resistant to penicillin.
today, about 90% are resistant!!

sexual reproduction may help us to stay afloat (ahead) in the race against pathogens.
- if all our offspring were identical to us, we could wipe out entire lines if we weren’t resistant to certain bacteria

32
Q

Pheromones

A

a chemical released by one animal that affects the physiology of another.

women who live together have their menstrual cycles entrain to one another.

vomeronasal organ – connected to nasal passage and projects to the accessory olfactory bulb. (in some animals like deers & rats it) Detects pheromones.

33
Q

Vomeronasal organ

A

– connected to nasal passage and projects to the accessory olfactory bulb. (in some animals like deers & rats it) Detects pheromones.

34
Q

The vomeronasal system – a pathway for pheromones?

A

from accessory olfactory bulb to medial nucleus of amygdala, preoptic area, anterior and ventromedial hypothalamus.
- might be that this is a system in humans for picking up pheromones (evidence on next slide)

35
Q

Claus Wedekind and the odour of love

A

major histocompatibility complex

the MHC complex is a set of genes that code for proteins that are involved in the immune system.

it is better to reproduce with individuals whose MHC complex is DIFFERENT to your own. (to improve immune system/increase spread of immunity)

the MHC genes also affect the smell of mouse urine.

female mice prefer the smell of male urine that comes from males with a different kind of MHC.

36
Q

Wedekind’s dirty T-shirts

A

Wedekind had men wear T-shirts for 2 days without wearing anything perfumed.

he then placed them in boxes and asked women to rate the attractiveness of the odour.

women preferred the T-shirts of men who had DISSIMILAR MHC complex (“It smells like my BOYFRIEND.”).

not so keen on T-shirts from men who had SIMILAR MHC complex (“It smells like my DAD.”).

37
Q

The progesterone connection

A

in mice, MHC odour preference SWITCHES during pregnancy.

in women using birth control pills, MHC preference ALSO SWITCHES.

not looking for a new mate – just friendly nest mate.

idea: when women are ovulating & are able to be impregnated, they may be looking for someone with an opposite MHC complex (looking for a suitable mate)
- strong; so hopefully your children would develop these good strong characteristics
(attracted to manly - study)

when they’re not ovulating & are not able to be pregnant, then that might switch off, b/c they’re just looking for a friendly partner (calm)
(attracted to boyish, good looking - study)

38
Q

Sexual selection

A

Many of the structural and behavioural differences between males and females follow naturally from the differences between sex cells.

All other considerations aside, the optimal mating strategy for a male is to distribute sex cells as widely as possible (MALE COMPETITION).

All other considerations aside, the optimal mating strategy for a female is to select the highest quality mates that are available (FEMALE CHOICE).

39
Q

Sex differences in physical appearance

A

The challenge for the male is to be chosen

males compete against one another for access to females (sex differences in physical size) and to be chosen by females (sexual display).
- almost across the entire animal kingdom, the more attractive animal tends to be male b/c he’s trying to attract female

The challenge for the female is to choose wisely.

females need to assess the fitness of the male – will their male offspring compete successfully? The function of courtship.

40
Q

The challenge for the male is ____

A

to be chosen

males compete against one another for access to females (sex differences in physical size) and to be chosen by females (sexual display).
- almost across the entire animal kingdom, the more attractive animal tends to be male b/c he’s trying to attract female

41
Q

The challenge for the female is _______

A

to choose wisely

females need to assess the fitness of the male – will their male offspring compete successfully? The function of courtship.

42
Q

Four stages of sexual behaviour

A
  1. sexual attraction - pretty male trying to attract female
  2. appetitive behaviour - female has to be interested for this to happen
  3. copulation
  4. post-copulatory behaviour - period where they’ll be less interest in copulation again (decrease 1st 2 stages after copulation - gonna be refractory period)

decrease in first two stages after copulation (refractory period).

43
Q

If female has appetite of beh. we say she’s ____

A

proceptive - she’s willing to be a partner potentially

44
Q

Sexual Attraction

A

necessary to bring the two sexes together.

could include appearance, movements, groupings, even construction of artifacts (Kakapo’s leks).

Ex:

  • Sage grouse courtship dance - sacs full of air that makes sounds & then female does something to indicate they want them
  • Staying alive….
  • Kakapo’s leks
45
Q

Appetitive behaviours

A

behaviours that establish, maintain, or promote sexual interaction.

females engaging in such behaviours are said to be proceptive.

proceptive behaviours often include movements, postures, vocalizations.

male appetitive behaviour is most often maintaining proximity.

46
Q

Appetitive behaviours (rats)

A

females proceptive behaviours in rats – sniffing genitals, dances.

female receptive behaviours for copulation – lordosis (arched back, moves tail aside).

47
Q

Mating systems

A
  • Promiscuity
  • Polygyny
  • Polyandry
  • Monogamy
48
Q

Promiscuity

A

– males mate with more than one female, females mate with more than one male.

49
Q

Polygyny

A

– one male mates with a group of females in a long-standing relationship (elephant seals, gorillas).

50
Q

Polyandry

A

– one female mates with a group of males in a long-standing relationship (jacana).

jacana - females are bigger b/c they go from nest to nest to try to find a new mate
- males guard the nest & big females come into someone else’s nest; kill the offspring & then offer themselves to mate to the males

51
Q

Monogamy

A

– one female mates with one male in a long-standing relationship.

52
Q

Mating and the menstrual cycle

A

some evidence that women are more likely to have intercourse when ovulating but…

in a stable monogamous relationship this effect is weak.

53
Q

Sexual orientation

A

male homosexuality unrelated to levels of sex hormones.

about 30% of female homosexuals have increased levels of testosterone (lower than in heterosexual males).

54
Q

Sexual orientation - 60 min vid

A

1 twin gay & 1 isn’t

  • womb envir. is imp. (as well as parents)
  • could be genes, hormones or both

Older brother effect - the more older brothers a man has, the greater that man’s chance is of being gay

  • for every older brother a man has, his chances of being gay increase by 1/3
  • theory is it happens in womb
  • older brothers affect a boy only if he’s right handed
55
Q

Sexual orientation

A

females tend to be less lateralized than males.
(females - language is more bilaterally spread)
(males - left hemisphere is smaller than right so stroke…)

stroke has more severe effects in males. (b/c utilateral damage is more devastating in most males b/c they have more lateralization to their functions (females tend to be more bilateral so tend to be better survivors typically of strokes b/c not everything is localized to 1 side)

longitudinal fasiculi – greater degree of myelination in males.

female corpus callossum – more fibres and different shape.
- a spread across the hemispheres, so there has to be better communication b/c the hemispheres

56
Q

Longitudinal Fasiculi

A

– greater degree of myelination in males.

57
Q

Female corpus callossum

A

– more fibres and different shape.

- a spread across the hemispheres, so there has to be better communication b/c the hemispheres

58
Q

Neural control of sexual behaviour

A

medial preoptic area: increased firing rate during copulation (destruction abolishes male sexual behaviour).

sexually dimorphic nucleus (SDN): 3 to 7 times larger in males – size controlled by amount of androgen; plays a role in male sexual behaviour.
- female + testosterone is larger than female without

59
Q

Neural control of sexual behaviour

A

ventromedial nucleus of the hypothalamus: electrical stimulation facilitates female sexual behaviours (ablation eliminates lordosis).

estradiol followed by progesterone primes and stimulates sexual behaviour in females (direct influence on the VMH).

unprimed by estradiol = less receptors

primed by estradiol (increased progesterone receptors)

60
Q

Parental investment

A

Males

Because males have enormous capacities for producing and distributing sex cells, the optimal strategy is to end relationship with offspring quickly.

Females

Because females have much lower capacity for producing offspring, the optimal strategy is to maintain relationship with offspring until they have a reasonable chance of survival.

61
Q

Parental behaviour and mating systems (some evidence that diff. in parental beh. may lead to some sex diff. we see b/t some species):

A

Typical POLYGAMOUS mammal:
MEADOW voles - Promiscuous
Female boundaries - where female hangs our (several diff. females in this group)
Male boundaries - b/c its promiscuous the males are having intercourse with more than 1 female - males tend to travel further distances than females b/c females stay to their areas, & male has to go from area to area)

Typical MONOGAMOUS mammal:
Prairie voles - Monogamous
Female boundaries & Male boundaries - stick to same areas b/c their in a monogamous relationship

62
Q

Parental behaviour and mating systems

A

the MPA (medial preoptic area) of monogamous species shows less sexual dimorphism.

and what about spatial cognition?
- are coming out of these beh. diff. b/t these mating styles

Prairie voles - monogamous (perform ~same)

Meadow voles - promiscuous (males performing better than females & are making fewer errors)
- males have to keep spatial maps in mind b/c they have to travel further distances to go from spot to spot

63
Q

After 6 weeks of prenatal development, the undifferentiated gonads are stimulated by
________ to form the ________ .
A) testis-deterring factor; ovaries
B) X chromosome; ovaries
C) testis-determining factor; testes
D) 22nd pair of chromosomes; external reproductive structures
E) Y chromosome; ovaries

A

C) testis-determining factor; testes

64
Q 
Which biological factor below is required to form the ovaries?
A) testosterone
B) the Sry gene
C) the X chromosome
D) the Y chromosome
E) No factor is required.
A

E) No factor is required. (default is female)

65
Q 
The Mullerian system structures are the precursors to the
A) male internal sex organs.
B) ovaries.
C) female internal sex organs.
D) testes.
E) penis and scrotum.
A

C) female internal sex organs.

66
Q

What major principle is demonstrated by Turner’s syndrome?
A) Ovaries are NOT necessary for development of the Mullerian system.
B) Female secondary sexual characteristics appear without the ovaries.
C) Ovaries are necessary for development of the Mullerian system.
D) Different hormones are required to develop or to suppress the development of the male
reproductive organs.
E) Male fetuses produce Mullerian-inhibiting substances.

A

A) Ovaries are NOT necessary for development of the Mullerian system.

67
Q 
Which of the following is an effect of androgens?
A) promotion of muscle development
B) growth of pubic hair
C) lowering of the voice
D) beard growth
E) All of the above are correct.
A

E) All of the above are correct.

68
Q

A pheromone is a
A) chemical located on the tongue that binds with sugar.
B) chemical that is released by one animal that affects the behavior of another of its species.
C) hormone released from the gut after the ingestion of fat.
D) substance used to prepare human perfumes.
E) type of enzyme that deactivates cyclic nucleotides.

A

B) chemical that is released by one animal that affects the behavior of another of its species.

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