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Neuroscience > Lecture 5 - Sex Differences 1 > Flashcards

Lecture 5 - Sex Differences 1 Flashcards

1
Q

What are the types of sex differences

A 
Genetic or chromosomal sex 
Gonadal sex
Internal reproductive system
External reproductive system
Pubertal sex changes 
Hormonal sex 
Brain sex 
Behavioural and cognitive sex
Sexual identity
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2
Q

What is genetic or chromosomal sex

A 
23 chromosomal pairs in humans 
1 pair sex chromosome
XX - female
XY - male
Genetic sex determined by speed 
Divide into 4 sex cells - haploid
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3
Q

Outline sexual differentiation

A

Genetic sex determines sex of gonads release hormone associated sexual differentiation
Activations effects of sex hormones produced by gonads
Hormone effects depend previous organisational effects

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4
Q

What are the sexual differentiation effects before birth

A

Organisational effects sex hormones produced by feral gonads

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5
Q

What are the permanent alterations in sexual differentiation

A

Permanent alterations in body or CNS induced by hormone at critical period in development

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6
Q

What is the development of sex organs

A

Gonads (ovaries and testes) and internal sex organs
Start with undifferentiated gonads and internal and external sex organs undifferentiated
Pre modial gonads and sex organs develop into make or female sex type organs

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7
Q

Outline SRY determining the development of make sex organs

A

SRY region Y chromosome codes for testis determining factor - transcription factor
Bond DNA cells undifferentiated gonads
Causes them become testes
Primordial gonads develop into testes

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8
Q

Outline testes in development make sex organs

A

Testes produce hormones defeminising
Anti mullerian hormone
Masculinising androgen effects
Mullerian system withers away

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9
Q

Outline what occurs with masculinising effects of Androgens

A

Androgens masculinising wolffian system develops vas deferns seminal vesicles prostate
Primordial external de italics develop into penis and scrotum

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10
Q

What is the Anti Mullerian Hormone

A

Peptide secreted by feral testes
Defeminising effects
Inhibits development of Mulleria System
By acting on anti mullerian hormone receptors in cells that system

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11
Q

What is the Mulleria System

A

Precursor of female internal sex organs

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12
Q

What 2 androgens determine male sex organs

A

Testosterone

Dihydrotestosterone

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13
Q

How does the Androgen Testosterone act as primary cause masculinisation during early development

A

Testosterone acts androgen receptors cells Wolffian System

Stimulates its development into male internal sex organs

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14
Q

How does testosterone act in the nucleus and lead to sexual differentiation before and after birth

A

Acts in nucleus as structure passes through membrane

Transcription factors trigger certain gene production

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15
Q

How does the Androgen Dihydrotestosterone act as primary cause masculinisation during early development

A

Acts on androgen receptors in primordial external genitals = higher affinity than testosterone
Critical stimulate their development into male genitals

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16
Q

Where and how is Dihydrotestosterone produced

A

Produced from testosterone by 5alpha reductase

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17
Q

Outline Testes determine factor study by Werner et al 1995

A

230 amino acid long protein coded for by SRY region of Y chromosome
Transcription factor binding DNA
Inducing conformational changes enable transcription
Mutations prevent development testes = hence internal and external male sex organs in XY organs
- be genetically male not develop testes due mutation SRY

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18
Q

How do genetics contrast to religion

A

Religion female secondary to male
Biologically default we are females first
By hormones become males

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19
Q

Outline the default of primordial sex organs developing in to female sex organs

A

Absence testis determining factor primordial gonads develop into ovaries
Absence androgens produced testes internal and external sex organs develop into female organs
Without any other normal influences

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20
Q

Outline how Primordial gonads develop into Ovaries

A

Mullerian system develops in to fimbriae Fallopian tubes uterus inner vagina

No hormones wolffian System without androgens withers away

Primordial external genitalia develop into clitoris labia outer vagina

21
Q

What is Swain 2017 discovery on Wolffian System

A

Wolffian System regression requires COUP-TF11

A nuclear reception so not passive process

22
Q

What are the different types of abnormal development of sex organs

A

XY sex reversal

Androgen insensitivity syndrome

Turners syndrome

Persistent Mullerian Duct Syndrome

23
Q

Outline abnormal development of sex organs: XY sex reversal

A

Point mutations in SRY region Y chromosome result female sex organs in XY individuals

24
Q

Outline abnormal development of sex organs: Androgen Insensitivity Syndrome

A

Conditioned caused by congenital lack functioning androgen receptors
In person XY sex chromosomes
Causes development female with testes but no internal sex organs

25
Q

Outline abnormal development of sex organs: Turners Syndrome

A

Presence only 1 sex chromosome X

Result in lack ovaries otherwise normal female sex organs and genitalia

26
Q

Outline abnormal development of sex organs: Persistent Mullerian Duct Syndrome

A

Congenital lack anti mullerian hormone causes development both male and female internal sex organs in XY

27
Q

Outline different primary sex characteristics and secondary sex characteristics

A

Primary sex characteristics - gonads internal and external sex organs. Present at birth

Secondary sex characteristics - enlarged breasts widened hips facial hair deep voice. Sexual maturity not developed until puberty

28
Q

Define secondary sex characteristics

A

Control reproductive functions and sexual behaviour

Axillary and pubic hair in females stimulated by testosterone produced by Cortex of adrenal glands

29
Q

How is puberty triggered

A

Hypothalamus secretion of gonadotropin releasing hormone
GnRH
Stimulates pituitary gland release gonad stimulating hormones
Same males and females
Either act in male gonads - testes or female gonads - ovaries
Producing testosterone or oestrogen

30
Q

Why do peptides stimulate gonads

A

Produce steroid sex hormones sit on outside of cells

31
Q

What are steroid hormones

A

Act in nucleus stimulate steroid receptors which are transcription factors

32
Q

What is the lordosis response in rats

A

Mounting response

33
Q

What gender is better at route learning and navigation

A

Males

34
Q

What is the basis of the organisation hypothesis

A

Exposed female rats and guinea pigs to androgen in utero

During critical periods altered their adult sexual behaviour

35
Q

What does Young et al 1964 propose as the Organisation Hypothesis

A

Proposed early androgens similar effects on sex organs
Organise developing CNS in masculine way, female behaviours less likely = defeminisation
Male behaviours more likely = masculinisation

36
Q

What would occur without the effects of androgens according to the Organisation Hypothesis

A

Animals behave by default in female way

Sex organs brain and behaviour by default develop in female way

37
Q

What have many neural sexual dimorphism in rodents been demonstrated depend on

A

Organisations effects androgens during critical developmental periods
- premature

38
Q

What does Breedlove 1994 and Morris Jordan and Breedlove 2004 argue are other neural sexual dimorphisms

A

Depend both organising and activating effects androgen
Others only involve activating (reversible)
Effects during adulthood - moved to organisational activation hypothesis

39
Q

Is there evidence neural sexual dimorphisms contribute substantially to sex differences in behaviour

A

Yes
Especially reproductive behaviours
Often conjunction activating effects of sex hormones on sexually dimorphic neural systems

40
Q

How are neural sexual dimorphisms described

A

Without obvious behavioural correlates
Of behavioural sex differences often produced hormone effects
Which no clear neural substrates have yet been identified
Interaction between environmental and hormonal influences

41
Q

What are the organisational and activational theory in sex differences in brain and behaviour of feminisation

A

XX -> Ovaries -> Feminisation -> Estradiol and Progesterone activation

42
Q

What are the organisational and activational theory in sex differences in brain and behaviour of testosterone

A

XY -> testes -> testosterone estradiol -> masculinisation and defeminisation -> testosterone activation

43
Q

Masculinising effects of oestrogen in brain and behaviour

A

Oestrogen as effective as testosterone in masculinising brain and behaviour in rodents
Many masculinising effects testosterone massages by oestrogen receptors

44
Q

Outline Aromatisation Hypothesis

A

Some cells CNS cells testosterone converted oestrogen by enzyme called aromatase before acts on oestrogen receptors to exert masculinising effects

45
Q

Protection hypothesis of sexual differences

A

Brain protecting from indiscriminate masculinising action of oestrogen by oestrogen binding protein - alpha fetoprotein in blood
Acacia age away oestrogen in blood of female embryo not testosterone

46
Q

Protection hypothesis of sexual differences role of testosterone

A

Testosterone not bound protein enter cytoplasm and into CNS cells converted oestrogen and exert masculinising effects

47
Q

Is the Protection Hypothesis supported

A

Strongly - finding alpha fetoprotein mutant mice show masculinised brains and behaviour
If protein missing females also develop male masculinised brain and behaviour

48
Q

What can we infer from the Protection Hypothesis

A

Aromatisation plays role in masculinising effects of testosterone in rodents
Not clear if plays role in other species

Neuroscience (12 decks)

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