Lecture 5 - Sex Differences 1

Question 1

What are the types of sex differences

Answer 1

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

Question 2

What is genetic or chromosomal sex

Answer 2

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

Question 3

Outline sexual differentiation

Answer 3

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

Question 4

What are the sexual differentiation effects before birth

Answer 4

Organisational effects sex hormones produced by feral gonads

Question 5

What are the permanent alterations in sexual differentiation

Answer 5

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

Question 6

What is the development of sex organs

Answer 6

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

Question 7

Outline SRY determining the development of make sex organs

Answer 7

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

Question 8

Outline testes in development make sex organs

Answer 8

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

Question 9

Outline what occurs with masculinising effects of Androgens

Answer 9

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

Question 10

What is the Anti Mullerian Hormone

Answer 10

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

Question 11

What is the Mulleria System

Answer 11

Precursor of female internal sex organs

Question 12

What 2 androgens determine male sex organs

Answer 12

Testosterone

Dihydrotestosterone

Question 13

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

Answer 13

Testosterone acts androgen receptors cells Wolffian System

Stimulates its development into male internal sex organs

Question 14

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

Answer 14

Acts in nucleus as structure passes through membrane

Transcription factors trigger certain gene production

Question 15

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

Answer 15

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

Question 16

Where and how is Dihydrotestosterone produced

Answer 16

Produced from testosterone by 5alpha reductase

Question 17

Outline Testes determine factor study by Werner et al 1995

Answer 17

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

Question 18

How do genetics contrast to religion

Answer 18

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

Question 19

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

Answer 19

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

Question 20

Outline how Primordial gonads develop into Ovaries

Answer 20

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

Question 21

What is Swain 2017 discovery on Wolffian System

Answer 21

Wolffian System regression requires COUP-TF11

A nuclear reception so not passive process

Question 22

What are the different types of abnormal development of sex organs

Answer 22

XY sex reversal

Androgen insensitivity syndrome

Turners syndrome

Persistent Mullerian Duct Syndrome

Question 23

Outline abnormal development of sex organs: XY sex reversal

Answer 23

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

Question 24

Outline abnormal development of sex organs: Androgen Insensitivity Syndrome

Answer 24

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

Question 25

Outline abnormal development of sex organs: Turners Syndrome

Answer 25

Presence only 1 sex chromosome X | Result in lack ovaries otherwise normal female sex organs and genitalia

Question 26

Outline abnormal development of sex organs: Persistent Mullerian Duct Syndrome

Answer 26

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

Question 27

Outline different primary sex characteristics and secondary sex characteristics

Answer 27

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

Question 28

Define secondary sex characteristics

Answer 28

Control reproductive functions and sexual behaviour Axillary and pubic hair in females stimulated by testosterone produced by Cortex of adrenal glands

Question 29

How is puberty triggered

Answer 29

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

Question 30

Why do peptides stimulate gonads

Answer 30

Produce steroid sex hormones sit on outside of cells

Question 31

What are steroid hormones

Answer 31

Act in nucleus stimulate steroid receptors which are transcription factors

Question 32

What is the lordosis response in rats

Answer 32

Mounting response

Question 33

What gender is better at route learning and navigation

Answer 33

Males

Question 34

What is the basis of the organisation hypothesis

Answer 34

Exposed female rats and guinea pigs to androgen in utero | During critical periods altered their adult sexual behaviour

Question 35

What does Young et al 1964 propose as the Organisation Hypothesis

Answer 35

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

Question 36

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

Answer 36

Animals behave by default in female way | Sex organs brain and behaviour by default develop in female way

Question 37

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

Answer 37

Organisations effects androgens during critical developmental periods - premature

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

How are neural sexual dimorphisms described

Answer 40

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

Question 41

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

Answer 41

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

Question 42

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

Answer 42

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

Question 43

Masculinising effects of oestrogen in brain and behaviour

Answer 43

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

Question 44

Outline Aromatisation Hypothesis

Answer 44

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

Question 45

Protection hypothesis of sexual differences

Answer 45

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

Question 46

Protection hypothesis of sexual differences role of testosterone

Answer 46

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

Question 47

Is the Protection Hypothesis supported

Answer 47

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

Question 48

What can we infer from the Protection Hypothesis

Answer 48

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