G01-Sexual Differentiation

Question 1

Describe the the distribution of diseases among sexes and give some examples

Answer 1

Unequal distribution
anorexia –> female
tourette’s syndrome –> male

Question 2

What is one behavior that varies between males and females that tells us there must be a difference between male and female brains

Answer 2

Sexual behavior

Question 3

Variations in problem solving also exists b/w genders, give an example

Answer 3

females are better at verbal fluency tests were males are better at 3D problem solving

Question 4

The third indicator for sexual dimorphism is?

Answer 4

hormones

Question 5

Gonadotrophin release (LH/FSH) is under control of what?

Answer 5

hypothalamus via the AP

Question 6

males vs females give the cycles

Answer 6

male –> acyclic pattern

women —> cyclic due to menstruation

Question 7

To no surprise, as it controls the endocrine system, ANS, behavior and motivation, gender variation is where?

Answer 7

hypothalamus

Question 8

What are the structures with identified differences between male and female brains (sexually dimorphic areas)

Answer 8

1. Sexual dimorphic nucleus (SDN aka INAH-1)
2. Interstitial nuclei of the Anteriro Hypothalamus (INAH-2,3,4)
3. Suprachiasmic Nucleus (SCN)(remember location of circadian clock)
4. Supraoptic nucleus ( SON)
5. Paraventricular Nucleus (PVN)
6. Ventromedial Nucleus (VMN)

Question 9

What are some other areas, besides, the hypothalamus that express dimorphism?

Answer 9

corpus callosum

anterior commissure

Question 10

Most sexual differences of morphological in nature such as?

Answer 10

size and number of neurons in a nuclei

Question 11

This is seen in the SDN where in the males it is larger or smaller and has greater or less neurons than females?

Answer 11

males it is larger

has more neurons than females

Question 12

What are other morphological dimorphisms in males and females?

Answer 12

neurotransmitter content, uptake, release and synthesis

Question 13

In terms of the hypothalamuc nuclei and sexual orientation. Who has a larger INAH-3 straight men or gay men?

Answer 13

heterosexual males have twice as large INAH-3 when compared to the INAH-3 of homosexual men

Question 14

What is the size difference in heterosexual vs homosexual women?

Answer 14

identical size variation between hetero and homo females

Question 15

What other structure is actually larger in homosexual males versus heterosexual males?

Answer 15

SCN is larger in homosexual males versus heterosexual males

Question 16

Based on the information studied is sexual orientation based on brain development?

Answer 16

yes sexual orientation is linked to structural dimorphisms

Question 17

what is the basic scheme for sexual differentiation?

Answer 17

Chromosomes –> gonads –> hormones –> body or brain

Question 18

Any y chromosome will create what?

Answer 18

a male

Question 19

What gene on the y chromosome codes for TDF (testes determining factor) hence creating a male

Answer 19

SRY (sex determining region of the y chromosome )

Question 20

If there is an absence of SRY then what happens?

Answer 20

TDF is also absent and baby will develop ovaries by default

Question 21

In experiments where XX genotypes have SRY gene added, what happens?

Answer 21

babies develop testes, thus SRY=male

Question 22

Leydig cells of the testes produce what hormones?

Answer 22

produce testosterone and androgen and therefore makes a male

Question 23

Ovaries produce what hormones?

Answer 23

estradiol and estrogen hence making a female

Question 24

Androgen Insensitivity syndrome is a genetic (x linked recessive) disease process. In genetic males (XY), the SRY gene is normally expressed and testes develop, but what happens?

Answer 24

the testes remain in the body cavity.

Question 25

Why in androgen insensitivity syndrome do the testes remain in the body cavity?

Answer 25

due to a mutated androgen receptor, testosterone produced by testicular Leydig cells has no effect on sexual differentiation

Question 26

What is the phenotype of these patients?

Answer 26

patients under go testicular feminization and have normal external female genitalia (breasts as well)

Question 27

When is it apparent that a child has androgen insensitivity syndrome?

Answer 27

when the patient lacks a menstruation cycle called amenorrhea and there is spare/absent pubic/axillary hair

Question 28

When is the critical period of sexual differentiation?

Answer 28

is at 12-20 weeks of gestation as a result of testosterone secretion to create a male there is no such phenomenon for female development

Question 29

Testosterone released during the critical period leads to what?

Answer 29

permanent structural differentiation of the body and brain

Question 30

Describe the molecular mechanism of Testosterone Action

Answer 30

Although testosterone is responsible for male differentiation, it DOES NOT act directly on the cells of the developing nervous system

Question 31

Testosterone is converted to what ?

Answer 31

to Estradiol (via aromatase) which binds to its receptor on the nucleus and alters gene transcription and translation

Question 32

Thus what two things are necessary in the critical period that leads to final masculinization?

Answer 32

both testosterone and estradiol

Question 33

Estradiol receptors are in the greatest concentration in which part of the brain?

Answer 33

hypothalamus, which should not be surprising as it contains most of the sexually dimorphic nuclei of the brain

Question 34

What happened to female babies with fetal exposure to Diethylsilbsetrol (DES)?

Answer 34

Prenatal exposure during the critical period caused an enlarged SDN in females

Question 35

What happens to babies with an enlarged SDN?

Answer 35

increased occurrence of bisexual and homosexual girls --> DES daughters

Question 36

Define Bulimia

Answer 36

an eating disorder characterized by recurrent binge eating, followed by compensatory measures, such as self induced vomiting

Question 37

Ventromedial nucleus decreases feeding behavior and is bigger in which sex?

Answer 37

bigger in males

Question 38

Lateral Hypothalamus increases feeding behavior and is bigger in which sex?

Answer 38

bigger in females

Question 39

what are some chemicals that may interfere with sexual differentiation of the brain?

Answer 39

``` Organochlorine pesticides PCBs Dioxins Alkylphenol polyethoxylates Phytoestrogens Alkylphenols Phthalate esters Bisphenol-A ```

Question 40

Summarize the nuclei and which is bigger in which sex

Answer 40

(i) SDN (INAH-1) , INAH-3, Ventromedial Nucleus---> All bigger in males SCN (ii) Lateral Hypothalamus --> All bigger in females (iii) SCN ---> larger in homosexual men