G01-Sexual Differentiation Flashcards
Describe the the distribution of diseases among sexes and give some examples
Unequal distribution
anorexia –> female
tourette’s syndrome –> male
What is one behavior that varies between males and females that tells us there must be a difference between male and female brains
Sexual behavior
Variations in problem solving also exists b/w genders, give an example
females are better at verbal fluency tests were males are better at 3D problem solving
The third indicator for sexual dimorphism is?
hormones
Gonadotrophin release (LH/FSH) is under control of what?
hypothalamus via the AP
males vs females give the cycles
male –> acyclic pattern
women —> cyclic due to menstruation
To no surprise, as it controls the endocrine system, ANS, behavior and motivation, gender variation is where?
hypothalamus
What are the structures with identified differences between male and female brains (sexually dimorphic areas)
- Sexual dimorphic nucleus (SDN aka INAH-1)
- Interstitial nuclei of the Anteriro Hypothalamus (INAH-2,3,4)
- Suprachiasmic Nucleus (SCN)(remember location of circadian clock)
- Supraoptic nucleus ( SON)
- Paraventricular Nucleus (PVN)
- Ventromedial Nucleus (VMN)
What are some other areas, besides, the hypothalamus that express dimorphism?
corpus callosum
anterior commissure
Most sexual differences of morphological in nature such as?
size and number of neurons in a nuclei
This is seen in the SDN where in the males it is larger or smaller and has greater or less neurons than females?
males it is larger
has more neurons than females
What are other morphological dimorphisms in males and females?
neurotransmitter content, uptake, release and synthesis
In terms of the hypothalamuc nuclei and sexual orientation. Who has a larger INAH-3 straight men or gay men?
heterosexual males have twice as large INAH-3 when compared to the INAH-3 of homosexual men
What is the size difference in heterosexual vs homosexual women?
identical size variation between hetero and homo females
What other structure is actually larger in homosexual males versus heterosexual males?
SCN is larger in homosexual males versus heterosexual males
Based on the information studied is sexual orientation based on brain development?
yes sexual orientation is linked to structural dimorphisms
what is the basic scheme for sexual differentiation?
Chromosomes –> gonads –> hormones –> body or brain
Any y chromosome will create what?
a male
What gene on the y chromosome codes for TDF (testes determining factor) hence creating a male
SRY (sex determining region of the y chromosome )
If there is an absence of SRY then what happens?
TDF is also absent and baby will develop ovaries by default
In experiments where XX genotypes have SRY gene added, what happens?
babies develop testes, thus SRY=male
Leydig cells of the testes produce what hormones?
produce testosterone and androgen and therefore makes a male
Ovaries produce what hormones?
estradiol and estrogen hence making a female
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?
the testes remain in the body cavity.
Why in androgen insensitivity syndrome do the testes remain in the body cavity?
due to a mutated androgen receptor, testosterone produced by testicular Leydig cells has no effect on sexual differentiation
What is the phenotype of these patients?
patients under go testicular feminization and have normal external female genitalia (breasts as well)
When is it apparent that a child has androgen insensitivity syndrome?
when the patient lacks a menstruation cycle called amenorrhea and there is spare/absent pubic/axillary hair
When is the critical period of sexual differentiation?
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
Testosterone released during the critical period leads to what?
permanent structural differentiation of the body and brain
Describe the molecular mechanism of Testosterone Action
Although testosterone is responsible for male differentiation, it DOES NOT act directly on the cells of the developing nervous system
Testosterone is converted to what ?
to Estradiol (via aromatase) which binds to its receptor on the nucleus and alters gene transcription and translation
Thus what two things are necessary in the critical period that leads to final masculinization?
both testosterone and estradiol
Estradiol receptors are in the greatest concentration in which part of the brain?
hypothalamus, which should not be surprising as it contains most of the sexually dimorphic nuclei of the brain
What happened to female babies with fetal exposure to Diethylsilbsetrol (DES)?
Prenatal exposure during the critical period caused an enlarged SDN in females
What happens to babies with an enlarged SDN?
increased occurrence of bisexual and homosexual girls –> DES daughters
Define Bulimia
an eating disorder characterized by recurrent binge eating, followed by compensatory measures, such as self induced vomiting
Ventromedial nucleus decreases feeding behavior and is bigger in which sex?
bigger in males
Lateral Hypothalamus increases feeding behavior and is bigger in which sex?
bigger in females
what are some chemicals that may interfere with sexual differentiation of the brain?
Organochlorine pesticides PCBs Dioxins Alkylphenol polyethoxylates Phytoestrogens Alkylphenols Phthalate esters Bisphenol-A
Summarize the nuclei and which is bigger in which sex
(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
