sexuality study guide

SRY Gene

The sex-determining region of the Y chromosome that directs the development of male gonads.

Wolffian System

The male internal organ development system that develops under the influence of testosterone.

Müllerian System

The female internal organ development system that develops in the absence of testosterone.

5-alpha-dihydrotestosterone

A hormone that develops the male external genitalia, specifically the penis and scrotum.

FSH (Follicle Stimulating Hormone)

A hormone secreted at the beginning of the menstrual cycle that causes the development of ovarian follicles.

LH (Luteinizing Hormone)

A hormone that triggers ovulation and the formation of the corpus luteum.

Corpus Luteum

The structure that forms from the empty follicle post-ovulation and releases progesterone.

Turner Syndrome

A condition in XO females often characterized by infertility and short stature.

Klinefelter’s Syndrome

A condition in XXY males associated with low testosterone and various physical and reproductive issues.

Congenital Adrenal Hyperplasia

A condition where females are exposed to excess androgens prenatally, leading to ambiguous genitalia, shows cognitive abilities similar to males, and an increased rate of homosexuality.

Androgen Insensitivity Syndrome

A condition where XY individuals are insensitive to androgens, developing externally as females with gonads as testes.

5 Alpha Reductase Deficiency

A condition where XY individuals are born with female genitalia and develop male genitalia at puberty due to lack of 5-alpha-dihydrotestosterone.

Lordosis

A behavior in female animals where they arch their spine to aid copulation, also linked to their ventromedial hypothalamus.

Mounting

A behavior in male animals where they mount other animals to aid copulation.

Organizational Effect

The permanent change in brain and body structure due to hormonal exposure during critical development periods.

Activation Effect

The temporary activation of behaviors by hormones in a time-specific manner. For example, testosterone masculinizes both the brain and body.

Anti-Mullerian Hormone

A hormone that degenerates the female (Müllerian) system in male fetuses.

Hypothalamus

A brain region linked to regulating sexual behaviors in animals.

Medial Preoptic Area

Lesions in rats will not impact sexual interest, but the animal is unable to copulate.

Stria Terminalis

A brain structure linking the amygdala and hypothalamus, found to be “female-like“ in size in transgender women.

Genetic Link for Homosexuality

There is a notable concordance rate for identical twins, indicating a genetic factor.

Testosterone Levels During Competition

Testosterone increases during competitive events.

Male-Female Brain Differences

Males have larger inferior parietal lobes, while females have larger structures for language.

Hormonal Difference in Pituitary Glands

Males and females exhibit differences in the hormonal signals received by their pituitary glands.

Behavioral Changes Post-Castration

Castrated males showed less mounting behavior but increased lordosis.

Estrogen Role in Follicle Development

Estrogens released from developing follicles prevent other follicles from maturing.

Progesterone Function

Secreted by the corpus luteum, it prepares the uterine lining and prevents further follicle development until fertilization occurs.

Impact of Testosterone on Sex Drive

Testosterone is strongly linked with sexual aggression and drive in animals, but weakly in humans.

Homologous Structures

No sexual differentiation until the 6th week of development.

At 3 months of development…

Wolffian and Mullerian system develops.

Pituitary Glands

Can produce the same hormones in males and females; the difference is in the signals from the brain to the gland.

Testosterone Treatment

Stops ovulation in adult female rats, but can be overcome by stimulation; stops ovulation in baby female rats and cannot be reversed.

Castration in Male Rats

Adult male rats cannot ovulate when a female system is implanted; baby male rats can begin to ovulate when a female system is implanted.

Testosterone Exposure in Female Baby Rats

Suppresses lordosis and increases mounting.

Excess Androgen Exposure

Females exposed to excess androgens early in development see higher rates of lesbianism. 1/3 of XX individuals with Congenital Adrenal Hyperplasia identify as homosexual.

Low Level Androgen Exposure

Males exposed to low levels of androgens show higher levels of homosexuality.

Biological Link for Transgenders

More trans women than men, possibly a 3:1 ratio, possible feminization of the brain.