Unit 3: Sexual Hormones and Behaviour Flashcards
(28 cards)
What does it mean to be sexually dimorphic?
When sexes of the same species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction.
How sexually dimorphic are humans?
Moderately
What the chromosomal make up for male & female?
XX Female
XY Male
Which chromosomal make up is default?
Female
How does the chromosomal make up change from female to male?
If the SRY gene is present then it provides instruction for making the sex-determining Y gene –> promotes development in the male direction
In terms of sexual differentiation, what occurs at 6 weeks after conception?
The chromosomal (genetic) determination of male/female depending if SRY is present
What occurs at 7 weeks after conception?
Either the mullerian ducts (female) or the wolffian ducts (male) develop.
Testes produce testoserone and MIS (Mullerian inhibiting substance) which prevemt the mullerian ducts and allows to wollfian ducts to develop
What is the difference between the Mullerian ducts and the Wolffian ducts?
Mullerian duct system is the female accessory sex organ: develops into fallopian tubes, uterus and cervix.
Wolffian duct system is the male accessory organ: develops into vas deferencs, seminal vesicle
What happens at 8 weeks after conception?
Testes synthesize androgens that promote the development of male external genitalia
- Androgens (testosterone and DHT?) hormonally influence the tissue around urogenital groove becoming a penis and scrotum.
In terms of sexual differentiation, what occurs at Puberty?
Secondary sex characteristics (not related to reproduction)
Levels of androgens or estrogens will determine whether male or female features develop.
Outline the HPG axis for males
Hypothalamus (released GnRH - Gonadotropin-releasing hormone)
Anterior pituitary (receives GrNH and releases 2 Gonadotropins - LH (luteinizing Hormone) & FSH (Follicle-stimulating Hormone)
Gonads (Testes) secrete androgens
Outline the HPG axis for females
Hypothalamus (released GnRH - Gonadotropin-releasing hormone)
Anterior pituitary (receives GrNH and releases 2 Gonadotropins - LH (luteinizing Hormone) & FSH (Follicle-stimulating Hormone)
Gonads (ovaries) secrete estrogens and progestins
How to steroid hormones alter gene expression and regulate cellular processes
Steroid hormones regulate cellular processes by binding the receptors
This then interacts with discrete nucleotide sequences (which alters gene expression)
What are 3 types of sex steroids?
Androgens (male)
Estrogens (female)
Progestins (female)
What is the name of the process of estrogen being created by androgens?
Aromatization- the enzyme aromatize causes androgens (T) to produce estrogens
What are the 3 exceptional cases of human sexual development?
Androgenic insensitive syndrome
5-a-reductase II definiciency “guevedoces”
Congenital adrenal hyperplasia (CAH)
What is an androgenic insensitive syndrome?
Chromosomal sex: XY (male)
Molecular basis: nonfunctioning androgen receptors therefore circulating androgens (T) cannot be utilized
Gonads: testes
External genitalia: feminized
Other notes
- Symptoms don’t occur until puberty
- Vaginal depth is short
- Undescended testes
- External genitalia is normal
- minimal/no acne
What is 5-a-reductase II deficiency “guevedoces”?
Chromosomal sex: XY (male)
Molecular basis: non functional 5-a-reductase II, leads to deficit in conversion of testosterone to DHT in target tissues
Gonad: testes
External genitalia: at birth feminized/ambiguous
What is 5-a-reductase II deficiency “guevedoces”?
Chromosomal sex: XY (male)
Molecular basis: non functional 5-a-reductase II, leads to deficit in conversion of testosterone to DHT in target tissues
Gonad: testes
External genitalia: at birth feminized/ambiguous
What is congenital adrenal hyperplasmia?
Chromosomal sex: XX (female)
Molecular basis: Defect in cortisteroid synthesis, leading to an increase in circulating androgens from the adrenals
Gonad: ovaries
External genitalia: At birth: virilized
What behaviours do a CAH (congenital adrenal hypothesis) females shown?
Increased male-typical toy, playmate and activity preferences
What are sex differences in infant visual interest in toys during the first year of life?
Eye tracking with infants (3 months)
FOUND: females are significantly more interested in doll than truck. Interest for boys was even between the 2 toys.
What are volumetric and connective sex differences in the brain?
Differences are observed mainly in brain areas interested in reproduction.
- SDN-POA (larger in the male than in the female)
- INAH-3
- BNST: medial amygdala
- SCN
- Lateralization: corpus collosum
What are organizational and activational effects?
Organizational: permanent effects on developing brain which direct adult hormonal responsiveness. This must occur in the sensitive period
Activational effect: occur at puberty & throughout the lifespan. Activated reproduction-related behavior and physiology.
