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PSYB64H3 Study Guide - Final Guide: Procedural Memory, Learning, Sensory Memory

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Janelle Leboutillier
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Chapter 10: Sexual behavior
Sexual chromosome abnormalities
moms provide X chromosome to all offspring, fathers provides X for female or Y for males
syndrome (XO)when child receives only a single X chromosome (XO) instead of the usual pair (XX
or XY)
lack of 2nd sex chromosome has impact on fertility, growth, hormone production
associated with higher risk of diabetes, osteoporosis, cardiovascular disease
normal female external genitals but ovaries develop abnormally
dont produce ova or nomal levels of female hormones = infertility
when X chromosome is missing in some but not all cells, or only portions of second
X are missing, women may be fertile
relatively short, increased skin folds at the neck
spcific deficits in spatial relationships & memory can occur
syndrome (XXY)one of most common genetic abnormalities related to sex chromosomes
male, but usually experience reduced fertility and requires hormone treatment @
puberty to promote development of facial hair, deeper voice, development of
external genitals, & to inhibit female characteristics such as breast development
extra X chromosome can be due to interference with process of x-inactivation,
where one X chromosome in each female cell is randomly silenced
normal intelligence marked by mild cognitive difficulties and social awkwardness
usually delayed & reduced verbal skills
left-handedness more common, suggests it might affect brain lateralization or
localization of specific fxns such as language in one hem or the other
XYY boys appear to be taller and leaner, suffer from acne, higher risk for minor
physical abnormalities of eye, elbow, chest
IQ is slightly below average, fertile but more likely to produce sperm with
chromosome abnormalities
Higher rate of antisocial and criminal behavior, property crimes more than
Abnormalities due to a 3rd sex chromosome appear to have mild effects
Sexual development
3 stages of prenatal development:
of GonadsBefore 6 weeks after conception: both male and female fetuses have identical
primordial gonads that have capacity to develop into ovaries or testes
After 6 weeks, a gene on short arm of Y chromosme (aka sex-determining region of Y
chromosome/ SRY) is expressed in male embryos
Testis-determining factor (protein encoded by SRY) switches on additional genes that
cause primordial gonads to develop into testes
Female embryos lack SRY gene
n of internal
Up until 3rd month of deveopment, both male & female fetuses posses a male Wolffian
system and a female Mullerian system
Wolffian system = seminal vesicles, vas deferences, prostate
Mullerian system = uterus upper portion of vagina, fallopian tubes
Males: testosterone (or androgen) & anti-Mullerian hormone promotes development
of Wolffian system
Anti-Mullerian hormone inities degeneration of Mullerian system
In female fetus: no additional hormones are needed for development


Unlike testes, ovaries are not active during fetal development
Nonfunctional remnants of Wolffian system remain throughout a womans life
Androgen insensitivity syndrome (AIS) disrupts normal development of Wolffian
system in males
Lacks androgen receptors, so leads to development of female external genitalia,
typical female gender identity & sexual behavior
Anti-Mullerian hormone is still there, so female Mullerian system also fails to
Results in shallow vagina and no ovaries, fallopian tubes/ uterus
of external
Male = penis & scrotum
Female = labia, clitoris, outer part of vagina
No hormonal activity is required in order to develop female external genitalia
But males need a particular androgen: 5-alpha-dihydrotestosterone, must be
recognized by receptor sites for male external genitalia to develop normally
If genetic females are exposed prenatally to excess androgens, their external
genitalia become masculinized
females with congenital adrenal hyperplasia (CAH) show ambiguous external
at pubertyaverage age of puberty has dropped dramatically over past century and a half
phthalates are compounds frequently found in plastics and cosmetics, found to
advance puberty in rats
children are esp sensitive to small amounts of hormone, so increased exposure from
external sources is cause for concern
at onset of puberty, gonadotropin-releasing hormone (GnRH) is released by
initiates release of 2 GnRH hormones by anterior pituitary gland: the follicle-
stimulating hormone (FSH) and luteinizing hormone (LH)
both sexes release them, but with diff effects
in response to these hormones: testes begin to produce more testosterone, ovaries
produce estradiol (and small amounts of opposite sex hormone)
males: muscular development, maturity of external genitals, facial hair, enlargement
of larynx (deeper voice)
females: breast growth, , uterus, changes in fat dist, menstrual cycle
5-alpha-reductase deficiency: affects last step, maturation of external genitalia
child is born with ambiguous genitalia but develops male secondary sex
characteristics at puberty
Sex hormonescholesterol is used to form sex hormones
Aromatization is the only step necessary to turn testosterone into estradiol
Both males and females have both testosterone and estrogen
Males have more testosterone, females have more estrogen
Sexual interest in females: Report slightly more interest around ovulation
oTestosterone has greatest impact on womens sexuality
oEstrogen & cognition: Best scores on spatial abilities tests when testosterone
levels high and worst when estrogen levels are high
oBest scores on verbal abilities and manual dexterity tests when estrogen levels are
Sexual interest in males: Testosterone levels increase in anticipation of competition
oIf androgen is in normal range, young mens testosterone levels dont predict
sexual frequency
oMarried men have lower testosterone than single or recently divorced men


oSpatial abilities advantage may be related to testosterone
Anabolic steroids: Synthetic versions of testosterone that build tissue
Build strength and muscle mass and improve recovery time following muscle damage
Significant side effects: acne, enlargement of clitoris or penis, lower voice, unusual
hair loss or growth, psychological disturbances, larger breasts in males, high blood
pressure and kidney disease
Sex differences in the nervous system
dimorphismTo display structural differences b/w the sexes
Sexually dimorphic structures:
1.Sexually dimorphic nucleus of preoptic area (SDN-POA)
Much larger in male rats then females
Reflects early organizing effects of hormone exposure
Rats: critical window exists within few days of birth where exposure to
androgens masculinizes the brain
If newborn male rat is castrate, SDN-POA is much smaller than normal
Lesions in this area of the hypothalamus generally reduce male sexual
2.Interstitial nuclei of the anterior hypothalamus (INAH)
Humans equivalent of SDN-POA
4 clusters of neurons in preoptic area of hypothalamus
INAH-2 and INAH-3 are 2x larger in males than females
INAH-3 might be human equivalent to rodent SDN-POA
Correlation b/w size of these nuclei and males s exual orientation
3.Hypothalamus, thalamus, white matter
Hypothalamus related to sexual behavior
4.Spinal cords of mammals
Spinal nucleus of bulbocavernosus (SNB) of rats: male rats have more motor
neurons here than female rats
Innervates bulbocavernosus muscles of rats penis
These muscles are missing in female rats
Prior to rats critical period of masculinization at birth, both sexes possess
these muscles and about same # of SNB cells
During critical period: low levels of androgens in female rats cause muscles
and most of SNB neurons to die
on of the brainRodents and other animals: aromatization masculinizes brains of many animals
Chemical rxn resulting in aromatic compound (6-carbon ring)
Testosterone is transformed into estradiol, producing masculinization
Female rats protected from these effects of mothers circulating estradiol by alpha
Other animals: mothers estradiol is blocked by placenta (except hyenas, cant do
Female hyenas possess physical & behavioral characteristics usually seen as
Humans: ppl with AIS are still overwhelmingly feminine; so aromatization is not
responsible for masculinization in human brain
Androgens appear to play a direct role in masculinization of human brain that is
not dependent on aromatization into estradiol
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