1. Development of Sexual Behavior and Correlated Characteristics
Lecture 36
PS Timiras

2. Inheritance of X and Y chromosomes

4. Neuroendocrinology Neuropsychoendocrinology
CNS modulates endocrine functions and hormones modulate CNS functions
CNS modulates endocrine functions
Hypothalamic hormones
ADH, Oxytocin
Hypophysiotropic hormones
GHRH, PLRH, CRH, TRH, GnRH, and respective inhibitors
Steroid Hormones
Androgens, Estrogens, Glucocorticoids, Mineral Corticoids
Insulin, PTH, Calcitonin, Thyroid Hormones, IGF-1, IGF-2

5. Hormones Modulate CNS Functions
Embryo
GH control of CNS growth centers (hypothalamus, feedback)
IGF-2 ??
T3, T4 CNS development
Androgens differentiation of sex organs and related CNS areas
Childhood
GH, GHRH, IGF-1, T3, T4
Puberty
Androgens, Estrogens, GH, IGF-1, T3, T4, PTH, Calcitonin, Insulin
Responses to Stress
CRH, ACTH, Adrenal Cortical hormones

6. Prenatal Sexualization
Sexualized Behaviors
Biological Factors
Prenatal Sexualization
Genes
Gonads Brain
Hormones steroids
Testosterone (Male)
No Testosterone (Female)
Reproductive
Structures
(Internal and External)
Environmental Factors
that cause biological responses
stress
drugs
pesticides
(endocrine disrupters)
Cerebral Cortex: cognitive skills (parenting; survival)
Hypothalamus: cyclic (female) or acyclic (male) reproductive
Cycles, mating, gender identity, sexual orientation
Spinal cord

9. preparation for adulthood
Sexualized Behaviors
Childhood
preparation for adulthood
Gonads Brain
Quiescent until puberty
Except for transient surge
of testosterone in male in
1st 3 months.
Genitals
Internal and external genitals
Are infantile
Practices parenting and
Survival skills. Acknowledges
Gender identity and sexual
Orientation
Interest in genitals and
Reproductive behavior

10. The actions of hormones can be categorized into:
Organizational
Regulatory
Examples:
-thyroid hormones T3 on growth and maturation on neural cells
-masculinizing actions of androgens on CNS structures
(e.g. hypothalamus sexually dimorphic nucleus of preoptic area SDN-POA)

11. Masculinization of Some CNS Structures
1. Depends on presence of androgens
at “critical” time
The “window” of androgens’ organizing actions is:
First 4 postnatal days in rats
Probably 3rd trimester of gestation in humans

12. Actions of Neonatal Androgens Males:
Larger (than in females) sexually dimorphic nucleus of the preoptic area (SDN-POA) in hypothalamus
Larger spinal nucleus of the bulbocavernosus (SNB) muscle
Development of male sexual behavior

13. Actions of Neonatal Androgens
Females
Smaller SDN-POA and SNB enlarge
Female sexual behavior is suppressed
(e.g. absence of lordosis)

14. Sexualized Behaviors Puberty
Doorway to adulthood
Brain turns on adult cycles of gonadal function.
Gonads begin production of adult levels of sex hormones.
Sex hormones stimulate adult male or female body types.
Sex hormones stimulate reproductive behavior
Status becomes a primary goal especially among boys
Desire for independence
Practice skills for attracting sexual partners
Peer Pressure

15. Sexualized Behaviors Social expectations Gender Conformity
Based on external genitals
Gender Conformity
Behavior is reinforced or
Rejected by family or society
Gender Expectations
Are reinforced and social
responses escalate

16. Sexual Attraction
In humans, ever vigilent brain circuits survey the environment for prospective mates with biological and psychological traits that signify fertility and evidence of good parenting skills.
Males and females evaluate each other by chemical attractants and by evidence of an anatomical, physiological and behavioral fitness
Females are attracted to:
Small Buttocks
Narrow Pelvis
Well developed muscles
Taller than she is
Unblemished skin, white teeth
Symmetrical features
Good posture
Signs of dominance when competing with other men
Treating her with affection and sensitivity
Signs of parenting skills
Signs of potential economic success
Not necessarily interested in his formal sexual experiences
Age is not an issue

17. Sexual Attraction For both sexes the most valued characteristics:
Men are Attracted to:
Large Breasts
Narrow Waist
Broad Pelvis
Fat deposition that rounds the shoulders and buttocks
Shorter stature than his
Female voice
Good posture and Graceful Gait
Full Lips and White Teeth
Very interested in her fertility, prior sexual activity
Her age
For both sexes the most valued characteristics:
Kindness and understanding
Intelligence
Tendency for co-operation and teamwork
The Ultimate Goal is to Reproduce and Be A
Good Parent

18. Left Hemisphere:
Controls the right
side of the body
Right Hemisphere:
Controls the left
side of the body

19. Gender Related Anatomical and Behavioral Characteristics
Differences in Digit Length
2D =4D in females
2D < 4D in Males
Cognitive Function
Conscious process of knowing of events (objects in the environment)
Using that knowledge for understanding and problem solving
Depend on Prenatal
Concentrations of
Testosterone

20. Cognitive Function Female Generally More Skilled in:
Caring for the Children
Foraging Close to Home
Managing Home Area
Better in
Verbal Fluency
Verbal Recall
Understanding Facial Expression
Memory of Object Location
Fine Motor Skills

21. Gender Related Differences in Cognitive Function
Males Are Better Equipped:
to Protect Territory
Go long distances to hunt for food
Better in visual and spatial tasks
Inferior portion of parietal lobe
Mathematical thinking
Navigating and Targeting