Development of Sexual Behavior and Correlated Characteristics Lecture 36 PS Timiras
NeuroendocrinologyNeuropsychoendocrinology
• 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
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
Sexualized BehaviorsBiological Factors
Prenatal Sexualization
Genes
Gonads Brain
Hormones steroids
Testosterone (Male)No Testosterone (Female)
Reproductive Structures
(Internal and External)
Cerebral Cortex: cognitive skills (parenting; survival)Hypothalamus: cyclic (female) or acyclic (male) reproductive
Cycles, mating, gender identity, sexual orientationSpinal cord
Environmental Factors
that cause biological responsesstressdrugspesticides(endocrine disrupters)
Sexualized Behaviors
Childhood
preparation for adulthood
Gonads Brain
Quiescent until pubertyExcept for transient surge of testosterone in male in 1st 3 months.
GenitalsInternal and external genitalsAre infantile
Practices parenting andSurvival skills. AcknowledgesGender identity and sexual Orientation
Interest in genitals and Reproductive behavior
The actions of hormones can be categorized into:
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)
Organizational Regulatory
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
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
Actions of Neonatal Androgens
Females
• Smaller SDN-POA and SNB enlarge
• Female sexual behavior is suppressed
(e.g. absence of lordosis)
Sexualized BehaviorsPuberty
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 behaviorStatus becomes a primary goal especially among boysDesire for independencePractice skills for attracting sexual partnersPeer Pressure
Sexualized BehaviorsSocial expectationsBased on external genitals
Gender ConformityBehavior is reinforced or
Rejected by family or society
Gender ExpectationsAre reinforced and social
responses escalate
Sexual AttractionIn 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 ButtocksNarrow PelvisWell developed musclesTaller than she isUnblemished skin, white teethSymmetrical featuresGood postureSigns of dominance when competing with other menTreating her with affection and sensitivitySigns of parenting skillsSigns of potential economic successNot necessarily interested in his formal sexual experiencesAge is not an issue
Sexual AttractionMen are Attracted to:Large BreastsNarrow WaistBroad PelvisFat deposition that rounds the shoulders and
buttocksShorter stature than hisFemale voiceGood posture and Graceful GaitFull Lips and White TeethVery interested in her fertility, prior sexual activityHer age
For both sexes the most valued characteristics:Kindness and understandingIntelligenceTendency for co-operation and teamwork
The Ultimate Goal is to Reproduce and Be A Good Parent
Right Hemisphere:Controls the leftside of the body
Left Hemisphere:Controls the rightside of the body
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 PrenatalConcentrations of Testosterone
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