Development of Sexual Behavior and Correlated Characteristics Lecture 36 PS Timiras

Inheritance of X and Y chromosomes

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

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

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

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

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)

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 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

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

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

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

Left Hemisphere: Controls the right side of the body Right Hemisphere: Controls the left side 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 Prenatal Concentrations 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

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