MCB 135E Discussion GSI: Jason Lowry Nov 29 – Dec 3

Topics Adolescence and Puberty Functional Changes During Adolescence Male Reproductive System Maturation Female Reproductive System Maturation

Adolescence and Puberty Adolescence –Period between onset of reproductive function and adulthood (maturation of functions) Puberty –Maturation of reproductive function –One of many physiologic changes occurring during adolescence

Puberty Gonadal Function in Children Characterized by: –Very low levels of sex hormones –Very low levels of GnRH and FSH/LH –Testis and Ovary are differentiated Indicates negative feedback is not functioning correctly

Gonadal Function

CNS Development and Sexual Maturation CNS Matures progressively from birth to late childhood by: –Dendritic branching and number of synapses –Glial Cell Number –These lead to better communication, better metabolism, more efficient neurotransmissions Due to a decreased threshold, neurons are responsive to lower stimuli levels

Role of the Limbic System Cognition Feeding Behavior Conation Sexual Behavior Fear and Rage Motivation

Experimental Evidence of Limbic System Immaturity Immature gonads transplanted into an adult animal will mature immediately and demonstrate normal reproductive function The pituitary taken from a prepubertal animal and transplanted into an adult will regulate normal reproductive function Trauma to the hypothalamus will prevent the prepubertal animal from developing normal reproductive function

Role of Hypothalamus Gonadostat –Onset of adolescence leads to diminished threshold to sex hormones –This stimulates GnRH neurons which begin the cascade of H-P-G hormones along with negative feedback

Functional Changes Adult Reproductive function is established during adolescence –Female – Cyclic –Male – Tonic Puberty Age –Female – 8-13 –Male – 9-14

Factors Influencing Onset Hormonal Nervous Somatic Environmental Social Genetic

Summary of Charts Peak accelerated growth corresponds with onset of menarche Decreased electrical threshold (developing rats) CNS-Endocrine relationship –Able to see electrical activity that corresponds to ovarian cycle Change in sleep patterns Increased growth during adolescence –Earlier for girls than boys Changes in, B.P., Respiratory volume, heat production, and metabolic rate

Male Maturation

Maturation Process Maturation of Testes Development of seminiferous tubules Initiation of gametogenesis Secretion of T from leydig cells Maturation of Secondary Sex Organs

Maturation of Males: Secondary Organs –Internal Genitalia Seminal Vesicles Prostate –External Genitalia Penis increase in size Scrotum pigmented and rugose Characteristics: –Voice becomes deeper –Hair growth Beard Hairline recedes Pubic hair –Body hair increase –Mental Changes Sex, Aggressiveness –Body changes – muscles, shoulders –Skin - Acne

Role of Androgens Major Male Androgen –Testosterone Develop and maintain male secondary sex characteristics Exert important protein, anabolic action, and growth promoting effects To exert inhibitory feedback on Pit LH secretion

Testosterone Problems Low T Induces reduction –Hair, bone and muscles, sex drive, sperm count –May result from: Castration, Hormonal Disorders, Diseases Excess T: –Caused by tumors, treatments –Risk of high red cell blood count, prostate gland enlargement, fluid build up, sleep and respiratory problems

Female Maturation

Ovarian Cycle

Ovarian Hormones Estrogen –Stimulates growth and maintenance of secondary sex organs and characteristics –Stimulates ovary and follicle growth –Stimulates growth of smooth muscle and epithelial linings of reproductive tract –Stimulates bone growth and epiphyses closure Protection against osteoporosis Progesterone –Stimulation of uterine gland secretions –Decrease contractility of uterine muscle –Feedback on hypothalamus and pituitary –Some water and electrolyte retention