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PSYC 3500 (7)

Lecture 1 Ch 1: Biological Transitions in Adolescence

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York University
PSYC 3500
Jennine S.Rawana

Lecture 2 Ch 1: Biological Transitions in Adolescence Recap - Why study teens? - Introduction o Boundaries & stages of adolescence o Contexts & psychological developments of adolescence o Theoretical perspectives on adolescence from biological to environmental perspectives Psychosexual Development - Organismic Theory Behaviourism – Learning Theory Puberty – biosocial Theory Intergenerational conflict – Sociological theory Adolescence as a `Social Invention`- Historical Theory Ch 1 Overview - What is puberty and what are its defining characteristics o What is the endocrine system o What triggers puberty - What are the physical changes of puberty What are the variations in puberty - What is the psychosocial impact of puberty o Early vs. Late maturation o Obesity and Eating Disorders - Physical health in adolescence Definitions of Puberty - From Latin word pubertas (means adult) - Period of lifespan in which an individual becomes capable of sexual reproduction - A period of rapid physical maturation involving hormonal and bodily changes that take places in early adolescence - Unique and integrated transition from childhood that culminates in attainment of fertility What are the first physical characteristics of females and males in puberty? - Girl: breast development - Boys: testicular growth Defining Characteristics of Puberty - Greatest growth and sexual development since fetal stages - Marked by development of secondary sex characteristics for each gender and marked alterations in height, body composition, and regional distribution of body fat - Primary Sex Characteristics: reproductive organs - Secondary Sex Characteristics: Traits that distinguish the two sexes of a species, but that are not directly part of the reproductive system (e.g. body hair, breasts) - No new hormones are produced and no new bodily systems develop at puberty The Endocrine System - Produces, circulates, and regulars hormone levels in the body; leads to physical changes o Hormones  Substances secreted by endocrine glands o Glands  Organs that stimulate particular parts _______ 8 Major Endocrine Glands 1. Pineal gland: related to melatonin which helps regulate our circadian rhythm 2. Pituitary gland: related to GH 3. Thyroid gland: tied to your metabolism/thyroxin 4. Thymus: related to your immune system 5. Adrenal gland: produces sex hormones a. Estrogen and androgen 6. Pancrease: insulin, regulates blood sugar levels 7. Ovary: produces estrogen and progesterone 8. Testis: androgen and testosterone What Role Do Hormones Play in puberty - Organizing Role o Prenatal hormones “program” the brain to be masculine or feminine (like setting an alarm clock) o Patterns of behaviour as a result of this organization may not appear until adolescence (e.g., sex differences in aggression) - Activating Role o Increase in certain hormones by the HPG Feedback Loop at puberty activates physical changes (e.g. secondary sex characteristics) Puberty is ignited by the HPG Feedback Loop - Level of sex hormones regulated by feedback systems called the HPG Axis: o Hypothalamus o Pituitary gland (master gland) o Gonads (testes and ovaries) - Gonads release sex hormones into bloodstream o Androgens and estrogens - HypothalamusPituitary glandgonadsandrogens + estrogens - LH-RF (luteinizing hormone-relasing factor) and FSH-RF (follicle-stimulating hormone-releasing factor) stimular puitiuary gland o After the pituitary gland is stimulated, LH-RF and FSH-RF stimulate the gonads What Triggers Puberty - 1A. Adrenarche (A-gen-ark) o Maturation of adrenal glands at ages 7-10 leads to physical changes o Increases levels of dehydroepiandrosterone (GHEA) that contributes to hair growth, growth spurts, oilier skins, body odour - 1B. Gonadarche o Second burst of DHEA leads to adult levels of DHEA and maturation of testes or ovaries o Girls – ovaries increase output of estrogen > development of female genitals, breast development o Boys – testes increase output of testosterone – development of male genitals, muscle mass, body hair - 2. Leptin may be the most important signal o Protein produced by fat cells o Must accumulate enough body fat (~11%) o Rising levels of leptin signal hypothalamus to stop inhibiting puberty (at least in females) o May explain why girls with significant weight gain between ages 5-9 show earlier puberty development - 3. Environmental signals trigger the HPG axis to ignite o Presence of mature sexual partners (pheromones)  Mammals living close to biological relatives have slower pubertal processes than mammals exposed to unrelated members of the opposed sex, which may accelerate puberty o Nutritional resources  There are international differences in puberty which relates to the different nutrition in different places of the world What are the Five Major Physical Changes of Puberty? - 1.Adolescent growth spurt o In girls, begins between 9.5-14.5 (avg age 10) o In boys begins between 10.5-16 (avg 12/13) o Peak Height Velocity = time that adolescent is growing most quickly o Boys, 10.3cm/yr at age 14, gain 28cm stops at age 15 o Girls, 9cm/yr age 12, gain 25cm, stops at age 15 o Average female growth spurt is 2 years earlier than the average male growth spurt o Girls mature earlier than boys because their development is more complex/labour intensive so the system decides to start earlier to give it a head start o Half of adult weight is gained in puberty o In boys, peak weight velocity occurs at the same time or slightly later than peak height velocity; age 14, 9kg/yr o In girls, PWV lags behind PHV by approximately 6 months, age 12.5 years, 8.3kg/yr - 2. Changes in body composition o Relative proportions of body fat/muscle change o Different for boys (more muscle) and girls (fat accumulation twice as fast in girls than boys) o PHV of boys corresponds to maximal loss of fat and increase in muscle mass in upper arms o Skeletal changes o Bones, especially in young men, become harder and denser o Closing of ends of long bones (epiphysis) - 3. Changes in circulation and respiration o Size and capacity of heart and lungs o By end of puberty, boys have larger hearts & lungs relative to their size, higher systolic blood pressure, lower resting heart rate, great capacity for carrying oxygen to the blood, more red blood cells - 4. Development of primary sex characteris
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