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  1. Adolescence9th edition By Laurence Steinberg, Ph.D. Insert Photo from DAL Chapter One: Biological Transitions

  2. Chapter 1 Overview What is puberty? What is the endocrine system? What triggers puberty? What are the physical changes of puberty? Variations in the timing and tempo of puberty What is the psychosocial impact of puberty? Early vs. late maturation Eating disorders Physical health in adolescence

  3. Puberty: An Introduction From Latin word pubertas (adult) Period of lifespan in which an individual becomes capable of sexual reproduction Hormones regulated by the endocrine system lead to physical changes No new hormones are produced and no new bodily systems develop at puberty

  4. The Endocrine System Produces, circulates, and regulates hormone levels in the body Hormones Substances secreted by endocrine glands Glands Organs that stimulate particular parts of the body to respond in specific ways Feedback loop (HPG axis) Set point (Example: thermostat)

  5. The Endocrine System: HPG Feedback Loop HPG Axis: Hypothalamus Pituitary gland (master gland) Gonads (testes and ovaries) Gonads release sex hormones into bloodstream Androgens and estrogens

  6. What Triggers Puberty? Although no new hormones in adolescence, something signals the HPG axis to kick on Presence of mature sexual partners Nutritional resources Physically mature enough to begin reproducing Leptin may be the most important signal Protein produced by fat cells Must accumulate enough body fat (~11%) Rising levels of leptin signal hypothalamus to stop inhibiting puberty (at least in females) Adrenarche Maturation of adrenal glands leads to physical (somatic) changes

  7. What Role Do Hormones Play? Organizing Role Prenatal hormones “program” the brain to be masculine or feminine (like setting an alarm clock) Patterns of behavior as a result of this organization may not appear until adolescence (Ex: sex differences in aggression) Activating Role Increase in certain hormones at puberty activates physical changes (Ex: secondary sex characteristics)

  8. Puberty is Affected by Context Timing of physical changes in adolescence varies by Regions of the world Socioeconomic class Ethnic group Historical era Example: Menarche (first menstruation) U.S. average 12 to 13 years Lumi (New Guinea) average > 18 years Insert picture from DAL

  9. What Are The 3 MajorPhysical Changes of Puberty? Adolescent growth spurt Development of primary sex characteristics (gonads) Development of secondary sex characteristics (breasts, pubic hair)

  10. Physical Changes of Puberty:Adolescent Growth Spurt Adolescent growth spurt Rapid acceleration in growth (height and weight) Simultaneous release of growth hormones, thyroid hormones, and androgens Peak Height Velocity (Time that adolescent is growing most quickly) Average female growth spurt is 2 years earlier than the average male growth spurt

  11. Physical Changes of Puberty:Adolescent Growth Spurt

  12. Physical Changes of Puberty: Sex Differences in Muscle and Fat Changes in body composition Relative proportions of body fat/muscle change Different for boys (more muscle) and girls (more fat) Body dissatisfaction among girls Closing of ends of long bones (epiphysis) Asymmetry of growth

  13. Physical Changes of Puberty: Sexual Maturation Development of secondary sex characteristics Measured in boys and girls by Tanner Stages Changes include Growth of pubic hair Changes in appearance of sex organs Breast development

  14. Sexual Maturation: Boys Spermarche typically occurs 1 year after accelerated penis growth Boys capable of fathering a child before they look like adults; opposite true for girls

  15. Sexual Maturation: Girls Sequence less regular than in boys Menarche typically occurs after other secondary sex characteristics; regular ovulation follows 2 years later Thus, girls appear physically mature before they are actually capable of reproduction

  16. Variations in the Timing and Tempo of Puberty No specific average age at onset or duration of puberty No relation between the age at which puberty begins and the rate of pubertal development Timing (early or late) and adult stature Small effect: late maturers slightly taller as adults, early maturing girls slightly heavier as adults Childhood height and weight Stronger correlation with adult height and weight

  17. Variations in the Timing and Tempo of Puberty

  18. Individual Differences in Pubertal Maturation Pubertal maturation Interaction between genes and environment Differences in timing/rate among individuals in the same general environment result chiefly from genetic factors Genetic predispositions Upper and lower age limits, not a fixed absolute Two key environmental influences Nutrition Health Exposure to pheromones Insert photo from DAL

  19. Group Differences in Pubertal Maturation Typically studied by comparing average age of menarche Across countries Age at menarche younger when not malnourished or suffering from chronic disease (Ex: Africa and United States) Over time Changes in the average age of menarche over the past two centuries

  20. Group Differences in Pubertal Maturation Secular trend (group trend within same region) Leveling off in industrialized nations Better sanitation, control of infectious diseases Onset of puberty has continued to occur earlier among African-American girls in the United States

  21. Group Differences in Pubertal Maturation

  22. The biological changes of puberty can affect the adolescent’s behavior in at least three ways

  23. How Do Researchers Study The Psychosocial Consequences of Puberty? Groups compared at different stages of puberty Cross-sectional study design Longitudinal study design Same adolescents tracked over time Comparison of early vs. late maturers When interested in the effects of pubertal timing on psychosocial outcomes

  24. The Immediate Impact of Puberty Self-esteem varies by gender and ethnicity Adolescent moodiness More fluctuations throughout the day than adults Not solely due to hormones Greatly influenced by environmental factors such as shifts in activities

  25. The Immediate Impact of Puberty • Changes in patterns of sleep • Delayed phase preference and later melatonin secretion • Environmental influences and school start times

  26. The Immediate Impact of Puberty Family relationships Increased conflict and distance between parents and children Peer relationships

  27. The Psychosocial Impact of Specific Pubertal Events Most adolescents react positively to pubertal changes Especially secondary sex characteristics Reactions to menarche are less negative than in the past Less known about boys’ reactions to first ejaculations Insert photo from DAL

  28. Psychosocial Impact of Early or Late Maturation: Boys Perception of being an early or late maturer is more important in affecting one’s feelings than the reality Pros of early maturation Popularity, better self-esteem More responsible, cooperative, sociable later in adulthood Cons of early maturation More drug and alcohol use, precocious sexual activity, greater impact of victimization Less creative, more humorless in later adulthood

  29. Psychosocial Impact of Early or Late Maturation: Girls Compared to early maturing boys, early maturing girls have more difficulties Maturational deviance hypothesis Developmental readiness hypothesis Cultural and contextual factors (valuing thinner body types) Pros of early maturation Popularity with boys Cons of early maturation Heavier and shorter stature later in life Precocious sexual activity, lowered self-image, higher rates of depression, eating disorders, anxiety

  30. Psychosocial Impact of Early or Late Maturation: Girls

  31. Eating Disorders Body Dissatisfaction Higher among early maturing girls Obesity The most common eating disorder among adolescents Disordered eating Unhealthy patterns of eating, attitudes, and behaviors

  32. Eating Disorders About ¼ of American adolescents are highly satisfied with their bodies Over ½ consider themselves overweight and have attempted to diet Deviation from the “ideal” physique can lead to loss of self-esteem and other problems in the adolescent’s self-image Studies of magazines, 1970 to 1990 Ideal body shape became slimmer and less curvaceous

  33. Eating Disorders:Bulimia & Anorexia Nervosa Adolescents with these eating disorders have an extremely distorted body image Bulimia Eating binges; force themselves to vomit to avoid weight gain 3% of adolescents are genuine bulimics Anorexia Starve themselves to keep weight down Fewer than one-half of 1% of adolescents Clinically defined bulimia and anorexia are 10 times more common among females

  34. Physical Health and Health Care in Adolescence Adolescent health care needs differ from those of children and adults Most health problems are preventable Field of adolescent health has shifted away from traditional medical models (diagnosis and treatment of disease) toward more educational approaches (prevention and promotion of good health). Insert photo from DAL

  35. Physical Health and Health Care in Adolescence PARADOX: Adolescence is a healthy period of the lifespan But nearly 1 in 15 adolescents experiences at least one disabling chronic illness: Mental disorders (depression) Respiratory illnesses (asthma) Muscular and skeletal disorders (arthritis)   Threats to health have psychosocial causes (not natural causes) Unhealthy behaviors, violence, and risky activity

  36. Adolescent Mortality Today 45% of teen deaths due to car accidents and other unintentional injuries Less experienced behind the wheel More likely to take driving risks 27% of teen deaths due to homicide and suicide 50 Years Ago Most deaths from illness and disease

  37. Promoting Adolescent Health Particular concern with improving the health of poor and ethnic minority adolescents Less access to medical care and more likely to: Suffer from chronic illness To be obese or have high blood pressure To be physically inactive To be victims of violent crimes To die from drowning To be murdered (leading cause of Black adolescents is homicide)