The Biological Revolution of Puberty: Hormonal Changes and Physical Growth - Although adolescence is culturally constructed, the biological changes of puberty are a Central part of development during adolescence - “Puberty” – Latin for “to grow hairy.” - The Endocrine System - The initiation of puberty in the Hypothalamus - Hormonal changes begin in hypothalamus - Gonadotropin-releasing hormone begins at puberty - Increased GnRH occurs once a threshold level of body fat is reached - Fat cells produce the protein leptin that provides the signal to release GnRH - The Pituitary Gland and the Gonadotropins - Gonadotropins release once GnRH reaches the pituitary gland - Follicle-stimulating hormone - Luteinizing hormone - The Gonads and the Sex Hormones - Ovaries and Testes = gonads, or sex glands - Sex hormones - Estrogens – most important is estradiol - Androgens – most important is testosterone - Adrenocorticotropic Hormone - Causes the adrenal glands to increase androgen production - The feedback loop in the endocrine system - Monitors and adjusts levels of sex hormones - Set point is the optimal level - Once set point is reached, hormone production goes down - Physical Growth During Puberty - Adolescent growth spurt – growth surges when puberty arrives - Peak height velocity is the growth spurt maximum - Girls – 3.5 inches per year - Boys – 41 inches per year - Asynchronically – uneven growth - Muscle growth spurt - Levels of body fat surge The Biological Revolution of Puberty: Sexual Maturity and Physical Functioning - Primary sex characteristics - Egg and sperm production - Menarche is first menstrual period - Ovum is a mature egg - Released every 28 days or so - Females release about 400 over their lives - Spermarche is first production of sperm - 30-500 million sperm per ejaculation - The Male and Female Reproductive Anatomy - Changes prepare body for sexual reproduction - Male penis and testes grow - Female releases an ovum with each monthly cycle - Female doesn’t start ovulating at first menstruation - Secondary Sex characteristics - Bodily changes that are not directly related to reproduction - Hair growth in public areas, under arms, face - Hairiness on arms and legs increases - Sweat glands in the skin increase production - Deepening of the voice - Males grow hair on chests, shoulder, and back - Females experience breast growth - The order of pubertal events - Female order - Pubic hair - Breast buds - Growth spurt - Growth of sexual and reproductive organs - Menarche - Underarm hair - Secretions of increased skin oil and sweat - Changes in Physical Functioning During Puberty - The Heart, the Lungs, and Physical Performance - Heart size doubles and heartrate falls - By age 17, average girl’s heartrate is 5 beats faster than the average boy - Lung vital capacity increases rapidly - Increases more for boys than girls - Boys overtake girls in physical strength - Obesity - Exceeding a specific body mass index - About 20% of American adolescents are obese - Diet and exercise major cause - Fast-food diet - American lifestyle more automobile-oriented - Steep decline in physical activity from middle childhood to adolescence - Soft drink and junk food machines in schools - Physical Functioning in Emerging Adulthood - Peak bone mass reached in the 20s - Maximum oxygen uptake - Peaks in early 20s - Cardiac output - Peaks at age 25 - Reaction time fastest in 20s Cultural Responses to Puberty - Culture and the timing of puberty - Puberty begins earlier in cultures where good nutrition and medical care are widely Available - Secular trends - Age of menarche - Within countries, adolescent girls from affluent families menstruate earlier than girls From poorer families - Reaction range – genes establish a range of possible development and environment Determines where it takes place within that range. - Cultural Response to Puberty: Puberty Rituals - Majority of cultures have some kind of ritual initiation into adolescence - Menarche often initiates a monthly ritual that lasts throughout a women’s Reproductive life - Puberty rituals for males do not focus on a particular biological event - Typically require the young man to display courage, strength, and Endurance - Often violent - Seen as necessary to face life’s challenges as a man Social and Personal Responses to Puberty - Parent-Adolescent relations and puberty - American majority culture - Relations become cooler - Conflict increases - Physical closeness less likely - Not the same in other traditional cultures - Girls often grow closer to mothers