Chapter 11

PHYSICAL DEVELOPMENT

• CONCEPTIONS OF ADOLESCENCE
• the transition between childhood and adulthood
• either biologically determined period of storm and stress or entirely influenced by the social environment
• adolescence = joint product of biological, psychological and social forces
• PUBERTY: PHYSICAL TRANSITION TO ADULTHOOD
• hormonal changes in middle childhood initiate puberty
• 2 years earlier for girls than for boys
• as body enlarges during the growth spurt, girls hips and boys shoulders broader. girls = more fat; boys = more muscle.
• puberty brings slow, gradual improvements in gross motor performance for girls, dramatic gains for boys.
• changes in primary and secondary sexual characteristics accompany rapid body growth
• menarche occurs late in the girl's sequence of pubertal events, after the growth spurt peaks. in boys, the peak in growth occurs later, preceded by enlargement of the sex organs and spermarche.
• heredity, nutrition, exercise and overall physical health influence timing of puberty. the emotional quality of family experiences may play a role.
• a secular trend toward earlier puberty has occurred with socioeconomic progress and improved physical well being. in some industrialized nations, rising obesity rates have extended this trend.
• changes in the brain: synaptic pruning in the cerebral cortex continues in adolescence, and growth and myelination of stimulated neural fibers accelerate, strengthening connections among brain regions, particularly those involving the prefrontal cortex. consequently, adolescents gain in diverse cognitive skills, but gains are gradual.
• neurons = more responsive to excitatory neurotransmitters, heightening emotional reactivity and reward seeking. changes in the brains emotional/social network outpace the development of the prefrontal cognitive-control network, resulting in difficulties controlling emotions and impulses.
• revisions occur in brain regulation of sleep, leading to a sleep phase delay. sleep deprivation contributes to poorer achievement, anxiety, irritability, depressed mood, and high-risk behaviors.