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  1. 3 A Topical Approach to LIFE-SPAN DEVELOPMENT Physical Development and Biological Aging John W. Santrock

  2. Physical Development and Biological Aging • Body Growth and Change • The Brain • Sleep • Longevity

  3. Body Growth and Change Patterns of Growth • Cephalocaudal pattern — growth occurs first at the top—the head—and gradually proceeds from top to bottom • Proximodistal pattern — growth starts at the center of the body and moves toward the extremities

  4. Body Growth and Change Height and Weight in Infancy and Childhood Infancy • Average 20 inches, 7 ½ lbs at birth • Triple weight by 1 year • ½ adult height, 20% adult weight by age 2 Early Childhood • Growth slows, patterns vary individually • Girls slightly smaller and lighter • Girls gain fat, boys gain muscle Middle and Late Childhood • Slower, consistent growth • Muscle mass and strength increase • Boys stronger, body proportions change

  5. Body Growth and Change Changes in Proportions of the Human Body During Growth Fig. 3.1

  6. Body Growth and Change Height and Weight in Infancy and Childhood • Why some children unusually short • Congenital factors • Growth hormone deficiency • Physical problem developed in childhood • Maternal smoking during pregnancy • Emotional difficulty

  7. Body Growth and Change Puberty • Period of rapid physical maturation involving hormonal and bodily changes that take place in early adolescence • Two phases: • Adrenarche — changes in adrenal glands • Gonardarche • Menarche • Spermarche

  8. Heredity Hormones Hypothalamus, pituitary gland, gonads Androgens (testosterone) Estrogens (estradiol) Adrenarche Gonadarche (menarche, spermarche) Weight and Body Fat Body Growth and Change Determinants of Puberty

  9. Body Growth and Change Hormone Levels by Sex and Pubertal Stage for Testosterone and Estadiol Fig. 3.2

  10. Body Growth and Change Pubertal Growth Spurt Fig. 3.3

  11. Normal Range and Average Development of Sexual Characteristics in Males and Females Fig. 3.4

  12. Body Growth and Change Changing Trends in Puberty • Onset of puberty beginning earlier • Norway — menarche at 17 in 1840s, now 13 • U.S. — menarche at 15 in 1840s, now 12½ • White girls at average age of 10 • African American girls at average age 8 to 9

  13. Body Growth and Change Body Image in Puberty • Adolescents become preoccupied by bodies • Overall, girls less satisfied, boys more satisfied • Throughout puberty… • Girls’ dissatisfaction increases — body fat increases • Boys’ satisfaction increases — muscle mass increases

  14. Body Growth and Change Body Image in Puberty • Early and Late Maturation • Early boys more positive, better peer relations • Late boys less positive but have more positive identity by 30s than early boys • Early girls positive but potential problems • Late girls more positive about bodies in late adolescence

  15. Body Growth and Change Early Adulthood • Physical changes may be subtle • Height is constant • Many reach peak of muscle tone and strength in late teens and twenties • Peak in joint functions in twenties • Decline in the thirties

  16. Body Growth and Change Middle Adulthood • Physical • Lose height, gain weight • More wrinkling, sagging in 40s and 50s • Youth-oriented culture motivates life style changes • Strength, bone density, flexibility decrease • 1 to 2 percent loss each year after age 50

  17. Body Growth and Change Middle Adulthood • Cardiovascular system and lungs • Cholesterol and clogged arteries • Blood pressure increases • Decreased lung capacity after age 55 • Sexuality changes • Climacteric — fertility declines • Menopause — menstrual periods cease

  18. Body Growth and Change Lung Capacity, Smoking and Age Fig. 3.5

  19. Body Growth and Change Late Adulthood • Variability in physical declines • Socioeconomic status is a big factor • Physical appearance • Wrinkles, age spots, height and weight loss • Gradual muscle loss; weightlifting can slow process • Circulatory system • Increased blood pressure; linked to chronic conditions and longevity

  20. The Brain Brain Physiology • Brain structure • Forebrain • Two hemispheres: usually work together and each lobe has a primary function • Cerebral cortex • Amygdala • Hippocampus

  21. The Brain The Brain’s Four Lobes Fig. 3.7

  22. The Brain Functions of Lobes of the Cortex Involved in voluntary movement, thinking, personality, and intentionality or purpose Frontal lobes Occipital lobes Function in vision Active role in hearing, language processing, and memory Temporal lobes Roles in registering spatial location, attention, and motor control Parietal lobes

  23. The Brain Brain Physiology • Neurons— nerve cells handling information processing at the cellular level • Axon, dendrites, synapses • Neurotransmitters: dopamine • Myelin sheath • Neural circuits • Lateralization— specialization of functions in one hemisphere of cerebral cortex

  24. The Brain The Neuron Fig. 3.8

  25. The Brain The Brain In Infancy • Extensive brain development in utero • Born with about 100 billion neurons • Enriched early experiences can enhance brain growth and functioning • Brain flexibility and resilience demonstrated in deprived environments • Experience determines brain connections • Shaken Baby Syndrome

  26. The Brain The Brain In Infancy • Changing neurons • Myelination • Rapid growth of myelin sheath, dendrite and synapse connections • Blooming and pruning of connections in brain • Peak synaptic overproduction: influenced by heredity and environment

  27. The Brain The Brain In Infancy • Electroencephalogram measures brain activity — spurt in EEG activity at 1½ - 2 years of age • At birth, left hemisphere specializes as infants listen to speech • Brain areas do not mature uniformly; skills affected by myelination and interconnections

  28. The Brain Dendritic Spreading Fig. 3.11

  29. Synaptic Density in Human Brain from Infancy to Adulthood Fig. 3.12

  30. The Brain The Brain in Childhood • During early childhood, the brain and head grow more rapidly than any other part of the body — growth curves • Some of brain’s increase due to mylenation and some due to increase in number and size of dendrites • Dopamine: considerable increase from ages 3 to 6 years

  31. The Brain Growth Curves for Head and Brain and for Height and Weight Fig. 3.13

  32. The Brain The Brain in Adolescence • Emotional processing differences between adolescents (10-18 years) and adults (20-40 years) • Adolescents: Gut responses • Adults: rational, reasoned responses • Limbic system structures (amygdala, hippocampus) increase in volume

  33. The Brain The Brain in Adolescence • Adolescent emotions — • Slow development of prefrontal cortex • Poor self-control; seek rewards and pleasure • Seek novelty; increased risk-taking • Lack of practical experiences; immature judgment

  34. The Brain Adulthood and Aging • The Shrinking, Slowing Brain • Brain loss: 5-10% of weight in ages 20 to 90 • Dendrites decrease; death of brain cells • Shrinkage of prefrontal cortex • General slowing of function in brain and spinal cord begins in middle adulthood and accelerates in late adulthood • Reductions in neurotransmitters

  35. The Brain The Adapting Brain • Grows new brain cells throughout life • Extent depends on environment • Dendrite growth continues through 70s • Brain rewires to compensate for losses • More myelination between frontal cortex and limbic system facilitates reflection • Less lateralization with age

  36. The Brain Preventing and Treating Brain Diseases • Brain has ability to grow and change, even in old age • Positive emotions linked to longevity • Intellectual stimulation • Folic acid reduces risks and damage

  37. Sleep Sleep in Infancy • Newborns average 16-17 hours a day • Varied sleeping patterns • Longest sleep period: 11 pm to 7 am • May change from longer to shorter sleep periods • Most close to adult patterns by 4 months • More REM sleep than any other time of life • Shared sleeping with parents is controversial

  38. Sleep Across the Human Life Span Fig. 3.18

  39. Sleep SIDS • Having siblings who died of SIDS • African American and Eskimo infants • Lower SES groups • Exposure to cigarette smoke • Infant stops breathing, usually during night, and suddenly dies without apparent cause • At highest risk • Infants ages 4 to 6 wks • Sleeping on stomachs, use of soft bedding • Low birth weight; diagnosed with sleep apnea

  40. Sleep Sleep in Early Childhood • Most young children sleep through the night and have one daytime nap • Nightmares: frightening dreams • Night Terrors: sudden arousal from sleep • Girls sleep longer than boys

  41. Sleep Sleep in Adolescence • Many adolescents are not getting enough sleep; average 9½ hours when available • Like to stay up late, sleep late in mornings • Try to make up sleep debt on weekends • Biological clocks shift • Melatonin production — about an hour later each day delays sleepiness at night

  42. Sleep Sleep in Adolescence • Sleep deprivation and school performance • Inattentive • Poor test performance • Discipline problems • Reports of illness and depression • Low self-esteem

  43. Sleep Adulthood and Aging • Many adults don’t get enough sleep • Middle age may bring sleep problems • Wakeful periods at night, less deep sleep • Many older adults go to bed earlier at night and wake up earlier in the morning • Afternoon naps • Insomnia increases in late adulthood

  44. Longevity Life Expectancy and Life Span • Life span — upper boundary of life, maximum number of years an individual can live • Life expectancy — number of years that an average person born in a particular year will probably live

  45. Longevity Life Expectancy • Females average 80 years, 74 years for males • Gender differences influenced by biological factors – extra X for females • Men more likely to die from U.S. leading causes of death • Associated with lifestyle and workplace stress

  46. Longevity Centenarians • Numbers increasing; affected by • Genes, heredity, and family history • Women who have never married • Ability to cope successfully with stress • Education, health, and lifestyle • Individual personality • Highest ratio in Okinawa

  47. Longevity Risks of Dying from Cancer in Okinawa, Japan, and the United States Fig. 3.20

  48. Longevity Biological Theories of Aging Cellular ClockTheory Maximum times that human cells can divide is about 75 to 80 People age because their cells’ metabolism produces unstable oxygen molecules (free radicals) Free-Radical Theory MitochondrialTheory Aging caused by decay of mitochondria Aging in body’s hormonal system can lower resistance to stress and increase likelihood of disease Hormonal Stress Theory

  49. 3 The End