LIFE-SPAN DEVELOPMENT

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 are unusually short • Congenital factors • Growth hormone deficiency • Physical problem developed in childhood • Maternal smoking during pregnancy • Emotional difficulty

7. Heredity Hormones Hypothalamus, pituitary gland, gonads Androgens (testosterone) Estrogens (estradiol) Thyroid gland and growth effects Cortisol may influence growth Body Growth and Change Determinants of Puberty

8. 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 • Weight and body fat

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 Secular 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

15. Body Growth and Change Body Image in Puberty • Early and Late Maturation • Early girls more at risk for problems • Smoking and drinking • Depression and eating disorders • Lower education and occupational attainment • Early dating and sexual experiences • Mental disorders and behavior problems

16. 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

17. Body Growth and Change Middle Adulthood • Physical • Lose height, gain weight • More skin 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 • Sarcopenia: age-related loss of muscle mass

18. Body Growth and Change Middle Adulthood • Cardiovascular system and lungs • HDL and LDL cholesterol, clogged arteries • Hypertension: blood pressure increases • Decreased lung capacity after age 55 • Sexuality changes • Climacteric — fertility declines • Menopause — menstrual periods cease

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

20. 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 • Weightlifting can slow process • Circulatory system • Increased blood pressure; linked to chronic conditions and longevity

21. The Brain Brain Physiology • Structure and function • Forebrain • Cerebral cortex has four lobes • Two hemispheres usually work together and each lobe has a primary function • Frontal, occipital, temporal, parietal lobes • Amygdala • Hippocampus

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

23. 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

24. Development of the Brain • Can skip pages 107-131 • By age 6, almost adult size. • Brain growth spurts: coincide with changes in cognitive behavior • Cerebellum, largest part of brain, divides into halves • Lateralization, specialties of each hemisphere; left: language and logical thinking; right: visual and spatial functions

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

27. The Brain The Neuron Fig. 3.8

28. The Brain The Brain In Infancy • Shaken Baby Syndrome • 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 • Enriched and deprived environments

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

30. The Brain The Brain In Infancy • At birth, greater activity in left hemisphere specializes as infants listen to speech • Motor control begins about 2 months • Brain areas do not mature uniformly; skills affected by myelination and interconnections

31. The Brain Dendritic Spreading Fig. 3.11

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

33. 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 • Greatest anatomical brain increases from ages 3 to 15 years

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

35. The Brain The Brain in Adolescence • Growth still occurs in adolescence • Corpus callosum: fiber bundle thickens • Prefrontal cortex grows: reasoning, self-control, and decision making • Amygdala matures early: emotions and anger • Implications for adolescent behavior, legal system, and death penalty?

36. 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

37. 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

38. The Brain The Adapting Brain • Grows new brain cells throughout life • Extent depends on environment • Dendrite growth continues in adults • Brain rewires to compensate for losses • Less lateralization with age, more adaptation • Findings from Nun Study

39. 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

40. Sleep Across the Human Life Span Fig. 3.18

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

42. Sleep Sleep in Early Childhood • Most young children sleep through the night and have one daytime nap • Nightmares: frightening dreams are more common • Night Terrors: sudden arousal from sleep

43. 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 have hormonal shift • Melatonin production — about an hour later each day delays sleepiness at night

44. Sleep Sleep in Adolescence • Sleep deprivation and school performance • Grogginess and inattentiveness • Poor test performance • Discipline problems • Reports of illness and depression • Low self-esteem • Ineffective stress management, exercise, diet

45. 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

46. Longevity Life Expectancy and Life Span • Life span — upper boundary of life, maximum number of years an individual can live; about 120 years of age • Life expectancy — number of years that an average person born in a particular year will probably live

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

48. 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

49. Longevity Risks of Dying from Cancer in Okinawa, Japan, and the United States Fig. 3.19

50. 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; oxidative damage Aging in body’s hormonal system can lower resistance to stress and increase likelihood of disease Hormonal Stress Theory Fig. 3.20