This document summarizes physical development and aging across the human lifespan. It discusses patterns of growth from infancy to puberty and changes that occur in early, middle, and late adulthood. Key topics covered include changes in height, weight, body proportions, hormones, sexuality, brain development, sleep patterns and longevity.

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

2. Body Growth and Change Patterns of growth Cephalocaudal pattern – from top (head) and gradual to bottom Proximodistal pattern – center of body outward to extremities Growth rate affected by SES, birth order, and maternal habits during prenatal development Growth hormone deficiency – pituitary gland

3. Fig. 3.1 Changes in Proportions of the Human Body During Growth

4. 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 Puberty Period of rapid physical and hormonal changes Physical changes; growth spurt Girls – menarche , hips widen, body hair Onset for most: 9 to 15 years of age Boys – first ejaculation, grow taller, body hair Onset for most: 10 to 17 years of age

6. Body Growth and Change Puberty Hormonal changes Powerful chemicals from endocrine glands Hypothalamus – eating and sexual behavior Pituitary gland – controls growth, regulates glands Gonads – male testes, female ovaries Gonadotropins – stimulate testes, ovaries

7. Body Growth and Change Puberty Hormones increase dramatically in adolescence Testosterone – voice change, genital growth Dominates male changes Estradiol – estrogen for breast growth Dominates female changes Onset affects social competence Behaviors and moods can affect hormones

8. Body Growth and Change Psychological effects of puberty, onset timing Early maturation Boys: positive self-image, better peer relations Girls: similar to boys, not as strong, at more risk of behavior problems Late maturation Boys: developed stronger positive self-image in their 30s

9. Body Growth and Change Early adulthood 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

10. Body Growth and Change Middle adulthood Physical appearance Loss of height (more for women), weight gain Skin wrinkles, sagging, aging spots appear in 40s or 50s Hair thins and grays, fingernails and toenails thicken Youth-oriented culture affects lifestyle changes Baby boomers desire plastic surgery, Botox

11. Body Growth and Change Middle adulthood Strength, joints, and bones Sarcopenia – muscle mass and strength loss 1% to 2% muscle loss after age 50 Cardiovascular system and lungs HDL and LDL cholesterol, clogged arteries Hypertension: blood pressure increases Decreased lung capacity after age 55

12. Body Growth and Change Middle adulthood Sexuality changes Climacteric — fertility declines Menopause — menstrual periods ceases Dramatic decline of estrogen; a negative experience for most women Males do not lose fertility

13. Fig. 3.4 Lung Capacity, Smoking and Age

14. Body Growth and Change Late adulthood Physical appearance more pronounced Facial wrinkles, age spots Weight loss after age 60; decreased by exercise and weight lifting Circulatory system Increased blood pressure, linked to chronic conditions and longevity

15. The Brain Brain physiology Structure and function Forebrain Cerebral cortex has four lobes Frontal, occipital, temporal, parietal lobes Deeper in brain: Hypothalamus, pituitary gland, amygdala, hippocampus

16. Fig. 3.6 The Brain’s Four Lobes

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

18. 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

19. The Neuron Fig. 3.7

20. The Brain Infancy Shaken Baby Syndrome Born with about 100 billion neurons Brain flexibility and resilience demonstrated in deprived environments Dramatic increases of neural connections Brain areas do not mature uniformly; skills affected by myelination and interconnections

21. The Brain Infancy Myelination; visual and auditory Rapid growth of myelin sheath, dendrite and synapse connections Blooming and pruning of connections in brain At birth, greater activity in left hemisphere Motor control begins about 2 months

22. Dendritic Spreading Fig. 3.12

23. The Brain Childhood The brain and head grow more rapidly than any other part of the body — growth curves Some brain size increase due myelination and number and size of dendrites Greatest anatomical brain increases from ages 3 to 15 years; distinct bursts of growth

24. Fig. 3.13 Synaptic Density in Human Brain from Infancy to Adulthood

25. The Brain Childhood Ages 3 to 6; most rapid growth in frontal lobe Age 6 to puberty; most dramatic growth in temporal and parietal lobes Promotes spatial relations and language Brain pathways and circuitry promote cognitive control (attention, thoughts, actions, choices)

26. Growth Curves for Head and Brain and for Height and Weight Fig. 3.14

27. The Brain Adolescence Brain continues growth Corpus callosum – axon fibers thicken Prefrontal cortex – increased reasoning, decision making, self-control Amygdala – seat of emotions, matures earlier Positive link between volume and duration of aggressive behavior toward parents

28. The Brain Adolescence Research on brain development and changes Thicker prefrontal cortex, more brain connections linked to peer pressure resistance Early ‘turbo charged’ emotions – more risky behaviors, drug use, legal system involvement? Brain change – result of biology, experiences

29. The Brain Adulthood and aging Brain loss: 5-10% of weight in ages 20 to 90 Dendrites decrease; myelin sheath damage Shrinkage is not uniform; most in prefrontal cortex General slowing of brain and spinal cord function Begins in middle age, accelerates with age Reductions in neurotransmitters

30. The Brain The adapting brain Exercise and activities influence development Remarkable repair capability Neurogenesis – new cells generated Dendrite growth; “rewiring” to compensate loss Less lateralization with age, more adaptation Results of the Nun Study

31. Sleep Infancy – sleep/wake cycle Newborns average 16-17 hours a day Varied patterns; longest period is 11 pm to 7 am At 1 month – infants sleep more At 6 mos – closer to adult-like sleep patterns Most common problem – night waking Culture affects sleep patterns

32. Sleep in Infancy 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 Sleep

33. Sleep REM sleep As infant, half of sleep pattern; begins sleep cycle May provide self-stimulation Cannot determine if infants dream like adults As adult, REM is 20% of sleep pattern; onset 1 hour after non-REM Shared sleeping – controversial issue Common outside United States and Great Britain

34. Sleep Across the Human Life Span Fig. 3.19

35. Sleep SIDS Infants stop breathing; most die suddenly in night Highest cause of infant death in United States Highest risk: ages 2 to 4 months Best prevention: infant sleeps on its back (prone)

36. Sleep SIDS Risk factors: No pacifier, soft bedding, no fan in room Low-birth weight, sleep apnea, lower SES Sleeping on stomach or side Passive exposure to cigarette smoke Another sibling died of SIDS, abnormal brain stem functioning Higher for African American, Eskimo infants

37. Sleep Childhood Recommended: 11 to 13 hours each night Sleep problems Inadequate sleep linked to depression, school problems, disagreeable families, living in unsafe neighborhoods, father in poor health Uninterrupted sleep and consistent patterns important – linked to behavioral problems Nightmares and night terrors

38. Sleep Adolescence Inadequate sleep patterns (less than 8 hrs a day) Linked to fatigue, moodiness, depression, more caffeine beverage use, falling asleep in school Sleep was 9½ hours when given the opportunity Sleep debt : try to make up lost sleep on weekend Biological clock and hormone melatonin cause later waking and going to sleep Starting school later would decrease absences

39. Sleep Adolescence Sleep deprivation and school performance More reported illnesses and absences More depressed, lower self-esteem Ineffective stress management Less exercise, unhealthy diet Grogginess, less attentive, poor test scores Discipline problems

40. Sleep Adulthood and aging Many are sleep deprived (less than 7 hrs a day) Work, school, social, or family obligations 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 and wake up earlier, Insomnia increases in late adulthood

41. Longevity 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

42. Longevity Life expectancy Highest in Japan – 81 years Racial differences in the U.S. Highest for Whites – 78 years White females – 81 years Females have higher expectancy than males Begins in mid-30s, gap increases with age Male lifestyle associated with more risks, biological factors

43. Longevity Centenarians Numbers increasing More women than men; health keeps improving Influenced by Biology, heredity, family history, coping ability Health (weight, diet, smoking, exercise) Education, personality, lifestyle Highest ratio in Okinawa

44. Fig. 3.22 Risks of Dying from Cancer in Okinawa, Japan, and the United States

45. Longevity Biological theories of aging Four major theories No consensus on which best explains aging

46. Biological Theories of Aging Cellular Clock Theory Maximum times that human cells can divide is about 75 to 80 Free-Radical Theory People age due to cells’ metabolism produces unstable oxygen molecules (free radicals) Mitochondrial Theory Aging caused by decay of mitochondria; oxidative damage Hormonal Stress Theory Aging in body’s hormonal system can lower resistance to stress and increase risks of disease

47. The End