Dev Psych.ch3.keynote

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A Topical Approach to LIFE-SPAN DEVELOPMENT

John W. Santrock

Chapter Three:

Physical Development

and Biological Aging

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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

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3Fig. 3.1

Changes in Proportions of the Human Body During Growth

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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

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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

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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

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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

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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

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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

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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

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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

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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

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13Fig. 3.4

Lung Capacity, Smoking and

Age

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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

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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

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16Fig. 3.6

The Brain’s Four

Lobes

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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

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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

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The Neuron

Fig. 3.7

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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

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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

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Dendritic Spreading

Fig. 3.12

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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

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24Fig. 3.13

Synaptic Density in

Human Brain from Infancy to Adulthood

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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)

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Growth Curves for Head and Brain and for Height and Weight

Fig. 3.14

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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

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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

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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

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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

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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

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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

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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

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Sleep Across the Human Life Span

Fig. 3.19

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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)

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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

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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

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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

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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

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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

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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

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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

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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

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44Fig. 3.22

Risks of Dying from Cancer in

Okinawa, Japan, and the United States

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Longevity

• Biological theories of aging– Four major theories– No consensus on which best explains aging

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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)

MitochondrialTheory

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

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The End