Slide 1
A Topical Approach to
LIFE-SPAN DEVELOPMENT
Chapter Three:
Physical Development
and Biological Aging
John W. Santrock
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Slide 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
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Changes in Proportions of
the Human Body During Growth
Fig. 3.1
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Height and Weight
in Infancy and Childhood
Average 20 inches, 7 ½ lbs at birth
Infancy
Triple weight by 1 year
½ adult height, 20% adult weight by age 2
Growth slows, patterns vary individually
Early
Childhood
Girls slightly smaller and lighter
Girls gain fat, boys gain muscle
Slower, consistent growth
Middle and
Muscle mass and strength increase
Late Childhood
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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Slide 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
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Body Growth and Change
• Middle adulthood
– Physical appearance
•
•
•
•
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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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Slide 13
Lung Capacity,
Smoking and
Age
Fig. 3.4
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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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Slide 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
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The
Brain’s
Four
Lobes
Fig. 3.6
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Functions of Lobes of the Cortex
Frontal
Occipital
Involved in voluntary movement, thinking,
personality, and intentionality or purpose
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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Slide 19
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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Slide 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
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Slide 22
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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Slide 24
Synaptic
Density in
Human
Brain from
Infancy to
Adulthood
Fig. 3.13
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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
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–
–
–
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
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•
•
•
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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Slide 32
Sleep
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
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Slide 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
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Slide 34
Sleep Across the Human Life Span
Fig. 3.19
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Sleep
• SIDS
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–
–
–
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:
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•
•
•
•
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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Slide 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
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Slide 39
Sleep
• Adolescence
– Sleep deprivation and school performance
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•
•
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•
•
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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Slide 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
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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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Slide 44
Risks of Dying
from Cancer in
Okinawa,
Japan, and the
United States
Fig. 3.22
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Slide 45
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)
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
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The End
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