Physical Development
and Biological Aging
 Body Growth and Change
 The Brain
 Sleep
 Longevity
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
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
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
Early
Body Growth and Change
Changes in Proportions of
the Human Body During Growth
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
Body Growth and Change
Determinants of Puberty
 Heredity
 Hormones
 Hypothalamus, pituitary gland, gonads
 Androgens (testosterone)
 Estrogens (estradiol)
 Thyroid gland and growth effects
 Cortisol may influence growth
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
Body Growth and Change
Hormone
Levels by Sex
and Pubertal
Stage for
Testosterone
and Estadiol
Body Growth and Change
Pubertal
Growth
Spurt
Normal Range and Average Development of
Sexual Characteristics in Males and Females
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
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
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
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
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
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
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
Body Growth and Change
Lung
Capacity
,
Smoking
and Age
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
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
The Brain
The
Brain’s
Four
Lobes
The Brain
Functions of Lobes of the Cortex
Frontal lobes
Involved in voluntary movement,
thinking, personality, and
intentionality or purpose
Occipital lobes Function in vision
Temporal lobes
Parietal lobes
Active role in hearing, language
processing, and memory
Roles in registering spatial location,
attention, and motor control
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
The Brain
The Neuron
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
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
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
The Brain
Dendritic Spreading
Synaptic
Density in
Human
Brain from
Infancy to
Adulthood
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.
The Brain
Growth Curves for Head and
Brain and for Height and Weight
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?
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
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
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
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
Sleep Across the Human Life
Span
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
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
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
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
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
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
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
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
Longevity
Risks of
Dying from
Cancer in
Okinawa,
Japan, and
the United
States
Longevity
Biological Theories of Aging
Cellular Clock
Theory
Maximum times that human cells
can divide is about 75 to 80
Free-Radical
Theory
People age because their 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 likelihood of disease