Physical Development and Biological Aging

Physical Development and Biological Aging

Body Growth and Change The Brain Sleep Longevity

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


• Slower, consistent growth• Muscle mass and strength increase•Boys stronger, body proportions change

Middle and Late

Childhood

• Growth slows, patterns vary individually• Girls slightly smaller and lighter• Girls gain fat, boys gain muscle

Early Childhood

• Average 20 inches, 7 ½ lbs at birth• Triple weight by 1 year• ½ adult height, 20% adult weight by age 2

Infancy

Changes in Proportions of the Human Body During Growth


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

Determinants of Puberty

HeredityHormones

Hypothalamus, pituitary gland, gonadsAndrogens (testosterone)Estrogens (estradiol)Thyroid gland and growth effectsCortisol may influence growth


PubertyPeriod of rapid physical maturation involving

hormonal and bodily changes that take place in early adolescence.

Two phases:Adrenarche-changes in adrenal glandsGonardarche

• Menarche• Spermarche

Weight and body fat


Hormone Levels by Sex and Pubertal

Stage for Testosterone and Estadiol


Pubertal Growth Spurt


Normal Range and Average Development of Sexual Characteristics in Males and Females

Secular Trends in PubertyBody Growth and Change

Onset of puberty beginning earlier:Norway — menarche at 17 in 1840s, now 13U.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 Image in Puberty Adolescents become preoccupied by bodies:

Overall, girls less satisfied, boys more satisfiedThroughout puberty:

• Girls’ dissatisfaction increases-• body fat increases

• Boys’ satisfaction increases-• muscle mass increases


Body Image in Puberty

Early and Late MaturationEarly boys more positive, better peer relationsLate boys less positive but have more positive

identity by 30s than early boys


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


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


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 50Sarcopenia: age-related loss of muscle mass


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



Lung Capacity, Smoking and Age

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


Brain PhysiologyStructure 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

The Brain’s

Four Lobes

Functions of Lobes of the Cortex

Frontal lobes

Occipital lobes

Temporal lobes

Involved in voluntary movement, thinking, personality, and intentionality or purpose

Function in vision

Active role in hearing, language processing, and memory

Parietal lobes 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 NeuronThe 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 SpreadingThe Brain

Synaptic Density in

Human Brain from Infancy to Adulthood

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 fromages 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 thickensPrefrontal cortex grows: reasoning, self-control,

and decision makingAmygdala 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

The Brain

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

Sleep Across the Human Life Span

SIDSSleep

Having siblings who died of SIDS

African American and Eskimo infants

Lower SES groupsPassive 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

• Infant stops breathing, usually during night, and suddenly dies without apparent cause

• At highest risk

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 availableLike to stay up late, sleep late in morningsTry to make up sleep debt on weekends

Biological clocks have hormonal shiftMelatonin 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-esteemIneffective 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

Sleep

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

Longevity

Risks of Dying from Cancer in Okinawa,

Japan, and the United

States

Biological Theories of Aging

Cellular ClockTheory

Free-Radical Theory

MitochondrialTheory

Maximum times that human cells can divide is about 75 to 80

People age because their cells’ metabolism produces unstable oxygen molecules (free radicals)

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

Longevity

Physical Development and Biological Aging

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