Physical Development

1
Chapter 3

• Physical Development Biological Aging

2
Changes in Body Proportions

• Growth occurs in a cephalocaudal (head to tail)
  pattern
• The head takes up one-fourth of total body length
  at birth, but only one-fifth at age 2.
• Growth occurs in a proximodistal (near to far)
  pattern.
• The head, chest and trunk precede the limbs and
  extremities.

3
Body Growth in Infancy

• Average North American newborn weight 7 ½ pounds
  and is 20 inches long.
• Birth weight triples in one year and quadruples
  by the end of two years.
• By the second year, the child is at 1/5 of its
  adult weight (30 lbs.) and ½ its adult height (30
  inches).
• Muscle tissue increases very slowly.

4
Facts about Physical GrowthEarly Childhood
Middle Childhood

• 2-3 inches per year
• 5 pounds per year
• Baby fat declines
• Posture and balance improve due to lower center
  of gravity.

• 2-3 inches per year
• 5 pounds per year
• Bones harden (skeletal age), lengthen and broaden
• ligaments are not yet firmly attached.
• Improved strength and muscle tone.
• Primary teeth are replaced with permanent teeth

5
Influences on Physical Growth Health

• Genetics
• Hormones
• Emotional well-being
• Nutrition
• Infectious disease
• Childhood injuries

6
Influences on Physical Growth Health
Pituitary Growth Hormones

• Growth hormone (GH) needed for development of all
  body tissues except CNS genitals
• Thyroid-stimulating hormone (TSH) causes the
  thyroid gland to release thyroxine, needed for
  normal nerve cell development and for GH to have
  a full impact on body size

7
Influences on Physical Growth Health
Emotional Well Being

• Psychosocial dwarfism
• Caused by extreme emotional deprivation
• Appears between 2 15 years of age
• Can interfere with the production of GH
• Very short stature
• Immature skeletal age
• Severe adjustment problems
• Can be treated

8
Body Growth and Gender

• Girls are shorter and lighter and have a higher
  ratio of body fat to muscle than boys.
• Children differ in the rate of physical growth.
• Skeletal age is the best way to estimate the
  childs physical maturity.
• African Americans mature faster than Caucasians
  and girls mature faster than boys.

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GROWTH IN ADOLESCENCE

• Chapter 3

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Definition of Adolescence

• Transition between childhood and adulthood
• Physically begins with puberty
• Culturally defined ends gradually with
  assumption of adult responsibilities
• Lasts nearly a decade (or more) in the U.S.
• culturally exaggerated due to education

11
The Growth Spurt of Puberty

• Most rapid growth since infancy
• Average of age 9 for girls 11 for boys
• Girls grow 3.5 inches/year boys 4 inches
• 50 of body weight gained in adolescence
• Also changes in leg length and facial structure

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Why Does Puberty Happen Earlier than it Used to?

• Nutrition ? Better than in earlier times
• Hormones ? Found in food supply
• Stress ?
• Fat ?

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Stress Theory of Early Puberty

• Hypothalamus ? pituitary? sex glands ? produce
  gonadotrophins
• Androgens (testosterone)
• Estrogens (estradiol)
• Pituitary ? thyroid gland ? produces growth
  hormone
• Cortisol (stress hormone) may trigger early onset
  (pituitary activity)

14
Fat Theory of Early Puberty

• Weight affects the timing of menarche (106 /- 3
  pounds)
• Athletes and anorexics become amenorrheic
• Fat and leptin may also be influential

15
Early vs. Late Maturation

• Early maturing girls have a less positive body
  image
• They are more likely to drink, smoke, be
  depressed, have an eating disorder or mental
  disorder, date and have sex earlier, and have
  lower educational and occupational attainment
• Berkley Longitudinal Study

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Early vs. Late Maturation

• Early maturing boys are leaders, athletes
• Late maturing boys have a more positive
  self-image in their 30s.
• Early maturers, both sexes are emotionally
  stressed, show academic declines
• Berkley Longitudinal Study

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Body Changes in Adulthood that Are Part of Normal
Aging

• Chapter 3

18
Physical Development in Early Middle Adulthood

• Early Adulthood, peak muscle tone joint
  function
• Middle Adulthood gradual changes,
• lose height, gain weight, in 40s 50s skin
  sags, wrinkles, age spots, hair thins, thicker
  finger- and toenails, yellow teeth

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Changes in Middle Adulthood (continued)

• Sarcopenia age-related loss of muscle mass
  strength
• Lose 1-2 per year starting at age 50
• Exercise can help to reduce this loss
• Also lose bone from the late 30s this
  accelerates in the 50s

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Changes in Middle Adulthood -Cardiovascular

• Cholesterol increases
• LDL leads to atherosclerosis
• Blood Pressure increases sharply for women at
  menopause
• Metabolic disorder hypertension, obesity,
  insulin resistance, high cholesterol, low HDL,
  weight gain (Part of normal aging?)
• Weight loss exercise help
• Lungs become less elastic

21
Changes in Middle Adulthood - Sexuality

• Climacteric loss of fertility
• Menopause ceasing of menstrual cycles (average
  age 52)
• Drop in estrogen, hot flashes, nausea, fatigue,
  rapid heartbeat
• Gradual decline for men (no andropause)

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BRAIN DEVELOPMENT

• Chapter 3

23
Brain Development

• At birth, the brain is at about 30 of its adult
  weight.
• At age 2, the brain is at about 70 of its adult
  weight.
• Brain reaches 90 of adult weight by age 6

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Brain Development

• Prenatal neurogenesis 2nd trimester, fetal
  period
• Post Natal (after birth) (cycle)
• Synaptogenesis dendrite formation
• Synaptic pruning
• Myelination

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Synaptic Transmission
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Brain Development - Synaptogenesis

• The human brain has 100 200 billion neurons at
  birth.
• During the first two years, fibers from these
  form synaptic connections at a rapid rate and
  some neurons die as a result.

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Brain Development Synaptic Pruning

• Experience determines brain development.
• Neurons not stimulated lose their synaptic
  connections.
• Neurons often stimulated strengthen connections
  by growth of new dendrites

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Brain Development Glial Cells and Myelination

• Glial cells multiply rapidly during the first two
  years. (About half the brains volume)
• Glial cells produce myelin to coat neuron axons.
  Myelination improves the efficiency of neural
  transmission.

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Cerebral Cortex

• The order in which cortical regions develop
  corresponds to the order in which capacities
  emerge in the growing child.

30
Cerebral Cortex

• In the first year, there is a burst of synaptic
  growth in the auditory and visual areas.
• Areas supporting language show dramatic growth
  during toddlerhood.
• One of the last regions to develop are the
  frontal lobes.

31
Brain Development

• Rapid frontal lobe growth at ages 3-6
• Myelination of cerebellum-cortex links, reticular
  formation, corpus callosum

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Cerebral Cortex Lateralization Plasticity

• Specialization of functions in the two
  hemispheres of the cortex is called
  lateralization.
• For most people, language, logic and positive
  emotion are processed by the left hemisphere.
  Spatial and wholistic tasks and negative emotions
  are right hemisphere.
• Lateralization is very plastic.

33
Brain Development Sensitive Periods

• Brain growth spurts, as measured by weight, size
  and EEG, occur
• 3 to 4- months reach for objects
• 8 months crawl, search for objects
• 12 months walk
• 1.5 -2 years talk
• Ages 9, 12, 15, 18-20

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Brain Development - Understimulation

• Results in deficits in
• Concentration
• Attention
• Anger and other impulse control

35
Brain Development - Overstimulation

• Does not result in geniuses.
• May cause infant withdrawal.
• May lead to disappointed parents.
• May cause strain between infants and parents.

36
Brain Development in Adolescence

• Reward and pleasure centers (limbic system)
  mature before judgment centers (pre-frontal
  cortex) do.
• Baird others (1999) found that 10-18 year olds
  process emotional information using the amygdala,
  20-40 year olds use the frontal lobe.

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Brain Changes in Adulthood

• Production of new neurons throughout life
• Growing new dendrites through the 70s
• Brains rewire themselves functional plasticity
• Myelination between cortex limbic system in
  40s 50s
• Decrease in lateralization

38
Mankato Nun Study

• Early-life idea density at 22 linked to fewer
  incidences of mild cognitive impairment
• Positive emotions linked to longevity
• Teachers showed more moderate intellectual
  declines
• Sisters with high folic acid levels showed little
  Alzheimer-like damage

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Theories of Aging

• Chapter 3

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Biological Theories of Aging

• Cellular clock (Hayflick)
• 70-80 cell divisions, based on telomeres
• 120-year lifespan
• Free-radical
• Calorie restriction
• antioxidants

41
Biological Theories of Aging

• Mitochondrial
• Cellular energy producers
• Linked to free radical theory
• Hormonal Stress
• hypothalamic-pituitary-adrenal axis
• Stress decline in immune function