Chapter Five

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Chapter Five

• First Two Years
• Biosocial Development

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Body Changes

• Rapid changes
• Consequences of neglect severe
• Most notable time for physical changes
• in each of the first 12 months they grow an inch
• birth weight usually doubles by 4 months and
  triples by end of first year
• head-sparing biological protection of the brain
  when malnutrition temporarily affects body growth

3
Sleep

• Newborns sleep about 17 hours per day
• needed for rapid growth
• REM sleeprapid eye movement sleepdeclines
• quiet sleep increases at about 3 months
• too immature to sleep through the night
• Infants sleep patterns influenced by brain waves
  and parents caregiving practices

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5
Early Brain Development

• Most critical biosocial aspect of growth
• newborns skull disproportionately large
• at birth, 25 of adult brain weight
• by age 2, 75 of adult brain weight
• Connections in the Brain
• Head measurement increases 35 in first year
• brain development changes in the brains
  communication system

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Growth in the First Two Years
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Areas of the Cortex
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Basic Brain Structures

• Neuronslong thin nerve cells that make up
  nervous system
• created before birth
• 70 in cortex (brains outer layer)
• Axonsnerve fibers that extend from neurons that
  send impulses
• Dendritesnerve fibers extending from neurons
  that receive impulses
• Each neuron has a single axon (nerve fiber) that
  extends from it and meets the dendrites of other
  neurons at intersections called synapses
• axons and dendrites dont actually touch at
  synapses
• electrical impulses trigger brain chemicals
  called neurotransmitters, which carry information
  from axon of sending neuron across synaptic gap
  to dendrites of receiving neuron
• synapses are critical communication links with
  the brain

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Connections in the Brain
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Exuberance

• At birth more than 100 million neurons are
  present
• Phenomenal growth is referred to as increase in
  dendrites in first 2 years transient
  exuberancefivefold
• As many as 15,000 connections may be made per
  neuron
• Specifics of brain structure and growth depend
  partly on experience
• exuberance is transienttransitional stage
  between newborn brains immaturity and the
  maturity of older childs or adults brain
• underused neurons are inactivated, or pruned
• (ex rose bush)

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Experience Enhances the Brain

• William Greenough identified 2 experience-related
  parts of brain growth
• experience-expectant brain functions
• require basic common experiences to develop
  normally
• experience-dependent brain functions
• depend on particular and variable experiences to
  develop
• Human brains are designed for expected
  experiences
• how the brain is structured and connected will
  depend on those experiences
• the brain expects certain experiences at certain
  ages (language the baby hears)
• these experiences critical if connections are to
  form if connections not formed, plasticity may
  allow new connections and pathways as experiences
  continue

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Sudden Infant Death Syndrome (SIDS)

• Risk factors?
• laying baby on stomach to sleep
• secondhand smoke
• low birthweight
• formula feeding rather than breast feeding
• Ethnicity and SIDS
• Asian babies less likely to succumb
• Babies of African descent more likely
• Infantcare routines in different cultures play a
  role

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Breast Is Best

• Breast Milk
• begins with colostrum, high-calorie nourishment
  before milk lets down
• easily digestible
• has antibodies and antibacterial properties
• better for babys health
• Bottle Feeding babies more likely to have
  allergies
• better option if mother is HIV-positive or using
  drugs
• Feeding on Demand