Chapter 4: Physical Development: Body, Brain, and Perception

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Chapter 4 Physical Development Body, Brain, and
Perception

• Development of the Brain and Nervous System

By Kati Tumaneng (for Drs. Cook Cook)
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Development of the Brain and Nervous System

• Brain is one of the first structures to form when
  tissue differentiation begins in embryo.
• At birth, the brain and head are more than a half
  their adult size. Newborn head is 1/4 of total
  length compare to adult head is 1/8 of height.
• Brain Development http//faculty.washington.edu/c
  hudler/dev.html

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Development of the Brain and Nervous System
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Structure of the Brain and Nervous System
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Structure of the Brain and Nervous System

• Spinal Cord Information superhighway
• Brain Stem Controls automatic functions
  regulates alertness
• Cerebellum Controls posture, body orientation,
  and complex muscle movements
• Cerebral Cortex Grey matter on the top of the
  brain, divided into 4 major lobes (frontal,
  temporal, parietal, and occipital)
• Motor Area Controls voluntary muscle movements
• Somatosensory Area Registers sensory input from
  all areas of the body

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Structure of the Brain and Nervous System

• Wernickes Area Speech input
• Brocas Area Organizes articulation for speech
  output
• Visual Area Visual processing
• Frontal Lobe Involved in organizing, planning,
  and other executive functions important for
  higher-level thinking, problem solving, and
  creativity
• Neurons Specialized cells that process
  information and allow communication in the
  nervous system

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Forming the Brain and Nervous System

• Weeks 4 (after conception) Embryo folds over to
  form a neural tube, precursor of central nervous
  system (brain and spinal cord)
• Week 7 Neurons form at neural tube
• Week 10 Neurons begin migrating to the top of
  the tube forms first layer of cortex with five
  more to follow
• Production of neurons peaks at 250,000 per minute
• Week 20 Cortex has 80 billion neurons, which is
  nearly full complement axons and dendrites have
  begun growing

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Forming the Brain and Nervous System

• Week 23 First synapses form, and focus now
  shifts to growth of connections
• Most synapses will form after birth,
  corresponding to growth spurts in brain
• Week 31 Cerebral cortex grown enough so that
  can begin folding inside the skull
• Brain weight increases 30 between 3 and 18
  months after birth, 10 between years 2-4, 6-8,
  10-12, and 14-16 with gender differences

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Forming the Brain and Nervous System

• Glial Cells Specialized cells in the nervous
  system that support neurons in several ways.
• Synaptogenesis Form of neuron maturation where
  dendrites and axons branch out to form an
  enormously large number of connections with
  neighboring neurons.
• Myelination A form of neuron maturation where
  the fatty insulation grows around axons.
• Synaptic Pruning Process where unused synapses
  are lost.
• Programmed Cell Death Process where many
  neurons die during periods of migration and heavy
  synaptogenesis.

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Parts of a Neuron
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The Role of Experience in Brain Development

• Experience-expectant development Development of
  universal experiences and activities (such as
  hand-eye coordination), where excess synapses
  form and are then pruned according to experience.
• vs.
• Experience-dependent development Development of
  specific experiences and activities (such as
  riding a skateboard), where new synapses form to
  code the experience.

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The Role of Experience in Brain Development

• Synaptic Pruning is important to cut down on the
  noise to the neural circuits that leads to
  ineffective processing in the brain (e.g., mental
  retardation associated with fragile-X syndrome).
• Exposure to stimulating environments is important
  for forming sophisticated neural networks in the
  young brain.
• Mozart effect
• http//www.mozarteffect.com/

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Synaptogenesis and Synaptic Pruning
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Neural Plasticity and Sensitive Periods

• Plasticity Brains tendency to remain somewhat
  flexible or malleable until synaptogenesis is
  complete and until the brains synapses have been
  pruned and locked into serving particular
  functions.
• Greatest before age 2, period when new synapses
  are still proliferating and have not yet been
  pruned
• Age 2 to adolescence Plasticity declines

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Larger Developmental Patterns in the Brain

• Visual areas peak in synapse density within four
  months after birth, decreases to adult levels by
  age 10
• Heavy growth in frontal lobes seen between 3 and
  6 years responsible for organizing and planning
  behavior
• Between 6 and 13 years, highest growth rate seen
  in temporal and parietal lobes

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What Does the Future Hold?

• With advances in technologies used to scan the
  brain and measure brain activity and an increased
  understanding of genetics and cell behavior, may
  soon be able to track true origins of disorders
  and possibly treat them before they develop.

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• Picture on Slide 2 from http//www.brainconnecti
  on.com/topics?mainfa/child-brain, retrieved
  December 6, 2005.
• Chart on Slide 3 from Cook, J. L., Cook, G.
  (2005). Child development Principles and
  perspectives (1st ed.) (p. 146). Boston Allyn
  and Bacon.
• Brain on Slide 4 from Cook, J. L., Cook, G.
  (2005). Child development Principles and
  perspectives (1st ed.) (p. 147). Boston Allyn
  and Bacon.
• Diagram of Neuron on Slide 10 from Cook, J. L.,
  Cook, G. (2005). Child development Principles
  and perspectives (1st ed.) (p. 148). Boston
  Allyn and Bacon.
• Chart on Slide 13 from Cook, J. L., Cook, G.
  (2005). Child development Principles and
  perspectives (1st ed.) (p. 150). Boston Allyn
  and Bacon.
• All other images retrieved from Microsoft
  PowerPoint Clip Art.