Physical Growth

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Physical Growth

• Neurological, Physiological, and Motor Development

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A. Neurological development

• Neural tube
• Prosencephalon (forebrain)
• Mesocephalon (midbrain)
• Rhombencephalon (hindbrain)

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Neural tube continues developing

• At the end of the bumpy neural tubetelecephalon
  followed by the diencephalon.
• Both make up the forebrain.

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Prenatal Neuronal Development

• Neurons glial cells proliferate rapidly in
  prenatal development.
• Fetus has majority of neurons it will have in
  life by third trimester (7-8 month).
• Neuronal migrationcells migrate to different CNS
  locations.

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What is a neuron?
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Prenatal synaptic development

• Synapses (synaptogenesis) are formed at a rapid
  rate.
• There are trillions of synapses present at birth.
  This drops dramatically by adulthood.

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What is a synapse
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Why do we lose cells?

• 1. Programmed cell death- as new synapses are
  formed, surrounding neurons die to provide space
  for the new connections.
• 2. Synaptic pruning- inactive neurons-- removed
  to free up room for active neurons.

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Brain Development Infancy

• Brain Growth
• myelination Areas associated with motor
  mental functions.
• cortical subcortical connections
• lobe activity
• neural plasticity capacity of brain to change
  in response to experience chemicals.

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Brain development Toddlerhood

• Rapid development 2nd 3rd yr
• Cerebral cortex
• Auditory Visual cortex
• Movement coordination
• Language
• Frontal cortex

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Brain Development Childhood

• By 6 yrs old brain is 90 of adult weight
• Increased connections between all brain regions
• Communication abilities
• Memory
• Motor control
• Cognitive abilities

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Brain Development Adulthood

• Aging Brain
• weight after 30
• How?
• -loss of white matter or loss of gray matter
• Prefrontal cortex
• connections

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Hemispheric Specialization

• Right H. Left H.
• Left side of body right side of body
• Music/melodies language/speech
• Visual-spatial abilities logic, analytic

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Infants show hemispheric specialization early.

• The majority of newborns process speech sounds by
  the left hemisphere as measured by scalp
  potentials.

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Neural Plasticity Rosenzweig study

• Rats from same litter put into 1 of 2
  environments enriched (E) or impoverished (I)
  for 3 months.
• E environment- large, well-lit, communal cages-
  with toys (wheels, ladders, platforms) changed
  daily. Rats also explored a maze once a day.
• I environment- each rat was placed in a small,
  isolated, dimly lit cage .

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Rosenzweig (1996) Findings

• 1. E rat brains weighed 4 more than I rat
  brains.
• 2. Occipital region of E rat brains showed
  greatest gain (6).
• Neurotransmitter enzyme levels were greater in
  the E rats.
• Dendritic connections were grater in E rat
  brains.

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B. Motor Development

• Infants--born with little motor development.
• Within a year, most infants crawl walk.

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Factors Influencing motor development

• 1. Maturation.
• 2. Enriched environmentinteresting novel
  stimuli promotes cortical development.
• 3. Caregiversencouragement works.

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1. Grasping

• Infants vary -grip on an object based on its
  size, shape, texture, their hand size.
• For small objects, infants use thumb index
  finger. They use all fingers of 1 hand or both
  hands for larger objects.
• Older infants (8 mos.) use visual cues to guide
  their grasping, younger infants rely on touch.

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2. Locomotion

• 1.First transition -infants show stepping reflex
  ends at 3-4 mos.
• 2. Second transition- in 2nd half of year,
  stepping movements occur again.
• 3. Third transition Infants walk unsupported
  (12 mos.)

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Theories as to how we learn to walk?

• 1. Motor cortex develops frontal lobe takes 1
  year to mature for us to walk.
• 2. Motor programs we develop motor programs in
  spinal cord that guide walking.
• 3. Cognitive plansinfants have mental
  representations for walking.
• 4. Dynamic Systems viewinteraction of multiple
  factors (perceptual, neurological, emotional,
  etc.)

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Factors that promote early walking

• 1. Physically handling infants
• 2. Giving infants practice in motor tasks
• Zelazo coworkers (1972) --mothers of newborns
  had infants practice stepping reflex a few min. a
  day.
• These babies walked--earlier than a control group
  given no practice.

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C. Physical Growth

• Why do we grow slowly?
• We need exposure to social environmental
  stimulation to develop the frontal lobes.

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Growth patterns in development

• 1. Cephalocaudal (from head downward).
• 2.  Proximal-distal (from center outward).
  Internal organs develop earlier than the arms and
  hands.

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Factors that influence height weight

• 1. Genetic factors accounts for most of the
  variance.
• 2. Gender-
• Girls-taller than boys from 2-9 yrs.
• Girls have growth spurt from 10-14 yrs.
• Boys show growth spurt from 10
• Weight pattern is similar.

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3. Hormonal influences-Growth Hormone (GH)

• GH, produced by the pituitary gland (brain),
  induces growth in the body.
• GH stimulates the liver skeleton to release
  somatomedin, which promotes cell duplication in
  the bones.
• This promotes growth beyond (4 feet).

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Environmental factors (growth)

• 1. Nutrition When healthy food is rationed,
  growth rates decline.
• E.g., During WWII growth rates declined. In
  prosperous times, when food is easy to come by
  growth rates increase.

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2. Does food supplementation improve growth
rates?

• Yes!!
• Super et al., (1990) showed that giving food
  supplements to families for 3-4 yrs, prevented
  growth retardation compared with controls.
• Also works with vitamin supplements.

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3. Can children with retarded growth catch up to
their peers?

• Yes. It depends on severity, duration, timing
  of deprivation (nutrition) therapy.
• Catch-up growth due to severe malnutrition may be
  limited to certain aspects of growth.
• Children starved early (prenatal) will show only
  modest gains if that.

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Are we growing heavier?

• Yes. Obesity rates are rapidly rising.
• Appears to have risen in children dramatically
  within the last decade.
• Why?
• Sedentary lifestyle
• High-fat food

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Why do kids gain too much?

• 1. Genetics-
• Adoption studies show biological children of
  heavy parents reared apartare more likely to
  be heavy themselves (Stunkard et al., 1986).
• 2. Modeling (what how do parents eat)
• 3. SES

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Critical periods for obesity

• 1. Infancy-
• 2. Child is 4 yrs-old