Looking Ahead Chapter 2: Infancy Module 2.1 Physical Development in Infancy
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How do the human body and nervous system develop?
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Does the environment affect the pattern of development?
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What developmental tasks must infants accomplish in this period?
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What is the role of nutrition in physical development?
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What sensory capabilities do infants possess?
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Physical Growth z
Rapid growth during first two years
GROWTH AND STABILITY
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Head-to-body size ratio changes dramatically
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Nervous System and Brain z
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Nervous system comprises the brain and the nerves that extend throughout the body Neurons are the basic cells of the nervous system
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Cellular Basis of Brain Development Migration of cells Formation and growth of axons z Formation of dendrites z Formation of synaptic connections z Myelination z z
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How brains grow z
Use it or lose it
Birth:
Synaptic pruning z Unused neurons are eliminated z Allows established neurons to build more elaborate communication networks with other neurons z Development of nervous system proceeds most effectively through loss of cells
– 100-200 billion neurons – Relatively few neuron-to-neuron connections z
During first two years: – Billions of new connections established and become more complex
But also note the importance of myelin
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Environmental Influences on Brain Development z Plasticity z Sensitive period
Form and Function: Brain Growth z
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Neurons reposition themselves with growth, becoming arranged by function – Cerebral cortex – Subcortical levels
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Don’t shake the baby! z
Shaken Baby Syndrome – Brain sensitive to injury – Shaking can lead to brain rotation within skull
MOTOR DEVELOPMENT
z Blood
vessels tearÆsevere medical problems, long-term disabilities, and sometimes death
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Major Reflexes in Full-Term Neonates: Survival
Reflexes: Inborn Physical Skills z
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Reflexes: learned, organized involuntary responses that occur automatically in presence of certain stimuli
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Breathing
permanent
Eye-blink
permanent
Pupillary
permanent
Rooting
Disappears over first few weeks; replaced by voluntary head turning
Sucking
permanent
Swallowing
permanent
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Major Reflexes in Full-Term Neonates: Primitive
Bibinski (plantar)
8 month-1 year
Palmar grasping
Swimming
3-4 months; replaced by voluntary grasping Arms and arching stop at 4-6 months 4-6 months
Stepping
First 8 weeks
Moro
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Motor Development in Infancy Milestones of Normal Motor Development
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Motor Development in Infancy Fine Motor Skills
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Developmental Norms
Nutrition in Infancy
Comparing Individual to Group Norms:
Fueling Motor Development z Without proper nutrition, infants cannot reach physical potential and may suffer cognitive and social consequences z Infants differ in growth rates, body composition, metabolism, and activity levels
– Represent the average performance of a large sample of children of a given age – Permit comparisons between a particular child’s performance on a particular behavior and the average performance of the children in the norm sample – Must be interpreted with caution z
So what is a healthy caloric allotment for infants?
Malnutrition
About 50 calories per day for each pound of weight z Most infants regulate their caloric intake quite effectively on their own z If are allowed consume as much they seem to want, and not pressured to eat more, they will be healthy
Children living in many developing countries z Slower growth rate z Chronically malnourished during infancy = later lower IQ score
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Learning about the World
Visual Perception: Seeing the World
Sensation z Perception
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Newborn’s distance vision ranges from 20/200 to 20/600 z By 6 months, average infant’s vision is already 20/20 z Other visual abilities grow rapidly
