Human Growth andDevelopment Chapter Five First Two Years: Biosocial Development PowerPoints prepared by Cathie Robertson, Grossmont College Revised by Jenni Fauchier, Metropolitan Community College
Body Changes Rapid changes Consequences of neglect severe
Body Size 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
Sleep Newborns sleep about 17 hours per day needed for rapid growth REM sleep—rapid eye movement sleep—declines quiet sleep increases at about 3 months too immature to sleep through the night Infant’s sleep patterns influenced by brain waves and parents’ caregiving practices
Early Brain Development Most critical biosocial aspect of growth newborn’s 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 brain’s communication system
Basic Brain Structures Neurons—long thin nerve cells that make up nervous system created before birth 70% in cortex (brain’s outer layer) Axons—nerve fibers that extend from neurons that send impulses Dendrites—nerve fibers extending from neurons that receive impulses
Basic Brain Structures, cont. Neurons—long thin nerve cells that make up nervous system created before birth 70% in cortex (brain’s outer layer) Axons—nerve fibers that extend from neurons that send impulses Dendrites—nerve 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 don’t 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 Basic Brain Structures, cont.
At birth more than 100 million neurons are present Phenomenal growth is referred to as transient exuberance—fivefold increase in dendrites in first 2 years As many as 15,000 connections may be made per neuron Exuberance
Specifics of brain structure and growth depend partly on experience exuberance is transient—transitional stage between newborn brain’s immaturity and the maturity of older child’s or adult’s brain underused neurons are inactivated, or pruned Experience Enhances the Brain
Reactions to Stress experiencing stress may cause overproduction of stress hormone developing brain can lose capacity to react normally to stress normal neuron connections may have been pruned for rapid response to repeated stress Experience Enhances the Brain, cont.
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 Experience Enhances the Brain, cont.
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 these experiences critical if connections are to form; if connections not formed, plasticity may allow new connections and pathways as experiences continue Experience Enhances the Brain, cont.
The Senses and Motor Skills Sensorimotor Stage cognition develops between senses and motor skills
All senses function at birth sensation—the response of sensory system when it detects stimulus begins with outer organ—nose, eyes, etc. Sensation and Perception
perception—mental procession of sensory information when brain interprets sensation • begins in the brain and requires experience • cognition—thinking about what was perceived
Begins prenatally and is acute at birth Certain sounds trigger newborns’ reflexes Newborns particularly attentive to human voice Newborns’ sensitive hearing combines with brain to distinguish sounds Listening
Vision the least mature sense at birth Visual experience combined with visual cortex maturation improves vision with time scanning becomes more organized, efficient, and centered Binocular vision—ability to focus two eyes in a coordinated manner to see single image Looking
taste—functions at birth; calmed by sugar, sensitive to sour touch—comforted by human touch; feel pain smell—can distinguish between odors and have preferences Early sensation is organized for social interaction comfort Tasting, Smelling, and Touching
Most visible and dramatic body change of infancy Motor Skills
Reflexes Reflexes for survival are categorized maintain oxygen supply (breathing) maintain body temperature (crying, kicking) manage feeding (rooting and sucking) swallowing aids feeding spitting up if too much has been swallowed crying when stomach empty
Involve large muscles and body movements crawling, creeping, walking Gross Motor Skills
Small, finely tuned movements, especially of hands and fingers, including successful grabbing fingering, pointing, and holding grasping a moving object transferring objects from hand to hand adjusting reach Fine Motor Skills
Age at which motor skills acquired varies greatly because of ethnicity inherited factors—genetic differences patterns of infant care individual rate of physical maturation Variations and Ethnic Differences
Newborn Care Immunizations Nutrition Public Health Measures
Immunization Immunization—process that stimulates body’s immune system to defend against attack by a particular contagious disease smallpox polio measles
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
Nutrition How Infants Are Fed
Breast Is Best Breast Milk begins with colostrum, high-calorie nourishment before milk “lets down” easily digestible has antibodies and antibacterial properties better for baby’s health Bottle Feeding: babies more likely to have allergies better option if mother is HIV-positive or using drugs Feeding on Demand
Severe Malnutrition brain does not have enough nutrition to develop normally no body reserves to protect from disease marasmus and kwashiorkor diseases are direct result of malnutrition Malnutrition