CHAPTER 5 PHYSICAL GROWTH FIRST 2 YEARS Changes in Height and Weight Average birth weight and height 7lbs 20 inches head to toe Birth weight typically doubles by 5 months 15 lbs o Triples by first birthday 22 lbs o Second year baby gains about 5 6 lbs o Third year gains about 4 5 additional lbs Height increases by about in the first year 30 inches o Second year an additional 5 6 inches Growth during first 2 years is rapid and tappers off after the 2nd year Babies grow in spurts not in even progression Changes in Body Proportions 2 fundamental principles of growth 1 Cephalocaudal head to tail principle growth of the head and upper body precede growth in the lower body a 8 weeks after conception the head is the fetus length b At birth the head is only 25 of the body length still roughly the length of its legs c By adulthood the head only 12 of the body and legs 50 2 Proximodistal near to far principle the body grows from the center outward a Early childhood the torso develops prior to arms and legs b The arms and legs develop prior to hands and fingers c Principle reverses just before puberty hands feet grow rapidly before other body parts Childproofing the Environment Susceptible to injury and accidents Childproofing light sockets covered by caps stairs and drop offs blocked by Childproofing secure gates and dangerous objects EX knives tools and substances EX bleach and insecticides securely stored to the rapidly increasing ability of the infant and toddle to defeat the protective hardware typically employed by parents and caregivers in day care facilities requires progressive adjustments and elaboration synchronized Nutrition in Infancy Breast milk nutrients in perfect proportion for the first 3 4 months of life Formula from modified cow s milk acceptable as well Infants need fats proteins carbohydrates minerals and vitamins met by both human milk AND formula Breast milk does show some more advantages o Promotes early development of the brain o Positive effects on long term cognitive intellectual development o More optimal brain development than bottle fed babies o Offers a more distinct immunological benefit that cannot be duplicated in formula o Positive effect on babies born premature Colostrum a thin yellowish fluid secreted by the breast for several days before milk is produced transmitted to the infant for immunological protection o Contains antibodies not duplicated by formula Breastfed first 4 months o 72 less likely to be hospitalized for respiratory illness o 64 less likely to be hospitalized for gastrointestinal disorders o 36 reduction in the incidence of Sudden Infant Death Syndrome SIDS o 30 decrease in the incidence of Type 1 Diabetes o Lower rates of obesity in childhood adolescence 50 less likely to be obese at age 9 o Somewhat less likely to develop Attention Deficit Hyperactivity Disorder ADHD at adolescence Mothers who breastfed return more quickly to their pre pregnancy weight o Breastfeeding show results of lowering rates of breast and ovarian cancer Only about 79 of woman breastfeed with considerable variation amongst racial and socioeconomic groups in the USA Less than 50 of babies continue to be breastfed after 6 months old DEVELOPMENT OF THE BRAIN CNS constitutes the most complicated physical structure of the body No greater risk to development than those forces that endanger CNS No greater opportunity than those forces which facilitate CNS development development Structure of the Brain Brain begins to take form only days after conception and continues to emerge throughout prenatal stage Nerve cells form rapidly during prenatal stage o 250 000 new nerve cells per minute o Approximately 100 billion nerve cells in a newborn Nerve cell production stops just before birth o Brain continues to evolve through the first 10 years of life Neurons complex biological structures that conduct electrochemical o Transmits impulses from dendrites cell body axon Neurons line up into sequences pathways that conduct impulses in impulses body o Nerve cells do not touch each other o Axons of one cell butts up against the dendrite of another cell microscopic gap called a synapse Plasticity of the Brain o Impulses are then transmitted across the synapse from cell cell by chemicals known as neurotransmitters 28 weeks of gestation a process known as myelination occurs axons develop an insulating fatty coating that improves the efficiency of nerve impulse transmission Synaptogenesis is the developing of synapses in very large number prenatally and continuing to increase in extraordinarily large numbers through the first 3 years of life o Highest level of synaptic density 3rd year of life architecture of the brain is formed Prenatal stage of development driven by genetic influences Nerve cells migrate to specific locations Neurons extend their axons toward dendrites in intricate patterns predetermined by genetic forces and fueled by proteins and enzymes Gestation nerve cells begin to fire sending impulses through pathways in the developing brain organizing brain function After the baby is born the brain is arranged by pattern stimulation from different sources particularly from routine interactions with caregivers leaving profound effects on the developing brain from infancy so on Fundamental structure of the Nervous System transfer of sensation perception learning and intelligence manage the storage and Brain must have the capacity to deal with typical requirements of the system and have the ability to adapt in the face of new and unanticipated challenges to survival Nervous System is an evolving system of circuits that is designed with more potential capacity than it is ever likely to need use If one part of the Nervous System becomes damaged or unable to function other parts of the system will be able to take over o This is plasticity of the human brain Hemispherectomy dramatic plasticity example is the radical removal of half of a child s brain in the treatment of extreme cases of brain seizures o The child s brain begins to reprogram itself capitalizing on the patient but persistent efforts of the parents therapists and educators Build ups in the pathways and synapses in the Nervous System can slowly At the end of year 2 but dramatically alter the structure and function of the brain for the first time synapses begin to disappear rate of production of new synapse levels decreases o The elimination process is based on a simple neurological principle pathways that get used
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