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PHYSICAL DEVELOPMENT IN INFANCY

Chapter 4. PHYSICAL DEVELOPMENT IN INFANCY. Learning Objectives. GROWTH AND STABILITY. Physical Growth: The Rapid Advances of Infancy. Infants grow at a rapid pace over the first two years of their lives (see Figure 4-1) 5 months: average birth weight doubles to around 15 #

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PHYSICAL DEVELOPMENT IN INFANCY

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  1. Chapter 4 PHYSICAL DEVELOPMENT IN INFANCY

  2. Learning Objectives

  3. GROWTH AND STABILITY

  4. Physical Growth: The Rapid Advances of Infancy Infants grow at a rapid pace over the first two years of their lives (see Figure 4-1) • 5 months: average birth weight doubles to around 15 # • 1 year: weight triples to about 22 pounds • End of 2nd year: average child weighs around four times as much as at birth

  5. How they grow… Continuous

  6. Physical Growth: The Rapid Advances of Infancy Not all parts of an infant's body grow at the same rate • At Birth: head accounts for one-quarter of newborn's entire body • During 1st & 2nd year: rest of the body begins to catch up

  7. An Interesting Head Count

  8. There are gender and ethnic differences in infant weight and length • Girls generally are slightly shorter than boys • Girls weigh slightly less than boys • Gender differences remain throughout childhood • Asian infants tend to be slightly smaller than NA Caucasian infants • African-American infants tend to be slightly bigger than NA Caucasian infants.

  9. Physical Growth:The Rapid Advances of Infancy4 Principles

  10. Nervous System and Brain:A Foundation of Development • Neurons are the basic cells of the nervous system • Nervous system comprises the brain and the nerves that extend throughout the body

  11. Brain Development Prenatal • Neurons multiply at an amazing rate prior to birth. • At some points in prenatal development, cell division creates some 250,000 additional neurons every minute. Birth • 100-200 billion neurons • Relatively few neurons-neuron connections During first two years • Billions of new connections established and become more complex Adult • A single neuron is likely to have a minimum of 5,000 connections to other neurons or other body parts.

  12. Babies are born with many more neurons than they need Use it or lose it! Although synapses are formed throughout life, based on our changing experiences, the billions of new synapses infants form during the first two years are more numerous than necessary • Synaptic pruning • Unused neurons are eliminated • Allows established neurons to build more elaborate communication networks with other neurons • Development of nervous system proceeds most effectively through loss of cells • Myelination • “Insulation” of the wiring • Protects & speeds information conduction • Activity-dependent effects on myelination cannot be considered strictly a developmental event. (Fields, D.,Myelination: An Overlooked Mechanism of Synaptic Plasticity? Neuroscientist 2005)

  13. Neuron Networks Over the first two years of life, networks of neurons become increasingly complex and interconnected.

  14. Coming to terms with your brain…

  15. Form and Function: Brain Growth Neurons reposition themselves with growth, becoming arranged by function • Cerebral cortex • upper layer of the brain • higher-order processes: thinking & reasoning • become more developed and interconnected • Subcortical levels • Lower layers of the brain • regulate fundamental activities: breathing & heart rate • most fully developed at birth.

  16. Brain Development: Influences and Definitions a specific, but limited, time, usually early in an organism's life, during which the organism is particularly susceptible to environmental influences relating to some particular facet of development the degree to which a developing structure or behavior is modifiable due to experience

  17. What do babies do all day? Integrating the bodily systems: Life cycles of infancy • Rhythms: repetitive, cyclical patterns of behavior • Wake • Sleep • Eat • Eliminate Initially like separate individuals all playing their own melody. Eventually they become like a jazz band still playing their own riff but weaving a single, harmonious, song.

  18. Rhythms and States State • One of major body rhythms • Degree of awareness infant displays to both internal and external stimulation • Change in state alters amount of stimulation required to get infant's attention • Electrical brain waves can be measured by electrocephalogram (EEG)

  19. Primary Behavioral States

  20. Primary Behavioral States

  21. Sleep: Perchance to Dream Major state • 16-17 hours daily (average); wide variations • heart rates increase and become irregular, their blood pressure rises, and they begin to breathe more rapidly Different than adult sleep • 2 hour spurts; periods of wakefulness • Cyclic pattern • By 16 weeks sleep about 6 continuous hours; by 1 year sleep through night

  22. Cycle of Infant Behavioral States

  23. REM Sleep • Period of active sleep • Closed eyes begin to move in a back-and-forth pattern • Takes up around one-half of infant sleep • May provide means for brain to stimulate itself through autostimulation • In Adults correlated with memory storage Why not in babies too?

  24. REM Sleep Through the Lifespan

  25. Did you find examples in the text that suggest that cultural practices affect infants’ sleep patterns? • the Kipsigis of Africa, infants sleep with their mothers and are nurse whenever they wake. • They accompany their mothers during daily chores, napping while strapped to their mothers’ backs • Kipsigis infants do not sleep through the night until much later than babies in Western societies, • the first 8 months of life, they seldom sleep longer than 3 hours at a stretch. • In comparison, 8-month-old infants in the United States may sleep as long as 8 hours at a time Much like US breast fed kids

  26. SIDS: The Unanticipated Killer • Sudden infant death syndrome (SIDS) is a disorder in which seemingly healthy infants die in their sleep • SIDS strikes about 2,500 infants in the United States each year • Although it seems to occur when the normal patterns of breathing during sleep are interrupted, scientists have been unable to discover why that might happen

  27. SIDS • Don’t shut the nursery door! • Use your EARS!

  28. Declining Rates of SIDS

  29. SIDS is found in children of every race and socioeconomic group and in children who have had no apparent health problems • SIDS strikes about 1 in 1,000 infants in the USA each year. • Although it seems to occur when the normal patterns of breathing during sleep are interrupted, scientists have been unable to discover why that might happen. • American Academy of Pediatrics now suggests that • babies sleep on their backs rather than on their sides or stomachs—called the back-to-sleep guideline. • parents consider giving their babies a pacifier during naps and bedtime. Back-to-sleep is important!

  30. MOTOR DEVELOPMENT

  31. Motor Development • Shape and proportions of newborn babies are simply not conducive to easy mobility • Young infants lack the strength to raise large heads • Movement is further impeded because limbs are short in relation to the rest of the body • Infant bodies are mainly fat, with a limited amount of muscle; the result is a lack strength

  32. Motor Development BUT • At birth newborns have an extensive repertoire of behavioral possibilities brought about by innate reflexes, and their range of motor skills grows rapidly during the first two years of life

  33. Reflexes: Inborn Physical Skills Reflexes • Learned, organized involuntary responses that occur automatically in presence of certain stimuli WHAT? No, No! Reflexes are wired up unlearned responses to stimuli!

  34. Some Basic Reflexes in Infants

  35. Some Basic Reflexes in Infants

  36. Why do neonate reflexes come and go? Evolutionary explanations of development: gradual disappearance of reflexes to result of increase in voluntary control over behavior that occurs as infants become more able to control their muscles. It may be that reflexes form the foundation for future, more complex behaviors. As these more intricate behaviors become well learned, they encompass the earlier reflexes. Perhaps reflexes stimulate parts of the brain responsible for more complex behaviors, helping them develop.

  37. Intensive practice of motor behaviors • May produce earlier appearance of certain motor activities • No evidence the activities are performed qualitatively better • Even when early gains are found • Do not produce a child w/ better motor skills • Do not produce an adult w/ better motor skills.

  38. Ethnic and Cultural Differences and Similarities in Neonatal Reflexes Reflexes • Genetically determined • Universal Cultural variations in ways displayed • Moro reflex Serves • Diagnostic tool • reflexes emerge and disappear on a regular timetable • their absence—or presence—at a given point of infancy • a clue that something’s wrong in an infant's development. • Social function • Survival function

  39. Moro Reflex: Some differences reflect cultural and ethnic variations Moro Reflex (Startle Reflex) - stretch out the arms, flex the legs, and grab. • Caucasian infants show a pronounced response. • Also cry and respond in a generally agitated manner. • Navajo babies react much more calmly. • Arms do not flail out as much and rarely cry.

  40. Milestones of Motor Development • Fifty percent can perform each skill at the month indicated in the figure. • Timing at which each skill appears varies widely. • 24% walk well at 11.1 months • 90% by 14.9 months

  41. Motor Progress • Young infants still are able to accomplish some kinds of movement. • When placed on their stomachs they wiggle their arms and legs and may try to lift their heavy heads. • As their strength increases, they are able to push hard enough against the surface on which they are resting to propel their bodies in different directions. • They often end up moving backwards rather than forwards, but by the age of 6 months they become rather accomplished at moving themselves in particular directions. • These initial efforts are the forerunners of crawling, in which babies coordinate the motions of their arms and legs and propel themselves forward. • Crawling appears typically between 8 and 10 months. • Walking comes around the age of 9 months; most infants are able to walk by supporting themselves on furniture, and half of all infants can walk well by the end of their first year of life. • Most are able to sit without support by the age of 6 months.

  42. Dynamic Systems Dynamic systems theory • Describes how motor behaviors are assembled • Motor skills do not develop in vacuum • Each skill advances in context of other motor abilities • As motor skills develop, so do non-motoric skills • Theory places emphasis on child's own motivation (a cognitive state) in advancing important aspects of motor development

  43. Developmental Norms Comparing Individual to Group Norms: • 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 • Brazelton Neonatal Behavior Assessment Scale (NBAS)

  44. Nutrition in Infancy Fueling Motor Development • Without proper nutrition, infants cannot reach physical potential and may suffer cognitive and social consequences • Infants differ in growth rates, body composition, metabolism, and activity levels

  45. So what is a healthy caloric allotment for infants? • About 50 calories per day for each pound of weight • Most infants regulate their caloric intake quite effectively on their own • If are allowed consume as much they seem to want, and not pressured to eat more, they will be healthy

  46. Malnutrition Malnutrition • Condition of having improper amount and balance of nutrients, produces several results, none good • More common in children living in developing countries • Slower growth rate • Chronically malnourished during infancy • later lower IQ score • Do less well in school • Effects linger even after improved diet

  47. Underweight Children Percent under five years who are moderately or severely underweight.

  48. Are problems of malnourishment restricted to developing countries?

  49. Undernutrition: Dietary Deficiencies • Undernutrition also has long-term costs, including mild to moderate cognitive delays • Up to 25% of 1- to 5-year-old US children have diets that fall below minimum caloric intake recommended by nutritional experts • 1/5 of US children go to bed hungry. • Do you believe these “statistics”?

  50. When Malnutrition Is Severe Maramus • Malnutrition in first year • Infants stop growing. • Attributable to severe deficiency in proteins and calories • Causes the body to waste away • Ultimately results in death Kwashiorkor • Found in older children • Child's stomach, limbs, and face swell • Body struggles to make use of few available nutrients

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