Chapter 4: Infancy

1. Chapter 4: Infancy Module 2 Physical Developmentin Infancy

2. GROWTH AND STABILITY

3. Physical Growth • Rapid growth during first two years 87

4. An Interesting Head Count

5. Nervous system comprises the brain and the nerves that extend throughout the body Neurons are the basic cells of the nervous system Nervous System and Brain 87

6. Quick Check • Neurons • Dendrites • Axons • Neurotransmitters • Synapses 87

7. The Brain Brain Physiology • Structure and function • Forebrain • Cerebral cortex has four lobes • Two hemispheres usually work together and each lobe has a primary function • Frontal, occipital, temporal, parietal lobes • Amygdala • Hippocampus

8. The Brain The Brain’s Four Lobes Fig. 3.7

9. The Brain Functions of Lobes of the Cortex Involved in voluntary movement, thinking, personality, and intentionality or purpose Frontal lobes Occipital lobes Function in vision Active role in hearing, language processing, and memory Temporal lobes Roles in registering spatial location, attention, and motor control Parietal lobes

10. Development of the Brain • By age 6, almost adult size. • Brain growth spurts: coincide with changes in cognitive behavior • Cerebellum, largest part of brain, divides into halves • Lateralization, specialties of each hemisphere; left: language and logical thinking; right: visual and spatial functions

12. The Brain Brain Physiology • Neurons— nerve cells handling information processing at the cellular level • Axon, dendrites, synapses • Neurotransmitters: dopamine • Myelin sheath and myelination • Neural circuits • Lateralization— specialization of functions in one hemisphere of cerebral cortex

13. The Brain The Neuron Fig. 3.8

14. The Brain The Brain In Infancy • Shaken Baby Syndrome • Extensive brain development in utero • Born with about 100 billion neurons • Enriched early experiences can enhance brain growth and functioning • Brain flexibility and resilience demonstrated in deprived environments • Experience determines brain connections • Enriched and deprived environments

15. The Brain The Brain In Infancy • Changing neurons • Myelination; visual and auditory • Rapid growth of myelin sheath, dendrite and synapse connections • Blooming and pruning of connections in brain • Peak synaptic overproduction influenced by heredity and environment

16. The Brain The Brain In Infancy • At birth, greater activity in left hemisphere specializes as infants listen to speech • Motor control begins about 2 months • Brain areas do not mature uniformly; skills affected by myelination and interconnections

17. Major Systems of the Brain • Brain stem • Limbic system • Cerebral cortex

18. Birth: 100-200 billion neurons Relatively few neurons-neuron connections During first two years: Billions of new connections established and become more complex How great brains grow! 88

19. Use it or lose it! 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 • Myelin 88

20. Form and Function: Brain Growth • Neurons reposition themselves with growth, becoming arranged by function • Cerebral cortex • Subcortical levels 89

21. Don’t shake the baby! • Shaken Baby Syndrome • Brain sensitive to form forms of injury • Shaking can lead to brain rotation within skull • Blood vessels tearsevere medical problems, long-term disabilities, and sometimes death 89

22. Environmental Influences on Brain Development • Plasticity • Sensitive period 89

23. Critical Period: specific time when a given event (or absence) has specific impact on development. Not absolutely fixed. Plasticity: ability to modify Sensitive Periods: especially responsive to specific type of experience

24. Without feedback from the environment (that is, without experience) how can further development occur? A child raised in a deprived environment with inadequate stimulation and feedback might fail to learn. The damage to a child is significant when love and attention are absent.

25. Critical & Sensitive Periods Critical and sensitive periods are both times when the organism is biologically primed to most benefit from a particular experience. Sensitive Periods: adverse effects caused by missing a sensitive period may be overcome at a later time, although with great difficulty.

26. Critical Periods: adverse effects caused by missing a critical period are permanent. The only clearly demonstrated critical period in human beings involves early stimulation of certain neural and body cells. Without such stimulation, these cells atrophy and die (e.g., visual neurons must have light during their early development or they will die. Depth perception may occur as well.

27. The first 5 to 6 years of childhood may be a critical period for the development of the brain. Even when a part of the brain is damaged, if damage occurs before age 5/6, the brain may compensate and take over the functions. After age six, highly unlikely.

28. Other ways a child may suffer permanent disability by early childhood: • occurrence of irreparable physical damage upon which later development will depend • a critical period that passes without the child’s obtaining the necessary experience or stimulation • a situation where the child is kept by their culture or environment from ever obtaining the learning necessary for proper development.

29. Do Baby Einstein programs really work?

30. What do babies do all day? Life Cycles of Infancy • Wake • Sleep • Eat • Defecate 89

31. 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 90

32. Sleep: Perchance to Dream • Major state • 16-17 hours daily (average); wide variations • 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 (See table 2-2) 90-91

33. 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 91

34. SIDS • Sudden infant death syndrome • Leading cause of death in children under 1 year of age • Back-to-sleep guidelines (AAP) • Differential risk • Boys • African American infants • Low birthweight • Low APGAR scores • Mother’s smoking • Some brain defects • Child abuse 92

35. SIDS is found in children of every race and socioeconomic group and in children who have had no apparent health problems Back-to-sleep is important! 92

36. Review and Apply 93 REVIEW • The major principles of growth are the cephalocaudal principle, the proximodistal principle, the principle of hierarchical integration, and the principle of the independence of systems. • The development of the nervous system first entails the development of billions of neurons and interconnections among them. Later, the numbers of both neurons and connections decrease as a result of the infant’s experiences.

37. Review and Apply REVIEW • Babies integrate their individual behaviors by developing rhythms—repetitive, cyclical patterns of behavior. 93

38. Review and Apply APPLY • What evolutionary advantage could there be for infants to be born with more nerve cells than they actually need or use? How might our understanding of synaptic “pruning” affect the way we treat infants? 93

39. MOTOR DEVELOPMENT

40. Reflexes: Inborn Physical Skills • Reflexes: learned, organized involuntary responses that occur automatically in presence of certain stimuli 93

41. What did you see? • Take two minutes to list the reflexes you saw in the clip.

42. Why do reflexes come and go?

43. Reflexes Genetically determined Universal Cultural variations in ways displayed Moro reflex Serves Diagnostic tool Social function Survival function Ethnic and Cultural Differences and Similarities in Reflexes 94

44. Motor Development in Infancy Milestones of Normal Motor Development 96

45. Motor Development in Infancy Fine Motor Skills 96

46. 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) 96

47. 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 98

48. 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 98

49. Malnutrition • Children living in many developing countries • Slower growth rate • Chronically malnourished during infancy = later lower IQ score 98

50. Are problems of malnourishment restricted to developing countries?