Chapter 5 Physical Development in Infancy and Toddlerhood CHD2220 Unit 2 Exam 1 Body Growth a Changes in Body Size and Muscle Fat Makeup i ii Infants and toddlers grow in tiny spurts usually fussy and hungry the day before a spurt Baby fat peaks at about 9 months helping maintain body temperature but muscle tissue increases very slowly iii Growth norms height and weight averages for children their age b Changes in Body Proportions c Skeletal Growth i Cephalocaudal trend from the Latin for head to tail during the prenatal period the head develops more rapidly than the lower part of the body Describes the growth pattern of a child s size increase ii Proximodistal trend growth proceeds literally from near to far from the center of the body outward i The best estimate of a child s physical maturity is skeletal age a measure of development of the bones of the body ii Cartilage the embryonic skeleton is first formed out of soft pliable tissue iii Epiphyses special growth centers that appear at the two extreme ends of each of the long bones of the body iv African American children tend to be slightly ahead of Caucasian children in skeletal age and girls usually ahead of boys v Fontanels the bones of the skull separated by these six gaps or soft spots at birth They permit the brain to overlap as the large head of the baby passes through the birth canal 2 Brain Development at birth brain is nearer to its adult size than any other physical structure we can look at the brain from two vantage points 1 the microscopic level of individual brain cells and 2 the larger level of the cerebral cortex a Development of Neurons i Neurons nerve cells that store and transmit information ii Synapses tiny gaps where fibers from different neurons come close iii Neurotransmitters chemical signals released by neurons that cross together but do not touch the synapse to send a message iv Prenatal neurons produced in the embryo s primitive neural tube and v migrate to form the brain and establish their functions Infancy and toddlerhood neural fibers and synapses increase at a rapid pace vi Synaptic pruning when neurons aren t stimulated soon they lose their synapses and return neurons not needed at the moment to an uncommitted state so they can support future development vii What causes dramatic brain size increase in the first two years About half the brain is make of glial cells which are responsible for myelination viii Myelination the coating of neural fibers with an insulating fatty sheath myelin that improved the efficiency of message transfer ix Gains in neural fibers and myelination are responsible for the extraordinary gain in overall size of the brain b Neurophysiological Methods i Neuroimaging techniques yield detailed three dimensional computerized pictures of the entire brain and its active areas ii Positron emission tomography PET depends on x ray photography and requires injection of radioactive substance iii Functional magnetic resonance imaging fMRI detects changes in blood flow and oxygen metabolism magnetically iv Near infrared spectroscopy NIRS infrared light is beamed at regions of the cerebral cortex to measure blood flow and oxygen metabolism while the child attends to a stimulus only testing where movement from child is okay but only can examine the functioning of the cerebral cortex c Development of the Cerebral Cortex i Cerebral cortex largest brain structure 85 brain s weight and contains most neurons and synapses Consists of two hemispheres that differ in functions each hemisphere receives sensory information from the side of the body opposite to it and controls only that side ii Left hemisphere responsible for verbal abilities and positive emotion process information in a piece by piece way iii Right hemisphere handles spatial abilities and negative emotion processes information in a holistic integrative manner iv Prefrontal Cortex controls body movement responsible for thought consciousness inhibition of impulses integration of information and use of memory reasoning planning and problem solving strategies v Lateralization specialization of two hemispheres vi Brain plasticity a highly plastic cerebral cortex in which many areas are not yet committed to specific functions has a high capacity for learning If a part of the cortex is damages other parts can take over the tasks it would have handled vii Newborns hemispheres have already begun to specialize most newborns favor the right side of the body in their head position and reflexive reactions viii Example deaf adults who learn sign language as a child a spatial skill depend on right hemisphere for language processing Toddlers who are advanced in language development show greater left hemispheric specialization for language than their slower age mates The process of acquiring language and other skills promotes lateralization d Sensitive Periods of Brain Development i Early extreme sensory deprivation results in permanent brain damage and loss of functions those reared from birth in stimulating environments show much denser synaptic connections ii Example babies born with cataracts who have corrective surgery within the first 6 months show rapid improvement but the longer the surgery is postponed the less complete the recovery If surgery is delayed until adulthood vision is severely and permanently impaired iii Example when children from a deprived Romanian orphanage were adopted into British families those younger than 6 months cognitive catch up was impressive but those who were older shows serious intellectual deficits Although improved they stayed below average iv Sensitive adult care helps normalize cortisol production in both typically developing and emotionally traumatized infants and young children e Changing State of Arousal 3 Influences on Early Physical Growth 4 Learning Capacities a Heredity b Nutrition c Malnutrition d Emotional Well Being a Classical Conditioning b Operant Conditioning c Habituation d Imitation 5 Motor Development a The Sequence of Motor Development b Motor Skills as Dynamic Systems c Dynamic Motor Systems in Action d Cultural Variations in Motor Development e Fine Motor Development Reaching and Grasping f Bowel and Bladder Control 6 Perceptual Development a Hearing b Vision c Object Perception d e Understanding Perceptual Development Intermodal Perception
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