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Chapter 5

Chapter 5 - Textbook Notes

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Psychology 2040A/B
Ian Mac Donald

CHAPTER 5AN OVERVIEW OF MATURATIONGROWTHIn the first few months of life babies gain over 280g per day and 25cm each month Dramatic increases in height and weight that we see are accompanied by a number of important internal developments in the muscles bones and CNS Changes in HeightWeightBabies grow rapidly in the first 2 yearsoften double their birth weight by age 46 months tripling it by the end of the first year Growth is very uneven in infancy By age 2 toddlers are already half their adult height and have quadrupled their birth weight From age 2 until puberty children gain about 5080cm in height and about 30kg in weight each year Pubertyadolescents enter a 23 year growth spurt After puberty there are typically small increases in height until full adult stature is attained in midlate teensChanges in Body ProportionsNewborns head is already 70 of its eventual adult size and representsof total body length same as the legs Cephalocaudal Development a sequence of physical maturation and growth that proceeds from the head cephalic region to the tail or caudal regiono Head downward directionAt 1 year of age childs head only accounts for 20 of total body length From age 1 until the adolescent growth spurt legs grow rapidly accounting for more than 60 of increase in height During adolescence trunk once again becomes fastest growing segment of the body When we reach our adult height our legs account for 50 of total height and our head only 12 Proximodistal Development a sequence of physical maturation and growth that proceeds from the center of the body the proximal region to the extremities distal regions o Center outward directiono During prenatal development chest and internal organs form first followed by arms and legs then hands and feeto During infancy and childhood arms and legs continue to grow faster than the hands and feeto This centeroutward growth pattern reverses just before pubertyhands and feet begin to grow rapidly and become first body parts to reach adult proportions followed by arms and legs and then trunkSkeletal Development Skeletal structures formed during prenatal development are initially soft cartilage that will gradually harden into bony material At birthnearly all bones are a source of blood cells most of the infants bones are soft pliable and difficult to breako Neonates cannot sit up or balance themselves because their bones are too small and too flexible Neonates skull consists of several soft bones that can be compressed to allow the child to pass through the cervix and birth canalo These skull bones separated by 6 soft spots fontanelles that are gradually filled in by mineralso Form a single skull by age 2 with pliable points at the seams where skull bones join these seams or sutures allow the skull to expand as the brain grows largerAnkles feet wrists handsdevelop more bones as the child matures Skeletal Age measure of physical maturation based on the childs level of skeletal developmento Using this technique researchers have found that girls mature faster than boysNot all parts of the skeleton grow and harden at the same rate Skull and hands mature firstLeg bones continue to develop until midlate teens Skeletal development completed by age 18 Width of the skull leg bones and hands increase slightly throughout lifeMuscular Development Neonates born with all of the muscle fibers they will ever have At birth muscle tissue is 35 water accounts for 1824 body weightMuscle fibers begin to grow as the cellular fluid in muscle tissue is bolstered by the addition of proteins and salts Muscular development proceeds in cephalocaudal and proximodistal directionsMuscles in the head and neck maturing before those in the trunk and limbs Maturation of muscle tissue occurs very gradually over childhood accelerates during early adolescenceo Members of both sexes become noticeably strongerBy mid20s skeletal muscle accounts for 40 of body weight of male 24 of female Variations in Physical Development Brain and head grow much faster and are quicker to reach adult proportions than the rest of the body Genitals and reproductive organs grow very slowly throughout childhood develop rapidly in adolescenceGrowth of lymph tissues part of immune system help children fight infections overshoots adult levels in late childhood decline rapidly in adolescence Individual VariationsIndividual differences in the rate of maturation not only result in visible differences in physical features but also contribute to differences in other areas of development
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