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PSYC 2110 (131)
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CH 6.docx

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York University
PSYC 2110
Gillian Wu

CH 6: PHYSICAL DEVELOPMENT AN OVERVIEW OF MATURATION AND GROWTH The first 2 years of life: babies grow rapidly doubling their weight by 4 to 6 months and tripling it by the end of the first year By age 2 toddlers are already at half the height they will be at when they reach adulthood Puberty is the only other time that people will go through a growth spurt in their life (any other phase, they will just grow by a little) A newborns head is 70% of its eventual adult size and during newborn stages, the head is also of the total body length; by one year the head will only be 20% the body length Development proceeds to be cephalocaudal (head down direction); 60% of growth by 1 year old to adolescents will be in the legs As adults are head is only 12% of our body length, while our legs are 50% Children also grow outward (proximodistal) as infants and children, their hands and feet will grow slower than their arms and legs; by puberty this role is reversed (hands and feet grow more rapidly at the beginning stages) One reason that neonates cant stand or sit up on their own is bc their bones are too small and flexible (bones are softer as a newborn) Fontanelles: the 6 soft spots between the skull bones these are used to allow the bones to compress so the baby can be pushed out of the cervix o By around 2, the fontanelles are filled with minerals to form a single skull; the points that they are mineralized become the sutures of the brain and allow the skull to expand while the brain is getting bigger Skeletal age: a measure of physical maturation based on a childs level of skeletal development (use an X-Ray on the wrist and hands to see the number of bones the child has) o This technique has shown has girls have matured faster than boys Neonates are born with all the muscle fiber they will ever have (although there tissue is filled with 35% water as a newborn, while decreases when more proteins and salts are surrounding the muscle tissue) o Development of muscles is cephalo..and proximo(so the head and neck muscles mature quicker than the trunk and limbs) the maturation increases rapidly when a child gets to adolescence o Muscle accounts for 40% of a males and 24% of a females weight by the mid-20s Different parts of the body develop at different speeds during different times of life o The brain and head develop during childhood and barely past adolescence o Genitals/reproductive organs grow rapidly during adolescence o The lymphoid tissue (immune system) develops very quickly in childhood, and decline greatly by adolescence Growth of different parts takes place at different times for different ppl (i.e. puberty) differences in maturation do not only lead to physical differences, but also lead to differences in other areas of development like cognition o Read more about experience-expectant stuff on slides There are also cultural variations to physical growth and development i.e. Asians being smaller than Europeans DEVELOPMENT OF THE BRAIN Brain growth spurt: last trimester and first 2 years after birth during this time, more than half an adults brain weight is added o This happens after the neurons are developed (see below), bc the glia cells begin to myelinate the neurons during this time th st o B/w the 7 prenatal month and 1 birthday the brain develops at more than 1 milligram/minute Synapses: electrical and chemicals signals that pass through neurons Neurons develop in the neural tube, which are then moved with guiding cells to form the major parts of the brain nd Majority of a persons neurons are developed by the end of the 2 trimester Neurons are able to serve any neural function but it only depends on where they end up (a neuron that is used for vision, and is moved to an area for hearing will then become an auditory neuron) Synaptogenesis: formation of synaptic connections among neurons proceeds rapidly during the brain growth spurt There are more neurons and synapses that happen during infancy than adulthood this is bc the neurons that do not make connection in infancy will eventually die or the ones that dont function correctly can also die Synaptic pruning: certain non-stimulated surviving neurons will eventually loose their synapse (remain in the brain in case they need to compensate for other faulty neurons bc of things like brain injuries) Plasticity: changes in the brain due to the shaping of ones experiences Use it or lose it neurons that arent use will die Myelinization: glia produce myelin to surround neurons and allow neural impulses to speed up when neurons between muscles and neurons have myelin, it allows the baby to start performing more complex motor activities like lifting her head and rolling over o The reticular formation and the frontal lobe develop myelin slower than other areas of the brain (not full until puberty); reason for attn.- span to be shorter for younger children Cerebrum: highest area of the brain that contains both hemispheres and the cerebral cortex (grey matter) Left hemi: used for language processing, decision making, expression of +ve emotion Right hemi: expression of ve emotion, processes music, touch Cerebral lateralization: involves the preference of using one hand or one side of the body more than another There are theories that assume that lateralization occurs during prenatal stages and is enhanced at birth i.e. most babies come out with their right ears facing outward (bc of the left hemispheres specialization in language processing) During puberty there is also some reorganization of the brain pruning still takes place and neurons are still myelinating at this time (reason why teenagers can process info quicker than younger children) MOTOR DEVELOPMENT A childs rate of motor development tells very little about the childs future development outcome so even though there are normative patterns to development, it doesnt mean that child that fall out of the norm will be any different in the future Just like the brain and muscles, motor development is both cepha/proxi development (although, children start kicking their feet earlier than touching with their hands) There are 3 explanations for the sequence and timing of motor development maturational, experiential, and dynamic viewpoints Maturational Viewpoint Describes motor development as the unfolding of genetically programmed sequences nerves and muscl
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