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Chapter 6.docx

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PSYC 2450
Anneke Olthof

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Chapter 6 - Physical Development: The Brain, Body, Motor Skills, and Sexual Development Changes in Height and Weight - Grow very rapidly during first 2 years, doubling birth weight by 4 to 6 months and tripling it by the end of the first year. - By age 2, toddlers are half of their eventual adult height and have quadrupled their birth weight. - From age 2 until puberty, children gain about 5 to 8 cm in height and about 3 kg each year. - Between ages 6 and 11, children seem to grow very little Development proceeds in a cephalocaudal (head downward) direction. Children grow outward according to proximodistal (Centre outward) direction. (Organs and chest first, followed by arms, legs, hands, feet) Skeletal Development - Skeletal structures during prenatal period are soft cartilage that hardens into bony material - At birth, nearly all bones are a source of blood cells. - Postnatal development  production of blood cells limited to a few specific bones - At birth, the bones are soft, pliable and difficult to break - Reason why they can’t stand or sit up  bones are too small and flexible. - Skull bones separated by 6 soft spots at birth and by age 2, they are filled in by minerals to form a single skull. - Skeletal Age: A measure of physical maturation based on the child’s level of skeletal development. Muscular Development - Infants born with all the muscle fibers they will ever have - At birth, muscle tissue is 35% water, and its 18% to 24% baby’s weight. - Proceeds in cephalocaudal and proximodistal directions with muscles in the head and neck maturing before limbs. - People from Asia, South America, and Africa are smaller than Americans and Europeans but they are more mature. Development of the Brain - Brain growth spurt: The period between the seventh prenatal month and 2 years of age when more than half of the child’s eventual brain weight is added. Neural development and plasticity - Brain and nervous system cells work by transmitting electrical and chemical signals across synapses. - Synapses: The connective space (juncture) between one nerve cell (neuron) and another. - Neuron: Nerve cells receive and transmit neural impulses. - Neurons are produced in the neural tube of the embryo - Glia: Nerve cells that nourish neurons and encase them in insulating sheaths of myelin. 1 - Synaptogenesis: Formation of connections (synapses) among neurons. - Occurs rapidly during the brain growth spurt. - Plasticity: Capacity or change; a developmental state that has the potential to be shaped by experience.  Cells highly responsive to the effects of experience. - Surviving neurons that are stimulated less often lose their synapses (synaptic pruning) and stand in reserve to compensate for brain injuries or to support new skills. The Role of Experience - Riesen: infant chimpanzees reared in the dark for period of up to 16 months. Dark-reared chimpanzees experienced decreased activity of the retina and the neurons that make up the optic nerve. Decrease was reversible if exposure was less than 7 months but if it was more than a year, it could result in complete blindness. Brain Differentiation and Growth - At birth, lower (subcortical) brain centers, which control consciousness, inborn reflexes, digestion, respiration, and elimination are the most developed. - Around that area is the cerebrum and cerebral cortex, areas most implicated in bodily movements, perception, learning, thinking, and language. - First areas of cerebrum to mature are the primary motor areas (waving arms), and the primary sensory areas (vision, hearing, smelling, tasting). Myelination - As cells grow, glia begins to produce a waxy substance called myelin, which forms a sheath around neurons. Acts like an insulator to speed the transmission of neural impulses, allowing the brain to communicate better. - Myelination: The process by which neurons are enclosed in waxy myelin sheaths that will facilitate the transmission of neural impulses. - Reticular formation and frontal cortex, concentration on a subject for a long time, is not myelinated until puberty. Cerebral Lateralization - Highest brain center is the cerebrum, consists of two halves connected by a band of fibers called corpus callosum. - Each half is covered by a cerebral cortex, outer layer of gray matter that controls sensory and motor processes, perception, and intellectual functioning. - Left half controls right side of the body, and speech, hearing, verbal memory, decision- making, language processing, expression of positive emotions. - Right half controls the left side and processing visual, spatial information, nonlinguistic sounds, music, tactile (touch) sensations, and expressing negative emotions. - Brain is a lateralized organ. - Cerebral laterization involves a preference for using one hand See picture 5.6 Motor Development See table 5.1 2 - Motor development proceeds in cephalocaudal (head downward) direction  head, neck, and upper body before legs and lower body. - Motor development proceeds in proximodistal (center-outward) direction  trunk, shoulders before hands and fingers. Maturational Viewpoint - Describes motor development as the unfolding of a genetically programmed sequence of events, where the nerves and muscles mature in a downward and outward direction. - As a result, children grain more control over the lower and peripheral parts of their bodies displaying motor skills as seen in table 5.1 - Comes from cross-cultural research o Practice had little impact, infants from around the world follow same sequence Experiential (Practice) Viewpoint - Believes that opportunities to practice motor skills are also important. - Concludes that maturation is necessary but not sufficient. - Practice makes perfect Dynamical Systems Theory - Differ from earlier theorists in two ways o They do not view motor skills as genetically programmed responses that simply “unfold” as said by maturation and opportunities to practice. o Instead they view each new skill as a construction that emerges as infants actively reorganize existing motor capabilities into new and more complex action systems. o Said that visual orientation, going after something they want, motivates the infant to approach interesting stimuli. o Represents an active and intricate reorganization of several existing capabilities that is undertaken by a curious, active infant who has a particular goal in mind. Fine Motor Development - Voluntary Reaching o 3 months of age or older, infants try to grasp onto things o Good at reaching for things that can either only hear or see o 5 months, infants proficient at reaching for and touching stationary illuminated objects or glowing objects that move in the dark o Proprioceptive information: Sensory information from the muscles, tendons, and joints that help one to locate the position of one’s bod
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