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Chapter 5

TEXTBOOK Chapter 5 - The Child's Growth: Brain, Body, Motor Skills, and Sexual Maturation

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Elizabeth Johnson

Notes From Reading C HAPTER 5: THE CHILD’S GROWTH : RAIN, BODY , MOTOR SKILLS,AND  EXUAL  M ATURATION (PGS.154­193) PART ONE: Brain Development - In prenatal period, the brain grows rapidly, and it continues to grow at an amazing pace - By the time the baby is about 6 months old, his brain weighs half of what an adult brain weighs, and the brain of an adult weighs 75% as much as an adult - Cerebrum – The two connected hemispheres of brain (largest portion of human brain) - Cerebral Cortex – The covering layer of the cerebrum that contains the cells that control specific functions, such as seeing, hearing, moving, and thinking Neurons and Synapses - Neuron – Acell in the body’s nervous system, consisting of a cell body, a long projection called an axon, and several shorter projections called dendrites o Neurons send and receive neural impulses, or messages, throughout the brain and nervous system o At birth, a baby’s brain has most of its neurons – 100-200 billion of them - Neuron Proliferation – The rapid proliferation of neurons in the developing organism’s brain o During embryonic period, neurons multiply about 250,000 neurons every minute - Glial Cell – Anerve cell that supports and protects neurons and serves to encase them in sheaths of myelin - Myelination – The process by which glial cells encase neurons in sheaths of the fatty substance myelin - Neural Migration – The movement of neurons within the brain that ensures that all brain areas have a sufficient number of neural connections - Synapse –Aspecialized site of intercellular communication where information is exchanged between nerve cells, usually by means of a chemical neurotransmitter o At these specialized junctions, the extended axon of one neuron transmits a message to the projected dendrites of another neuron - Synaptogenesis – The forming of synapses o Beings early in prenatal life; brain forms many more synapses than neurons - Neuronal Death – The death of some neurons that surround newly formed synaptic connections among other neurons - Synaptic Pruning – The brain’s disposal of the axon and dendrites of a neuron that is not often stimulated - The goal of both neuronal death and synaptic pruning are to increase the speed efficiency, and complexity of transmissions between neurons and allow room for new collections Sequential Development of the Brain - As the baby moves from mostly reflexive behaviour in the early months of life to voluntary control over movements, the motor area of the brain develops most rapidly - At about 2 months old, motor reflexes, such as rooting and the startle response, drop out, and the motor cortex begins to oversee voluntary movement, (reaching, crawling) - As a result, infants’visual capacities are greatly enhanced – more skilled at focusing on objects at different distances Hemispheric Specialization - Hemispheres – The two, left and right, halves of the brain’s cerebrum - Corpus Callosum – The band of nerve fibres that connects the two hemispheres of the brain - LEFT- AND RIGHT- BRAIN FUNCTIONS Notes From Reading CHAPTER  5: HE CHILDS GROWTH : BRAI, BODY, MOTOR SKILL,AND  EXUAL  MATURATION PGS.154­193) o Hemispheric Specialization – Differential functioning of the two cerebral hemispheres; for example, the control of speech and language by the left hemisphere and of visual-spatial processing by the right o Left hemisphere of the motor cortex controls simple movement in the right side of the body, and right hemisphere controls body’s left side o Lateralization – The process by which each half of the brain becomes specialized for the performance of certain functions o Right hemisphere processes visual-spatial information, non-speech sounds like music, and the perception of faces o Damage in right hemisphere = difficultly attending to a task requiring visual- spatial perception, their drawing skills may deteriorate, may have trouble following a map or recognizing friends or become spatially disoriented o As right hemisphere is also involved in processing emotional information, damage can cause difficultly interpreting facial expressions o The left hemisphere of the brain is associated with language processing o Damage to left hemisphere may cause trouble understanding what is being said to them or in speaking clearly themselves o If brain injury occurs in the early yeas of life, because brain is not fully developed and hemispheric specialization is not yet complete, infants and young children often recover their losses - CONSEQUENCES OF BRAIN LATERALIZATION o The degree to which a newborn’s brain is lateralized in processing speech sounds has consequences for the child’s language ability three years later o Infants whose left hemisphere differentiates among speech sounds and whose right hemisphere differentiates among non-speech sounds exhibit better language skills at age three than infants who do not show such strong lateralization o Dyslexia – Aterm for the difficulties experienced by some people in reading or learning to read o Handedness is another function that is lateralized The Brain’s Plasticity: Experience and Brain Development - Plasticity – The capacity of the brain, particularly in its developmental stages, to respond and adapt to input from the external environment - One type of experience that influences brain development is touch, patterned visual input, sounds of language, affectionate expressions from caregivers, and nutrition o Trigger synaptic development and pruning and are critical for normal brain development o When there are interference with this normal stimulation, basic abilities are impaired - The second kind of experience that influences brain development are experiences that are unique to individuals o Experiences encountered in particular families, communities, and cultures o Brain responds to different environment by developing synaptic connections that encode specific and unique experiences - Animal research shows that the size, structure, and even the biochemistry of the brain can be modified by experience - Enriched environments tend to increase the complexity of neurons as measured by the number of dendrites they development Notes From Reading CHAPTER  5: HE  CHILDS GROWTH : RAIN, BODY, MOTOR  KILLS,AND SEXUAL  MATURATION (PGS.154­193) o More dendrites means more synapses formed with other neurons, which in turn means that more information can be sent via these synaptic connections - Exposure to music can also enrich brain development o The natural harmonics of music may help the brain develop a wiring diagram that promotes spatial-temporal reasoning - Lack of stimulation or exposure to traumatic events, in contrast, can damage the brain and cause it to malfunction - Positron-Emission Tomography (PET) – shows the effects on the developing brain of early deprivation PART TWO: Motor Development Hand Skills - Newborns display a grasping reflex and a rudimentary form of reaching, “prereaching”, that involves uncoordinated “swipes” at objects that babies notice - At about 3 months of age, infants initiate a new and more complex and efficient pattern, namely, directed reaching - By 5 months old, they generally succeed in reaching in for an object and successfully grasping it - “Putting the pieces” together view involves all parts of the system that are ready to work together for infant to become competent in reaching and grasping objects o Involves muscle growth, postural control, control over the movement of arms and hands, and a variety of perceptual and motor abilities o It is consistent with the dynamic systems view of development - One component of the dynamic system is visual perception o If the infant has nothing to look at, there is no incentive to reach out o Enriching infants’could advance their abilities to attend to objects and to reach for them by hanging colourful toys over their cribs, providing them with multi- coloured sheets and bumper pads, and ensuring handled more often by caregivers - Another component involves the motor ability to grip an object o Infants vary their grip according to the size and shape of an object and the size of their own hand relative to the object’s size o They use a grip involving the thumb and index finger for small objects, but for large objects they use either all fingers of one hand or both hands Locomotion - The development of locomotion involves three phases or transitions o First: hold a baby upright and let his feet touch a flat surface, tilting his body slightly from side to side, the baby responds by reflexively moving his legs in a rhythmic stepping motion that resembles walking (disappears 2 months old) o Second: The second of the baby’s first year; the reappearance of stepping movements o Third: at about 1 year of age, infants begin to walk without support - Thelen’s dynamic systems theory suggests that walking sills are determined by the interplay of a variety of emotional, perceptual, attentional, motivational, postural and anatomical factors - As with walking, dynamic systems approach provides the best explanation of this developmental progression How Locomotion MayAffect OtherAspects of Development - One important consequence of locomotor development is increased independence Notes From Reading CHAPTER  5: HE  CHILD’ G ROWTH : RAIN, BODY, MOTOR  SKILL,AND  SEXUAL MATURATION  PGS.154­193) - Perception-Action Coupling approach suggests that motor or action systems are functionally interrelated to sensory or perceptual systems o Such that changes in one aspect influence the development of the other aspect The Role of Experience and Culture - When parents or other caretakers give babies special physical attention, including manipulation, massage, exercise, and specific practice of skills, the infants achieve motor milestones somewhat earlier than children not given such care and opportunities - Astudy suggested that infants born in the summer or fall months acquired motor skills later than infants born in the winter or spring months o Group would begin to develop locomotor skills in winter to early spring, a time when motor skills might be constrained due to more restrictive clothing, activity- reducing illnesses, and less time for free movement because of shorter days o This study examined infants who’s parents maintained home temperature P
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