Biological Psychology

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Chapter Five Development and Plasticity of the Brain 1 of 33 James W. Kalat Biological Psychology, 8th Edition Chapter 5: Development and Plasticity of the Brain
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Growth and Differentiation of the Brain CNS begins to form when embryo is two weeks old By 7 weeks the hindbrain, midbrain and forebrain are differentiated At birth, brain weighs 350g About 9 months after birth the prefrontal cortex is developed enough for child to achieve “object permanence” At end of first year brain weighs 1000 grams, close to adult weight of 1200-1400 grams 2 of 33 James W. Kalat Biological Psychology, 8th Edition Chapter 5: Development and Plasticity of the Brain
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Figure 5.3 Human brain at five stages of development. The brain already shows an adult structure at birth, although it continues to grow during the first year or so. Figure 5.3 3 of 33 James W. Kalat Biological Psychology, 8th Edition Chapter 5: Development and Plasticity of the Brain
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Growth and Development of Neurons Proliferation: cells in ventricles divide some stay as stem cells some become primitive neurons and glia that go to new destination Migration: cells follow chemical path toward final destination Gene or poison that interferes with proliferation and migration can produce mental retardation 4 of 33 James W. Kalat Biological Psychology, 8th Edition Chapter 5: Development and Plasticity of the Brain
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Growth and Development of Neurons cont. Differentiation: axons and dendrites are formed while migrating Myelination: addition of insulating sheath that speeds transmission (still forming up to 20 years of age) Synaptogenesis: formation of synapses continues throughout life 5 of 33 James W. Kalat Biological Psychology, 8th Edition Chapter 5: Development and Plasticity of the Brain
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Determinants of Neuron Survival We produce more neurons than we need, probably to be sure that there are enough for each receiving cell Survival requires two conditions must form synapse with target cell and receive a nerve growth factor (a neurotrophin) from that cell must also be stimulated to release neurotransmitters into synapse Apoptosis: programmed cell death that occurs when synapses receive little NGF Competition among neurons for survival is a selection process that has been termed neural Darwinism 6 of 33 James W. Kalat Biological Psychology, 8th Edition Chapter 5: Development and Plasticity of the Brain
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Chemical Pathfinding by Axons Axons seek specific connections Weiss (1924): axons from normal leg branched to corresponding muscles of grafted leg Sperry (1943): cut axons from optic nerve to tectum and rotated eye of newt, but axons returned to their original site (newt saw world upside down and backwards) Axons follow chemical gradients In newt, protein (TOPDV) is concentrated more in the dorsal than ventral retina, and more in the ventral than dorsal tectum axons from retina follow paths to sites on tectum with
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chapter 5 - James W. Kalat Biological Psychology, 8th...

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