CHAPTER 13.docx

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Janelle Leboutillier

CHAPTER 13 NEURAL DEVELOPMENT Early DevelopmentNeural plate forms from the ectoderm of embryoa patch of cells on the dorsal surface of embryowhich eventually becomes the nervous systemCells of the dorsal ectoderm in the neural plate are stem cells that are pluripotent have the potential to develop into different types of nervous system cellsThe neural plate starts to form a groove which fuses to form the neural tubeDifferent sections of neural tube become different parts of nervous system with the interior surface becoming the ventricles and the central canal of spinal cordTelencephalon develops from the cortical plateAs migration occurs from the inside out the deepest layer of neurons develop firstAlthough development of axons and dendrites occurs both prenatally and postnatally cell differentiation is essentially complete at birthProblems with any phase of development can lead to significant abnormalities in the CNSComplete failure of the closure of the neural tube is fatal resulting in a condition known as cranioachischisis characterized by the CNS appearing as a groove in the top of the head and bodyhowever is rareAnencephaly partial closure of the rostral neural tube and is characterized by a general absence of the cerebral hemispheresSpina Bifida partial closure of neural tube posterior results in neurological difficulties that are associated with locomotion rather than cognitive difficultieseffects spinal cordNeurons undergo a long period of synaptogenesis and dendritic branching producing far more synapses and dendrites than are needed in the adult brainDendritic branching occurs slowlyit is on the dendritic spines that most synapses occurSynaptogenesis or synapse formation is relatively sparse and occurs relatively independent of experienceshortly after birth to about 2 years undergoes a period of rapid growthfollowed by synapse reduction Prenatal DevelopmentPrenatalenvironment can have significant effects on CNSPlastic change the ability of the CNS to alter itself in response to environmental stimuliCritical Periods of plastic change in which the environment can have a maximal effect on the CNSDuration and timing of these critical periods vary by specieslonger lived animals ie humans have a prolonged critical period that often occurs later in lifePlasticity during critical periods occurs in response to specific experiences can be referred to as either a Experience expectant plastic changesThose CNS changes that are dependent on experiences during the critical period for specific synapses to develop as they should ie sensory cortex has theseif an organism doe not experience sensory stimulation during the critical period longlasting impairments in the sensory modality occur
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