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Psychology 304: Brain and Behaviour Lecture 19 1 The Development of the Nervous System 1. What are the phases of prenatal neurodevelopment? 2 By the end of today’s class, you should be able to: 1. discuss the process of prenatal development of the nervous system and other bodily organs. 2. describe the directions and mechanisms associated with cell migration. 3. explain how cells differentiate into region-specific neurons and glial cells. 3 What are the phases of prenatal neurodevelopment? • Prenatal neurodevelopment is marked by a number of discrete phases: 4 1. Development of the neural plate and neurogenesis. Shortly after conception, the embryo shows three cell layers: The ectoderm, mesoderm, and endoderm. The nervous system develops from the neural plate, which is evident 3 weeks after conception. 5 Develops into the PNS. Formation of Neural Tube 6 Electron Micrograph of Neural Tube Closure 7 Electron Micrograph of Neural Tube Closure 8 Neural Tube 9 Embryonic Neural Tube Development 10 Once formed, the cells that line the inner surface of the neural tube—that is, the ventricular zone—divide and proliferate. The anterior end of the neural tube ultimately develops into the forebrain, midbrain, and hindbrain. The posterior end of the neural tube ultimately develops into spinal cord. 11 Forebrain Midbrain Hindbrain Spinal cord CNS Development from the Neural Tube 12 2. Cell migration Once cells have developed in the ventricular zone, they migrate to target locations. Migration occurs in two directions: radial migration and tangential migration. 13 Directions of Migration 14 Cells migrate via two mechanisms: somal translocation and glia-mediated migration. Cell migration is guided be cell-adhesion molecules. 15 Processes of Migration 16 Glial-Mediated Migration 17 3. Cell differentiation Once cells have reached their target locations, they differentiate into region-specific neurons and glial cells. Cell differentiation is determined by genetic programs and cell-cell interactions (i.e., induction). 18 The Development of the Nervous System 1. What are the phases of prenatal neurodevelopment? 19