9.2

• The inside of the neural tube eventually becomes the cerebral ventricles and spinal canal.
• Once the lips of the neural groove have fused to create the neural tube, the cells of the tube begin to increase greatly in number. This is what we call the

  Neural Proliferation
• True or False: This neural proliferation occur simultaneously or equally in all parts of the neural tube.

  False, in each species, the cells in different parts of the neural tube proliferate in a particular sequence that is responsible for the pattern of swelling and folding that gives the brain of each member of that species its characteristic shape.
• The complex pattern of proliferation is in part controlled by chemical signals from two organizer areas in the neural tube:

  Floor Plate and Roof Plate
• This organizer area runs along the midline of the ventral surface of the tube.

  Floor Plate
• This organizer area runs along the midline of the dorsal surface of the tube.

  Roof Plate
• The stem cells created in the developing neural tube are virtually always radial glial cells.
• Cells whose cell bodies lie either in the ventricular zone or subventricular zone and have a long process that extends to the outermost part of the developing neural tube.

  Radial Glial Cells
• This play a key role in cell migration during development.

  Radial Glial Cells
• Once cells have been created through cell division in the ventricular zone of the neural tube, they migrate to the appropriate target location. This happens through a process called the _________.

  Neural Migration
• Two major factors govern migration in the developing neural tube: time and location.
• True or False: In a given region of the tube, subtypes of neurons arise on a precise and predictable schedule and then migrate together to particular destinations.

  True
• Cell migration in the developing neural tube is considered to be of two kinds:

  Radial migration and Tangential Migration
• Radial migration proceeds from the ventricular zone in a straight line outward toward the outer wall of the tube.
• Tangential migration occurs at a right angle to radial migration—that is, parallel to the tube’s walls.
• True or False: The only way cells get from their point of origin in the ventricular zone to their target destination is through Radial Migration.

  False, Radial and Tangential Migration are used by cells to migrate to their target destination.
• Two mechanisms by which developing cells migrate

  somal translocation and radial-glia-mediated migration
• In somal translocation, the developing cell has a process that extends from its cell body that seems to explore the immediate environment.
• Somal translocation allows a cell to migrate in either a radial or tangential fashion.
• In radial-glia-mediated migration, the developing cell uses the long process that extends from each radial-glia cell as a sort of rope along which it pulls itself up and away from the ventricular zone. It allows a cell to migrate in only a radial fashion.