Review Questions

1. What cell processes determine the number of cells in an organ?
2. What is the main function of oligodendrocytes?
3. What makes the optic nerve one of the simplest parts of the central nervous system?
4. What determines the final number of oligodendrocytes in the optic nerve?
5. What is the evidence that OPCs and oligodendrocytes need signals from other cells in order to avoid apoptosis?
6. What might be the advantage for animals to have such a ‘death by default’ mechanism, whereby their cells need constant signaling from other cells to avoid apoptosis?
7. Most cells in your body develop from precursor cells that divide a limited number of times before they stop dividing and differentiate into specialized cells, which usually do not divide again. How does this apply to oligodendrocyte development?
8. Some OPCs in the developing optic nerve divide more than other OPCs in the same nerve?
9. What is the most likely explanation for these differences?
10. What is the evidence for this explanation?
11. What is the function of p27, and what is the evidence that it is part of the cell-intrinsic timer that helps determine when OPCs stop dividing and differentiate?