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| in the brain what are three barriers that restrain regenerative capacity | the consequences of local injury to the brain tissue often lead to neuronal cell death. 2. several other cell classes, particularly glial cells, actively inhibit the growth of axons over long distances. 3 although neural stem cells are retinaed in teh adult brain, most of these stem cells are constraine in their ability to divide, migrate, and differentiate |
| 3 types of brain repair | • A. regrowth of axons from nerve cells in peripheral ganglia or those in the central nervous system whose peripherally projecting axons are severed. restoration of damaged nerve cells in the CNS that, while injured, nevertheless survive. Wholesale genesis of new neurons to replace those that have been lost |
| The major cellular elements that contribute to peripheral axon regrowth and the reinnervation of targets | o Schwann cells, the peripheral glial cells that myelinate peripheral axons o Macrophages, immune system cells that clear the degenerating remains of severed axons o In addition to their respective roles in supporting intact axons and removing debris, both of these adult cell types secrete molecules that are essential for successful regeneration o Schwann cell plays important role in insuring the appropriate cellular and molecular milieu for regeneration following injury |
| a crushed axon | • When a peripheral axon is severed, the axon segmented distal to the site of cut degenerates. When the axon is crushed, however, more rapid recovery occurs bc the damaged distal segments provide a helpful guide to regenerating proximal axons |
| a severed axon | • In the case of a completely severed axon, only Schwann cells in the distal stump of the nerve and the basal lamina components secreted by the Schwann cell are available to stimulate and guide regeneration |
| importance of Schwann cells in regeneration | 1. increase the amount of cell adhesion molecules on their surface in response to axon injury: 2. • Schwann cells near the injury increase expression and secretion of number of neurotrophins which acts both to promote growth state as well as defining a local target distal to the site of damage to grow toward: the cells and the milieu they create are the dominant factors in promoting peripheral axon regeneration. |
| 3 ways damage to CNS | 1. trauma to brain or spinal cord. 2. Hypoxia-lack of oxygen. 3. Neurodegenrative diseases |
| new nerve cells in the CNS are seen reliably in these 2 regions | 1. olfactory bulb 2. hippocampus |
| in the CNS new nerve cells are primarily... | internuerons |
