A stem cell continuously divides to self-renew and generate daughter cells that function as replacement neurons for those that have died. Stem cells have been shown to function in the replacement of oligodendrocytes and neurons. Stem cells release growth factors that promote re-myelination of spared axons, restoration of neuronal circuitry, enhanced protection of astrocytes and oligodendrocytes that might have died. Stem cells also increase the release of beneficial chemicals from the existing nerve cells. These chemicals stimulate the growth of nerve cells, nerve axons and myelin. Stem cells increase blood vessel growth increasing blood flow. Stem cells promote bridging of cysts or cavities such as the glial scar. Stem cell release chemicals that reduce inflammation or gliosis (excessive growth of astrocytes). Stem cells stimulate local or regional stem cells and create a favorable environment for repair and regrowth of nerve function. See Figure 6.