Neural network. Artwork of nerve cells (neurons, green) connected by nerve processes (dendrites and axons) to form a neural network. The dendrites are the green projections, while the axons are the purple projections, covered in an insulating material called myelin. This insulation allows electrical impulses to pass from one nerve cell to the next, using chemical transmitters to cross the synaptic gap between cells. Many nerve cells are connected together in the human body, forming networks within the brain and spinal cord, which together are called the central nervous system (CNS).