The tectal neuropil contains structures including periventricular neurons axons and dendrites. The optic nerve is composed of retinal ganglion cell axons and glial cells. In the peripheral nervous system axons are myelinated by glial cells known as Schwann cells. Neurons do not immediately form neural circuits through the growth of axons and dendrites. The axons and dendrites of these interneurons stay within the striatum. These transmit axons of upper motor neurons. Both axons and dendrites are highly branched. Actin is predominately found at the tips of axons and dendrites during neuronal development. There are different internal structural characteristics between axons and dendrites. How do axons and dendrites form during development? These neurons are amacrine cells, meaning that they have no axons. In vertebrates, not all axons are myelinated. The project name comes from myelin, an electrically insulating layer that surrounds neurons' axons. This differentiates the CNS from the PNS, which consists of neurons, axons, and Schwann cells. Larger diameter axons and more myelin insulation lead to faster signal propagation.