Neurons and glia are cells in the nervous system and are broad categories, within which are many types of cells that differ based on their structure, chemistry and function. Neurons are the most important cells for the unique functions of the brain: they sense the changes in the environment, communicate these changes to other neurons, and command the body"s responses to these sensations. Glia (glial cells) are thought to contribute to brain function mainly by insulating, supporting, and nourishing neighboring neurons. The axon is of uniform diameter throughout its length, and if it branches, the branches generally extend at right angles. Axons can travel long distances (a meter or more); dendrites, however, rarely extend more than 2 mm in length. Cajal"s contribution: argued that the neuritis of different neurons are not continuous with one another and must communicate by contact, not continuity, this became known as the neuron doctrine and the brother won a nobel prize.