In most tissues of the body, cells found in a particular type of tissue are relatively uniform in structure. Muscle cells in your neck and leg are similar, and muscle cells are similar across species. Neurons, on the other hand are highly diverse, even within a single neural structure. Neurons are diverse, even within a single anatomical structure Cajal's drawing of a frog's retina illustrates the many kinds of neurons found in this structure. The synapse Synapses are specialized sites for communication between neurons, where cell membranes come into close proximity or contact.
All nervous systems contain glial cells.