The Central Nervous System
The human brain consists of two types of cells: roughly 100 billion neurons and a greater number of glia. Neurons are highly specialized cells that have an important and unique functional property that is not shared with any other cells in the body. Neurons communicate with each other through both electrical and chemical mechanisms. More importantly for the theme of this book, neurons communicate through circuits, and these circuits form the structural bases of feelings, thoughts, and behavior, the ultimate functional output of the brain.