The basic buildings blocks of the nervous system. The nerve cells are linked together in circuits. Three main parts: a cell body, dendrites, and an axon. Contains the biochemical structures needed to keep the neuron alive. Its nucleus carries the genetic information that determines how the cell develops and functions. Where incoming information from the dendrites is processed. The surface has receptors areas that can be directly stimulated by other neurons. Specialized receiving units that are like antennas that collect messages from neighboring neurons and send them onto the cell body. Conducts electrical impulses away from the cell body to other neurons, muscles, or glands. Absorb toxins and waste materials that might damage neurons. Prevents many substances, including many toxins, from entering the brain. The cell membrane is semi-permeable: allowing only certain substances to pass through ion channels into the cell while refusing or limiting passage to other substance.