The Neuron is a fundamental unit in the brain and a specialized cell intended to transmit information to muscle, gland cells and other nerve cells. Depending on the species, the brain could contain anywhere between 1 billion and 100 billion neurons. A neuron consists of dendrites, an axon, a cell body and synaptic terminals. Axons transmit information from the neuron on to other neurons to which it is interconnected. To speed up the transmission of electrical signals along the axon, many axons are covered in a myelin sheath. Dendrites receive information transmitted by the axons of other neurons. Both axons and dendrites partake in specialized contact points called synapses.
There are 3 main kinds of neurons. Motor neurons control the activity of muscles and are in control of all forms of behavior. Sensory neurons are entwined with receptors to detect and also respond to changing attributes of the internal and external environment. For example receptors sensitive to changes in light would subserve the modality of vision, and so on. Interneurons not only arbitrate simple reflexes but are responsible for highly complex functions of the brain.