A neuron, also known as a nerve cell, is the fundamental unit of the brain and nervous system. Neurons are responsible for receiving sensory input from the external world, sending motor commands to our muscles, and transforming and relaying electrical signals at every step in between. They are information messengers that use electrical and chemical signals to send information between different areas of the brain, as well as between the brain, the spinal cord, and the entire body.
A neuron has three basic parts: a cell body, an axon, and a dendrite. The cell body contains the nucleus, which controls the cells activities and contains the cells genetic material. The axon looks like a long tail and sends messages from the cell, while the dendrite looks like the branch of a tree and receives messages for the cell. Neurons communicate with each other by sending chemicals, called neurotransmitters, across a tiny space called a synapse, between the axons and dendrites of nearby neurons.
There are different types of neurons, both in the brain and the spinal cord, and they are generally divided according to where they originate, where they project to, and which neurotransmitters they use. For example, sensory neurons carry information from the sense organs to the brain, while motor neurons control voluntary muscle activity and carry messages from nerve cells in the brain to the muscles.
While neurons have a lot in common with other types of cells, they are structurally and functionally unique. They have specialized projections called axons that allow them to transmit electrical and chemical signals to other cells, and they can also receive these signals via rootlike extensions known as dendrites. Neurons vary in structure, function, and genetic makeup, and there are thousands of different types.
