Motor neurons are cells that carry information from the central nervous system to the muscles and glands, while sensory neurons send signals from body parts to the central nervous system. Sensory neurons are found over the body, such as in the skin, ears, eyes, nose and tongue. Interneurons in the central nervous system allow information to flow between motor and sensory neurons.
The cell body of a neuron holds a nucleus and organelles that carry out basic cell functions, such as protein synthesis, transporting materials and producing energy. A neuron also has special parts that allow information to move. Dendrites are branch-like structures that receive signals. The axon, which often resembles a long tail, takes messages away from the cell. The axon ends in a terminal containing a chemical called a neurotransmitter, which allows the signal to move across the space between the cell that sends information and the cell that receives it. When axons and dendrites of different cells are bunched together, they create nerves. Ganglia are groupings of many neurons' cell bodies.
The processes conducted by nerve cells happen incredibly fast, in thousandths of a second. That is why the human body reacts so quickly to stimuli in the environment. A hand touching a hot stove is removed almost immediately so that serious injury does not occur.