The Three Types of Neurons

Did you know that there are actually three types of neurons - each corresponding to the three major functions of the nervous system? These major functions are sensory input, integration and motor output. What's the difference?

The sensory input is carried out by sensory (afferent) neurons that detect a stimuli. Signals are then sent to the brain and spinal cord to be processed in the second stage known as integration. Integration is carried out by interneurons in the brain and spinal cord that interpret the messages from sensory neurons. After processing the input, interneurons relay the message to body parts, where a response is produced at the effector organ in the third and final stage known as the motor output. The motor output is carried out by motor (efferent) neurons that receive messages from interneurons and then activate certain body parts to respond to the stimuli.

Afferent? Efferent? They sound so similar! A trick to remember the difference between the two is to look at the first letters: "a" and "e". "A" comes before "e" in the alphabet, and the sensory input occurs before the motor output. This way, you know that "afferent" corresponds to sensory neurons, and "efferent" corresponds to motor neurons.

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