What Is a Neuron?
A neuron is a highly specialized cell which is capable of conducting information in the form of neurotransmitters, chemical signals which can trigger a variety of activities or responses. These cells operate in a binary fashion: they are either on or off, depending on which neurotransmitters they have received. Neurons make up the building block of the nervous system, including the brain, spinal cord, and individual nerves of the body. There are several different types of neurons designed for specific activities, ranging from the cells which cluster together to make the gray matter of the brain to the motor neurons at the tip of the toes.
Every neuron has a cell body, known as the soma, which contains a number of organelles, along with dendrites, extensions which can receive information as it is transmitted to the neuron. Type I neurons also have an axon, a long tail which can emit neurotransmitters when the neuron is excited, while Type II neurons lack this feature, or have significantly shorter axons. The axon and dendrites may emerge from opposite ends of the cell body, or the same end, depending on the type of neuron and its location.
The three main kinds of neurons are: motor neurons, sensory neurons, and interneurons. A motor neuron carries data from the central nervous system to the rest of the body, while sensory neurons return sensory data along an afferent pathway, meaning that they move information towards the brain. Interneurons can allow motor and sensory neurons to communicate directly.
Within these basic categories, neurons can also be classified by shape and function. Some examples of specific types of neurons include: pyramidal, basket, anterior horn, medium spiny, granule, and Renshaw cells. These neurons can be found in various parts of the nervous system, performing different functions, from regulating breathing and other autonomic tasks to interpreting visual information. When someone reads, for example, sensory neurons in several areas of the brain fire as the brain interprets the visual image, deciphers the writing, and converts the written words into understandable language.
Somewhat unusually, neurons do not divide and replicate themselves like other cells of the body do. Neurons in the brain cannot replace or repair themselves when they are damaged, although the brain can sometimes remap itself to accommodate damage and function normally. Some neurons, such as those found in the arms, can regrow parts of themselves, which is why a severe injury sometimes causes a loss of sensation which slowly returns over time as the nerves recover.
Written by S.E. Smith
