What are neurons?
What is the brain made of?The bulk of the brain is made up of structural cells termed glial cells and astrocytes. Lying in amongst these cells are neurons, specialized cells that conduct electrical impulses along their processes. It has been estimated that the average human brain contains about 100 billion neurons and, on average, each neuron is connected to 1000 other neurons. This results in the generation of vast and complex neural networks that are the mainstay of the brain's processing capabilities.
What is a neuron?Neurons are the basic data processing units, the 'chips', of the brain. Each neuron receives electrical inputs from about 1000 other neurons. Impulses arriving simultaneously are added together and, if sufficiently strong, lead to the generation of an electrical discharge, known as an action potential (a 'nerve impulse'). The action potential then forms the input to the next neuron in the network.
What do neurons look like?Well, to begin with, you can't see them without the aid of a microscope! But when you do get to see them, you see that they have a very specialized structure. They have a cell body or soma and fine processes that run from it. These processes are split into two types - dendrites are the highly branched processes that carry the incoming information, in the form of electrical impulses, to the soma; the action potential leaves via the axon. Axons can be very short (if the communicating cells are very close together) or very long (if the two cells are in different parts of the brain or even the body!!). They can also be highly branched, so neurons not only receive information from many neurons, they pass the result of the processing to many other neurons, forming the dense neural networks that are such a feature of the brain.
Axons are usually surrounded by a fatty substance called myelin. Myelin allows action potentials to propagate quickly from one neuron to another, allowing for rapid signal transmission. It is a critical part of the nervous system and it's absence has devastating effects, as seen in conditions such as multiple sclerosis.