A neuron is a cell that is located in the brain or spinal cord. It is the "basic functional unit of the nervous system" (Encarta World English Dictionary, 2001).
There are 10 billion neurons that are interconnected in the brain. Neurons communicate with each other by using biochemical reactions. The main goal of neuron is to bring important information about the world to the brain, or to cause a change in a target cell such as a muscle or glandular cell (Lewis, 1999).
The Main Structural Components of a Neuron:.
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Each neuron is made up of three main components:.
1. a cell body which is also called a soma.
2. a nerve fiber which is called an axon .
3. a system of branches called dendrites.
The cell body contains the cell nucleus, and cytoplasm with a lot of different organelles in the cytoplasm. (Toga, 2001) Its main function is to take care of all of the maintenance functions of the neuron.
The axon carries electrical signals away from the cell body. Axons length can vary from 0.1 millimeters to a meter in length (Lewis, 1999). Most axons are covered with neurilemma cells that wrap around a part of the axon and cover it with a protective covering called myelin, which itself is made up of fats and proteins. They help protect and insulate the axon. For example, the myelin sheath stops nerve impulses from jumping from one neuron to another. It also helps nourish the axon (Lewis, 1999). Other axons that do not have this protective covering are called unmyelinated axons. They are called nodes of Ranvier, and allow impulses to travel from one neuron to another (Lewis, 1999).
Dendrites bring electrical signals to the cell body. They are shorter than axons, and are multiple with many branches. .
Overview of Neuronal Function:.
The brain functions by nerve cell circuits. The communication between neurons is both electrical and chemical. The signals travel from the dendrites - through the soma - out the axons- and then to the dendrites of another neuron.