Neurons: Cells Of The Nervous System

Neurons are the elements of the nervous system that send signals in order to communicate information throughout the body.

Neurons, or nerve cells, constitute the nervous system and are the structures that allow the nervous system to communicate with the body. For example, when sensory information is received externally, information is sent to the nervous system via neurons. However, neurons do more than send sensory signals. They are also involved in controlling muscles and, storing and recalling memories in the brain. In fact, neurons control all behavioral responses and changes in physiological processes that happen internally.

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There are several components that make-up the structure of a neuron. These include the cell membrane, cell body and the nucleus. It also consists of a cytoplasm, dendrites and an axon.

The Cell Membrane, Cell Body and Nucleus of a Neuron

The cell membrane is an external barrier that protects the body of the cell. Proteins such as ion channels are located within a double lipid layer located in the membrane and it is these ion channels that allow ions to move in and out of the neuron. The flow of ions in and out of the neuron determines whether a neuron will fire or send a signal.

The cell body of a neuron can also be called a soma or perikaryon. It consists of a cytoplasm that is protected by the cell membrane. It also contains a nucleus, the contents of which are protected by a nuclear membrane that contains tiny pores which substances move through. The material of the nucleus is called chromatin and within it is a nucleolus. The cell body controls for a neurons metabolic activity, and is where phospholipids, proteins and macromolecules are synthesized.

Dendrites and Their Function

Dendrites have a tree-like appearance and are attached to the cell body of a neuron. The primary function of dendrites is to receive signals from other neurons. Once this information is received, signals are sent down the branches, to the cell body.

Signals received by dendrites come from the axonal structures that they are synapsed with. As such, dendrites function to increase the surface area for receiving such signals.

What is an Axon?

An axon is a long, single structure that has a branch-like ending. It is also attached to the cell body and is the nerve fiber that carries signals away from the cell body towards the dendrites of other neurons. This transmission of signal is the way in which neurons communicate with one another and is called an action potential. During an action potential, the electrical charge of the axon changes, causing it to fire. When the axon fires, terminal buttons located on the ends of the branches release a chemical substance which either excites or inhibits the neuron receiving the signal.

References
Carlson, N. & Buskist, W. Psychology: The Science of Behavior. 5th Ed. Allyn & Bacon, MA
Siegal, A & Sapru, H. Essential Neuroscience. 2nd Ed. Lippincott Williams & Wilkins, MD.