How The Human Nervous System Works
The Nervous System
The nervous system is a network of specialized cells and tissues which is present in all animals consisting of several cells (multicellular) to a greater or lesser degree, but with the exception of sponges. The operation of the nervous system and its activity consists of electrical impulses which are caused by the movement of chemical ions, or in other words, those chemical ions are potassium and sodium.
The nervous system includes receptors, and these receive information from the surrounding environment and are called sensory. These are concerned and related with the senses such as sound, sight, touch and pressure and they transmit the information which they detect along nerves called the sensory nerves, and these travel to the central nervous system. If you refer to the image above: number 1 is the brain, 2 is the central nervous nervous system (the brain and the spinal cord), and the 3 is the spinal cord.
In the simpler animals such as invertebrates (having no spinal column), this often consists of a paired nerve cord with swellings along its length called ganglia (ganglion). In vertebrates (having a backbone or spinal column), the central nervous system is very complex and consists of the brain and spinal cord.
Within the central nervous system all the information is decoded and, if appropriate, a response is initiated. This often consists of a signal being sent outwards along a nerve which is called a motor nerve, which travels to a muscle causing a contraction to occur. In vertebrate animals, a part of the nervous system is concerned with the control of the involuntary or smooth muscle of the body. This is called the autonomic nervous system (ANS) and consists of two divisions, the sympathetic and parasympathetic which act in opposite ways, known as antagonistic.
It is sometimes called involuntary or the visceral nervous system because its activity regulates the internal environment of the body and it supplies the smooth muscle such as the heart and gut and other muscles for example, and glands with their motor nerve supply.
Diagram of the Nerve Cells
Basic explanation of the nerves
A nerve is made up of several nerve cells also known as neurons or can be spelled as neurones. SO basically some nerves are sensory, others are motor and yet others are mixed carrying both types of nerve cells (neurons). Each neuron has a cell body, containing the nucleus, and many fine projections called dendrites. Dendrites from surrounding neurons are able to communicate with one another across a gap called a synapse. A long, fine projection runs out from the neuron cell body and this is called an axon (please refer to the diagram for all the scientific terms). It may be surrounded by a fatty sheath called a myelin sheath which is restricted at intervals at sites which are known as nodes of Ranvier.