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The nervous system is the communication network of humans and other animals that conveys information through a group of specialized cells. Using this network, an animal's actions are both intentional and autonomous in response to stimulus from the outside world. The various parts of the nervous system are divided into a peripheral portion and a central portion.
Outside and inside stimuli are identified by the peripheral nervous system and translated through impulses that travel along neurons and connect with the central nervous system. In response to this information, the central nervous system processes signals and sends them to glands and muscles throughout the body. This system is strongly interconnected and complex. Various electrochemicals and neurotransmitters enable neurons to transfer information to one another. This interaction of the nervous system is the primary reason for an animal to maintain a specific perception, and the ability to remain interactive with the world. These systems vary greatly in complexity between species.
Above Right: Nervous System (Provided by Persian Poet Girl at Wikimedia Commons; Public Domain; http://en.wikipedia.org/wiki/File:Nervous_system_diagram.png)
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Central Nervous System
The largest part of the nervous system is the central nervous system. This portion is comprised of the brain and spinal cord. The brain is divided into two main sections: the prosencephalon and the brain stem.
The prosencephalon is the main portion of the brain, responsible for maintaining body temperature, reproduction, sleeping, eating and emotional displays. In humans and other advanced animals, it is also the portion of brain that is responsible for higher cognitive functions.
The brain stem is responsible for passing information from the prosencephalon to the spinal cord and the rest of the body. It also controls motor function, sensations such as pain and temperature and regulates the respiratory and cardiac systems. Along with the brain, this is protected by the skull and a number of membranes.
The spinal cord is a bundle of nerve tissues that runs along the spine of vertebrates. It is protected by a series of bones that form a long column. Its primary job is to act as a relay center for neurological signals, however it is capable of a variety of autonomic responses such as reflexes.
Above: Central Nervous System (Provided by Grm wnr at Wikimedia Commons; Public Domain; http://en.wikipedia.org/wiki/File:Central_nervous_system.svg)
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How Do Nerve Cells Work?
Nerve cells are the basic functioning component in the nervous system. Every part of the system, whether peripheral or central, is comprised of neurons that collect and distribute information to make the body function. Different types of nerve cells exist that respond to light, sound, touch and other stimuli.
The basic structure of a neuron helps it to perform its function. Signals propagated by chemical ions distribute an electrical charge that proceeds from neuron to neuron, passing information. The nucleus is surrounded by the dendrite, which receives signals from other neurons or cells. This electrical charge is then transferred through the cell body called the soma and onto the axon. The axon is long thin part of the neuron covered by myelin sheath. This information then reaches the axon terminal and again transfers the electrical charge to another cell.
Right: Neuron Structure (Provided by Selket at Wikimedia Commons; GNU Free Documentation License; http://en.wikipedia.org/wiki/File:Neuron-no_labels.png)
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