Nervous system

From ArticleWorld

The nervous system is a complex ensemble, involving biological components like nerves and neurons. It coordinates the activity of the muscles, monitors the working of the organs, constructs and processes input from sensors and initiates actions. In higher-evolved organisms, it can conduct thoughts or emotions, while only dealing with stimuli and actions in the case of less evolved animals that have no brains.

The nervous systems of vertebrates

The nervous systems of vertebrates are generally divided into a CNS (central nervous system) and a PNS (peripheral nervous system). The central nervous system includes the brain and the spinal cord, while the peripheral nervous system includes the rest of the neurons and nerves that are not included in the CNS. In fact, most nerves are part of the peripheral nervous system.

The peripheral nervous system is also divided in two components: a somatic component and an autonomic component. The somatic component coordinates body movement and receives external stimuli. The autonomic component is the involuntary part of the nervous system, handling internal maintenance of the organism.

The autonomic component has three parts. The sympathetic part deals with responding to danger, stress and difficult situations. It is responsible for creating the state of alertness associated with such situations, by triggering various physiological changes (like accelerating heartbeat by releasing adrenaline into the blood). The parasympathetic deals with relaxing situations, by triggering various physiological changes as well (for example, decelerating heartbeat or dilating the pupils). There is also an enteric, but its function is still subject to scientific research. The enteric part has many interactions with the other parts of the autonomic components.

Metabolism

The cells of the nervous system can't metabolize proteins for energy, mainly because of the functions they need to perform. This is why they generally rely on carbohydrates as energy source. When carbohydrates are not available, they rely on the body's ability to use fat as energy source.