Evolution

In the process of the evolution and with the high development of individual departments of the animal realm a clear tendency is to be determined for the concentration and thus accompanying specialization of parts of the nervous system. While with primitive animals still to some single neurons special functions are assigned (e.g. Pacesetter Neurone, which give the clock for elementary body movements of worms), perform special tasks in high-complex nervous systems up to several billions neurons in the group.

In nervous systems with central ganglia the excitation line of the Neurone in Afferenzen (from the sensors to the brain) and Efferenzen can (from the brain to the Effektoren, e.g. Muscles) to be partitioned.

Coelenterates

As most primitive nervous systems the relatively homogeneous nerve nets of sponges and Nesseltieren are considered. With Nesseltieren one finds Mark strands. See also: Coelenterates, polyp, Quallen

Flat/round worms

Flat and round worms (tapeworms, plan air, reeling worm) possess a nervous system.

With the it already comes to the training of higher processing centers in form of several nerve knots (ganglia). These ganglia are cord leader-like connected by two nerve strands, why one speaks here of a cord leader nervous system. With most of these animals the upper throat ganglion is particularly largely trained. It takes over already functions one "„brain "“, in particular the processing of sensory stimuli. The ganglia of the body segments steer frequently the movements of the leg and wing musculature as far as possible autonomously. The cord leader nervous systems lie (with exception of the upper throat ganglion) below the digesting apparatus. Therefore one speaks also of belly Marks.

See also: insects, spiders, cancers,

and vertebrate animals

The nervous systems of and vertebrate animals are particularly strongly centralized. With them a great many functions of the nervous system are central steered and muscles. One speaks therefore of a central nervous system. This consists back Marks of the brain and that.

The neural structures lying outside of the central nervous system are ranked among the peripheral nervous system. The peripheral nervous system is subdivided again into the somatic nervous system and the vegetative nervous system (also viszerales or autonomous nervous system, consisting of Sympathikus, Parasympathikus and enterischem nervous system). The vegetative nervous system is predominantly entrusted with the controlling of the activity of the bodily functions running off outside of consciousness.

Structure

Basic module of the nervous system is the nerve tissue. It consists of interlaced neurons (nerve cells), whose as Somata (or Perikarya) and their extensions are called nerve fibers (axons and dendrites).

With higher organisms the nerve tissue consists of a net of neurons and glial cells. The latters support the activity of the nerve cells, without being directly in the forwarding involved by sensory stimuli.

Related links

• http://www.bio2.rwth-aachen.de/teaching/WS99/neurows9900.html

Articles in category "Nervous system"

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