Brain, spinal cord, meninges
English: CNS, Central Nervous System
The CNS (Central Nervous System) consists of the brain (cerebrum, encephalon) and the spinal cord (medulla spinalisIn its entirety, it is probably the most complex organ known to man.
It contains more than 100,000,000,000 (100 billion) nerve cells (Neurons) and at least twice as many special connective tissue cells (Glia).
This enormous number of cells communicate with each other in a wide variety of ways in order to guarantee the organism to cope with its complex way of life.
As an overall product, amazing capabilities such as:
Precise is also of the utmost practical importance Movement coordination of the body (Motor skills) and the associated recognition of one's own body (sensitivity) in a constantly changing environment, which is captured by sensory impressions.
All of this ultimately still requires the regulation of all body functions to maintain our internal conditions (Homeostasis).
So far, no machine has succeeded in imitating the aforementioned services that we take for granted.
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When one speaks of the fact that nerve cells communicate with one another, this essentially happens through the release of chemical messengers (transmitters, Neurotransmitters) near another Nerve cell (Neuron).
The process is similar to a simple conversation between two people. One pours out words that the other processes. Such a small functional unit is called a synapse. Most neurons have thousands of them Information interfaces (synapses) per se!
So the incoming information (Affinity) mostly on tree-like protuberances of the nerve cell (Dendrites) offset and by a leading away cell extension (Axon) to the efference!
Within a single nerve cell, the information is not transmitted through a transmitter, but rather electrically via a Current flow forwarded (Action potential).
A nerve cell has many dendrites, which act as a kind of connecting cable to other nerve cells in order to communicate with them.
Basically one differentiates in the CNS one gray tissue substance (Substantia grisea) from one white tissue substance (stoffia alba).
This classification relates to which part of the nerve cells in which part of the body you are looking at.
They are in the gray matter Nerve cell body (Perikaryen, Soma), a seemingly confused mass of nerve processes (Neuropil) and above all astrocytes (connective tissue cells), which belong to the so-called glial cells.
The appendages of the annoy (Connecting lines) are often not encased in the gray matter by oligodendrocytes with their cell extensions and thus not myelenized (see Myelenization, nerve sheaths), that means they don't have a nerve sheath.
In contrast, the white matter bundles of nerve cell fibers (Connecting lines), which usually are myelenized by oligodendrocytes, i.e. have a cervical sheath.
This is how the white substance got its name: the myelin sheath contains a lot of fats, so that it shimmers whitish and contrasts with the surrounding tissue.
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The CNS is in the head area by the skull bones and on the back by the Vertebral bodies protected, which form a vertebral canal inside.
It is placed in the so-called "Peripheral nervous system ” away, which emerges with its more or less long nerve fibers from the bony sheaths of the CNS. Both systems are functionally inseparable; the division is made for reasons of clarity.
The brain and spinal cord can in turn be broken down into numerous subunits:
the brain contains:
The gray matter is in the brain, i.a. The cell bodies (perikaryen) of the nerve cells, both in the cortex and in the underlying (subcortical) core areas. The subcortical nuclei form a medullary bed, which is embedded in white matter.
The spinal cord extends from the occiput to the 1st or 2nd lumbar vertebrae and experiences different characteristics during the passage in the spinal canal.
In cross-section, it reveals its internal structure: gray matter in the center, the shape of which is reminiscent of a butterfly. This is surrounded at the front, back and sides by several bundles of white matter, which, depending on their location, are referred to as the front strand (funiculus anterior), side strand (funiculus lateralis) and rear strand (funiculus posterior).
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It is characteristic of the CNS (central nervous system) that each section has cavities (inner and outer liquor spaces on the brain, only one channel in the spinal cord), which are filled with a water-clear, colorless liquid (liquor cerebrospinalis, "nerve water"):
The liquor (nerve water) is a well-controlled filtrate from the cells of the choroid plexus (singular plexus choroideus) with several functions:
Upholstery by significantly lowering the effective weight of the brain and cushioning vibrations like a pillow.
The brain and spinal cord swim in water (liquor = brain water) and are thus well protected against impacts.
Communication between nerve cells and in the sense of informing the nerve cells about the composition of the blood as well as the control of the environment (extracellular fluid) of nerve cells and glial cells are also part of the tasks of the CSF (Nerve water).
