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Central Nervous System

German: Zentralnervensystem

1 Definition

The central nervous system (CNS) of the human body comprises all nerval structures of the brain and the spinal cord that account for the central processing of external stimuli, meaning the integration and coordination of sensory information that is received from the periphery.

In addition, voluntary motor function is initiated in the CNS that makes direct reactions on environmental conditions possible. It is also responsible for all cognitive functions.

The CNS is topographically distinguished from the peripheral nervous system (PNS).

2 Background

The discrimination between CNS and PNS is purely based on a topographic difference. Functionally they do not work as independent systems. The cell bodies of motor neurons for example belong to the CNS while the axons are assigned to the PNS. Contrarily, the cell bodies of sensory neurons are frequently located within the PNS, extending their nerve fibres into the CNS.

3 Classification

Based on its macroscopic appearance the tissue of the CNS is roughly divided into two matters:

  • white matter (Substantia alba) and
  • gray matter (Substantia grisea)

The grey matter of the brain is located outside but lies central within the spinal cord. It predominantly consists of the cell bodies (somata) of neurons. In contrast, the white matter mainly consists of nerve fibres (axons) that form cords between adjacent nerve cells. However, within the white matter there are also insular clusters of cell bodies, the so called ‘nuclei’.

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