Structure of the nervous system
Synonyms
Brain, CNS, nerves, nerve fibers
English: nervous system
Fine tissue structure (histology)
The nervous system consists primarily of nerve tissue. This includes the nerve cells or ganglion cells (= neurons; these are the most essential part of the nerve tissue; this is where the nervous excitation, the action potential, arises), the nerve fibers (which transmit this excitation) and the neuroglia (= glial cells. These are directly related to the nervous processes nothing to do, but mainly have supportive, nourishing and isolating functions).
With the naked eye (= macroscopically) one can see the nerve tissue in the gray matter (Substantia grisea) and the white matter (Substantia alba) subdivide. The gray matter consists as a rule of nerve cell bodies, which appear darker, while the white matter appears white because it mainly contains the fatty myelin: this is what they consist of Medullary sheathswho have favourited the nerve cell fibers that Axons, envelop.
In the brain (Cerebrum and cerebellum) the gray matter lies on the outside and forms the Cerebral cortex (cortex) while the white matter is inside. Only single clusters of nerve cells, so-called Core areas, still form individual islands of gray matter in the middle of this fiber network. In the spinal cord, on the other hand, the medullary nerve fibers and thus the white matter are on the outside, while the gray matter is on the inside and surrounds the central canal.
structure
The nervous system is divided into two main departments:
- the cerebrospinal nervous system and
- the autonomic nervous system.
The cerebrospinal nervous system is named after its two central organs:
- the brain (= Latin cerebrum) and
- the spinal cord (= Latin medulla spinalis).
It regulates our relationships with the environment (“environmental nervous system”) and comes into contact with the “outside” by absorbing stimuli from this environment, processing them and reacting to them appropriately. It is also called the somatic nervous system (soma = body) and is usually subject to arbitrariness: we initiate a movement, e.g. raising an arm, fighting or running away when danger is detected, or communication.
The cerebrospinal nervous system can in turn be divided into a central and a peripheral nervous system. However, both are part of a coherent system, a functional unit.
The central nervous system (CNS) consists of the central organs brain and spinal cord and resembles a "switchgear", while the peripheral nervous system (PNS) contains the entirety of all cerebral and spinal cord nerves with the ganglia (nerve cell collections), i.e. in principle everything from and to the center leading line cables with all their branches and ramifications, and thus resembles a "tail unit".
The autonomic nervous system controls and regulates the activity of our internal organs and glands and sensibly coordinates all vital and mostly unconscious processes, e.g. the regulation of:
- Digestion of food
- breathing or
- of reproduction
(= vegetative functions; therefore the autonomous nervous system is also called vegetative nervous system).
This nervous system is autonomous because these processes are beyond our arbitrary control and are subject to their own laws - they work e.g. even when unconscious.
The autonomic nervous system consists of three functional parts: the sympathetic and the parasympathetic, which oppose each other, and the intramural system (intestinal nerve plexus).
The cerebrospinal and autonomic nervous systems do not function independently of each other, but are linked to form a meaningful unit.
The story of the wild animal that terrifies Stone Age people may serve as an example: the cerebrospinal nervous system recognizes the danger (the eyes see the wild animal, the brain evaluates it as larger and stronger and the situation as potentially life-threatening), whereupon the autonomic nervous system immediately all bodily functions that are necessary for survival start: the pupils dilate, the muscles are better supplied with blood, the blood pressure, the breathing and the heart rate increase, while the digestive functions are reduced (dry mouth). The Stone Age man can now fight or flee ("fight-or-flight reaction").
Today we rarely face wild animals, but stressful or fear-inducing situations still cause the same physical reactions: the near-traffic accident, the lecture in front of the assembled team.
