brain, CNS, nerves, nerve fibers
The nervous system is a superordinate switching and communication system present in all more complex living beings. The nervous system is used in a simplified way to integrate and coordinate information for an organism:
- The absorption of stimuli (information) that affect the body from the environment or arise in the body itself (e.g. pain, sensory impressions…)
- The transformation of these stimuli into nervous excitations (nerve impulses, so-called action potentials), their transmission and processing
- The sending of nervous excitations or impulses to the organs, muscles etc. (i.e. to the periphery) of the body.
For each of these subtasks there are special facilities in the nervous system: This functional division of the nervous system into three parts – stimulus reception, stimulus processing and reaction to stimuli – also corresponds to its spatial structure: A single component in the nervous system is called a conduction arc.
A conduction arc is the meaningful functional connection of two or more neurons (= nerve cells with their extensions).
- For the absorption of information, certain recording or receiving apparatuses, the receptors in the nervous system, are responsible. Like the sensory organs (e.g. ears, nose, eyes, etc.
), they are restricted to certain parts of the body and are specialized for certain stimuli, e.g. light or sound waves (see e.g. the topic of vision). They are particularly numerous in the skin for the absorption of tactile, vibration or temperature sensations, but also on the other organs (think of stomach or headaches).
- All information (nervous excitation) generated in these receiving apparatuses flows through afferent nerves to the central collecting points, the brain and the spinal cord, also known as the central nervous system (CNS).
There they are collected, processed and meaningfully linked to each other so that these two central organs can be understood as THE superior control center of all events in our body.
- The results of this central processing in the nervous system and the connection of nerve impulses are now sent by leading (or efferent) nerves as information to the organs (usually called periphery) of the body. There they cause corresponding reactions, such as movement (when the impulses lead to the muscles), expansion or contraction of vessels (e.g. pale with fright) or an influence on glandular activity (e.g. when we look at food or think of a lemon, the water in our mouths runs together because the salivary glands are activated).
In relation to a simple reflex, for example the patellar tendon reflex, this means: perception of the stimulus (extension stimulus on the tendon) connection to the corresponding muscle execution of the movement (leg extension). Often many of these “cables” are tied together and run through the body as one nerve. However, it is not possible to tell from a nerve which part carries the incoming and which carries the outgoing information from the brain.