Synonyms in a broader sense
Parasympathetic nervous system, sympathetic nervous system, nervous system, brain, nerve water, spinal cord, nerveThe parasympathetic nervous system is responsible, in addition to the sympathetic nervous system, for part of the autonomic nervous system and for physical activity under resting conditions. Consequently, the sympathetic nervous system is characterized as the active part of the autonomic nervous system. Organ | Effect Heart | Slower and less vigorous beating (Decreased heart rate and contraction force) Lungs | Narrowing of the airways Eye | Narrowing of the pupils Salivary glands | Increased salivary secretion Gastrointestinal tract | Increased digestive activity (increased motility) Liver | Increased glycogen production Urinary bladder | Promotion of urination and urinationThe task of the parasympathetic nervous system, which is ultimately achieved at the organ, must be generated in “encrypted” form by the original cell and then directed along the cell processes to the organs.
The electrical stimuli are transmitted via so-called neurotransmitters. Neurotransmitters are chemical messengers which – as the name suggests – can transmit information to different places, they are therefore a kind of “messenger”. A distinction is made between excitatory (excitatory) and inhibitory (inhibiting) neurotransmitters.
The neurotransmitters are used for chemical information transmission, while the electrical potentials that run through the cell and its extensions (axons and dendrites) are used for electrical information transmission. The chemical transmission of information is always important when the information is to pass from one cell to another, because there is always a gap between cells, even if it is relatively small, which the information cannot simply skip. However, since the human body is large, it needs a whole network of cells, because one cell cannot span our entire organism (although there are nerve cells whose extensions can grow to a length of up to one meter).
Once the electrical line has reached the “end” of a cell, i.e. its axon end, it ensures that a type of neurotransmitter is released from the axon end. The axon end from which it is released is called the presynapse (pre = before, i.e. the synapse before the synaptic cleft). The neurotransmitter is released into the so-called synaptic cleft, which is located between cell 1 (information line) and cell 2 (information reception), between which it is necessary to switch.
After its release, the neurotransmitter “migrates” (diffuses) through the synaptic gap to the extension of the second cell, the post-synapse (post = to, i.e. the synapse after the synaptic gap). This contains receptors that are designed for exactly this neurotransmitter. Thus, it can bind to it.
Through its binding, an electrical potential is now generated again at the second cell. When the information switches from one cell to the next, the sequence of information types is as follows: Cell 2 can now react in two ways by binding the neurotransmitter: Either it is excited and generates a so-called action potential or it is inhibited and the probability that it generates an action potential and thus excites further cells decreases. Which of the two ways a cell takes is determined by the type of neurotransmitter and the type of receptor.
In both the sympathetic and parasympathetic systems, there is a strict sequence of information transmission: Example of a parasympathetic task The first cell (original cell) in the skull (cranial parasympathetic part) or in the lower spinal cord (sacral parasympathetic part) is excited by higher centers (e.g. the hypothalamus and the brain stem). The excitation continues through its entire axon up to the first switching point. In the parasympathetic system, this is located either in a nerve node (ganglion), in a nerve plexus or directly in the wall of the organ to be influenced.
There, as a result of the forwarded excitation of the neurotransmitters, acetylcholine is released from the presynapse. Acetylcholine diffuses through the synaptic cleft towards the synapse of the second cell (post-synapse) where it binds to a suitable receptor. The cell is excited by this binding (because acetylcholine is one of the excitatory neurotransmitters).
Just like in the first cell, this excitation is again transmitted through the cell and its extensions to the recipient: the organ.There – as a result of the excitation – another neurotransmitter – this time it is acetylcholine – is released from the synapse of cell 2. This neurotransmitter then acts directly on the organ. The parasympathetic nervous system thus works – in contrast to the sympathetic nervous system – with only one neurotransmitter, namely acetylcholine.
- Electrically to the axon end of the first cell
- Chemical in the synaptic cleft
- Electrically from the binding of the neurotransmitter to the second cell
- Original cell (cell 1)
- Cell in a ganglion/plexus/organ wall (cell 2)
- Organ
