The thread – “how to maximize the number of neuron connection?” in the section – “cognitive neuroscience” prompted me to write this article to clarify with popular language some qualitative processes conducted in nervous system, i.e. to show that explanations of processes, happening in living organism not always can be grounded on quantitative analysis:
Nervous system can be divided into two parts: central and peripheral. The central part bears the function of analyzer, but peripheral part – the function of receiving and conducting internal or external irritation. By function itself the nervous system can be divided into 1. motor system and 2. sensitive systems. (We must single out particularly a vegetative nervous system, but more about that later). The first has functions connected with volitional actions: for instance: flexion, straightening, rotation, elevation are the functions of motor nervous system. From the functions of sensitive nervous system we can note sense of touching, of cold and warm, of vision, of tasting, of hearing, of smelling… Motor nervous system is centrifugal, i.e. conducts motor impulses from the cerebral cortex to the periphery (to make active/passive particular muscle or group of them).
Sensitive nervous system is centripetal, i.e. conducts sensitive impulses from the periphery to cerebral cortex.
But right now I’d like to attract your attention to vegetative nervous system and its correlation in the organism: Vegetative or local nervous system consists of two pairs of nerves: sympathetic and parasympathetic. Anatomically
central parts of sympathetic nervous system (Symphaticus) and parasympathetic nervous system (mainly Vagus, which is one from the 12 cranial pairs (X)), i.e. their nuclei are situated in several places of nervous system.
The essential, that we can say about these two nerves from anatomical point of view is that they branch out inside the organism and unlike of motor and sensitive nervous systems (the latters have 1.their own zones in a cerebral cortex, 2.conductive system and 3.particular, special place of starting or termination in a periphery) the formers reach all internal organs, glands of secretion, all muscles and vessels, i.e. fall into tiny, superfine branches (i.e. have many places of termination). At the same time whiles motor nervous system conditions volitional actions, the vegetative nervous system (the truth – under the control of the cerebral cortex) conditions non-volitional processes (such as starting of intestinal peristalsis or its blocking, dilatation or constriction of vessels, rising or lowering of heart’s pulsation, dilatation or constriction of alveoli of lungs etc…)
The essential as well, what we can say about these two nerves (sympathetic and parasympathetic, i.e. Symphaticus and Vagus) is that they are antagonists of each other and within the limits of any particular internal organ act as opposites of each-other (for instance: the increasing of activity of Vagus results in lowering of heart’s
pulsation, but increasing of activity of Symphaticus - in increasing of
it). To say briefly Symphaticus figuratively is called the nerve of activity or the day’s nerve, but Vagus – as the nerve of passivity, or the nerve of night. Below is shown the scheme of behavior of each of them:
"Answers of working organs during stimulation symphatetic and parasimphatetic nerves"
(Haulica, J., 197
The most important I’d like to emphasize, is the mechanism of forming of these two systems and its analysis regarding to the process of evolution: Until indicating the practical example, I’d like to touch briefly such functions of cerebral cortex as are functions of irritation-inhibition, and phenomenon of dominant: All (motor or sensitive) parts of nervous system have their prevailing zones in a cerebral cortex: for instance, in a human’s organism central part in cortex for lower extremities occupies a zone of parietal lobe – so called pre-central convolution (gyrus), but for the eyesight – the large as well zone in occipital lobe.
Each sphere of nervous system has as well associative, convergative connections to other parts of
cortex, i.e. the parts, which doesn't’t present a prevalent specific zone for mentioned sphere. For instance the sphere of reproduction is characterized by richest associative connections with almost every other motor and sensitive nervous system zones in the cortex.
The phenomenon of dominant consists in following:
Under the influence of some (any complex, any single) external or internal stimulants on the organism the irritation of corresponding zone of cerebral cortex automatically results in simultaneous inhibition of other needless cerebral zones, even sometimes the generalized inhibition spreads over almost thorough cortex (except for irritated zone of it). For instance, in a moment of syngenesis, sexual function and connected with it supplementary associative functions become active, leading process with synchronous spreading of inhibition over functions (needless for this period) of nutrition and self-preservation.
Let’s consider simple particular example taken from wild nature: a deer escaping from tiger, i.e. example of pair: predator-prey in a period of chasing (because the chasing can be the best example of crucial moment) and their nervous systems’ activities (specifically of vegetative nervous system‘s) during and after ending of chasing period.
During the period of chasing the extremities carry out the prevalent, leading function (lower extremities - in case of human) i.e. dominant in this particular case becomes the central part, respective to extremities (part of cortex) with synchronous inhibition spreading over all other “needless” zones: I.e. to say briefly both animals are concentrated on developing of highest possible acceleration within the period of chasing.
I think that very interesting is behavior of vegetative nervous system: i.e. correlation between sympathetic and parasympathetic systems as antagonistic systems: During the period of chasing in both organisms happens “turning on” of Symphaticus:
- Pulsation increases, i.e. the quantity of beating of pulse for a minute increases.
- The quantity of systole volume (the volume of blood, pumped over to Aorta, i.e. to circulatory system with one compression of heart) increases.
- coronary arteries (i.e. arteries of heart) dilate, as muscles of loaded heart need more supply with blood.
(The bloody stream to muscles of heart increases). - Blood-vessels of extremities dilate. (The bloody stream to extremities increases).
- Lung’s alveoli dilate as well, i.e. supply with oxygen increases (oxidation increases).
- Metabolic processes increase.
- Intestinal peristalses experiences blocking, i.e. gastrointestinal tract is in “hung-up” condition, but sphincters (pyloric, anal...) are tensed.
- Urinary bladder’s detrusor is relaxed, sphincter - tensed.
- Blood-vessels of brain are constricted, blood supply to brain decreases…
- Glycogenolysis increases because the glucose is needed as energetic source…
(For people who don’t know, the detrusor and sphincter are antagonist muscles of urinary bladder, when sphincter is relaxed, the detrusor is active (urination) and vice-versa (inhibition of urination), and I’d like to emphasize as well that successive activation-blocking of the system detrusor-sphincter of urinary bladder may happen anytime but mainly the sphincter is constricted ( i.e. it’s active) in the period of chasing, but after it becomes passive (precisely opposite of detrusor’s activation-blocking processes)).
And it happens on every “level” of organism: the organ that’s needless is passive, but all rest organs – active… and choosing of internal organs’ active and passive conditions during a crucial moment and after it within the whole organism happens by vegetative nervous system’s automated functioning (formed throughout the period of evolution) …
And very interesting is “conduct” of uterus in the period of chasing: pregnant uterus is in constricted condition (to carry a fetus), non-pregnant - is in relaxed condition (because of absence of carrying function), but in both cases determinative is Symphatetic system (Symphaticus)…
After ending of chasing (either deer escapes or tiger catches it) survived organism at once experiences changing of activity of vegetative nervous system in radically opposite direction (i.e. at once happens choosing of most favorable conditions for resting):
Parasympathetic system (Vagus) becomes “turned on”:
- Pulsation decreases, i.e. the quantity of beating of pulse for a minute decreases.
- The quantity of systole volume decreases.
- coronary arteries constrict, as muscles of heart need less supply with blood.
(The bloody stream to muscles of heart decreases). - Blood-vessels of extremities constrict. (The bloody stream to extremities decreases).
- Lung’s alveoli constrict as well, i.e. supply with oxygen decreases (oxidation decreases).
- Metabolic processes decrease.
- Intestinal peristalsis experiences activation, i.e. gastrointestinal tract is in “active”, “waving” condition, but sphincters (pyloric, anal...) are relaxed.
- Urinary bladder’s detrusor is active, sphincter - relaxed.
- Blood-vessels of brain are dilated, blood supply to brain increases…
- Glycogenolysis decreases…
I.e. as a conclusion we can say that during the activity of any part of central nervous system there exists a dominant, and activation as well of connected with dominant of associative supplementary systems with simultaneous inhibition of “needless” nervous and somatic systems. Different processes have their different specific dominant in a cerebral cortex and associatively bind with it relatively stable irritational-inhibitional stereotype formed during the process of evolution....
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