The antinociceptive system of the human body is a clearly demarcated structure of nerve endings located in all areas and in all departments of the central nervous system. Their totality has a kind of hierarchy of active neurochemical levers that have the ability to suspend the functionality of pain structures included in the nociceptive system.
Action of the antinociceptive system
In the anti-pain system, as a rule, an opiotergic regulatory scheme is used. It consists in the interaction of opiate receptors with opioid ligands. The mediators of the antinociceptive system are able to suppress uncomfortable unbearable sensations at various levels. Thanks to the work of this mechanism, pain and discomfort have not become a predominant feeling in human life. Even when pain sets in, the active elements of the antinociceptive system are put into action, which can be felt at the moments of pain relief, pauses. This is the main function of this protective mechanism in the body of any person.
The importance of narcotic painkillers today
Interest in drugs, by the way, also gave rise to the antinociceptive system. Physiologyof the human body clearly outlined the purpose of narcotic substances in medicine: they are used as the strongest anesthetic drug that can help the antinociceptive system overcome pain or act as its substitute.
Today, narcotic substances are the only option for effective symptomatic treatment of cancer patients. This may well justify the use of drugs, given their analgesic effect. However, everyone knows the main disadvantage of such drugs: they are able to turn an adequate, mentally stable person into a dependent being, experiencing unearthly torment and, probably, ending his life path prematurely.
Differences between nociceptive and antinociceptive systems
The antinociceptive system is a pain determinant that guarantees one hundred percent perception of pain. Considering this term, the differences between this concept and the term "sensory system" can be easily determined. Since only a separate fragment of the sensory system can be called the fundamental accepted “device”, i.e., thus the determining analyzer, the nociceptive and antinociceptive systems in total represent not just a determinant, but a rather complex self-governing somatic system.
To understand what this means, it is necessary to give an example. Medical practice knows rare cases of the absence of a feeling of pain in a person, which is congenital. Meanwhile, the main nociceptive pathways work for them as usual, i.e.mechanism to prevent pain activity is functioning.
How does pain and pain shock appear?
By the 70s of the last century, scientific researchers finally formed an opinion about such a component of the central nervous system as the antinociceptive system of the brain. At that time, scientists managed to establish its ability to limit pain excitation, prevent overstrain of the structures of the nociceptive department. Increasing irritation in the nociceptive system provokes active inhibition of this process by anti-pain elements.
Pain shock can occur only when the antinociceptive system fails to suppress the influence of extraneous factors due to excessive effects on the body. A decrease in inhibitory function is fraught with overexcitation of the nociceptive system and the generation of unforeseen unexpected pains of a psychogenic nature in absolutely normal, unaffected organs.
Structure of the anti-pain system of the body
Considering the concept of antinociception (antinociceptive system), attention should be paid to its individual components. Among them, first of all, it is worth noting the elements of the spinal, middle and medulla oblongata (gray matter, the nucleus of the reticular formation and the nuclei of the raphe, the gelatinous component of the spinal cord).
Thanks to them, the main blocking of pain occurs. A person ceases to feel the pain syndrome when the upward flow of nociceptive excitation is suppressed. This function belongs to the downward control of pain. Mainopioids and some hormones, such as serotonin, act as active substances in the inhibitory work. It is more correct to call them modulators, since they change the initial position of the final neurons, while not transmitting any excitatory effect in their direction.
Mediators and pain receptors in the anticiceptive system
The main and predetermining neurons of the pain system are those located in the gray matter of the midbrain. Important here is the role of axons, which are ascending pathways to the hypothalamus and other mechanisms of the left hemisphere of the brain. They are also involved in the opposite direction to the spinal cord. The mediators of these neurons are pentapeptides, which include subspecies of enkephalins. Such mediators in the form of amino acids should receive methionine and leucine.
Enkephalins are able to excite all opiate receptors in a fairly short time. In opiatergic synapses, such receptors are located mainly on the membrane, which performs the tasks of the postsynaptic "cushion". Synapses that did not participate in the process become painful, then mediators should be released through the membrane, directing uncomfortable excitation from a particular neuron to another.
The endogenous antinociceptive system has characteristic opiate receptors that are more metabotropic. They are often associated with a bioregulator causing inhibition of adenylate cyclase through intracellular recognition. Consequence of everythingof the above is a violation in the process of synthesis of the anti-pain system. In addition to the pathological reduction in calcium intake in the human body, the main mediators of the pain syndrome are turned on, i.e., the body begins to produce them on its own. The most common pain mediators are:
- substance P;
- cholecystokinin;
- somatostatin;
- glutamic acid.
The hypothalamus and the left hemisphere of the brain are activators of action
The structure of the anti-pain system includes the anti-pain structures of the hypothalamus and the somatosensory area of the cortex of the left cerebral hemisphere. The boundlessness of their inhibitory effect on human nociceptive mechanisms is achieved due to:
- downward inhibition of the effect on spinal cord neurons;
- upward inhibition of influence on thalamic neurons;
- activated impact on the above top-down brake control system.
Self-elimination of pain in the body
Nociceptive and antinociceptive systems of the body are in direct coordination. The latter produces opioid endogenous components, which in fact are drugs inside us.
These include endorphins, dynorphins, etc. A feature of their chemical composition are broken peptide sequences, like tiny protein molecules, which consist of amino acids.
The role of opioid and non-opioid peptides
On the predominant number of neurons, which includesThe antinociceptive system contains special receptors for such substances. For example, when receptors come into contact with opioids, subsequent inhibition often appears at the level of the work of individual neurons. In this case, the nociceptive pain system becomes inhibited and practically does not respond to pain. The task of small neurons of the analgesic system is to create obstacles for the transmission and distribution of pain excitation along the chain of subsequent endings.
Not only opioid peptides are involved in the regulatory process of pain sensations. Non-opioid peptides (for example, neurotensin) also have an impact on the final pain perception of a person. Arising from many sources, pain can be inhibited by noadrenaline, dopamine, serotonin, and other catecholamines.
How does the pain suppression mechanism work?
The antinociceptive system of the body can function in several ways:
- Emergency mechanism. There is a reaction of a painful stimulus, as a result of which there is an excitation of synapses in the system of descending inhibitory control. Within the posterior horns of the spinal cord at this time, one can observe a limitation of afferent nociceptive excitation. This mechanism is involved in the main analgesia. When pain is suppressed, two pain stimuli act simultaneously.
- Mechanism of short duration. The launch is performed by the hypothalamus, involving the inhibitory control systems of the descending type of the spinal, middle and oblongbrain. To activate the mechanism to limit pain excitation at the level of the spinal cord, and sometimes the brain, stress factors are needed.
- Mechanism of long action. The main centers are located in the hypothalamus, are activated with constant pain. The ascending flow of pain excitation is transmitted in all areas of descending control. The emotional coloring of pain is connected to the nociceptive system. Such evaluation is in most cases not objective.
- Tonic mechanism. Thanks to him, the constant activity of the antinociceptive system is maintained by the centers of the orbital and frontal zones of the cerebral cortex. They are located in the frontal lobe, behind the eyes. The activity of the nociceptive structure is provided by a constant inhibitory effect. By the way, this process can be seen even in the complete absence of pain.
What kind of pain is it?
Ancinociceptive system of the body, which controls the structures of the cerebral cortex, helps to prepare for the painful effect, and then accept the pain stimulus with a decrease in unpleasant, uncomfortable sensations.
From all of the above, we can make a simple conclusion that the intensity and nature of pain are predetermined by the peculiarities of the functioning of two systems: nociceptive and antinociceptive. The first is pain, the second is anti-pain. The specificity of their interaction predetermines the nature of pain experienced by a person. The pain can be different, namely:
- Hyperalgesia - a condition with increased sensitivity to pain, a consequencewhich can be either high arousal of the nociceptive system, or low arousal of the antinociceptive system.
- Hypoalgesia is a state of decreased sensitivity to pain resulting from the opposite effect: the antinociceptive pain system is increased and the excitation of the nociceptive system is reduced.
Both conditions can have a positive effect on the body, while they largely depend on the threshold of pain. This value is a non-static moving indicator, varying with the characteristics of the pain and analgesic systems. Both antinociceptive and nociceptive structures form a single complex of pain, being only its elements.
What threatens a person with pain?
A fairly complex sensory system of pain perception is necessary for a person to keep the body and its individual parts intact. In addition, disorders of the functions of these systems (pain and anti-pain) affect the life of a person in the most negative way. For acute short-term or chronic pain, the following occurs:
- Sleep disorders.
- Lack of sexual desire.
- Irritability, inattention.
- Decrease in motor activity.
- Depression, depressed psycho-emotional state.
Pain shock - death
Intense pain can slow down breathing, sometimes even stop it completely, while mild background pain can cause it to speed up. With severe pain, the heart rate increases, blood pressure rises, which threatens the development of spasm of peripheral blood vessels.
First, the skin becomes pale, but with short-term pain, dilated vessels cause its hyperemia. The secretion of saliva, the production of gastric and pancreatic juices decreases, intestinal motility stops, which often leads to anuria. The development of pain shock with a sharp pain is fraught with a fatal outcome.
