Pain Sensations

Pain Sensations, unique sensations that serve as an indication of the presence of irritants (mechanical, chemical, biochemical, electrical, etc.) that might cause damage and, ultimately, even the death of tissue elements, and which depend on the excitation of special nerve apparatuses, most studied in human skin in the form of intraepithelial nerve endings—pain points. On average, there are about 100-120 such points per 1 sq. cm. They are much more numerous than the points for other skin sensations—pressure and temperature. Their distribution in tissues is uneven, which is why different parts of the body and organs react differently to painful irritation: most sensitive—the cornea of the eye, fingertips, external mucous membranes; less sensitive—muscles, tendons, joints, periosteum, outer layer of pleura and peritoneum, meninges; insensitive—cavity organs, inner layer of pleura and peritoneum, and the brain. - Measurement of pain sensations by algésimeters of various designs does not yield any precise results. Complete insensitivity to pain—analgesia (see)—can be a consequence of various diseases of the central nervous system (syringomyelia); general analgesia is achieved by introducing cocaine into the spinal cavity, local—by the use of cold, anesthetics, ligation of limbs, and also—in suggestible subjects—by means of hypnosis and suggestion in the waking state. Increased pain sensitivity—hyperalgesia—is often associated with psychoneurotic conditions (neurasthenic, hysterical, and hypochondriacal types). The question of pain-conducting nerve pathways is not entirely resolved: some (Frey, Landois, Weizecker, Ebbinghaus) admit special nerves for this purpose, others (Goldscheider, Ziehen, Wundt, Meyer) attribute this function to the general sensory conductors. In the brain, pain centers have been found in the thalamus and in some cortical areas. Sensitivity to pain depends: 1) on age (children, for example, are more sensitive than adults), 2) on sex (women, supposedly, on average, are less susceptible, i.e., more enduring and patient compared to men), 3) on psychological development: idiocy, retardation, psychopathies give a decrease in pain sensitivity; hysteria represents sharp deviations in both directions depending on the psychological content of the patient at the given moment; violent emotions—ecstasy, anger, fear and generally everything that helps to distract attention from the painful stimulus sharply inhibits perception (so, for example, in the heat of battle, wounds are sometimes not noticed); conversely, expectation and apprehension intensify pain. At night, pain is stronger due to the absence of distracting factors. Subjective qualities of pain are distinguished, depending on the structure of the organ, on the concentration or spread of the irritant, on the properties of pathological processes. Pain is stabbing when small tissue surfaces are irritated, drilling—when the sensation fluctuates between maximum and minimum, pulsating—when corresponding to the pulse wave, etc. Also distinguished are gnawing, pulling, burning, piercing, sharp, dull, pressing, lightning-fast pains, etc. The quality of pain can have diagnostic value (lancinating pains in tabes). As a rule, pain is connected with a feeling of displeasure. Closely related to the interests of self-preservation, pain is as it were the first link in a long chain of protective reactions: withdrawal of limbs, deviation of the body, covering its parts (closing the eyes), reflex inhibition of all movements until complete immobility. From the side of internal organs, pain causes disturbances of respiration, blood circulation, fluctuations in blood pressure, sometimes even paralysis of the heart, and from the side of the psyche—insomnia, gloomy excitement, sometimes suicide attempts, clouding of consciousness with a character of confusion.