The ways of pain are inscrutable; The degree of pain produced by a harmful stimulus depends on both the context and the stimulus itself. In the dentist’s chair, an elite soldier may flinch at the slightest touch, even if the dentist is simply feeling a healthy tooth. The expectation of pain favors its experience. On the battlefield, this same soldier can sustain a terrible injury and continue fighting without realizing that he is injured.
“Pain is not a mere alternative emotion to pleasure, but it is asensationsuch as tactile, visual or olfactory, in which theaffective componentpresent in all other sensations isvery exaggerated“, says Dr. Carlos Belmonte, director of the Institute of Neurosciences, at the Miguel Hernández CSIC University, in Elche. The biological function of this unpleasant sensory and emotional experience is evident: it always appears that any tissue has been injured and makes the individual react by eliminating or moving away from the painful stimulus.
Undoubtedly,pain guarantees our survival and physical integrity: People with neurological problems that make them insensitive to pain are continually injured and die easily. “As a complex experience that it is, pain has different dimensions: a discriminative sensory, referred to the ability to distinguish the characteristics of the painful stimulus in space and time -location, extension, intensity and duration-; an evaluative cognitive, referred to the perception of the stimulus and the understanding of its meaning, and an affective-emotional one, which corresponds to the feelings of displeasure that evokes the knowledge of what is happening and the desire to avoid harm “, explains Professor Belmonte.
A network and exclusive neurological system is responsible for managing pain signals. These are perceived by nociceptors-nightderives from latinfor wounded-, special nerve endings that transform aggression into nerve impulses. These nervous snitches appear distributed in the superficial layers of the skin, as well as in some internal tissues, such as the periosteum, arterial walls and articular surfaces. Like other sensory receptors, nociceptors are born in the ganglia of the dorsal roots or in the trigeminal ganglion – case of pain in the face – and send an axionic connection – nerve cable through which electrical impulses are transmitted – towards the periphery and another to the interior of the spinal cord.
With exceptions, allnociceptive impulsesThey are guided by two types of fibers: the myelinic fibers Ad, which conduct painful information at high speed (20 m / s); and the unmyelinated C, which send the stimuli at speeds generally less than 2 m / s. Stimulation of the former causes a sharp, intense and well-defined pain, like that caused by a burn. C fibers, however, are responsible for a dull, vague, and deep aching sensation that is well known to chronic pain sufferers.
Scientists have discovered that, after damage to the body, a host of substances appears in the injured area that increases the response capacity of nociceptors. This results in a phenomenon known as hyperalgesia: stimuli that would not normally produce pain are perceived as painful and sensations that would normally be painful are significantly more so. Receptor inducers include potassium, prostaglandins and leukotrienes released by damaged cells, bradykinin in blood plasma, and histamine produced by mast cells – cells that participate in inflammatory processes. Even the electrical activity in the nociceptors themselves causes the nerve fibers to release substance P, also known to neurologists as the pain peptide.
The pain signal thus generated begins its journey to the brain. As already mentioned, the axons of the nociceptive nerve cells enter the spinal cord through the dorsal roots and make contact with a second neuron, which originates three ascending nerve bundles. It is the neospinothalamic bundle, which appears to be important in the topographic location of pain; the palaospinothalamic tract, which plays a prominent role in the qualitative evaluation of the painful stimulus; and the spinoreticulothalamic tract, which is credited with managing the affective component of pain. Through these and other parallel pathways, the nociceptive impulse reaches brain structures, specifically the thalamus. From this kind of control tower, numerous nerve radiations depart towards the ascending reticular formation, the hypothalamus, the limbic system and the cerebral cortex or cortex.
“The existence of all these projections explains the increase in vigilance, neuro-vegetative and emotional reactions, cognitive assessment of pain and relationships, decisions and taking actions to avoid it,” says Dr. Jose Luís González de Rivera, director from the Center for Psychosomatic Research, in Madrid. And he adds: “Precisely, the connections of the pain pathways with the limbic system and the cerebral cortex cause the painful experience to be influenced by ethical and cultural values, the mental state and personal attitudes and interpretations.”
But the neurological circuit of pain is much more complex. Indeed, the nociceptive impulse is capable of being amplified or attenuated when passing through certain relays located along the nerve pathways. For example, neurologists have found that at these critical points, such as the dorsal horn of the spinal cord, the nucleus of the raphe magnum, and the periaqueductal gray matter, natural opiate receptors are concentrated: enkephalins, dynorphins, and b- endorphins. These peptides induce a state of analgesia, without altering motor activity, probably through a descending inhibitory pathway. In the words of Professor Belmonte, “this ability of the nervous system itself to cut the passage of painful information upward is the basis of phenomena as diverse as the absence of pain in moments of life risk, such as fight and flight; and partly in hypnosis and during acupuncture. “
But pain does not always fulfill a protective function. At times, it rages on the body and becomes a terrible chronic disease.
So it hurts him and her
Through a wide range of stratagems – from morphine to neurostimulation systems – doctors say they can tackle the most sordid and stubborn pain. If so, why do many patients continue to writhe in pain in hospitals?
Many mothers are convinced that if the trance of childbirth had fallen on men, the human species would have disappeared hundreds of centuries ago. Stereotypes about how men and women tolerate pain are deeply ingrained in our society: women are more delicate, but they resist childbirth; the men are stoic, but they shake like a mercury in the dentist’s chair. Is the female sex really more resistant to pain?
Recent research confirms thatwomanpresents ahigher riskof suffering from pathologies associated withchronic pain. Without going any further, migraines, arthritis and fibromyalgia -a syndrome that is characterized by muscular discomfort- are diseases that prevail in women. In addition, they experience aexperience of the most intense and distressing pain, as evidenced by clinical trials. The lower female tolerance to pain is not a trivial matter, since it has an important impact on the management and treatment of painful processes, as well as on the future development of “à la carte” analgesics. For a few decades, it has been known that certainPain relievers work differently for both sexes.
“Numerous studies confirm that women respond markedly better than men to kappa opiates, drugs that bear some resemblance to morphine,” says Dr. Roger B. Fillingim of the University of Florida, Gainesville. Something similar can be said for hydrocodone, a derivative of codeine that doctors prescribe to men in higher doses to combat back pain. Additionally, some preliminary research suggests that the analgesic action of ibuprofen – a non-steroidal anti-inflammatory drug (NSAID) – is more potent in men than in women.
In the words of Dr. Jeffrey Mogil, from the University of Illinois at Urbana-Champagne (USA), “the neural processing of pain and analgesia is qualitatively and quantitatively different in the two genders.” Scientists have proposed numerous mechanisms to explain these sexual nuances. “Nociceptive perception is influenced by a number of factors,” says Dr. Fillingim. And he adds: “Pain is not only what travels through the nerves, but it is about our personal experience.”
In this sense, they aredeterminant psychosocial factors, as the way in which men and women have to express suffering; for example, “crying is for girls”. Interacting with these, the biological conditioning factors that modulate pain perception are counted. At the forefront are female hormones. That’s how it is; Laboratory tests indicate that female tolerance to painful stimuli fluctuates in relation to the phases of the menstrual cycle.Right before period, pain threshold plummets. The reason: estrogens act as excitators and can amplify the transmission of nociceptive signals in the peripheral nervous system, the spinal cord, and the brain.
Progesterone, on the other hand, shows the opposite effect, since it prints a sedative action on the nervous system. For example, in the third trimester of pregnancy, this hormone reaches maximum blood levels that put the future mother in a deep state of analgesia for childbirth. “Outside the gestation period, women are usually less resistant to pain,” says Jon Levine, a neuroscientist at the University of California, San Francisco. This researcher has discovered that female hormones alter the biochemical signals involved in inflammatory processes and tissue repair. Estrogens, for example, shut down the production of the peptide bradykinin, a powerful inflammatory mediator that protects injured tissues. It should not be forgotten that the inflammatory process itself increases the responsiveness of nociceptive endings. Levine thinks that this biochemical disadvantage is closely related to the therapeutic efficacy of opioids in men and women.
For Dr. Maria Adele Giamberardino, from the University of Chieti, in Italy, the special nervous connection of the internal organs in women constitutes another physiological factor that puts women at a disadvantage. Giamberardino believes that the way female viscera talk to each other can cause pain caused by one internal organ to be amplified or muffled by nociceptive signals from another. At least, this is what clinical practice suggests: the Italian doctor has found that patients with kidney stones experience more sordid back pain – caused by stones in the urinary tract – in months with painful periods.
Giamberardino’s thesis is that the reproductive organs of women have close nervous links with other viscera, which would explain whycertain chronic pathologies are more painful in women.
But the physiological heterogeneities do not end with hormones and visceral nerve wiring. How could it be otherwise, the brain plays a leading role in the nociceptive experience. The rheumatologist Anthony Jones knows a lot about this, investigating in his laboratory at the University of Manchester which areas of our brain are responsible for certain painful responses. With the help of medical imaging equipment such as functional magnetic resonance imaging and positron emission tomography, Jones has found that the female brain is more prone to process painful stimuli preferably in areas related to attention and emotions. This researcher suggests that women tend to process sensory input in a more affective way than men and to fight pain before it is too late.
WOMAN
– Migraine
– Tensional headache
– Arthritis
– Irritable bowel syndrome
– Cystitis
– Gallbladder disorders
MAN
– Cluster headache
– Pancreatitis
– Duodenal ulcer
– Back problems
The broken heart
Psychiatrists explain why negative emotions – such as those caused by disappointment in love – can cause physical pain.
The memory of a recently deceased loved one can split the heart in two, and the evocation of a bad experience automatically triggers a stomach cramp. The thought of a surgical intervention reopens the wound and melancholy plunges the soul into existential agony. There is no doubt thatcertain emotions cause excruciating physical pain. Lord Byron (1788-1824) estimated that “the memory of joy is no longer joy; while the memory of pain is still pain.” The poet’s quote is endorsed today by neuroscience: the painful experience is not always linked to a stimulation of nociceptive receptors.
When this occurs, psychologists and psychiatrists speak of psychosomatic pain. “The neurological circuit of pain is highly complex, since it has ramifications that are at the service of other biological tasks other than sensory experience, but that interfere with the perception and reaction of the organism to a painful stimulus”, says the professor of psychiatry José Luis González de Rivera, director of the Center for Psychosomatic Research, in Madrid. “For a long time – he adds – we have known that it is possible to unleash a sordid pain by electrical stimulation of specific areas of the brain. The same effect can be achieved without using the electrodes, but only by memory.
Indeed, given the wealth of neural associations that pervade our brain, a person can experience an old pain again simply by remembering the situation that caused it. This is so because we have a sensory memory, apart from the cognitive one, that is, the one that concerns the mere storage and retrieval of data. But both types of memory are connected by the so-called limbic association cortex, a kind of neurological crossroads that makes a certain pain acquire an emotional meaning, and vice versa.
“The connections of pain pathways with the limbic system – a ring of interrelated brain structures that regulate emotions – and the cortex of the cerebral hemispheres cause the painful experience to be influenced by the character of the person, ethical values and cultural, the degree of psychic activation, and personal attitudes and evaluations “, says Dr. González de Rivera. In this sense, a value that influences nociceptive perception is the commitment that the individual acquires with what triggers it. “This explains, for example, why women who want to have a child endure the moment of childbirth better than women in labor who have a very different version of motherhood,” says Dr. González de Rivera. It is thepsychogenic dimension of pain; With few exceptions, any thought is associated with an emotion and this is usually accompanied by a physical sensation. For this reason, romantic breakups cause a throbbing pain in the heart similar to a heart attack. Those kinds of mind-brain associations are imprinted on our neural circuits.
“As a rule we are used to expressing memories in words, but this is not always the case. I recently treated a patient with severe back pain that the doctors were not able to diagnose. When at one point in the interview I asked about her husband, the woman got up as if impelled by a spring and shouted Ay !, at the same time she put her hand behind her back. The conflictive relationship with the spouse was encoded by the patient in the form of pain in the lumbar region “, explains the doctor González de Rivera.
In the words of this psychiatrist, there are psychologically sophisticated people who, faced with a situation like the one described, realize that it is a false codification and that the way to resolve the conflict is through its verbal expression. “Certain people, however, find in psychophysical suffering the only way to process and refer psychological conflicts”, points out González de Rivera. This undesirable situation is aggravated when certain basic emotional states are altered. Depression seems like a clear example.
A girl cries over the body of one of the 15 victims caused by the explosion of a homemade mine placed in Tuy Homa by the Viet Cong, during the Vietnam War. Unpleasant and shocking psychic experiences can cause bodily pain.
A girl cries over the body of one of the 15 victims caused by the explosion of a homemade mine placed in Tuy Homa by the Viet Cong, during the Vietnam War. Unpleasant and shocking psychic experiences can cause bodily pain.“There is no doubt that the affective state is a conditioner of the painful expression, this being more intense when it is accompanied by a depressive syndrome”, says the psychiatrist. Melancholy and pain frequently coexist in medical practice. In the words of Dr. Juan Medrano, from the Álava Psychiatric Hospital, in Vitoria, “in people with chronic pain, it is common to find depressive syndromes in a highly variable and disparate percentage of patients, ranging from 7 to 100 percent.” In turn, pain is a common symptom in depressions. Some authors estimate that between 33 and 64 percent of the depressed show painful symptoms. “In melancholic states, the pain compensation mechanisms appear disturbed. This is the case of the endorphin system, a group of natural opiates manufactured by the brain,” says Dr. González de Rivera.
Recent research indicates that depressed brains present, to put it simply, a greater difficulty in processing sensory information at the central nervous system level. This situation entails a greater tendency to carry out poor and primitive mental encodings, which translate into psychogenic pain.
“When the depressive state is treated, it improves the functioning of the brain in a non-specific way and, therefore, the painful codings of a psychosomatic type disappear or are attenuated”, comments this psychiatrist.
