Pain is the greatest evolutionary mechanism that allows a person to notice danger in time and react to it. Pain sensitivity receptors are special cells that are responsible for receiving information, and then transmit it to the brain in the pain center. You can read more about where these nerve cells are located and how they act in this article.
Pain
Pain is an unpleasant sensation that neurons transmit to our brain. Discomfort does not appear just like that: it signals actual or potential damage in the body. For example, if you put your hand too close to the fire, a healthy person will immediately pull it away. This is a powerful defense mechanism that instantly signals possible or current problems and forces us to do everything to fix them. Often the pain indicates specific injuries or injuries, but it can also be chronic, exhausting in nature. In some people, pain receptors have increased sensitivity, as a result of which they have a fear of any touch, since they cause uncomfortable sensations.
You need to know the principle of action of nociceptors in a healthy body in order to understand what the pain syndrome is associated with, how to treat it, and also what causes the excessive sensitivity of neurons. Currently, the World Health Organization has recognized that no one should endure any kind of pain. There are many drugs on the market that can completely stop or significantly reduce pain even in cancer patients.
Why do you need pain?
Most often, pain occurs due to trauma or illness. What happens in the body when, for example, we touch a sharp object? At this time, receptors located on the surface of our skin recognize excessive stimulation. We still do not feel pain, although a signal about it is already rushing along the synapses to the brain. After receiving a message, the brain gives a signal to act, and we pull out the hand. This whole complex mechanism takes literally thousandths of a second, because human life depends on the speed of the reaction.
Pain receptors on the hairline are located literally everywhere, and this allows the skin to remain extremely sensitive and sensitively respond to the slightest discomfort. Nociceptors are able to respond to the intensity of sensations, fever, as well as various chemical changes. Therefore, the expression "pain only in your head" is true, since it is the brain that forms the unpleasant sensations that force a person to avoid danger.
Nociceptors
The pain receptor is a special type of nerve cell that is responsible for receiving and transmitting signals about various stimulations, which are then transmitted to the central nervous system. Receptors release chemicals called neurotransmitters, which pass through the nerves, the spinal cord, to the person’s main “computer” to the pain center with great speed. The entire signaling process is called nociception, and the pain receptors that are located in most known tissues are called nociceptors.
The mechanism of action of nociceptors
How do pain receptors in the brain work? They are activated in response to some kind of stimulation, be it internal or external. As an external stimulation, you can give an example of a sharp pin, which you accidentally touch with your finger. Internal stimulation may be caused by nociceptors located in internal organs or bones, for example, osteochondrosis or curvature of the spine.
Nociceptors are membrane proteins that recognize two types of effects on the membrane of a neuron: physical and chemical. When human tissues are damaged, receptors are activated, which leads to the opening of cationic channels. As a result, sensitive neurons are excited and a pain signal is sent to the brain. Depending on the kind of effect on the tissue, different chemicals are released. The brain processes them and selects the "strategy" by which to act. In addition, pain receptors not only receive a signal and transmit it to the brain, but also release biologically active compounds. They dilate blood vessels, help attract cells of the immune system, which, in turn, help the body recover faster.
Where are they located
The human nervous system permeates the entire body from the fingertips to the abdomen. It allows you to feel and control the whole body, is responsible for the coordination and transmission of signals from the brain to various organs. This sophisticated mechanism also includes warning of injury or damage that starts with pain receptors. They are located in almost all nerve endings, although most often they can be found in the skin, muscles and joints. They are also common in connective tissues and in internal organs. On one square centimeter of human skin, from 100 to 200 neurons are located, which have the ability to respond to changes in the environment. Sometimes this amazing ability of the human body brings a lot of problems, but mainly helps to save a life. Although at times we want to get rid of pain and feel nothing, this sensitivity is necessary for survival.
Painful skin receptors are perhaps the most common. However, nociceptors can be found even in the teeth and periosteum. In a healthy body, any pain is a signal of any malfunction, and in no case can it be ignored.
Difference in nerve types
The science that studies the process of the occurrence of pain and its mechanisms is quite difficult to understand. However, if we take as a basis the knowledge of the nervous system, then everything can turn out to be much simpler. The peripheral nervous system is key to the human body. It goes beyond the limits of the brain and spinal cord, so with the help of it a person can not think or breathe. But it serves as an excellent “sensor”, which is able to detect the smallest changes both inside the body and outside. It consists of cranial, spinal and afferent nerves. It is afferent nerves that are located in tissues and organs and transmit a signal to the brain about their condition. There are several types of afferent nociceptors in the tissues: A-delta and C-sensory fibers.
A-delta fibers are covered with a kind of smooth protective shield, so that they transmit pain impulses most quickly. They respond to acute and clearly localized pain, which requires immediate action. Such pain can include burns, wounds, injuries and other injuries. Most often, A-delta fibers are located in the soft tissues and in the muscles.
C-sensory pain fibers, in contrast, are activated in response to non-intense, but prolonged pain stimuli that do not have a clear localization. They are not myelinated (not covered with a smooth membrane) and therefore transmit a signal to the brain somewhat more slowly. Most often, these warfare fibers respond to damage to internal organs.
Pain Signal Travel
Once the pain stimulus is transmitted through afferent fibers, it must pass through the spinal horn of the spinal cord. This is a kind of repeater that sorts the signals and transmits them to the corresponding sections of the brain. Some pain stimuli are transmitted directly to the thalamus or brain, which allows a quick response in the form of an action. Others go to the frontal cortex for further processing. It is in the frontal cortex that the conscious realization of the pain we feel arises. Because of this mechanism, during emergency situations, we do not even have time to feel unpleasant sensations in the first seconds. For example, with a burn, the most severe pain occurs in a few minutes.
Brain reaction
The final step in transmitting a pain signal is a response from the brain that tells the body how it needs to respond. These impulses are transmitted along the efferent cranial nerves. During the transmission of pain signals in the brain and spinal cord, various chemical compounds are released that either reduce or increase the perception of the pain stimulus. They are called neurochemical neurotransmitters. They include endorphins, which are natural analgesics, as well as serotonin and norepinephrine, which enhance the perception of pain by a person.
Types of pain receptors
Nociceptors are divided into several types, each of which is sensitive to only one type of irritation.
- Receptors of temperature and chemical irritants. The receptor responsible for the perception of these stimuli is called TRPV1. It began to be studied back in the 20th century in order to get a medicine that can relieve pain. TRPV1 plays a role in oncology, respiratory diseases and many others.
- Purine receptors respond to tissue damage. At the same time, ATP molecules enter the intercellular space, which in turn affect the purinergic receptors that trigger the pain stimulus.
- Acid receptors. Many cells have acid-sensitive ion channels that can respond to various chemical compounds.
A variety of types of pain receptors allows you to quickly transmit to the brain a signal about the most dangerous injuries and produce the corresponding chemical compounds.
Types of pain
Why sometimes something hurts so badly? How to get rid of pain? Humanity has been asking these questions for several centuries, and finally it has found the answer. There are several types of pain - acute and chronic. Acute often appears due to tissue damage, for example, when a bone fracture. It can also be associated with headaches (which affect most of humanity). Acute pain goes away as quickly as it appears - usually immediately after the source of pain (for example, a damaged tooth) is removed.
With chronic pain, the situation is somewhat more complicated. Doctors still can not completely rid their patients of chronic injuries that have bothered them for many years. Chronic pain is usually associated with long-term illnesses, unknown causes, cancer, or degenerative diseases. One of the main contributing factors to chronic pain is an unknown cause. In patients who experience pain for a long time, depression is often observed, and pain receptors are modified. The chemical reaction of the body is also disrupted. Therefore, doctors are doing everything possible to establish the source of pain, and if this is not possible, prescribe painkillers.
Painkillers
Painkillers, or painkillers, as they are sometimes called, usually work with the help of neurochemical mediators. If the drug inhibits the release of "secondary messengers", then the pain receptors simply do not activate, as a result of which the signal does not reach the brain. The same thing happens if the brain's response to the stimulus is neutralized. In most cases, painkillers can only temporarily affect the situation, but they cannot cure the underlying problem. All that is in their power is to prevent a person from feeling pain associated with a chronic illness or injury.
Summary
Pain receptors of the scalp, lymph and blood allow the human body to quickly respond to external stimuli: changes in temperature, pressure, chemical acids and tissue damage. Information activates nociceptors that send a signal through the peripheral nervous system to the brain. That, in turn, immediately reacts and sends a reverse impulse. As a result, we pull our hand away from the fire before we have time to realize this, which can significantly reduce the degree of damage. Pain receptors have perhaps such an effect on us in emergency situations.