The most important feature of pain is that it can be easily changed by other factors. The strength of the pain signal varies depending on other sensory information coming to the spinal cord at the same time. Nerve fibers and extensions that carry pain information from distant parts of the body to the spinal cord are not all of the same structure. The fibers that carry sudden, sharp, fast pain information and the fibers that carry slow, widespread, continuous and throbbing pain information are different from each other. Although they both have extensions that go to the spinal cord and stimulate the cells there, their pain transmission methods and structures are different. (A)
Gate Control Mechanism regarding how pain information is transferred to the brain and managed by the brain. (A) When a neuron in the spinal cord (x) is stimulated by a painful stimulus, it informs the brain that something painful is happening. These pain fibers carry both fast and slow pain information. (B) is a more realistic model of how the system actually occurs. It shows why sudden and slow pain information is separated. In case of sudden pain, the fast pain fiber (x) stimulates the neuron and the pain signal is sent to the brain for a short time. The immediate pain fiber also stimulates the y nerve cell, which is an intermediate neuron that will inhibit the (x) nerve cell with a delay. On the other hand, the slow pain fiber stimulates the x nerve cell and inhibits the y nerve cell. Therefore, y cannot inhibit xi and x continues to send pain signals to the brain and a slow and widespread pain is felt. (C) Both excitatory and inhibitory fibers coming from the brain can send information to the x nerve cell and change its sensitivity to incoming pain information. Therefore, it can either increase or decrease the sensitivity of the brain The first of these is the neuron, marked X, which carries pain information to the brain. The second neuron, marked (Y), is regional and is known as the interneuron. When Y is stimulated, it inhibits the activity of X. Depending on the connection type, when a sharp and painful stimulus is felt, this information is sent to the fast nerve fibers, which stimulate both X and Y neurons. As a result, X sends this pain signal to the spinal cord. melts, but soon after, Y steps in and shuts down X. In this case, the brain feels a short-term, sharp pain, just like when a needle pricks your hand. On the other hand, information about situations where a not very strong, throbbing and widespread pain is felt is sent through the slow fiber. The slow fiber communicates with both the X and Y nerve cells, but the process develops differently than in the fast fiber. Likewise, the X neuron is stimulated and informs the brain that something painful is happening. However, this time the slow fiber prevents the Y neuron from activating. Y remains silent, X continues to be activated. Your brain feels a long-lasting, widespread, throbbing pain, like the pain that lasts for hours or days after you've been burned on one side. Although these two nerve fibers can interact with each other, sometimes we knowingly and willingly force them to do so. Let's say you have some kind of constant, throbbing pain. A tired muscle is like a painful wound. Briefly stimulating the fast fiber may cause you to experience a sharp pain for a short time, but since you will also stimulate the intermediary neuron Y, you will turn off the pulsating system for a while. It is like blocking the widespread and throbbing pain of our tired muscles for a while with a strong massage, or dulling the pain by vigorously scratching the area around an unbearably throbbing insect bite. In all of these cases, the slow, chronic pain pathway is closed for a few minutes.
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