Wondering how do you experience the feeling of pain? Read on to learn facts about the sensory tracts and the nervous system through the gate control theory of pain.

Gate Control Theory

Ron Melzack and Patrick Wall gave out the ‘Gate theory’ of pain in 1962. The theory proposes that physical pain is not a direct result of activation of pain receptor neurons, but rather a perception that is modulated by interaction between different neurons. Gate theory of pain is an attempt to discuss about how pain sensation is transmitted. Pain is the sensation of uneasiness and physical discomfort, caused due to tissue damage of some kind. The sensation of pain is made possible because of the network of nerves that spreads throughout the human body. There is still no exact idea though as to how pain is sensed and a response to pain gets processed to the brain. Gate control theory argues that human thoughts, beliefs and emotions affect the amount of pain felt from a given physical sensation. The basis of this theory is that both the psychological and physical factors guide the brain’s interpretation of painful sensations and subsequent response. Read on to get more detailed information about the gate control theory of pain.
Gate Control Theory Of Pain
  • The gate control theory of pain argues that the sensory messages travel through the body’s pain highway i.e. from the stimulated nerves to the spinal cord. The messages undergo reprocessing here and then get transferred to thalamus, the brain’s depot for tactile information. This gets transferred through the open gates to the brain. Sharp pains stimulate different nerves as compared to wearing away or dull pains. Once the nerve signal reaches the brain, the sensory information is processed depending on the individual’s current mood, state of attention and previous experiences. The integrating affect of all these information determines how much pain one experiences and how one responds.
  • Now, it depends on how the brain responds to this sensory information. It is the brain that determines the extent of pain one experiences. If the brain sends the message down to close the gates, the pain signal to the brain is blocked and we experience less pain. However, if the brain responds in a way to open the gates wider, then the pain signal intensifies and we can experience excruciating pain. The message may be carried by endorphins, natural painkillers in the body that are chemically similar to morphine.
  • The structure of the gate through which the pain pathways send signal to the nervous system needs to be understood first. The input signals to the gates are of two types, small nerve fibers and the large fibers. Both these input paths are connected to the projection cells that carry signals through the spine thalamic tract. It is the projection cells that control the elements of the gate. Both the nerve fibers, which are connected to repressive inter neurons, are situated in the dorsal horn of the spinal vertebrae. These fibers can suppress the pain transmission through the spinothalamic tract, by controlling the projection cells.
  • The pain transmission takes place in three different forms - no input gate stays closed, large sensory input closes the gates and pain receptor nerve input open gates. In the first case, if there is no incoming response from both the fibers, then the inhibitory neurons prevent transmission of signals through the projection cells. In the second case, if the input signals are large, then the inhibitory neurons get activated and prevent the transmission of pain through projection cells and we feel no pain. The third case occurs when there is an input signal from the small pain receptor and the sensory neurons input is not large enough to activate inhibitory cells, which allows the projection cells to pass the signal to the central nervous system.
  • Therefore, the gates theory of pain projects that if we distract ourselves through some muscular movement and think to create large sensory signals, the pain receptors may be stopped, due to the closing of the gate by high input signals from the large nerve fibers. The amount of pain we feel is determined by the superimposition of the signals by the large sensory nerve fibers and the pain receptor fibers. This is how the gate pain theory explains how pain perception can be affected by our emotions and response of the central nervous system. 
  • This theory explains that the sensation of pain can get dampened or aggravated by thoughts of the people. This is how some people are able to withstand a large amount of pain through sheer willpower. This theory gave a totally new way of thinking about pain and pain management.

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