Author: Branden Chen
Editors: Vincent Chang and Liane Xu
Artist: Aurora Chen
Ouch! Touching a hot stove does not feel pleasant. Our body perceives the burning shock as pain. We all feel pain, whether it’s physical or emotional, but imagine a world where we do not feel pain at all—no more feeling pain when you burn your hand or get a paper cut or stub your toes. As amazing as this sounds, pain keeps us alive and prevents us from experiencing further physical damage. So, how and why do we feel pain? The answers to this question lie in the control center of our bodies: the nervous system.
Say you prick your finger on something sharp, like a thumbtack or a pin. The sharp object causes tissue damage, which is detected by microscopic pain receptors, known as nociceptors,
In your skin. The pain acts as stimuli for the nociceptors, causing them to send an electrical signal up the nerve fiber of a neuron. The nerve fiber, bundled with many other nerve fibers, forms the peripheral nerve. The electrical signal travels through the neuron in the peripheral nerve to the spinal cord. In the dorsal horn of the spinal cord, the signal is transferred from one neuron to another through the synapses (junctions) and neurotransmitters. The signal is then sent up into the brain, and from there, the thalamus of the brain relays the signal to different parts of the brain, such as the somatosensory cortex (responsible for processing physical sensation), frontal cortex (responsible for thinking), and limbic system (responsible for processing emotions). The final result is the pain. Sometimes, the pain can result in a reflex response in the spinal cord, where motor neurons are activated, moving your hand away from the sharp object before you even have time to think about it!
Medical professions categorize pain into five types: nociceptive, neuropathic, psychogenic, acute, and chronic pain. Nociceptive pain is primarily caused by tissue damage, like a cut, burn, or fractured bone. Neuropathic pain is caused by irregular occurrences in the system that interprets pain, like the spinal cord or brain. This type of pain is typically characterized as a burning or tingling sensation. Individuals with neuropathic pain usually have a heightened sensitivity to pain, feeling pain from normal, light stimuli. Psychogenic pain is caused and worsened by psychological factors. Acute and chronic pain refers to the timeframe in which pain is experienced, with acute pain being a short-lived pain and chronic pain lasting much longer due to ongoing tissue damage.
Another important aspect of pain is the Gate Control Theory of Pain, explained by Ronald Melzack and Patrick Wall in 1965. The theory proposes the idea that there is a neurological “gate” in the dorsal horn of the spinal cord that regulates whether or not a signal can be sent to the brain. The theory explains the experience of chronic pain and the different intensities of pain. For example, signals may be readily sent to the brain, resulting in more intense pain, but other pain signals may be minimized or completely cut off from traveling to the brain, resulting in little or no pain. Although the theory is influential and likely one of the most widely known theories for pain, it lacks research to support it.
Next time you accidentally touch something hot or prick your finger, you can thank pain for triggering your reflexes to bring you away from harm. However, for those experiencing chronic or intensified pain, pain is not always a response to harm and can be an indicator of a more serious neurological condition.
Citations
Cherry, K. (2021). Gate Control Theory for Pain Signals to the Brain. Verywell Mind.
Jones, M. (2018). Pain and how you sense it - myDr. MyDr.