Remember when you wanted to hang a picture of Grandma Nana? You brought the hammer and aimed at the nail, your left hand stabilized, and you started installing slowly and carefully, gaining confidence you went faster but you smashed your finger instead. What comes next? Pain, of course. You may scream, run, hold the finger, or even cry; the suffering persists for days or maybe weeks nonstop. Isn’t that fascinating? Regardless of your action, only the brain sets the termination. Sometimes you don’t even know where the pain came from. Neuroscience is our map to know if the pain we feel is a product of our mind or physically present. It is the eye that sees how the brain narrates the story of pain.
Feeling pain begins with a stimulus that attracts attention to the tissues within an affected area. The tissues release cytokines such as prostaglandin, which stimulates the nociceptors, also known as free nerve endings. This process which is shared between PNS and CNS is called nociception. There are three types of nerve fibers: A, B, and C. A-type fibers are thin, myelinated, and carry pressure, cold, and acute pain signals. B-type fiber’s primary role is to transmit autonomic information, with a slower velocity and less myelination than A-type fibers. C-type fibers are unmyelinated with a larger diameter than A and B fibers, their signals are slow and propagate mechanical and temperature stimuli but can’t be exactly localized. When tissues are injured, nerve terminals release substance P which travels up C-type fiber to the spinal cord and brain. The C-type fibers play a significant role in the spinothalamic tract which conveys the flame of warning by second-order neurons to the somatosensory cortex. Within the higher center, three parts of the brain welcome the pain stimulus: The somatosensory cortex that perceives the types, intensity, location, and memory of pain. The reticular system for the motor response. Lastly, the limbic system is for the emotional response along with your memory. To distinguish between harmful stimuli and peaceful sensations, our bodies require inhibitory mechanisms. Endogenous opioids ( endorphins and enkephalins), serotonin, norepinephrine, GABA, oxytocin, acetylcholine, and neurotensin are the body’s natural painkillers. Pathologically speaking we can categorize pain into nociceptive, neuropathic, and nociplastic pain.
Nociceptive pain occurs when nociceptors receive stimuli from injured tissue or potentially harmful signals, such as chemicals, extreme temperatures, or physical force. It often feels sharp, aching, or throbbing, and patients may experience it as musculoskeletal pain, such as joint pain. Nociceptors detect physical damage to the skin, muscles, bones, or connective tissue. This type of pain is typically acute and subsides when the underlying condition has resolved.
Neuropathic pain is distinguished from other pain conditions by the pain generator that begins with disease or injury of neural tissues. Neuropathic pain originates from damage to the somatosensory nervous system. It is manifested as electric shocks, burning, numbness, itching, or tingling. Neuropathic pain typically affects a specific dermatomal distribution, and the area of pain is limited anatomically. It also can be caused by many different conditions, including Alcoholism, Diabetes, HIV/AIDS, and Multiple Sclerosis. Even individuals who have undergone limb amputation may experience neuropathic pain. Which is called phantom limb syndrome.
Nociplastic pain can be defined as pain that comes from an altered perception of pain accompanied by emotional distress without any tissue injury or damage. It has been divided into five categories: chronic widespread pain (e.g., fibromyalgia), complex regional pain syndrome, chronic primary headache and oro-facial pain, chronic primary visceral pain, and chronic primary musculoskeletal pain.
To put it simply, pain is what keeps us safe and is essential for surviving threats, it is an alarm telling us that something is not right. Our brain sets limits on the stimuli it perceives as alarming or dangerous, and once the threat subsides, the pain should diminish. If the pain persists, it can lead to chronic suffering as seen in nociplastic pain, which requires a more complex form of investigation and management.
