Why Does the Body Feel Pain?

Pain is your body's warning system that tells your brain something's wrong. It's part of your body's safety net that protects it in times of injury, illness, and trauma.

While nobody likes feeling pain, imagine what might happen if you never felt the cut that's causing you to bleed profusely or the heart attack that's threatening your life? In both of these situations, pain is what grabs your attention so you can take immediate care of your body.

The sensation of pain feels differently in various parts of your body because your nerve cells are specific to each area, and there are particular reactions involved in sending pain signals to the brain.

Pain can be broken down into two major categories—nociceptive pain and non-nociceptive pain.

Nociceptive Pain

It's pain you feel because specific pain receptors are stimulated by injury, heat or cold, vibration, stretch, or chemicals such as when you get a burn, cut, sprain, or salt in a wound. Nociceptors (nerve endings that perceive pain) are distributed throughout the body in either somatic or visceral structures.

Somatic structures include the skin, muscles, cartilage, bones, joints, and connective tissues. When pain is felt in a somatic structure, it's usually easy to identify where it's coming from and what's causing it because it's localized and often related to a specific event or injury like an accident or wear and tear. It's the type of pain you feel with arthritis when nociceptors warn the body there's not enough padding between the bones to accommodate movement.

Once a somatic structure is irritated, a series of chemicals are released from the damaged cells to start an inflammatory response that sends protective body fluids to the injury. This causes nociceptor stimulation, which sends a pain message to the brain. In the event of a cut, the nociceptors in the skin react. If it's arthritis, it's the bone-on-bone irritation that causes the release of chemicals that tell the brain to be careful.

Visceral structures include major organs like the heart, stomach, and uterus. Nociceptors located in the organs aren't as sensitive to cuts, burns, hot, or cold as somatic structures, but they are sensitive to inflammation, lack of oxygen, or being stretched. That's what causes the chemical response that tells the brain there is pain. Unlike nociceptors in somatic structures, however, it's often difficult to figure out exactly where visceral pain is coming from. Instead of being localized to one specific area, visceral pain tends to be diffuse. Visceral pain is the kind felt during a heart attack or with menstrual cramps.

Non-Nociceptive Pain

It comes from the nervous system itself. If a nerve is injured, its ability to send signals correctly is impaired. It misfires and the brain interprets these confused signals as pain. That's what people feel when they have trapped nerves. While it can be quite painful in the area around the irritated nerve, the pain isn't directly caused by tissue damage. There are two kinds of non-nociceptive pain—neuropathic and neuroplastic.

Neuropathic pain is the kind experienced with multiple sclerosis or carpal tunnel syndrome and results from damage to or dysfunction of the nervous system. The nerve fibers misfire and send pain signals to other pain centers. The nerve fibers themselves might be damaged or they might not function properly because of inflammation, degeneration, infection, pressure, diabetes, strokes, autoimmune disorders, and other illnesses.

Neuroplastic pain occurs when there are changes within the nervous system, but there is little or no actual tissue or nerve damage. Amputees who feel pain in a limb they no longer have experience neuroplastic pain.

Whatever the cause or type of pain you're experiencing, it serves the purpose of telling you something has to change. Maybe you need first aid or emergency care. Maybe you need to change your diet, get some exercise, or reduce your stress. Or maybe you need a complete physical. Whatever the reason, listen to your body and give it the attention it deserves. 




PubMed - National Institutes of Health

Annals The New York Academy of Science  2001 Mar;933:157-74.

Central neuroplasticity and pathological pain.
Melzack R, Coderre TJ, Katz J, Vaccarino AL.
Department of Psychology, McGill University, Montreal, Quebec, Canada.

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