What Do You Really Know About Pain?

Have you ever wondered about how pain works? Why some injuries hurt and others do not? Why your little child doesn’t start crying after getting a minor injury until someone points out that he is bleeding or that he should be hurting? The next two posts will try to explain how pain works, its importance, and strategies for managing the pain.

All pain is real and never “made up.” Most commonly, pain will occur when the body’s “alarm system” alerts the brain to actual or potential tissue damage. Pain can involve all of the body’s systems and the responses that occur are aimed at protection and healing. If the brain thinks that experiencing pain is not in the best interest of the body at the time, then it may not be felt at the time of the initial injury. Pain can be very misunderstood, but understanding it can be an effective means to dealing with the it. A study in the Clinical Journal of Pain shows that understanding the physiology of pain changes the way people think about pain, reduces its threat value, and improves their management of it.

Physiology of Pain – The Foundation

Pain is a normal response to what the brain thinks are threats to the tissues. Surprisingly, the amount of pain you experience does not relate to the amount of tissue damage sustained. An article in the New England Journal of Medicinein 1994 showed that in low back pain, the amount of disc and nerve damage rarely relates to the amount of pain experienced. Also, the context of the injury can affect the pain experience. For example, a person that relies on his hands for a living will likely have a more intense pain experience with an injury to a finger than will a person who does not rely on his hands because the injury is a greater threat to the person who relies on his hands. 

Studies have also shown that the brain can remember pain. Even if the issue causing the pain has been removed, there is still pain because that particular area of the brain has become “smudged.” In other words, the signals from the body to the brain are not clear (think a pristine glass window versus a dirty glass window).

Although signals from the body are ultimately sent to the brain, there are no pain receptors in the body. Instead there are sensory receptors that respond to different types of stimuli (namely, mechanical, temperature, and chemical stimuli). These sensors can be found in skin, muscles, joints, discs of the spine, nerves, and other tissues. Sometimes injuries to these tissues can be sustained to such a minute degree that images such as x-rays or MRIs do not pick up on them; however the brain hasdetected a threat and has sent a pain signal out. This is seen a lot, specifically with nerve injuries/irritations.

When an injury occurs, the sensors read information and send it to the spinal cord, which then sends the information up to the brain. The brain decides whether the information received poses a threat to the tissues of the body and if a reaction or “alarm” needs to be made. The signal sent from the spinal cord to the brain only says “danger.” It does not say “pain.” If a threat is posed, the brain will send pain signals as an “alarm” to your body. The brain is very powerful when it comes to pain and management of pain. These sensors have a short lifespan; they live for a few days and then are replaced by fresh sensors. This means that the sensitivity of your body is constantly changing.  If you have pain this may be good news because the sensitivity of your body is not fixed.

However, there is a special type of sensor that will respond to all types of stimuli. These sensors respond when the stimuli are sufficient to be dangerous. Activation of these special sensors sends a prioritized alarm signal to your spinal cord which may be sent on to the brain. Activation of these sensors is called “nociception”. Nociception is the most common precursor to pain, but it does not always end in pain. Everyone has nociception happening all of the time. Only when the brain determines there is a threat and will be beneficial for your body to experience pain, does it send the signal out.

When your brain receives information from the sensors in the spinal cord (that it determines is a threat), it sends the pain signal and activates several systems in the body that work together to get you out of danger. These systems are designed to work well for a short period of time, and once the damage to the tissues is healed, the process stops (they are sprinters, not marathoners).

In the next post, we will get into more of the science behind pain. For now, what are your beliefs about pain? What are your beliefs about YOUR pain?

(The information presented here has been adapted from Butler and Moseley. Explain Pain.2008.)