Brief Introduction to Nociception and Pain: Part 1
February 28, 2017
This is a 3 part series on pain. It is meant to help educate you about the pain experience. The first part of this series is to help you better understand the initial processes that take place when you are injured.
Pain is an emotion that you experience that is like an alarm system on a car. The alarm system in a car is there to prevent a robber from breaking in. Your body has an alarm system as well in order to protect you when you are injured or there is a threat to your body. When you first experienced pain, this was the alarm system being set off in order to make you aware that there is a threat to your body. After the initial threat, your body may leave the alarm system set extra sensitive as you heal or seek help. This would be like the alarm system on your car being set sensitive after it had been broken into. Since the alarm system is now sensitive, even the wind can set it off.
Your bodies pain system is the same and can now be easily set off as you heal.This would explain why light touch and simple movements now feel painful. In most cases, as the tissue heals the alarm system will gradually go back to its normal state. In rare cases, your bodies pain alarm system stays set sensitive even though everything has healed. This is chronic or persistent pain which will be discussed further in future posts.
When you're first injured or experience pain there are receptors in nerve endings that are affected by chemicals that are released in order to promote healing. These chemicals will irritate nerve ending receptors that are plugged into the tissue making them sensitive. The irritated nerve endings will send information to the spinal cord and brain known as nociception. Nociception is not made up of pain messages. It is simply information about the injured tissue. It is your brain that creates the output of pain.
There may have also been small tiny micro-tears of the muscle or ligament that disrupted mechanoreceptors. Mechanoreceptors are for feeling stretch and pressure when you are moving any part of your body. These mechanoreceptors are now sensitive and can be easily irritated when you move the injured tissue.
The inflammatory chemicals may stay in the tissue for days. These chemicals can trigger your body to create more receptors on the nerve endings which can lead to increased sensitivity. Your body does this in order to protect you and make you aware of the injured area so that it can heal. Now the injured area becomes very responsive to movement and pressure. Only a tiny bit of movement or pressure can cause pain. This would explain why lightly bumping the area or blankets touching you can be painful.
The intensity of pain that you feel is due to the sensitivity of the nerve endings and not the severity of the injury. As the tissue heals the receptors will decrease and the nerve ending will no longer be sensitive. In rare cases, the tissue heals but the nerve endings do not go back to their original state and remain sensitive. This is persistent or chronic pain.
When you are injured or first develop pain there are 3 stages of recovery that you will experience. Professor Patrick Wall MD described these three stages when you are hurt or first develop pain as withdrawal, protection and resolution.
We will discuss the 3 stages of pain in greater detail in Part 2 of this series.