Mechanism of Pain

Mechanism of Pain

While some may mistake nociceptive signals as pain, nociception is actually a noxious signal warning our brain of potential or actual injury. It doesn’t hurt until after our brain has collected the raw afferent data, evaluated our environment, and assessed the history of this kind of signal.

Raw Data Isn’t Felt

A music album on a CD that hasn’t been played is just a piece of plastic with data encoded on it. While the information on that CD could play a song, it is just data until it is played for someone to hear. For the CD to inspire an emotion, it first must be heard. Afferent signals operate the same way.

First Order Neurons

Data sent to the brain does not have a sensation; it is an afferent signal. Afferent signals are raw information that lack sensation until they are processed by the brain’s neural matrix.

Examples of afferent input our brain receives as raw data are interoception, exteroception, and nociception.

All sensation is an output, produced after raw data has been collected and translated by the brain into a sensation or an emotion. Like the X on a treasure map,  our brain marks the location of our pain on our somatosensory map.

Nociception

When a stimulus occurs, such as an injury, whether through physical force, extreme temperatures, or chemical changes that physically distort or irritate a nerve ending, it triggers nociception.

Nociception is a biological mechanism that acts like an alarm system, increasing awareness to protect the area from further damage.

This prompts a chemical soup of prostaglandins, bradykinin, and histamines to flood the area. Specialized receptor channels (doors) in nociceptors, such as TRPV1 and Nav1.7 ion channels, respond to this chemical mix. The chemical soup physically alters the “doors”, telling them to take note of prior injuries.

Protective Hypervigilance

Under normal circumstances, traumatic force or extreme heat is required to open these doors, but if a prior injury has occurred in these areas, the receptors become more sensitive. This may cause a danger response to trigger even if the area is not threatened.

Sometimes local nociceptors in the peripheral system become hypersensitive, lowering their thresholds to levels that are no longer beneficial. Hyperalgesia, hyperesthesia, and allodynia are examples of this.