Gate Control Theory of Pain

This article or area is currently under construction and may only be partially complete. Please come back soon to see the finished work! (21/04/2022)

Original Editor - Kapil Narale

Top Contributors - Kapil Narale  

Introduction

The Gate Control Theory of Pain is a mechanism, in the spinal cord, in which pain signals can be sent up to the brain to be processed and accentuate the possible perceived pain, or attenuated at the spinal cord itself.

The 'gate' is the mechanism where pain signals can be let through or restricted. One of two things can happen, the gate can be 'open' or the gate can be 'closed':

• If the gate is open, pain signals can pass through and will be sent to the brain to perceive the pain.

• If the gate is closed, pain signals will be restricted from travelling up to the brain, and the sensation of pain won't be perceived.

If someone experiences painful (noxious) stimulus, the application of a non-noxious (soothing or light rubbing) stimulus can help activate the gate control mechanism, and reduce the pain. (find a source)

There are also other factors which can help facilitate the pain gate theory in reducing the perceived pain. These will be further outlined below.

Physiological explanation

Physiology

The pain gate mechanism is located in the dorsal horn of the spinal cord, specifically in the Substantia Gelatinosa. The interneurons within the Substantia gelatinosa are what synapse to the primary afferent neurons, and are where the gate mechanism occurs. Thus, the substantia gelatinosa modulates the sensory information that is coming in from the primary afferent neurons.

Primary neurons come in three different types:

• A-β fibers, large diameter fibers, have a quick transmission of impulses, due to their myelination - these type of fibers are activated by non-noxious stimuli (find a source for this)

• C fibers, with a smaller diameter fiber, have a slower transmission of impulse since they are not myelinated - these type of fibers are activated by heat and/or chemical stimuli (find a source for this)

• A-δ fibers, are similar to C fibers - these type of fibers are stimulated by noxious stimuli (find a source for this)

If the interneurons in the substantia gelatinosa are stimulated by the non-noxious large diameter A-β fibers, an inhibitory response is produced and there are no pain signals sent to the brain, and in this instance the 'pain gate' is closed.

When the interneurons are stimulated by the smaller diameter A-δ or C fibers, an excitatory response is produced. In this case pain signals are sent to the brain, these can be modulated, send back down through descending modulation, and perceived as pain.

(the pain gate chemical process)

(picture)

(parts of the brain that can send varying messages)

Modulation of the Pain ad Application to the General Population

The painful sensation that is perceived and experienced isn't only driven by the sensory event, but also the pain signals sent from the brain (through the descending modulation) due to thoughts, attitudes, emotions, and feelings that surround the painful experience.

This relates to the biopsychosocial model, and can help increase or decrease the pain perceived. If someone has worrisome or anxious thoughts, emotions, past experiences, or receives negative social feedback, pain signals will be sent own from the brain passing through an 'open gate', and the pain perceived will be worse. However, positive thoughts and emotions about the painful experience, relaxation, or positive social feedback, will cause the gate to close, and the person will essentially experience less pain.

Th usage of TENS activates the pain gate mechanism to inhibit pain signals going up to the brain, and to reduce the sensation of pain.

Rubbing, massaging, TENS, paing?

Resources

• bulleted list
• x

or

1. numbered list
2. x