The dorsal column where the nerves synapse The activation of the large diameter A-β fibers also can help reduce and inhibit the transmission of the small diameter A-δ and C fibers. In this case, pain signals are sent to the brain, these can be modulated, sent back down through descending modulation, and perceived as varying amounts of pain. When the interneurons are stimulated by the smaller diameter A-δ or C fibers, an excitatory response is produced. 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. C fibers, similar to A-δ fibers, have the slowest transmission of impulse since they are not myelinated - these type of fibers are activated by pain and temperature, namely prolonged burning sensations.A-δ fibers, a smaller diameter fiber - they are thinly myelinated, and are stimulated by noxious stimuli, such as pain and temperature, specifically sharp, intense, tingling sensations.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, such as light touch, pressure, and hair movement.Primary neurons come in three different types: Thus, the substantia gelatinosa modulates the sensory information that is coming in from the primary afferent neurons. The interneurons within the Substantia gelatinosa are what synapse to the primary afferent neurons, and are where the gate mechanism occurs.

The pain gate mechanism is located in the dorsal horn of the spinal cord, specifically in the Substantia gelatinosa. There are also other factors which can help facilitate the pain gate mechanism in reducing the perceived pain. If someone experiences a 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. 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 the gate is open, pain signals can pass through and will be sent to the brain to perceive the pain.One of two things can happen, the gate can be 'open' or the gate can be 'closed': The 'gate' is the mechanism where pain signals can be let through or restricted.

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 to accentuate the possible perceived pain, or attenuate it at the spinal cord itself.

3.1 Transcutaneous Electrical Nerve Stimulation (TENS).

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