A patient with chronic back pain is prescribed a TENS (Transcutaneous Electrical Nerve Stimulation) unit. Why does TENS often reduce pain perception?

💡 Explanation

TENS activates large-diameter A-beta fibers, which stimulate inhibitory interneurons in the spinal cord, increasing enkephalin release. This process is called the gate control theory of pain modulation, because enkephalins inhibit nociceptive signal transmission. Therefore, pain is reduced, rather than other mechanisms such as decreasing A-delta firing or altering substance P release directly.

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