Providing straightforward information pertaining to drugs, drug use & drug policy. The Grey Pages promotes drug-related literacy and advocates a system of viable and tolerant drug policies. This is my personal collection of commentaries, essays, tid-bits, and other such writings on everything ranging from drug use, drug policy and drug-myths, to drug-science, addiction, human behavior, and the workings of the human brain. I started this blog with a particular focus on opioids, and over the past year have found my interest gravitate toward the intriguing, ever-changing world of designer intoxicants (i.e. "research chemicals" or "designer drugs").

Saturday, October 30, 2010

The Perception of Pain: An Overview of Nociception

The human nervous system is equipped with a complex set of sensory nerves with the specific purpose of sensing threatening or painful stimuli.

pain flow chart
Sensory receptors (nerve endings) are located throughout skin, muscle, bones, organs, and other tissue. A sensory receptor that detects painful stimuli is typically known as a nociceptor. Nociceptors use the process of "nociception" to detect painful situations, encode pain signals and transmit these signals to the central nervous system - up through spinal neurons (delta A and C fibers), on up the spinothalamic tract, and ultimately to key pain processing areas of the brain, to be interpreted by the conscious mind and the autonomic brain; thus triggering a physical and emotional response to pain.

A number of different types of pain receptors (nociceptors) have been identified, each with the ability to sense specific type of stimulus, above a certain threshhold; nociceptors can be classified by the specific stimulus they respond to, whether it be thermal, mechanical, chemical, or somatic (physical damage); the latter of which may only respond to actual injury or trauma.

Basic map of neurotransmission
The primary neurotransmitter involved in carrying peripheral pain signals to the brain is known simply as Nociceptin - A peptide which binds to the nociceptin receptor (NOP-1), generally acting as a potent algetic (pain transmitter) and anxiomimetic (anxiety inducing agent). Substance P plays a role in pain transduction at the spinal and hindbrain (lower brain) levels. It is also involved in the transmission of signals associated with anxiety, and stress.

Several classes of drugs are useful in relieving pain, both non-narcotic and narcotic. Yet almost any effective analgesic, with few exceptions, will directly or indirectly enhance the endogenous opioid system. Furthermore, any effective analgesic has a direct or indirect effect on the process of peripheral or spinal nociception.


  1. Very well written blog, explaning the Perception of Pain with good/easy diagrams.

    It helped me a lot to understand the process.I am training in and researching on alternative therapies to relieve aches and pains; therefore trying to understand perception of pain to begin with.

    Thank you for the blog.

    Bless you,


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