The entries in this section, “Pain Management,”
are about pain and its treatment. Entries dis-
cussing health conditions for which pain may be a
symptom appear in the system section appropriate
for the condition.
The Mechanisms of Pain
Pain can be a potent symptom, pointing to a sig-
nificant injury or disease process within the body.
Pain can also be a measure of HEALING, marking
the body’s progress toward wellness. And pain can
be an indicator of dysfunction, persisting when
there is no apparent reason for its existence. At a
primal level, pain is a sensory survival mecha-
nism. It tells the body to rapidly move to avoid its
source or cause. The SPINAL CORDconveys pain sig-
nals directly to several regions of the CENTRAL
NERVOUS SYSTEM, such as the thalamus, that regu-
late the body’s REFLEXresponses.
The message of pain begins with specialized
molecules, called nociceptors, that line the den-
drites of peripheral neurons. Dendrites are
branchlike networks that extend from a NEURONto
capture electrical signals and convey them to the
NERVE body, which focuses them into a more
organized nerve impulse. Nerve impulses travel
along chains of neurons (nerve fibers) until they
reach the large nerve clusters, the dorsal ganglia,
that feed into the spinal cord. The dorsal ganglia
further sort and focus nerve impulses, blocking
many from continuing to the BRAINbut allowing
passage for others. At this point the pain messages
transition from the PERIPHERAL NERVOUS SYSTEMto
the centralNERVOUS SYSTEM.
The first structure within the brain to receive
the nerve signals of pain is the thalamus. The
thalamus further filters the impulses and takes
rudimentary action to address certain aspects of
the pain response. It initiates reflex reactions for
pain signals that require it, dissipates some
impulses that it interprets as meaningless, and
sends the remainder on to the cerebral cortex for
more sophisticated interpretation. Neuron activity
in the cerebral cortex determines how the person
will perceive the pain—whether the signals are
indeed pain and what it will feel like (sharp, dull,
stabbing) and how intense it will be (mild, moder-
ate, severe). Pain generally results in one of two
actions: removing the involved body part from the
source of the pain or limiting the movement of
the body part.Traditions in Medical History
For thousands of centuries people have used nat-
ural substances to relieve pain. Willow bark con-
tains salicylic acid, the basis of aspirin. Oil of
wintergreen (Gualtheria procumbens) also contains
salicylic acid. Opium occurs naturally in the
poppy species Papaver somniferum. The leaves of
the coca plant (Erythroxylum coca) contain COCAINE.
Many modern analgesics contain synthetic prepa-
rations or derivations of these potent pain reliev-
ers. Some substances ancient healers turned to for
pain relief had very narrow margins of safety:PAIN AND PAIN MANAGEMENT
PAINis an unpleasant, subjective sensation associated with numerous health conditions and circumstances. Pain spe-
cialists are physicians who have additional education and training in the treatment and management of pain. Pain
specialists may be anesthesiologists, internists, neurologists, orthopedic surgeons, psychiatrists, or physiatrists.
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