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The
nociceptive pathway
Nociceptive
stimuli are stimuli that injure or potentially injure tissue,
and therefore excite nociceptors. Thus a nociceptive stimulus
may or may not lead to the actual sensation of pain depending
on an individual's specific environment.
For a nociceptive
stimulus to be interpreted as pain, the nociceptive information
must be transmitted from the periphery to the cerebral cortex.
The "classic," and simplest, pain pathways use a three-neuron
pathway to transmit nociceptive information:
- A primary
sensory (or afferent) neuron in the peripheral nervous system
that conducts nociceptive information from the periphery
(such as skin) to the central nervous system (spinal
cord and brain).
- A secondary
sensory neuron in the spinal cord or brain stem that transmits
the information to the thalamus.
- A tertiary
sensory neuron that conveys the nociceptive information from
the thalamus to the cerebral cortex.
This three-neuron
pathway is primarily involved with localizing a nociceptive stimulus.
More complex pathways contribute to the suffering quality of pain.
In this chapter,
we will:
- Describe
the major pathways that play a role in transmitting nociceptive
information from somatic structures (e.g. skin and muscle),
- Discuss
some general differences in nociceptive transmission between
somatic structures versus visceral structures, and
- Examine
in detail the neurophysiology of cardiac pain or angina pectoris.
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