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.
pathway is primarily involved with localizing a nociceptive stimulus.
More complex pathways contribute to the suffering quality of pain.
In this chapter,
the major pathways that play a role in transmitting nociceptive
information from somatic structures (e.g. skin and muscle),
some general differences in nociceptive transmission between
somatic structures versus visceral structures, and
in detail the neurophysiology of cardiac pain or angina pectoris.