When incoming nociceptive afferents activate interneu-
rons, it may lead to the phenomenon of
the sensation of pain is experienced at a site other than the
injured or diseased tissue. For example, during a heart attack,
a person often experiences pain in the left arm. Referred pain
occurs because both visceral and somatic afferents often con-
verge on the same neurons in the spinal cord (
Excitation of the somatic afferent ﬁ bers is the more usual source
of afferent discharge, so we “refer” the location of receptor acti-
vation to the somatic source even though, in the case of visceral
pain, the perception is incorrect.
shows the typi-
cal distribution of referred pain from visceral organs.
Pain differs signiﬁ cantly from the other somatosensory
modalities. After transduction of the ﬁ rst noxious stimuli into
Referred pain. (a) Convergence of visceral and somatic afferent neurons onto ascending pathways. (b) Regions of the body surface where we
typically perceive referred pain from visceral organs.