Table 1: Distinctive features of visceral spinal afferents relative to somatic.

(1)Dual extrinsic afferent system
(2)Convergence of afferents on somatic and other visceral afferents within the spinal cord
(3)Widely overlapping receptive fields
(4)Dichotomization of fibers where a single neuron innervates two viscera
(5)Collateral activation of autonomic and enteric nervous system
(6)Larger cell bodies within dorsal root ganglia
(7)Wide overlapping receptor fields
(8)Lack of specialized nerve terminals
(9)First-order afferents arborize over several spinal segments
(10)Greater expression of transient receptor potential (TRPV1), sodium (Na 1.8), acid (ASIC3) ion channels, and calcitonin gene-related protein (CGRP)
(11)Limited number of stimulus responses (distension, ischemia, and inflammation)
(12)More discrete location of first-order terminals within the spinal cord (superficial dorsal horn, lamina V, and central)
(13)Afferents ascend with parasympathetic and sympathetic neuronal projections
(14)Viscerovisceral hyperalgesia and hypersensitivity
(15)Visceromotor responses and referred pain to somatic sites innervated by the samespinal cord level
(16)Second-order afferents ascend in the dorsal column
(17)Nonsomatotopically arranged input in dorsal column and central lateral thalamus unlike the lateral spinothalamics
(18)Poor representation in S1 cortex
(19)Greater emotional and autonomic responses to pain than somatic pain