Autonomic Reflex Arc

• First link: Visceral autonomic afferents to the CNS

  • Non-myelinated, carried to the cerebrospinal axis by autonomic nerves (e.g.vagus and splanchnic)

  • Some autonomic afferents from skeletal muscle blood vessels and integumental structures may be carried in somatic nerves

  • Cell bodies of visceral afferents: (a) spinal nerves--in dorsal root ganglia; (b) cranial nerves-- in sensory ganglia

  • What information gets transmitted?

• Mediated Information:

  • visceral sensation (pain;referred pain)

  • vasomotor reflexes

  • respiratory reflexes

  • viscerosomatic reflexes: Definition: Viscerosomatic: Pertaining to the viscera and body

• Substance P is an important sensory neurotransmitter, probably especially important in nociception, and is found in:

  • sensory afferent fibers

  • dorsal root ganglia

  • dorsal spinal cord horn

• Other agents found in sensory neurons

  • Somatostatin

  • Vasoactive intestinal peptide (VIP)

  • Cholecystokinin (CCK)

  • Calcitonin gene-related peptide (CGRP) (found with Substance P in cardiovascular sensory nerve fibers)

• Dorsal Spinal Cord (substantia gelatinosa) Interneurons

  • Enkephalins: Antinociceptive due to inhibition of substance P release and reduced transmission to higher centers

Category: Pharmacology Notes