The Innervation of the Alimentary Canal
REGULATORY CENTERS & AFFERENT PATHWAYS
CENTRAL NERVOUS SYSTEM (CNS)
Visceral regulatory centers in the cortex, limbic system (olfactory areas, hippocampus, amygdala, cingulate cortex, septal area), hypothalamus, reticular formation.
AUTONOMIC NERVOUS SYSTEM (ANS)
Parasympathetic neurons are located in the brain stem nuclei, (Superior and inferior salivatory nuclei, lacrimal, and the dorsal nucleus of the vagus) and in the intermediolateral cell columns of the spinal segments S2-S4 and synapse with interneurons of the Enteric nervus system. Preganglionic sympathetic neurons are located in the intermediolateral columns of the spinal segments T1-L3. They synapse in the celiac, superior and inferior mesenteric plexuses with postganglionic neurons the endings of which terminate on axo-axonal synapses on both parasympathetic and ENS intrinsic fibers.
ENTERIC NERVOUS SYSTEM (ENS)
Neurons of the ENS are located in the myenteric and submucosal plexuses of the alimentary canal. The enteric plexuses contain sensory neurons, interneurons, and effector (excitatory and inhibitory) neurons.
Vagal afferent fibers originate in the solitary nucleus of the medulla. -
Splanchnic fibers originate:
a) in the intermediomedial cell column of lamina VII in the spinal cord segments T1-L2, and in the segments S2-S4. The ascending fibers are included in the spinoreticular and spinothalamic tracts
b) in the neurons located in the dorsal root ganglia which send axons to
1) the prevertebral ganglia
2) a second-order neuron in the dorsal horn of the spinal cord which crosses the spinal cord, ascends in the spino-thalamic and spino-reticular tracts to synapse with a third- order neuron in the thalamus and reticular formation.
From the medulla and spinal cord fibers reach the reticular formation of the brain stem, hypothalamus, and ventral posterior nucleus of the thalamus and from these areas neurons project to the somatosensory cortex and the anterior cingulale gyrus.