Structure of the Parasympathetic Division
As mentioned, cell bodies of the parasympathetic preganglionic neurons are found in nuclei in the brain stem and in the lateral gray matter of the 2 nd through 4 th sacral segments. Axons emerge as part of a cranial nerve or as part of the ventral root of a spinal nerve. Cranial Parasympathetic Outflow : consists of preganglionic axons that extend from the brain stem in 4 cranial nerves which innervate the structures of the head. Vagus nerve carry nearly 80% of the total craniosacral outflow. Vagus axons extend to many terminal ganglia in the thorax and abdomen. Passing through the thorax, axons are sent to the heart, and airways of the lungs. In the abdomen, it supplies the liver, stomach, pancreas, SI, and part of the LI. Oculomotor extend to eyes
Facial extend to the lacrimal & salivary glands glossopharyngeal extend to the salivary glands
Sacral Parasympathetic Outflow : consists of preganglionic axons in the ventral roots of the 2 nd through 4 th sacral spinal nerves. As mentioned, these nerves become splanchnic nerves which synapse with parasympathetic postganglionic neurons located in the pelvic ganglia or terminal ganglia in the walls of visceral organs. From there, the postganglionic axons innervate smooth muscle and glands in the walls of the colon, ureters, urinary bladder and reproductive organs.
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