Posted by DK on October 11, 2009 at 11:27:01:
In Reply to: cranial nerves posted by Mitchell Sternlieb on October 08, 2009 at 22:52:24:
Short answer: read embryo.
Not-as-short answer: SVE fibers are innervating muscles derived from pharyngeal arches. They will be found only in the trigeminal, facial, glossopharyngeal, vagus, and spinal accessory nerves. Since these are voluntary muscles, I have a hard time calling them parasympathetic or sympathetic.
GVE fibers are found in the oculomotor, facial, glossopharyngeal, and vagus nerves. We already know that the vagus does parasympathetic innervation of, well, a lot of the viscera. The facial and glossopharyngeal carry parasympathetic innervation from the superior and inferior salivatory nuclei, respectively. The oculomotor nerve does parasympathetic innervation of the eye. So, GVE fibers are only parasympathetic innervation.
Here's another way of thinking about it. The parasympathetic nervous system evolved first. That's why it is embedded in the other structures of the body (i.e. short post-ganglionic neurons). Therefore, anything in the cranial nerves that is part of the autonomic nervous system should be parasympathetic. The sympathetic nervous system evolved second and is just kind of pasted on to the body. Remember, sympathetic neurons only originate from T1-L3. To borrow from Dr. Evey, that's something you can hang your hat on.
: Hi,
: As I study the tutorial, I had a question regarding SVE and GVE nerves. I am having difficulty classifying SVE or GVE fibers as parasympathetic or sympathetic. I feel that I can find clarity if I can understand the answers to the following two questions:
: 1. Must all SVE or GVE functional components be composed of parasympathetic or sympathetic fibers as opposed to somatic fibers?
: 2. Can we assume, if the answer to question 1 is yes, that SVE or GVE fibers that stimulate digestion and slow non-digestion related functions (such as cardiovascular related functions) are all parasympathetic?
: Thanks,
: Mitch