Lecture 19Outline of Last Lecture I. Cranial NervesII. Names of the Cranial NervesIII. Functional Grouping of Cranial NervesIV. Visceral Sensory ComponentsV. Visceral Motor FibersVI. Comparing Cranial Nerves and Spinal NervesVII. The Autonomic Nervous SystemOutline of Current LectureI. The 2 parts of the Autonomic SystemII. Parasympathetic III. Sympathetic IV. Control of the ANSV. Visceral Sensory NeuronsVI. The EyeCurrent LectureI. The two parts of the autonomic systema. Parasympathetic and Sympathetic, they come from different parts of the CNS i. Almost all visceral organs are supplied by both sympathetic and parasympatheticii. Antagonistic to each other: opposite effects on an organ’s musculature or glandsiii. Parasympathetic neurons activate the organs of digestion1. Resting and digestingiv. Sympathetic neurons tend to shut down digestive organs 1. Fight, fright, and flightv. Many functional differences between the 2 vi. Anatomical and Biochemical differences:1. Attach to different parts of the CNS2. Parasympathetic is cranio-sacrala. Motor axons come off the brain stem and sacral spinal cord3. Sympathetic is thoraco-lumbara. Motor axons arising from the thoracic and upper-lumbar spinal cord4. Parasympathetic: long pre-G, short post-G5. Sympathetic: short pre-G, long post-G6. Parasympathetic NT is acetylcholine7. Sympathetic NT is norepinephrine8. We have cholinergic (acetylcholine-releasing) vs. adrenergic (noradrenaline-releasing) axon terminals 9. At preganglionic terminals, the NT for both the sympathetic and parasympathetic is acetylcholineII. Parasympathetic Division (Craniosacral)a. Cranial Part BIOL_315 1nd Editioni. Cranial parasympathetic fibers: preganglionics run within four of the cranial nerves: oculomotor, facial, glossopharyngeal, and vagusii. Cell bodies are located in visceral motor nuclei along the brain stem iii. The cranial parasympathetic outflow innervates the smooth muscle and glands ofthe head 1. Oculomotor nerve (III)a. Signal a smooth muscle in the iris of the eye to constrict the pupilb. Signal the ciliary muscle to cause the lens to bulge (allows for focusing)c. Pre-G bodies of III are in visceral motor nucleus in the midbraind. Post-G bodies are behind the eye in the orbit, in ciliary ganglion 2. Facial nerve (VII)a. Signal several glands in the head to secreteb. Salivary glands and nasal glandsc. Pre-G bodies are in visceral motor nucleus in the pons d. Post-G cell bodies in two ganglia in the face, pterygopalatine ganglion posterior to the maxilla, and the submandibular ganglion which lies medial to the mandible, near its angle3. Glossopharyngeal nerve (IX)a. Stimulate the secretion of single salivary gland, the paraotidb. Pre-G cell bodies in vmn in the medulla oblongata c. Post-G cell bodies in otic ganglion , inferior to the foramen ovaleThe trigeminal is the only mixed cranial nerve that has no pre-g autonomic fibers of its own4. Vagus nerve (x)a. Innervate the visceral muscle and glands of the organs in the thorax and most of the abdomen b. Wanders widely c. Stimulate digestion, slow the heart rate, and constrict the bronchi in the lungs, among other functionsd. Pre-G in medulla oblongata e. Post-G mostly in the ganglia in the walls of the visceral organs being innervated i. Intra-mural ganglia “within the walls”b. The sacral part of sympathetic divisioni. Outflow comes from the 2nd -4th sacral segments of the spinal cordii. Innervates the pelvic visceral organs iii. Signals the bladder and rectum to empty, causes erectioniv. Pre-G in the gray matter of the sacral spinal cordv. Post-G mostly intra-mural vi. Pre-g run first in the ventral roots, then branch off of the ventral rami as pelvic splanchnic nerves to the pelvic organs III. Sympathetic Division (Thoracolumbar)a. Introductioni. Arises from pre-G cell bodies in the thoracic and upper-lumbar parts of the spinalcordii. Sympathetic division more complex (both functionally and structurally) than the parasympathetic iii. Because the sympathetic innervates the internal visceral organs and the visceral structures in the periphery of the body 1. The arrector pili muscles in the skin and sweat glands (no parasympathetic innervation)iv. All arteries and veins have smooth muscle in their walls that is innervated by sympathetic fibers v. More ganglia , 2 types 1. Sympathetic trunk gangliaa. Paired and arranged segmentally b. 22-24 pairs of trunk gangliac. One pair / spinal cord segment from cervical to sacral 2. Prevertebral gangliaa. Fewer in number b. Lie in midline of the body c. Anterior to the vertebral column d. The major ones include: coeliac, superior mesenteric, inferior mesenteric, and hypogastric ganglia e. All located in the abdomen and pelvic region b. General Arrangement of the sympathetic division i. The pre-G sympathetic neurons located in visceral motor zone of spinal cord (T1-L2)1. Collectively form a pointed lateral bulge of gray matter called the lateral gray horn 2. The pre-G fibers extend through the ventral root into the spinal nerve 3. Then turn ventrally and form a nerve called the white communicating ramus to a sympathetic trunk in ganglion 4. In the trunk ganglion, 1 of 3 things can happen to the fiber a. Can synapse with post-G cell body in the 1st sympathetic trunk ganglion it entersb. The pre-G fiber can pass through the sympathetic trunk ganglion, run in a splanchnic nerve, then synapse in a prevertebral ganglioni. Like internal abdominal organs: stomach and intestines c. The pre-G fiber can run through the sympathetic trunk ganglion, without synapsing, then ascend or descend to synapse in another trunk ganglion or prevertebral ganglion c. Detailed sympathetic pathwaysi. Sympathetics to the periphery of body1. Innervation of sweat glands and arrector pili muscles in the skin, muscularwalls of the peripheral arteries and veins 2. But how do these fibers get to the peripheral region?a. Pre-G fibers run in ventral roots, spinal nerves, ventral rami, synapse with cell bodies of post-G neurons b. Post-G fibers enter the dorsal or ventral ramus and either follow out to the skin or leave to jump upon a blood vessel, innervating all branches of this vesselWhite rami are present only on the sympathetic trunk ganglia in the region of sympathetic outflow from the spinal cord, but gray rami are on all the trunk ganglia, from the cervical to the sacral region.Rami are in PNS and gray/white matter are in the CNSii. Sympathetics of the head1. Head supplied by
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