FUNCTIONS OF THE AUTONOMIC NERVOUS SYSTEM 



6 7 I 



The Tenth and Eleventh Cranial Nerves. The vagus or tenth cranial 

 nerve is perhaps the most composite of all the autonomic nerve pathways. 

 It together with the roots distributed to it from the accessory supplies 

 inhibitory fibers to the heart; motor fibers to the bronchi, esophagus, 

 stomach and intestine; and secretory fibers to the gastric glands, pancreas 

 and liver. The pre-postganglionic unions are found in small terminal 

 ganglia such as the local cardiac ganglia. 



The Sacral Autonomies. These fibers arise from the sacral cord at the 

 level of the second and third sacral nerves. The fibers do not join the 



M 



S 



FIG. 4iqA. Diagrammatic representation of the scheme of innervation of the ali- 

 mentary canal. A, mucosa; B, sensory nerve endings; C, gastric or intestinal wall; 

 D and E, sensory and motor cell bodies in the enteric plexus; M, motor neurons, 

 vagus fibers for the stomach and upper portion of the intestine, sympathetic fiber 

 lower down; S and S', afferent sensory nerves; Sy, sympathetic ganglion, pre-post- 

 ganglionic synapse, inhibitory path for the mammalian canal. The fiber S' is introduced 

 to Dixon's original figure on the basis of his foot-note. (Greene, modified from Dixon.) 



main sympathetic chain but are distributed in the nervus erigens by way 

 of the ganglia of the pelvic plexus. The nerves furnish motor fib,ers to the 

 bladder, the descending colon and rectum; inhibitory fibers to the sphinc- 

 ter muscles of the bladder. They also contain vasodilators for the rectum, 

 anus and penis; also inhibitory fibers to the retractor penis muscle. The 

 urogenital system obviously receives its double innervation in part from 

 the thoracic autonomies and in part from the sacral autonomies. 



The Enteric Nervous System. The enteric autonomies consist of those 

 ganglia and fibers lying between the muscle walls of such hollow organs as 

 the stomach, intestine, etc. Among all the numerous peripheral ganglia 

 of the body the ganglia in the stomach and intestinal wall are the only ones 



