SENSE ORGANS AND NERVOUS COORDINATION 



595 



thetic fibers leave the central nervous system through the ventral roots 

 of spinal nerves in the thoracic and anterior lumbar regions (Figs. 29.10 

 and 29.12), and pass through the ramus communicans to a sympathetic 

 cord, one of which lies on each side of the vertebral column. These 

 fibers may synapse with the postganglionic fibers in the sympathetic 

 ganglia in the sympathetic cord, or they may continue from the sympa- 

 thetic cord through splanchnic nerves to collateral ganglia located at 

 the base of the coeliac and mesenteric arteries. Postganglionic sympa- 

 thetic fibers continue from the ganglia to the organs they supply. Those 

 to the skin reenter the spinal nerves, but the others tend to follow along 

 the arteries to the organs. Preganglionic parasympathetic fibers are dis- 

 tributed to the organs through the oculomotor, facial, glossopharyngeal 

 and vagus nerves, and through a pelvic nerve derived from certain spinal 



■Midbrain 



iary ^anolion— 



snopalatine 

 ganglion- 



,j^^ >rj;^Lacrimal dl 



■ 4^^ZZ^^^^~ Subrnaxillary gland 

 77^^ — Sublingual ol^ind 



Spinal 

 cord 



First 

 thoracic 

 segment 



"--.^ Otic OanOlion^ -^ i>uJ3lin0u< 



nOual oland 

 ti" 

 gla.nd 



-Heart 



^^^::y-Thyroid 

 ^ -'—Stomach. 



First 

 lumbair 

 segment 



Second 



sacral 



Segment 



land 



mucosa. 



Liver 



Pancreas 



■Adrenal 



medulla 



Small 

 intestine 



Figure 29.12. The human autonomic nervous system. Sympathetic fibers are drawn 

 in solid Unes; parasympathetic fibers in broken lines. The sympathetic fibers that go 

 to the skin are not shown. (After Howell.) 



