120 



HUMAN PHYSIOLOGY 



had their rise in the eyes, the ears, and the muscular 

 apparatus. It is as constantly sending out impulses 

 destined to modify the action of the skeletal muscles 

 and through them to assist in preserving equilibrium. 



The Autonomic System. This term is used to dis- 

 tinguish that part of the efferent nervous system trans- 

 mitting impulses from the central axis to the heart, 

 the glands, and the smooth muscle of the entire body. 



FIG. 31. Above is shown the typic motor neuron extending from 

 the central nervous system to the fibers of skeletal muscle. 



Below is the autonomic type of path. The neuron which leaves the 

 central nervous system does not span the whole interval but ends in 

 synaptic union with ganglion cells. These in turn send axons to the 

 tissue controlled in this case smooth muscle. 



The name autonomic is nearly equivalent to " self- 

 acting" and is used to emphasize the contrast which 

 exists between these mechanisms and the skeletal 

 muscles -the latter being more definitely under our 

 control. Autonomic pathways lead away from the 

 central system at every level from the third cranial 

 nerve to the most posterior portion of the cord. 



We have seen that the paths from the brain and cord 



