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PHYSIOLOGY FOR NURSES 



The elements of the central nervous system are the 

 brain, divided into the two hemispheres of the cerebrum, 

 two crura, connecting links between the cerebrum and 

 the lower portions of the nervous system, the pons, the 

 medulla or ~bulb, the two hemispheres of the cerebellum 

 and the spinal cord. All of these component parts, ex- 

 cept the last, are found in the skull, enclosed in. the 

 three membranes of the brain, while the cord, also en- 

 closed in three similar membranes, continuous with 



Fig. 22. Schema of simple reflex arc: r, receptor in an epithelial mem- 

 brane; a, afferent fiber; s, synapsis; c, nerve cell of center; e, efferent fiber; 

 m, effector organ. (Pearce-Macleod, Fundamentals of Human Physiology.) 



those of the brain, is in the spinal canal which runs 

 through the vertebral column. 



The peripheral nervous system is made up of the cra- 

 nial and spinal nerve trunks and ganglia and their nu- 

 merous endings in various parts of the body. 



The sympathetic system is a chain of ganglia and con- 

 necting fibers situated on each side of the spinal col- 

 umn, connected with both cranial and spinal nerves, and 

 witie 



