SECTION XI 



THE NERVOUS REGULATION OF THE 

 BLOOD-VESSELS^ 



CHAPTER XXXIV 



THE INNERVATION OF THE BLOOD-VESSELS OF DIFFERENT 



ORGANS 



General Discussion. — The nervous control of 

 the vascular system is effected by two groups of 

 elements, one of which is concerned with the control 

 of the activity of the heart, and the other with that 

 of the caliber of the blood-vessels. The former, as 

 we have seen, are acceleratory and inhibitory in 

 their nature and are dominated by nervous ele- 

 ments situated in the medulla oblongata. The 

 latter, on the other hand, are apportioned to the 

 peripheral vascular system and regulate the size of 

 the blood-bed. For this reason they are designated 

 as vasomotor elements. The general arrangement 

 of this mechanism is the same as that controlling 

 the function of the heart. It consists of a central 

 mass of ganglion cells and of two sets of nerve fibers 

 which conduct either in an afferent or in an efferent 



1 Vershuir (Diss. Groningen, 1766) observed that the me- 

 chanical excitation of the walls of such arteries as the caro- 

 tid and femoral, led to a marked constriction of their lumen. 

 Wedemeyer (Kreisl. des Blutes, Hanover, 1828) obtained 

 the same results with electrical stimulation. In 1831, E. H. 

 Weber (Archiv fiir Anat. und Physiol., 1847) explained the 

 phenomenon of flushing and paling upon the basis of varia- 

 tions in the resistance to the blood which are brought about 

 by the muscular contractions following nervous discharges. 

 Claude Bernard (Compt. rend., 1851) then called attention 

 to various vascular changes connected with the cutting of 

 the cervical sympathetic nerve, while Brown-Sequard (Phila- 

 delphia Med. Exam., Aug., 1852) ascertained that the excita- 

 tion of the proximal stump of this nerve led to a constriction 

 of the blood-vessels. Very similar results were obtained 

 by Waller (Compt. rend., 1853), but their publication was 

 deferred until 1853. 



411 



Fig. 221.— Re- 

 flex Circuit for 

 Vasomotor Actions. 



R, receptors; A, 

 afferent path; VMC, 

 vasomotor center 

 which is intimately 

 connected with 

 other centers, for 

 example, the cardiac 

 (CC) and respiratory 

 centers (RC); E, 

 efferent path; B, 

 effector in blood- 

 vessel. Stimulation 

 between fl and VMC 

 gives rise to pressor 

 and depressor 

 effects, stimulation 

 between VMC and 

 B to vasoconstrictor 

 and vasodilator 

 effects. 



