A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . d depressor the question arose as to whetherthey contain two distinct varieties of nerve fibersor whether the different results depend only on thecondition of the centers and the character of thestimuli used. That both of these factors mayinfluence the result can be easily shown. A sensorynerve like the , whose stimulation regularlyproduces vasoconstriction and rise of blood pressurein an animal under curare (Fig. 743) wUl frequentlygive a fall of pressure
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . d depressor the question arose as to whetherthey contain two distinct varieties of nerve fibersor whether the different results depend only on thecondition of the centers and the character of thestimuli used. That both of these factors mayinfluence the result can be easily shown. A sensorynerve like the , whose stimulation regularlyproduces vasoconstriction and rise of blood pressurein an animal under curare (Fig. 743) wUl frequentlygive a fall of pressure when chloral or ether is usedfor the anesthetic. Again, mechanical stimulationof the sensory nerves in muscles by kneading ormassage regularly causes reflex vasodilatation, whileelectrical stimulation of the same nerves gives reflexconstriction. On the other hand there is strongevidence for the view that there are both pressorand depressor or reflex vasodilator fibers inthe sciatic and other peripheral trunks. The pressorfibers ordinarily have the Tipper hand, but by sub-jecting the nerve to the action of cold or stimulating. Fig. 74.*^.—Pressor Effect Produced by Stimulatins: the Cen-tral End of the Sciatic of a Curarized Cat Under Morphine. Timetracing in seconds. Reduced one-half. the nerve at a certain stage of regeneration aftersection, the depressor effect may be obtained. Thedepressor fibers seem to retain their power of con-duction longer than do the pressor fibers when cooled,and when the nerve is cut and sutured they regenerateearlier. There is also a certain amount of evidenceto indicate that the fall of pressure from stimulationof the sciatic and similar nerves is of a differentnature from that resulting from stimulation of tliedepressor nerve of the heart (Fig. 744). In theformer case the dilatation occurs largely in thelimbs and is probably due to a reflex stimulationof dilator fibers, so that the name reflex vaso-dilators has been suggested for this of f
Size: 2070px × 1207px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorbuckalbe, bookcentury1900, bookdecade1910, bookyear1913
