. Elements of human physiology. Physiology. RESPIRATION 409 . /»3 n, deprivation of oxygen having tirst an excitatory and later a paralytic ect. In asphyxia the first centres to feel this effect are those of the cortex, d during the first stage there is mental excitation terminating rapidly in abolition of consciousness at the end of this stage. During the second stage here is a discharge of energy, which spreads throughout the whole nervous system, beginning in the bulbar centres and causing a great rise of blood pressure with slowing of the heart, and extending thence to all the spinal centr
. Elements of human physiology. Physiology. RESPIRATION 409 . /»3 n, deprivation of oxygen having tirst an excitatory and later a paralytic ect. In asphyxia the first centres to feel this effect are those of the cortex, d during the first stage there is mental excitation terminating rapidly in abolition of consciousness at the end of this stage. During the second stage here is a discharge of energy, which spreads throughout the whole nervous system, beginning in the bulbar centres and causing a great rise of blood pressure with slowing of the heart, and extending thence to all the spinal centres with the production of muscular spasms. At this stage, too, there is a discharge of impulses giving contraction of the pupil, and a little later dis- charge along the whole sympathetic system producing the various phenomena of vaso-constriction, erection of hairs, sweating, salivation, which are generally brought about by stimulation of different parts of this system. The phenomena of the third stage are due to a gradual exhaustion of the nerve-centres, accom- panied or preceded by an exhaustion and dilatation of the hea»t, the circulation failing before the excitation of the lower centres has entirely come to an end. In this third stage, however, it is impossible by the strongest stimuli to evoke any reflex, and the general phenomena are those of exhaustion. Although we must regard the specific sensibihty of the respiratory centre to COo as the most important factor in determining the depth and rhythm of the respiratory move- ments, these movements and the condition of the respiratory centre itself are modified in a large degree by impulses arriv- ing at the centre along both vagi. Through other sensory nerves of the body the respiratory movements can be altered reflexly, but it is only through the vagi that a continuous stream of impulses passes to the centre under normal circum- stances, so that exevy respiratory movement is modified by these impulses. iuG. /] Nor
Size: 1692px × 1477px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectphysiology, bookyear1
