Observations on the cardio-accelerator reflex from stimulation of the skin temperature receptors

Abstract

Under our experimental conditions, the heart rate appears to be not only affected and controlled more by the skin temperature than by the body temperature, but our results also seem to indicate that the acuity and efficiency of this control decrease with the age of the individual, depending to some degree, however, upon the heating medium used. The efficiency factor has been derived by dividing the “change in heart rate” by the “change in bath temperature,” measured in degrees Fahrenheit and is represented by CHR CBT . When the heating medium is a hot air-radiant heat bath, the value of CHR CBT is about 5 times greater in a twenty-year-old individual than it is in one fifty-nine years old. The highest value obtained was from a twenty-year-old individual, namely 0.945, and the lowest value for CHR CBT was from a fifty-nine-year-old individual, namely 0.161. Four suggestions are submitted aiming to explain how the efficiency factor CHR CBT may change in value with the individual's age. In its effect on the heart rate, the hot water bath is about seven times as stimulating as is the dry air-radiant heat bath. That is, the average derived value of CHR CBT in the dry air-radiant heat experiments was 0.475 while the average derived value from the water baths was 3.3. The effects of the water bath upon the heart rate do not seem to vary according to the individual's age, as is the case with the effects from the dry air-radiant heat bath. The reason for this appears to lie in the much greater heat stimulation delivered by the water, and to an increased heat conductivity in the superficial skin layer, in turn caused by the imbibition of water by the older dryer skins. Upon the basis of the results obtained, it appears that the truest significance of a change in heart rate, if induced by temperature changes—water bath excepted—can be best obtained by considering such changes in relation to the individual's age, on a basis similar perhaps, to that of blood pressure. No definite relationship was observed between the baths and the metabolic rate, and in the few cases in which an increase in metabolism was noted, such an increase seemed to be related more closely to the skin temperature than to the body temperature.