98 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



changes in pressure. In addition, the treppe phenomenon makes possible 

 a study of temperature and pressure on the activation process per se. 



In a resting auricle stimulated only for testing (35) the tension in- 

 creases with temperature and reaches an upper limit which may be main- 

 tained up to 30°C provided the exposure to the higher temperature is 

 brief (fig. 7^4-11. An auricle responding in this manner may be con- 

 veniently designated as 'non-treppe.' In contrast, the tension in a resting 

 heart, which may be termed a 'treppe heart,' rises to the upper limit 

 at 9°C, but thereafter decreases progressively with a rise in temperature 

 (fig. 7^4-2). At 9°C the tensions in the treppe and non-treppe hearts are 

 identical. In the treppe heart repetitive stimulation at a suitable fre- 

 quency causes an increase in tension at all physiological temperatures 

 above that of the optimum at 9°C. At each of these higher temperatures 

 the maximum tension resulting from repetitive stimulation approximates 



10 15 



TEMPERATURE 



Fig. 7. A: Isometric tension 

 in relation to temperature in 

 turtle auricular muscle: (1) non- 

 treppe heart, (2) treppe heart, 

 (3) treppe heart with 80% CO2. 

 B: Logio [y/(l — y)] for auricu- 

 lar tension in relation to tem- 

 perature. For description see 

 text. 



35 36 



l/Tobs.X 10 



that obtained at the optimum at 9°C, i.e. approximates that of a non- 

 treppe heart (36, 37). As will be indicated subsequently, the treppe phe- 

 nomenon relates to the activator mechanism, and may be omitted from 

 the immediate considerations of tension. 



In the non-treppe heart, the tension-temperature relation resembles 

 that for the tetanus tension in striated muscle. In both, a constant tension 

 is maintained over a wide range of temperatures. In the tetanus this is 

 attributed to the fact that the 'active state' is sustained long enough for 

 the maxmum tension to develop at each temperature. A similar expla- 

 nation may be put forward for the heart, from which it would follow 

 that in the non-treppe heart the fall-off in tension above the optimum 

 temperature would result from a termination of the 'active state' before 

 tension development has been completed. 



In both the treppe and non-treppe heart the tension-temperature re- 

 lation is similar up to the optimum temperature (fig. 7.4-1 and 2) . Since the 

 duration of the 'active state' is sufficient for maximum tension at the 



