. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LIMULUS NEUROMUSCULAR TRANSMISSION 215 a spike but the second will lead to one and vice versa, the process being reversed again after a while. The spike mechanism either fatigues very easily or it is a very labile response. With prolonged repetitive stimulation, whether there is spiking or not, a plateau of depolarization builds up and is maintained. Brief bursts of stimulation illustrate the way in which the plateau builds up (Fig. 4ii, b-d). At the higher frequencies spikes, taking off from the depolarization plateau, may
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LIMULUS NEUROMUSCULAR TRANSMISSION 215 a spike but the second will lead to one and vice versa, the process being reversed again after a while. The spike mechanism either fatigues very easily or it is a very labile response. With prolonged repetitive stimulation, whether there is spiking or not, a plateau of depolarization builds up and is maintained. Brief bursts of stimulation illustrate the way in which the plateau builds up (Fig. 4ii, b-d). At the higher frequencies spikes, taking off from the depolarization plateau, may just reach and occasionally overshoot the zero baseline (Fig. 4i, c). The total tetanus tension and also the rate of rise of tension, continue to increase with increasing frequency of stimulation up to a maximum at about 200 per second (Fig. 6). The tetanus tension measured at the tip of the tarsus then exceeds 100 gm. The tetanus/twitch ratio is ordinarily about 30: 1 but it increases as the preparation ages, eventually becoming infinite as the twitch response just fails. -O normal & 6O sec 30 20 IO& 15 5. lOOmsec FIGURE 7. Records of tension developed in response to a single shock applied at various intervals (as indicated in seconds) after a brief tetanus (100 shocks at 100/sec.)- The electromechanical transducer used was a fluid potentiometer. When lightly- loaded it recorded the twitch tensions associated with the slow axon of gm. and less. Under these loading conditions the tension records did not have the usual shape for a twitch but instead showed a plateau of tension. This may have been caused in part by sluggishness of the potentiometer, but the plateau was too long to be due entirely to this. Thus, in the absence of a large restoring force (the twitch is normal in appearance with a spring attached to the load), tension is maintained for about half a second, after which relaxation occurs. Post-tetanic potentiation. Following a very brief tetanus there is a
Size: 2522px × 991px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
