504 HANDBOOK OF PHYSIOLOGY ^^ CIRCULATION I 



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and during stellate ,gan.a;lion stimulation (SS). 

 During stimulation a shift of the ventricular function 

 cur\e to the left was observed when either mean 

 left atrial pressure (VFCl^) or left ventricular end 

 diastolic pressure (VFClv) is plotted against stroke 

 work just as when norepinephrine is administered 

 (fig- 2). 



The shortening of systole observed during stellate 

 stimulation, while the ventricle produces an increased 

 work from any given end diastolic pressure, indi- 

 cates a greater increase in stroke power than in stroke 

 work. In the experiment shown in figure 13^, during 

 stellate stimulation the shortened duration of ven- 

 tricular systole from any given end diastolic pressure 

 was such that the increase in power was an average 

 of 25 per cent greater than the increase in work. 

 The increase in stroke work produced during stellate 

 stimulation is consistently accompanied by a shorten- 

 ing of systole (105). 



Figure i^A demonstrates the type of response ob- 

 tained when applying frequency graded stimulation 

 to the left stellate ganglion. The heart rate was held 

 constant by atrial pacing. The rami to the right 

 stellate ganglion and both vagi were sectioned. The 



isolated left stellate ganglion was stimulated at 7 

 volts with an impulse duration of 10 msec. The num- 

 ber at the top of each segment of tracing shows the 

 impulse frequency used. Each time the stimulus 

 frequency (with supramaximal voltage) is increased 

 from zero up through 4 per sec, the fall in left and 

 right atrial pressures and the rise in aortic pressure is 

 accompanied by an increased cardiac output and, 

 since heart rate is held constant, by a proportional 



