5o6 



HANDBOOK OF PHYSIOLOGY 



CIRCUL.^TION I 



70 



0.2 5 fa] 10 2.0 



4.0 



n ! v "prri — 1 ■ 1 x 



rtr 



^»««i 



UjglB B B(| ■ BBB BBBB HwBI 



FIG. 14 



cardiac output and heart rate are held constant and 

 the total coronary venous outflow is metered, sampled, 

 and analyzed by the trihydroxyindole technique of 

 Lund (61), as modified by Crout (31), show clearly 

 that a graded increase in the frequency of cardiac 

 sympathetic nerve stimulation produces a graded 

 increase both in the coronary venous concentration 

 and total efflux of catecholamine from the heart. 



It seems not unreasonable to assume that there is a 

 similar directional \ariation of catecholamine con- 

 centration in the myocardium as the stimulation 

 frequency is increased. 



END DI.^STOLIC PRESSURE-LE.NGTH REL.ATION. As shown 



ai:)ove, the administration of catecholamines or car- 

 diac nerve stimulation increases the vigor of ven- 



