Relative importance of nervous control of cardiac output and arterial pressure.

Abstract The relative amounts of control that the nervous system exercises over arterial pressure versus cardiac output were studied in 41 dogs divided into 2 groups—intact dogs and dogs with all or most of the central nervous system destroyed. Responses of both groups were compared during 3 different types of circulatory stress: (1) opening and closing arteriovenous (A-V) fistulas, (2) massive infusion of blood, and (3) stimulation of muscle contraction. The results showed that the intact dogs controlled arterial pressure many times as effectively as did the dogs with the central nervous system destroyed. On the other hand, there was little difference in the control of cardiac output in the 2 groups of animals. Quantitative comparisons showed a feedback gain for nervous control of arterial pressure of −6.4 versus a feedback gain for control of cardiac output of −0.23. These experiments suggest that the nervous system is of much less importance for control of cardiac output than for control of arterial pressure.