Properties of the CVS. The system properties of the CVS were investigated by simulating the response on MAP, CO, HR and TPR after inhibiting HR (A), SV (B) or TPR (C). Inhibiting HR, SV or TPR always resulted in a decrease in MAP, which demonstrates that feedback cannot be stronger than the primary effect. In addition, the delayed response of the MAP was longer when the drug effect was on SV as compared with TPR.