The arterial baroreflex arc is implemented according to the feedback system illustrated in Figure 4. This system is aimed at tracking a setpoint ($ sp$) pressure through the following sequence of events. The baroreceptors sense $ P_a(t)$ and relay this pressure to the autonomic nervous system (ANS). The ANS compares the deviation between the sensed pressure and $ P_a^{sp}$ with zero and then responds by adjusting four parameters of the pulsatile heart and circulation in order to keep the ensuing $ P_a(t)$ near $ P_a^{sp}$. The four adjustable parameters are $ F(t),ドル $ C_{l,r}(t)$ at end-systole ( $ C_{l,r}^{es}(t)$), $ Q_v^0(t),ドル and $ R_a(t)$. The ANS controls these parameters based on the history of $ P_a(t)-P_a^{sp}$ specifically according to the following nonlinear, dynamical mapping:
The cardiopulmonary baroreflex arc is also implemented according to a feedback diagram analogous to Figure 4. However, the sensed pressure here is defined to be the effective right atrial transmural pressure ( $ P_{\text{\lq\lq $ra$''}}^{tr}(t)=P_{\text{\lq\lq $ra$''}}(t)-P_{th}(t)$) of the pulsatile heart and circulation model.
The direct neural coupling mechanism between respiration and heart rate is characterized by a linear, time-invariant impulse response which maps fluctuations in instantaneous lung volume ($ Q_{lu}(t)$; see Section 2.3) to fluctuations in $ F(t)$. The impulse response is defined here by a linear combination of $ s(t)$ and $ p(t),ドル each of which are advanced in time by 1.5 s in order to account for the noncausality of this mechanism [6,9].
