Figure 5. Comparison between open-loop and closed-loop-spontaneous transfer functions.

Solid and dashed lines represent the mean and mean + SD, respectively, obtained from all animals (n = 10). A, red lines are open-loop transfer functions of the neural (H_n-open, left panels) and peripheral arcs (H_p-open, right panels) identified in protocol 1. Blue lines are closed-loop-spontaneous transfer functions (blue lines) of the neural (H_{n-closed-spon}, left panels) and peripheral arcs (H_{p-closed-spon}, right panels) identified in protocol 2. The gain (top), phase (second), coherence (third) and normalized random error (bottom) functions are shown. Units of gain are [a.u. mmHg⁻¹] for the neural arc and [mmHg a.u.⁻¹] for the peripheral arc, respectively. The closed-loop-spontaneous baroreflex transfer function for the neural arc is markedly different from the open-loop transfer function, whereas that for the peripheral arc partially matches the open-loop transfer function. B, step response (Step res.) calculated from the open-loop (red lines) and closed-loop-spontaneous (blue lines) transfer functions. The units are [a.u.] for the neural arc and [mmHg] for the peripheral arc, respectively. a.u., arbitrary unit; CSP, carotid sinus pressure; SNA, sympathetic nerve activity; AP, arterial pressure; Step res., step response.