Fig. 7

a Averaged transfer functions from sympathetic nerve stimulation (SNS) to heart rate (HR), coherence functions (Coh.), and the corresponding step responses before (thin lines) and after (bold lines) the administration of metoprolol. Metoprolol reduced the dynamic gain and disrupted the HR transfer function. Coherence was lower after metoprolol compared with the control condition. The step response was nearly absent after metoprolol. b Averaged transfer functions from SNS to R–R interval (RRI), coherence function, and the corresponding step response before (thin lines) and after (bold lines) the administration of metoprolol. Metoprolol decreased the dynamic gain and disrupted the RRI transfer function. Metoprolol abolished the negative step response of RRI. c The mean transfer functions calculated for the HR response and the RRI response are only displaced along the ordinate in the gain plots, both before (top panel) and after (bottom panel) metoprolol. bpm beats/min. The solid and dashed lines in panels a and b indicate mean and mean ± SE values (n = 6)