The arterial baroreflex is an important blood pressure short-term control system. Its response characteristics are modulated under several conditions. Previous literature analysing the baroreflex under strict steady state conditions postulated that a central feed-forward command and some peripheral reflexes are responsible for the baroreflex modulation. A seminal work that analysed the baroreflex dynamics during a rest-to-exercise transient hypothesised that the central command may act through vagal withdrawal. The aim of the current work was to test this hypothesis by analysing the dynamic response of the baroreflex characteristics during unsteady state conditions characterised by different vagal activity. Four experiments investigated the light-to-moderate exercise transient, the rest-to-exercise transient in hypoxia, the abrupt postural change, and the fast cardiovascular response to breath holding at high lung volumes. The baroreflex was analysed through the linear relationship between the pulse interval and the mean arterial pressure. The results were in line with the tested hypothesis.