Central and reflex effects to standing on cardiac interval response

Summary form only given. We examined the central and reflex actions on the changes in cardiac interval to standing in healthy human subjects. The experiments were preformed in two ways using light emitting diodes (LED1 and LED2). The LED1 light was used as a standing demand signal whereas the LED2 light was used as a standing stop signal. When the LED2 light was delayed by 500 ms after the LED1 light, the reflex effect of cardiac interval responses to the LED1 was eliminated and only the central effect remained. The central effect to the standing demand signal appeared initially within 2-4^th cardiac cycles whereas the reflex effect appeared dominantly after 2-10^th cardiac interval.