Rowell L B
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle 98195.
Int J Sports Med. 1992 Oct;13 Suppl 1:S25-7. doi: 10.1055/s-2007-1024583.
Current theory is that circulatory control in exercise is governed by central command which sets basic patterns of effector activity that is modulated by arterial baroreflexes and chemo- and mechanoreflexes from active muscle. Because central command acts on vagal activity rather than sympathetic nerve activity (SNA), and because muscle chemoreflexes are not normally active during mild to moderate dynamic exercise, current theory cannot explain why SNA to virtually all organs, including active muscle, increases even during mild exercise. Are arterial baroreflexes involved? Baroreflex sensitivity is maintained during exercise, and most importantly, the reflex is reset to higher blood pressure (BP). A new hypothesis is that central command works by resetting the baroreflex to a higher BP and withdraws vagal activity to raise heart rate, cardiac output and BP at the onset of exercise. The key to the hypothesis is that the rise in cardiac output at exercise onset must be fast enough to raise BP to its new reset level immediately, otherwise a BP error occurs that must be corrected by baroreflex and SNA.
当前理论认为，运动中的循环控制由中枢指令主导，中枢指令设定效应器活动的基本模式，该模式会受到动脉压力反射以及来自活动肌肉的化学和机械反射的调节。由于中枢指令作用于迷走神经活动而非交感神经活动（SNA），并且由于在轻度至中度动态运动期间肌肉化学反射通常不活跃，当前理论无法解释为什么即使在轻度运动期间，几乎所有器官（包括活动肌肉）的SNA都会增加。动脉压力反射是否参与其中？运动期间压力反射敏感性得以维持，最重要的是，反射被重新设定为更高的血压（BP）。一个新的假说是，中枢指令通过将压力反射重新设定为更高的血压来起作用，并在运动开始时撤回迷走神经活动以提高心率、心输出量和血压。该假说的关键在于，运动开始时心输出量的增加必须足够快，以便立即将血压提高到其新的重新设定水平，否则就会出现血压误差，必须通过压力反射和SNA进行纠正。
