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正常时,人体站立较长时间时,下肢的血池作用将引起交感神经反射性兴奋性增加,进而通过提高窦性心率及下肢血管收缩而被代偿。但对老年或体弱者,此时窦率虽然加速,但周围血管的代偿性收缩不正常,而使部分充盈的心室收缩力减弱,结果刺激了左心室迷走神经的机械感受器,并能触发不希望发生的迷走神经反射,该神经反射可引起神经介导性晕厥:窦性心率下降,动
Normal time, the human body standing for a long time, the role of the lower limb blood pool will cause sympathetic reflex excitability increased, and then by improving sinus heart rate and lower extremity vasoconstriction and be compensated. However, for the elderly or infirm, although the sinus rate is accelerating at this time, the compensatory contraction of the peripheral blood vessels is abnormal and partial filling of the ventricular contraction force is weakened. As a result, the left ventricular vagal nerve receptors are stimulated and the unwanted Occurrence of vagal reflex, the reflex can cause nerve-mediated syncope: sinus heart rate decreased, moving