Macefield V G, Elam M
Prince of Wales Medical Research Institute & The University of New South Wales, Sydney, Australia.
Acta Physiol Scand. 2003 Mar;177(3):247-53. doi: 10.1046/j.1365-201X.2003.01078.x.
Single-unit recordings from muscle vasoconstrictor, cutaneous vasoconstrictor and sudomotor neurones in awake human subjects have shown that they tend to fire only once per sympathetic burst. We review the firing properties of human sympathetic neurones and examine the idea that the short duration of a sympathetic burst may limit the number of times a neurone can fire, using the human skeletomotor system as a model for the sympathetic nervous system.
It is known that human alpha motor neurones usually fire in long trains during voluntary contractions, but what of their pattern when constrained by a brief burst? We recorded from single motor units in the tibialis anterior muscle while subjects generated brief electromyogram bursts in the intervals between heart beats, with a duration similar to that of muscle sympathetic bursts. Eight motor units fired mostly one spike per burst, with a pattern identical to that of sympathetic neurones.
These results suggests that were it not for the constraint of the bursting pattern, individual sympathetic neurones would--like alpha motor neurones--tend to fire in long trains.
对清醒人类受试者的肌肉血管收缩、皮肤血管收缩和发汗运动神经元进行的单单位记录表明，它们往往在每次交感神经爆发时仅发放一次冲动。我们回顾人类交感神经元的放电特性，并以人类骨骼运动系统作为交感神经系统的模型，研究交感神经爆发的短暂持续时间可能限制神经元放电次数的观点。
已知人类α运动神经元在自主收缩期间通常以长串放电，但当受到短暂爆发的限制时，其放电模式如何？我们在受试者心跳间期产生短暂肌电图爆发时记录胫骨前肌的单个运动单位，爆发持续时间与肌肉交感神经爆发相似。八个运动单位每次爆发大多发放一个动作电位，其模式与交感神经元相同。
这些结果表明，如果不受爆发模式的限制，单个交感神经元会像α运动神经元一样倾向于以长串放电。
