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一、全或无原则 单条骨骼肌纤维的收缩具有“全或无”特征。所谓全是指,当单条肌纤维(活组织)受到一次阈刺激或阈上刺激时,均能引起一次兴奋而后发生全力收缩反应,其兴奋幅度与收缩张力不因刺激强度的增加而增大;所谓无是指,当单条肌纤维只受到阈下刺激(即小于阈强度的刺激)时,不能引起肌纤维的兴奋与收缩反应。因此,仅单条肌纤维的“上半部分”或“下半部分”发生收缩反应是不可能的。如果一条肌纤维没有受到刺激,或只受到阈下刺激,那么该条肌纤维将不会产生收缩。
First, the whole or no principle Single skeletal muscle fibers with “all or no” feature. The so-called all means that when a single muscle fiber (living tissue) by a threshold stimulation or threshold stimulation, can cause an excitement and then full contraction, the excitement and contraction tension does not increase due to the stimulation intensity; the so-called No means that the excitatory and contractile responses of muscle fibers can not be induced when a single muscle fiber is subjected only to subthreshold stimulation (ie stimuli less than threshold intensity). Therefore, it is not possible for the “upper half” or “lower half” of only a single muscle fiber to undergo a contractile response. If a muscle fiber is not stimulated, or only under the threshold stimulation, then the muscle fibers will not produce contraction.