. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Muscle and Electric Organs 599 Wiersma and his associates found that the branching of axon terminations on crustacean muscle is extensive, forming a sort of ;*' They postu- lated that conduction in the muscle is entirely by the nerve elements and that within each muscle fiber there are separate contractile systems each ac- tivated by its own nerve fiber. Inhibition is most effective oh slow contrac- ti(ms and can act either between nerve impulse and muscle potential or be- tween muscle potential and
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Muscle and Electric Organs 599 Wiersma and his associates found that the branching of axon terminations on crustacean muscle is extensive, forming a sort of ;*' They postu- lated that conduction in the muscle is entirely by the nerve elements and that within each muscle fiber there are separate contractile systems each ac- tivated by its own nerve fiber. Inhibition is most effective oh slow contrac- ti(ms and can act either between nerve impulse and muscle potential or be- tween muscle potential and contraction. Evidence for a different interpretation of the fast and slow systems has been presented by Katz and Kuffler.'^"- ^^â * A muscle consisting of many parallel fibers (extensor of carpopodite in crab or crayfish) was exposed and stimulated directly; simple diphasic impulses which were propagated as in. Fig. 231. Electrical responses from extensor of carpopodiie of crab to paired shocks. Interval between stimuli to fast axon successively from above 24, 12, , 8, , and sec. End-plate jxjtentials to second shock show summation and propagated spike appears in lower 3 records. From Katz and ;" vertebrate skeletal muscle were recorded. In other preparations some nerve branches were cut, leaving isolated branches intact; when the nerve was then stimulated and a recording electrode moved about on the muscle, local nega- tive potentials with all of the properties of the vertebrate end-plate potentials ('s) were observed (Fig. 231). The fast system has large 's which give rise to conducted muscle spikes; the "fast" 's show little facilitation. The fast system fatigues rapidly, the excitatory process falling to one half in 5 msec. The "slow" system, on the other hand, has small 's which show much facilitation; at frequencies of 50 per sec., for example, the grows to 3 times its initial size, and
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