Summary
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1.
In the legs of brachyuran Crustacea, the stretcher and opener muscles share a single motoneuron and have separate specific inhibitory neurons.
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2.
During passive joint movements, reflex activity of the inhibitors is coordinated to prevent contraction of the muscle in the unstimulated segment (Fig. 2).
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3.
Within the reflex hursts of activity, the inhibitory impulses are centrally coupled to excitor impulses, producing patterned output. The opener inhibitor tends to fire closely following each excitor spike while the stretcher inhibitor fires preceding each excitor spike (Fig. 4).
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4.
Stretcher inhibitor impulses are frequently observed to occur as doublets, with spikes both preceding and following an individual excitor impulse (Figs. 2, 3).
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5.
The observed excitor-inhibitor coupling is optimal in each case for the reduction in height of ejp's recorded in the muscles (Figs. 5, 6). This impulse spacing also corresponds to the maximally effective spacing for reduction of muscle tension (Fig. 8).
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I wish to thank Drs. Edward G. Boettiger, William D. Chapple, Robert B. Northrop, and Richard S. Norman for their criticisms and suggestions, Stephani Schaefer for her art work, and Drs. William H. Evoy and Donald Kennedy for critical reviews of the manuscript. Supported by NIH Predoctoral Biological Engineering Traineeship CMS-1388 and NICHHD Training Grant HD00187.
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Spirito, C.P. Reflex control of the opener and stretcher muscles in the cheliped of the fiddler crab, Uca pugnax . Z. Vergl. Physiol. 68, 211–228 (1970). https://doi.org/10.1007/BF00297696
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DOI: https://doi.org/10.1007/BF00297696