Encoding of force increases and decreases by tibial campaniform sensilla in the stick insect, <Emphasis Type="Italic">Carausius morosus</Emphasis> |
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Authors: | Sasha N Zill Ansgar Büschges Josef Schmitz |
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Institution: | (1) Department of Anatomy and Pathology, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25704, USA;(2) Department of Animal Physiology, Zoological Institute, Biocenter, University of Cologne, 50923 Cologne, Germany;(3) Department of Biological Cybernetics, University of Bielefeld, 33501 Bielefeld, Germany |
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Abstract: | Detection of force increases and decreases is important in motor control. Experiments were performed to characterize the structure
and responses of tibial campaniform sensilla, receptors that encode forces through cuticular strains, in the middle leg of
the stick insect (Carausius morosus). The sensilla consist of distinct subgroups. Group 6A sensilla are located 0.3 mm distal to the femoro-tibial joint and
have oval shaped cuticular caps. Group 6B receptors are 1 mm distal to the joint and have round caps. All sensilla show directional,
phasico-tonic responses to forces applied to the tibia in the plane of joint movement. Group 6B sensilla respond to force
increases in the direction of joint extension while Group 6A receptors discharge when those forces decrease. Forces applied
in the direction of joint flexion produce the reverse pattern of sensory discharge. All receptors accurately encode the rate
of change of force increments and decrements. Contractions of tibial muscles also produce selective, directional sensory discharges.
The subgroups differ in their reflex effects: Group 6B receptors excite and Group 6A sensilla inhibit tibial extensor and
trochanteral depressor motoneurons. The tibial campaniform sensilla can, therefore, encode force increases or decreases and
aid in adapting motor outputs to changes in load. |
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Keywords: | |
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