Reflexes to stretch and contraction of antagonists around ankle joint

Abstract

The reciprocal effects of stretch and contraction have been compared with the direct effects by testing monosynaptically the responses from the gastrocnemius and peroneus profundus nerves while either the gastrocnemius or the tibialis anticus has been activated by itself, the rest of the leg being completely denervated (cats). The dominant effect of gastrocnemius activation on the deep peroneal motoneurones was facilitation, that of tibialis anticus activation on the gastrocnemius motoneurones inhibition. Patterns of innervation other than the dominant ones were also found. The dominant reciprocal effect of the gastrocnemius receptors thus correlated with their autogenetic inhibition, while the dominant reciprocal effect of the tibialis anticus receptors correlated with their autogenetic facilitation. The gastrocnemius autogenetic inhibition and its reciprocal facilitation of the antagonist flexors was more effectively mobilized by contraction than by stretch.