Summary
Stimulation of single dynamic α or β axons by very brief trains of shocks (2–3 shocks at 2–500/sec) or by single shocks, which at constant muscle length have a negligible effect on the discharge of primary endings, may strongly excite these endings when applied during dynamic stretch.
This effect was studied by the technique of frequencygrams (Bessou et al., 1968) on de-efferented soleus and tenuissimus cat spindles. Muscles were submitted to periodic changes of length of triangular symmetrical form and the stimulation of the axons was applied at preset position during stretch. Stretches of 3–4 mm of amplitude with velocities ranging from 0.8 mm/sec to 32 mm/sec were used. Frequencygrams showed a fast rising phase followed by a slow decay, the whole response lasting about 0.4 sec; their amplitude increase with the velocity of stretch. Increases of 200 impulses/sec in the firing rate of the endings were observed.
The intrafusal distribution of a dynamic axon eliciting this effect in a tenuissimus spindle was determined by the glycogen-depletion method. This axon selectively supplied the bag1 fibre of the spindle.
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Emonet-Dénand, F., Laporte, Y. (1981). Muscle stretch as a way of detecting brief activation of bag1 fibres by dynamic axons. In: Taylor, A., Prochazka, A. (eds) Muscle Receptors and Movement. Palgrave Macmillan, London. https://doi.org/10.1007/978-1-349-06022-1_7
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DOI: https://doi.org/10.1007/978-1-349-06022-1_7
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