Encoding of Muscle Contractile Tension by Golgi Tendon Organs
The discharges of tendon organs of peroneal muscles were recorded in deeply anaesthetized cats during unfused contractions of single motor units. The tension developed during unfused contractions displays oscillations, in phase with the stimulation, superimposed on a steady level of static tension.
In responses to such tension profiles, the discharge frequency of individual tendon organs provided information about the frequency of tension oscillations but none about their amplitude and the level of static tension. However, observations made on several tendon organs activated by the same motor unit showed that such information is present in the ensemble discharge of these receptors. The average instantaneous frequency was calculated from the pooled discharges of all the activated tendon organs. It showed variations which followed the variations of contractile tension.
Upon combined stimulation of two motor units, there was approximately linear summation of tensions. The ensemble discharges of tendon organs did not display linear summation although they still followed the variations of the tension profile. The dynamic components of contractile force, rather than its static level, prevail in the information provided to the Central Nervous System by the total Ib afferent discharge.
KeywordsMotor Unit Contractile Force Discharge Frequency Single Motor Unit Linear Summation
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