Abstract
1. Reflex tension, electromyograph (EMG) and afferent discharges were observed during sinusoidal movement in the gastrocnemius and soleus muscles of decerebrated cat.
2. The amplitude of tension began to decrease at over 9Hz in the gastrocnemius and at over 5Hz in the soleus. The phase angle of reflex tension showed the phase lead at low frequencies and the phase lag at over 14Hz in the gastrocnemius and at over 7Hz in the soleus. The alternate cycle fluctuation of tension was observed at over 22Hz in the gastrocnemius and at over 14Hz in the soleus.
3. The phase lead of EMG was amplified with increasing frequency but began to recede at over 8Hz in the gastrocnemius and at over 4Hz in the soleus, while the amplitude of EMG increased. The alternate fluctuation of EMG was seen at the same frequency as the alternate cycle fluctuation of tension.
4. The effect of reflex tension on stretch receptors was investigated by simultaneous recording of dorsal rootlet GIa and GIb discharges, reflex tension and EMG. The GIa discharges increased with sinusoidal movement but partial acceleration and pause of the discharges were observed during a cycle. EMG group discharges were seen after the acceleration and during the GIa discharge pause. GIb discharge pause was not seen during a cycle but discharge acceleration was observed after EMG group discharges.
5. The shift in the GIb discharge possibly occurring as a result of its own reflex tension suggests that it acts as an inhibitor to successive GIa discharges and may be the cause of the alternate cycle fluctuation of the EMG at high frequencies.
6. These results were discussed by introducing the reflex system time lag due to the conduction time of the nerve and the contraction time of the muscle.
