Summary
Tetanic stimulation of ipsilateral Triceps surae afferents leads to a reflex increase in the “initial burst” from the primary spindle afferents during ramp stretch in both intercollicular decerebrate and spinal preparations. The dynamic index does not change significantly.
Slow, low-amplitude sinusoidal muscle stretches (1.6 Hz, 0.55 mm peak-peak) disclose an increased dynamic sensitivity of primary afferents during reflex activation. The same activation in the statically adapted muscle results in a great many cases in little or no increase in spindle discharge rate.
In the frequency-stretch relation, the discharge rates of primary afferents in the spinal cat and of secondaries in decerebrate animals are greatly increased by combined fusimotor activation and low-amplitude sinusoidal stretch.
We conclude that both static and dynamic γ motoneurons are implied in this reflex.
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Sontag, K.H. The effects on primary and secondary spindle afferents of fusimotor reflex during ramp and sinusoidal muscle stretch. Pflugers Arch. 331, 266–274 (1972). https://doi.org/10.1007/BF00589133
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DOI: https://doi.org/10.1007/BF00589133