Muscle spindles in muscle control

Abstract

Afferent discharges from single muscle spindles in the frog were recorded from the dorsal root ganglion in the reflexively active loop and in the same loop opened by cutting the dorsal roots. The closed loop response (i.e. pulse frequency) to muscle stretch was smooth and without “dead zones”, as compared to the response to the same stretch when the loop was open. The variations in gain between the open and closed loop modes of operation are shown to be small, both for muscle spindle afferent outflow and for muscle tension.