Can neck muscle spindle afferents activate fusimotor
neurons of the lower limb?
and reafferent origin of the sense of force and weight.
The therapeutic effects of BTX-A seemed to be due not only to partial denervation of extrafusal muscles but also to fusimotor
denervation of intrafusal fibers that tonically control the sensitivity of spindle sensory afferents [19-21].
(1999) believe these adjustments are due to the rapid modulation of neural pathways caused by stretch reflex responses within athletes, using either pre-synaptic inhibition or fusimotor
action as previously described by Stein and Capaday (1988).
The effects of brushing and icing are to increase fusimotor
activity so making the neuromuscle spindle more responsive to stretch stimuli when these are applied secondarily.
A slight increase in spindle fusimotor drive, along with increased skeletomotor drive, has been observed during visually-guided manual tracking tasks which required increased precision (46).
In addition, plausible investigation of proprioception should measure the degree of correlation between intensity of fusimotor activity and ensembles of afferents.
Elevated intramuscular concentration of bradykinin in jaw muscle increases the fusimotor
drive to neck muscles in the cat.
In this study assessment of JPS by active reproduction of limb position requires muscle contraction, this increases the fusimotor
drive which heightens muscle spindle sensitivity and hence proprioceptive acuity [12, 13, 30, 31].
The after-effects of stretch and fusimotor
stimulation on the responses of primary endings of cat muscle spindles.
It is also possible that given the functional role proposed for the fusimotor
system in providing spindle endings with a background discharge so they can initiate appropriate reflex correction (Burke et al 1978), that a preexisting central and/or peripheral muscle spindle or neural deficit might impair movement sensibility and reflex response mechanisms, or produce movement incoordination (Ernfors et al 1994), regardless of any ankle injury.