Proprioceptor responses and convergence of proprioceptive influence on motoneurones in the mesothoracic thoraco-coxal joint of locusts
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In the mesothoracic thoraco-coxal joint ofLocusta movements of the coxa or mechanical stimuli applied to proprioceptors elicit characteristic afferent patterns. Most of these are phasic in response to certain directions and velocities of the rotary movements applied to the coxa (anterior joint CO, posterior joint CO, CO-system, pleurotrochantinal SR, joint condylus MS) and/or tonic in response to certain coxal positions (anterior joint CO, pleuro-trochantinal SR, joint condylus MS). Only one population of multipolar sense organs (joint condylus MS) is sensitive to load on the thoraco-coxal articulation.
The phase relationships of the responses from different proprioceptors to coxal movements can change when the plane of stimulation is altered from movement about one principal axis to another.
Responses in motoneurones of the coxal protractor, retractor, rotator and levator muscles to stimulation of the anterior joint CO only are described. Their temporal relationship is different from that produced by afferents of the CO-system alone during the same kind of stimulation.
When both anterior joint CO and CO-system are stimulated independently but simultaneously the afferent responses elicited converge onto motoneurones in an additive way and produce new patterns of motoneurone discharges.
This cooperative effect of just two proprioceptors may represent a more general coordinating principle for movement control: (i) Proprioceptors of one joint respond dynamically different to the same movement. (ii) Different movements of the joint alter the phase relationships between proprioceptive afferents. (iii) The influences from different proprioceptors converging to the level of motoneurones can be mutually inhibited or enhanced and new patterns of motoneurone coordination emerge with every change of the axis of movement.
KeywordsPrincipal Axis Rotary Movement Movement Control Temporal Relationship Mechanical Stimulus
chordotonal organ system of the mesothorax
strand receptor with central cell bodies
multipolar sensillum (sensilla)
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