A method of analysing the responses of spindle primary endings to fusimotor stimulation

Abstract

SUMMARY1. The superposition of records of 'instantaneous' frequency of discharge of spindle primary endings after stimulation of single fusimotor fibres leads to the construction of graphs called 'frequencygrams'.2. The superposition is made on the screen of a storage oscilloscope, the time base of which is synchronized with the stimulus. It is essential that the stimulus be delivered at all possible intervals with respect to the impulse of the resting discharge which precedes it.3. Frequencygrams obtained by stimulating some static fusimotor fibres by single stimuli display a response with a fast rising phase, a pause, and a slower decreasing phase.4. Frequencygrams may give some information on the time course of the contraction of intrafusal muscle fibres elicited by stimulating their motor axons.

Frequencygrams of spindle primary endings elicited by stimulation of static and dynamic fusimotor fibres

“…This is in agreement with the time interval, of about 6 msec, for which complete summation of two responses is obtained (Bessou et al 1968) and with the observations of Harvey & Matthews (1961) and Bessou, EmonetDenand & Laporte (1962) on the rate of stimulation giving maximal activation of the primary endings.…”

“…The succession of two impulses at a short interval increases markedly the refractoriness of the ending, as shown originally by the mode of resetting of the rhythmic discharge after an antidromic impulse (Matthews, 1933). This explains, at least partly, the reason why no impulse can be initiated for a certain time after the rising phase (see Bessou et al 1968).…”

“…The declining phase lasts 30-45 msec. These large responses which served for developing the frequencygram method have been described in detail by Bessou et al (1968).…”

“…In a preceding paper (Bessou et al 1968) a method of analysing discharges of spindle primary endings was described. This method which gives indirect information on the contraction of intrafusal muscle fibres leads to construction of graphs called 'frequencygrams'.…”

Cinematographic analysis of contractile events produced in intrafusal muscle fibres by stimulation of static and dynamic fusimotor axons.

“…In the first one, sensory endings have been INTRAFUSAL MUSCLE FIBRE CONTRACTIONS used as a natural mechanical transducer to obtain some information on the mode of contraction of intrafusal muscle fibres activated by their motor axons. The superposition of responses of spindle sensory endings recorded with an instantaneous frequency-meter (Bessou, Laporte & Pages, 1968a) has been the method employed to obtain as complete as possible information on the time course of underlying contractions. Such frequencygrams of cat spindle primary endings (Bessou, Laporte & Pages, 1968b), of cat spindle secondary endings (Bessou & Pages, 1969) and of rabbit spindle primary endings (Emonet-Denand & Laporte, 1969) provided interesting data on the contractile phenomena produced in muscle spindles by stimulation of static and dynamic, y axons.…”