The mammalian muscle spindle and its central control

Hulliger, M.

doi:10.1007/bfb0027694

Cited by 241 publications

(160 citation statements)

References 447 publications

(557 reference statements)

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“…We cannot rule out á_linked dynamic ã action (Murphy, Stein & Taylor, 1984;Greer & Stein, 1990;Murphy & Martin, 1993), because our technique of subtracting the predicted from actual afferent firing only identifies biasing. Some ãd fibres do have a significant biasing action on spindle primary endings (Hulliger, 1984;Prochazka, 1996). Though the estimates are rather crude, the amount of á-linked ã action implied by the present analysis of the triceps surae spindle primary data certainly seems larger than previously proposed in publications from this laboratory (e.g.…”

Section: Discussionmentioning

confidence: 99%

Ensemble firing of muscle afferents recorded during normal locomotion in cats

Procházka

Gorassini

1998

The Journal of Physiology

152

129

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The main purpose of this study was to collate population data on the firing characteristics of muscle afferents recorded chronically during normal stepping in cats. Ensemble firing profiles of forty‐seven muscle spindle and tendon organ afferents were compiled from stored data. The relationships between the firing profiles and the displacement and force signals were analysed with the help of mathematical models of the response characteristics of spindle primary and secondary afferents and tendon organs. Whereas the firing of hamstring spindle afferents could be predicted with reasonable accuracy from the length and velocity signals alone, the firing profiles of triceps surae spindle afferents deviated from the predicted profiles, particularly during electromyogram (EMG) activity. This indicated that the components of fusimotor action linked to extrafusal muscle activity were significant in triceps surae, possibly because this muscle is more strongly recruited in the cat step cycle. From the limited data available, it was not possible to identify the ‘best’ or most general mathematical function to predict spindle secondary firing. In the two triceps surae spindle secondary units studied, firing was well predicted by using the simplest possible model, rate proportional to displacement, whereas in the hamstring spindle secondary data, a more complex linear transfer function was needed. The results of modelling the spindle secondary data were consistent with a modest amount of phasic, static fusimotor action linked to EMG activity. The averaged ensemble of tendon organ afferent activity from the triceps surae gave predictions of whole‐muscle force that agreed well with separate triceps force measurements in normal cat locomotion. This supports the idea that ensembles of tendon organ afferents signal whole‐muscle force. Our overall conclusion is that to a first approximation, large muscle afferents in the cat hindlimb signal muscle velocity, muscle length and muscle force, at least in movements of the speed and amplitude seen in locomotion.

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Section: Discussionmentioning

confidence: 99%

Ensemble firing of muscle afferents recorded during normal locomotion in cats

Procházka

Gorassini

1998

The Journal of Physiology

152

129

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“…Over the years various theories of y function have MNS 1254 P. R. MURPHY ANDG. R. HAMMOND been proposed (for review, see Matthews, 1972;Stein, 1974;Hulliger, 1984) but they have been difficult to test and develop in view of the lack of direct recordings from classified static and dynamic y-efferents during normal movement. However, such recordings have been achieved in cat preparations during three types of rhythmic movement: respiration (Eklund, Euler & Rutkowski, 1964;Sears, 1964; Corda, Euler & Lennerstrand, 1966;Euler & Peretti, 1966;Greer & Stein, 1990), jaw movements (Appenteng, Morimoto & Taylor, 1980) and locomotion (Murphy, Stein & Taylor, 1984).…”

Section: Introductionmentioning

confidence: 99%

The locomotor discharge characteristics of ankle flexor gamma‐motoneurones in the decerebrate cat.

Murphy

Hammond

1993

The Journal of Physiology

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SUMMARY1. The discharge patterns of ankle flex.or, tibialis anterior (TA), y-motoneurones were recorded during locomotion in the decerebrate cat.2. At rest y-efferents had no background discharge. During locomotion two patterns of y activity could be distinguished. Most units (16) were phasically recruited with homonymous electroneurogram (ENG) activity, while the remainder (5) were tonically active throughout the step cycle.3. The modulation of phasic units was greater (P < 001) than tonic neurones. Phasic units had lower (P < 0-02) mean, but higher (P < 0-01) peak, rates during the step cycle.4. The discharge rate of both types of efferent increased around the onset of ENG activity and peaked during ENG activity, or shortly after its cessation. The conduction velocities of phasic and tonic units overlapped widely.5. It is proposed, on the basis of muscle spindle afferent recordings during locomotion, that TA phasic and tonic units correspond to static and dynamic ymotoneurones, respectively. This correspondence is functionally advantageous for the role of ankle flexor muscles during locomotion. Thus phasic static y discharge during flexion would aid muscle contraction via increased I a afferent activity, while tonic dynamic y firing would enhance I a afferent stretch sensitivity throughout the step cycle. Such enhancement during flexion would oppose unexpected muscle lengthening while, during extension, it would contribute to reciprocal inhibition of ankle extensor muscles.6. The results are discussed in relation to strategies of y usage during rhythmic movements. It is postulated that, for such behaviour, muscle contraction is accompanied by coactivity in static and dynamic y-motoneurones. A functional rationale is suggested for this strategy.

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“…They adjust the responses of the primary and secondary endings to the length and changes in the length of the muscle [21]. Dynamic gamma neurons innervate the bag 1 fibre by a p2 plate ending.…”

Section: Structure Vascular Supply and Innervation Of The Muscle Spimentioning

confidence: 99%