Structural Features relative to the Function of Intrafusal Muscle Fibres in the Cat

Gladden, M. H.

doi:10.1016/s0079-6123(08)60722-0

Cited by 88 publications

(60 citation statements)

References 8 publications

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“…The silver impregnation was adequate or good for histological analysis in experiments C689, C700 and C883. With such material it is now possible to identify the three types of intrafusal muscle fibre in virtually all cases, principally by details of the primary sensory ending (Banks, Barker & Stacey, 1982), but also by the differences in polar length and diameter and by the distribution of elastic fibres (Gladden, 1976). The bag fibres can be traced individually from end to end, whereas chain fibres usually cannot; however, in locating motor nerve endings there was no doubt when one was dealing with a chain fibre.…”

Section: Methodsmentioning

confidence: 99%

The distribution of static gamma‐axons in the tenuissimus muscle of the cat.

Banks¹

1991

The Journal of Physiology

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SUMMARY1. The distribution of static y-axons within and among muscle spindles of the tenuissimus muscle has been studied in the anaesthetized cat, on the basis of the effects on the responses of primary endings when bag2 or chain fibres or both are activated by static y-stimulation.2. Locations of spindles were marked for subsequent histological analysis using teased, silver-impregnated preparations.3. Static effects were classified into: (i) biassing; (ii) driving; or (iii) indeterminate categories.4. Critical correlations established that the biassing type was produced by bag2 activity, either alone or in combination with chain fibres, whereas the driving type was produced by chain fibres active alone. Indirect evidence suggested that indeterminate effects were produced by bag2 and chain fibres active together.5. The static y-axons showed some differential distribution according to their conduction velocities: faster-conducting axons were likely to be more widely distributed among spindles but less likely to innervate chain fibres alone than were more slowly conducting axons.6. The results are discussed in terms of their possible functional and developmental significance.

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Section: Methodsmentioning

confidence: 99%

The distribution of static gamma‐axons in the tenuissimus muscle of the cat.

Banks¹

1991

The Journal of Physiology

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“…An alternative explanation of a reduction in position sensitivity during static y axon stimulation would be that an active static nuclear bag fibre is less extensible than the prominent elastic fibres through which it is attached to the muscle (Gladden, 1976), whereas when inactive it may be equally or more extensible. Further, if the stretch of the spindle as a whole, and hence of the dynamic nuclear bag fibre, is proportionately less than that applied to the muscle because of activity in the static nuclear bag fibre, this would provide a mechanical explanation of the reduction in the dynamic index of the Ia discharge during static y axon stimulation.…”

Section: Glycogen Depletion In Intrafusal Fibresmentioning

confidence: 99%

Control of dynamic and static nuclear bag fibres and nuclear chain fibres by gamma and beta axons in isolated cat muscle spindels.

Boyd¹,

Gladden²,

McWilliam³

et al. 1977

The Journal of Physiology

189

132

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SUMMARY1. The behaviour of nuclear bag and nuclear chain intrafusal fibres in isolated cat muscle spindles with a blood supply, during stimulation of dynamic y axons, dynamic f axons, or static y axons in ventral root filaments was observed and recorded on still and moving film.2. Most spindles were controlled by one dynamic y axon (sometimes a f axon) and three static y axons, one of which was often non-selective in distribution. A large majority of fusimotor axons controlled one pole of the spindle only.3. Dynamic y and ft axons produced focal contraction in only one of the two nuclear bag fibres in any spindle and this fibre was never activated by static y axons. Maximal tetanic contraction was attained slowly and the primary sensory spiral on this fibre was stretched by a small amount only. This fibre has been named the 'dynamic nuclear bag fibre'.4. Static y axons produced either: (a) focal contraction in the second of the two nuclear bag fibres only; (b) local contraction in the bundle of nuclear chain fibres only; or (c) contraction in one nuclear bag fibre and the nuclear chain fibres together. Maximum tetanic contraction of this nuclear bag fibre stretched its primary sensory spiral considerably and the time to plateau was relatively short. This fibre has been named the 'static nuclear bag fibre'.5. 'Driving' of the Ia afferent discharge could always be produced by non-selective static y axons, frequently by static y axons controlling nuclear chain fibres alone, and was probably due to mechanical oscillation in nuclear chain fibres. It was never produced by dynamic y axons and on one occasion only by a static y axon controlling a nuclear bag fibre alone.6. The conduction velocities of dynamic y and static y axons overlapped extensively, though dynamic y axons were absent from the lower end, and I. A. BOYD AND OTHERS static y axons innervating nuclear chain fibres only were absent from the upper end, of the range of velocities.7. The observations are correlated with spindle structure and histochemistry. Dynamic and static nuclear bag fibres are shown to correspond with 'bag1 fibres' and 'bag2 fibres', respectively (Ovalle & Smith, 1972).8. The possible origin of the dynamic and static actions of fusimotor axons and the role of the dynamic and static intrafusal systems in motor control are discussed.

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“…1953). The evidence is that nuclear chain fibres do not respond to SCh (Gladden, 1976). In the presence of SCh, spindle resting discharge rises and there is a large increase in the response to a ramp stretch as a result of the intrafusal contractLure (Rack & Westbury, 1966;Dutia, 1980).…”

Section: Resultsmentioning

confidence: 98%

“…This was done in two ways. First, it is known that in the presence of the depolarizing neuromuscular blocker succiinyl choline (SCh), nuclear bag intrafusal fibres undergo a contracture (Gladden, 1976) which can be blocked with curare (Hunt, 1952;Granit el al. 1953).…”

Section: Resultsmentioning

confidence: 99%

“…Supporting evidence was provided by the experiments using SCh. Observations on isolated spindles suggest that depolarizing drugs like acetylcholine (ACh) excite the spindle by producing contractures in bag1 and bag2 fibres but not in chain fibres (Gladden, 1976). It is reasonable to assume that the excitatory action of SCh on intrafusal fibres is similar to ACh.…”

Section: Discussionmentioning

confidence: 99%

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Blockade of intrafusal neuromuscular junctions of cat muscle spindles with gallamine

Yamamoto

Morgan²,

Gregory³

et al. 1994

Experimental Physiology

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SUMMARYThis is a report on the resistance to block of the motor terminals on intrafusal fibres of cat soleus muscle spindles using the drug gallamine triethiodide (Flaxedil). To minimize diffusion barriers and to permit accurate measurements of time courses, rather slow rates of gallamine infusion were used (0-15 mg min-1). The main finding made was that after gallamine infusion, when extrafusal tension had dropped to half, all dynamic fusimotor effects and eight of twenty static effects had fallen to 40 % or less of their control value. The remaining static effects persisted at 60-80 % of their control value. Where fusimotor fibres were stimulated together with one or two skeletomotor fibres, the influence of the skeletomotor axons was significant only after spindle biasing had fallen to low levels. When gallamine infusion was stopped extrafusal tension returned to control levels within 20-75 min, depending on the length of the block, while fusimotor responses did not fully recover within the recording period of up to 150 min. The combination for some fusimotor responses of an early fall and a late recovery when compared with extrafusal tension, suggested a greater sensitivity of these endings to the drug. A comparison of spindle responses to the drug succinyl choline (SCh) and to fusimotor stimulation in the presence of gallamine showed that SCh responses were rapidly reduced by gallamine and had a long recovery time course, as were some fusimotor responses. From this it is argued that fusimotor effects with a high sensitivity to gallamine blockade were associated with nuclear bag fibre contractions and the more resistant effects with nuclear chain fibre contraction. It is generally believed that intrafusal neuromuscular junctions are more resistant to neuromuscular blockers than extrafusal junctions. The present experiments provide evidence to the contrary for some intrafusal junctions. Since muscle relaxants are often used in general anaesthesia it is interesting to speculate about the recovery of function of proprioceptive reflexes and of kinaesthesia during the immediate post-anaesthetic period, in view of the large difference in recovery time for transmission at intrafusal and extrafusal junctions.

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Structural Features relative to the Function of Intrafusal Muscle Fibres in the Cat

Cited by 88 publications

References 8 publications

The distribution of static gamma‐axons in the tenuissimus muscle of the cat.

The distribution of static gamma‐axons in the tenuissimus muscle of the cat.

Control of dynamic and static nuclear bag fibres and nuclear chain fibres by gamma and beta axons in isolated cat muscle spindels.

Blockade of intrafusal neuromuscular junctions of cat muscle spindles with gallamine

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