The ultrastructure of cat fusimotor endings and their relationship to foci of sarcomere convergence in intrafusal fibres

Arbuthnott, E. R.; Ballard, Kathleen J.; Boyd, I. A.; Gladden, M. H.; Sutherland, Fiona I.

doi:10.1113/jphysiol.1982.sp014373

Cited by 60 publications

(44 citation statements)

References 29 publications

(39 reference statements)

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“…This is not contradicted by any example from the present experiments and is further supported by the similarity between the proportion of driving-category effects (overall 28 % of static responses due to y-stimulation) and the proportion of chain-selective, presumed static y-axonal branches found in spindles in this study and several others (C883 30 %; overall 35 %; Barker, Emonet-Denand, Laporte, Proske & Stacey, 1973;Banks et al 1981;Arbuthnott et al 1982;Kucera, 1985;R. W. Banks, unpublished observations).…”

Section: Discussionsupporting

confidence: 63%

“…Fusimotor axons are usually branched intrafusally, but each axon commonly supplies only one type of intrafusal fibre in individual spindle poles, as shown by reconstructions from serial sections carried out independently in three laboratories (Banks, 1981;Banks, Barker & Stacey, 1981; Arbuthnott, Ballard, Boyd, Gladden & Sutherland, 1982;Kucera, 1985). Kucera (1985) reported a higher proportion of axons that were distributed exclusively to a single type of muscle fibre than did the other two groups; nevertheless all three found that a small proportion (3-4%) supplied both the bag, and one chain fibre, usually MS 9016 the longest, whereas a much larger proportion (up to 29 %) supplied the bag2 and at least one chain fibre.…”

Section: Introductionmentioning

confidence: 99%

“…The segregation of static y-axons into two or three types was based on two main lines of evidence; firstly, a histological description of different types of intrafusal motor ending, especially two types of neuromuscular junction on chain fibres (the ma and m, plates of Arbuthnott et al 1982; ; and, secondly, the similarity of the effects of stimulating a single static y-axon on the responses of more than one spindle (Boyd, Gladden & Ward, 1983;Boyd, 1986). The use of this evidence to support the case for subdivision of static y-axons has been criticized previously (Banks, Barker & Stacey, 1985a), when it was shown that variation in quantifiable features of intrafusal motor endings was correlated with polar location of the endings (Banks, Barker & Stacey, 1985b;Kucera & Walro, 1986); and that the methods used by Boyd and his colleagues (1983; 1986) would result in unconscious bias if, as is quite possible, the actual distribution of a single group of y-axons among the two different effectors, bag2 and chain fibres, is subject to random variation in different spindles.…”

Section: Introductionmentioning

confidence: 99%

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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: Discussionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Banks¹

1991

The Journal of Physiology

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“…Axon terminals of ma plates lie superficial to chain fibres at all levels of section through the plate, whereas m, plates have a pronounced sole plate and sections through the centre of such plates reveal axon terminals indented between finger-like protrusions of muscle sarcoplasm. Individual static y-axons end in either ma plates or m, plates but never in a mixture of the two (Arbuthnott, Ballard, Boyd, Gladden & Sutherland, 1982;Sutherland, Arbuthnott, Boyd & Gladden, 1985).…”

Section: Review)mentioning

confidence: 99%

Two Types of Static Γ‐axon in Cat Muscle Spindles

Boyd

1986

Exp Physiol

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SUMMARYThe action of single static y-axons in 'single fibre' ventral root filaments was tested on the responses of from two to eight spindles in the same tenuissimus muscle in anaesthetized cats.The type of intrafusal fibre activated in each spindle by a particular axon was diagnosed from its effect on the discharge of primary and secondary sensory endings, frequently in the same spindle. One or two spindles were subsequently isolated in most experiments and the type of intrafusal fibre activated by the axon was observed directly. Except in the case of a few weak actions which could not be interpreted, the diagnosis made from the afferent recordings was always correct. Twenty-four static y-axons activated the chain fibres in every spindle they supplied on which their action was tested; the static bag2 fibre was also involved in about 20 % of the spindles though its contraction was quite often weak. Eleven static y-axons activated the static bag2 fibre in every spindle they supplied on which their action was tested; some chain fibres were activated as well in about 20% of the spindles. There were only two possible exceptions to the general rule that a static y-axon activates either the chain fibres or the static bag2 fibre in every spindle it supplies and never activates only the chain fibres in one spindle, and only the static bag2 fibre in another spindle. Direct observation ofisolated spindles provided preliminary evidence that some non-selective connexions of static y-axons have a pronounced physiological action by way of their terminals on one type of intrafusal fibre while the terminal(s) on the other type of fibre produce such a weak contraction that the sensory endings are not affected. Other non-selective connexions do, however, have a significant physiological effect by way of their terminals on both the static bag2 fibre and the chain fibres. It is proposed that there are two types of static y-motoneurone.

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“…As the gradient in 5mm stretch is different from the gradient of 3mm stretch ( Fig.1), the second gradient of PSD between 15Hz and 35Hz changes when the muscle length changes and when intrafusal fibers are stimulated electrically. It implies the second gradient shows how much intrafusal muscle fibers are activated, probably in the static type of intrafusal muscle fibers like static nuclear chain fibers and a static nuclear bag fiber [9], [10].…”

Section: The Second Gradient Between 15hz and 35hz In Psd;mentioning

confidence: 99%

Quantitative estimation of sensitivity to muscle stretches in the tonic muscle spindle discharges of cats

Mizote

Matsuzaki

2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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Abstract-Joint interval histogram (JIH) and power spectrum density (PSD) of GIa unitary discharges were obtained while muscle of an anesthetized cat was stretched steadily. The PSD curve was approximated three lines in the following frequency band, below 15Hz, 15 to 35Hz and above 35Hz. The gradient between 15 to 35 Hz was steep and corresponds to how much the intrafusal fibers were activated. In a pattern of JIH, Ia discharges distributed wide in general. But, interval was regular and histogram made a group when intrafusal fibers were activated by electric stimulation on the ventral rootlet. In particular conditions, peaks were observed around 50 to 60 Hz in PSD. Keywords -Joint interval histogram, a power spectrum density, muscle spindle, intrafusal muscle fibers I. INTRODUCTIONMizote has found two types in afferent discharges of a shortened cat muscle by a combination of steady stretch and vibratory stretch. One is a discharge which comes from a dynamic nuclear bag fiber and the other comes from a static nuclear bag fiber or a nuclear chain fiber [1], [2]. But, response pattern of afferent fibers to vibratory stretches is varied as the muscle is extended and the separation in the afferent discharges was impossible because many impulses with several kinds of amplitude were recruited.We have estimated quantitatively the sensitivity of cat intrafusal muscle fibers to the muscle stretch by the joint interval histogram and by the power spectrum density of inter spike interval of spindle discharges. II. METHODOLOGY A. SubjectsExperimental data, which had already been reported [1] and had been recorded on a magnetic tape, were used for analyses of inter spike interval of cats muscle spindle discharges. Cats were anesthetized intraperitoneally and muscles were dissected free of surrounding tissue, while keeping the blood supply intact as much as possible. All other nerves in the hindlimb were cut except the gastrocnemius and soleus nerves. A laminectomy was performed to expose the dorsal and ventral roots between L5 and S1. They were cut at the entry into the spinal cord. The dorsal root was split into fine filaments for the isolation of single primary afferent fiber, which were identified as spindle endings by their behavior during twitch contractions of the muscle elicited by stimulating its nerve. The initial muscle length was determined by the single shock stimulus of ventral root. The muscle tendon through a steel hook was stretched steadily. Muscle was stretched to several mm till spindle discharges kept firing. Inter spike interval of the tonic discharges of muscle spindle was analyzed.Ventral root L7 was separated into six bundles. Each bundle was used as gamma fusimotor stimulation. Extrafusal muscle fibers were immobilized by gallamine injection, while respiration was kept by a respirator.Because original recordings of experimental data included responses to the vibratory stimuli or (and) to the electric stimulation of ventral rootlet, discharges during vibrations or during ventral stimulations were ejected...

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The ultrastructure of cat fusimotor endings and their relationship to foci of sarcomere convergence in intrafusal fibres

Cited by 60 publications

References 29 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.

Two Types of Static Γ‐axon in Cat Muscle Spindles

Quantitative estimation of sensitivity to muscle stretches in the tonic muscle spindle discharges of cats

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