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At least 73 records · Page 4Linked to original sources
PubMed2001

Quantitative study of muscle spindles in suboccipital muscles of human foetuses.

The proprioceptive inputs from the cervical musculature play an important role in head-eye co-ordination and postural processes. Deep cervical muscles in humans are shown to have high spindle content. The density, distribution and morphology of muscle spindles were studied in superior oblique capitis, inferior oblique capitis and rectus capitis posterior major and minor three small suboccipital muscles. The muscles were obtained, post-mortem from stillborn human foetus. The spindle density was calculated as the ratio of mean spindle content to the mean wet weight of that muscle in grams. The distribution and arrangement of spindles within the muscle and their arrangement was studied. The spindle density of superior oblique muscle was found to be 190, that of inferior oblique was 242 and the rectus capitis posterior contained 98 spindles per gram of muscle. No tendon organs were seen. The serial transverse sections of inferior oblique muscle revealed muscle spindles of varying sizes, length varying between 100-650 microns and, diameter 50-250 microns. A complex parallel arrangements of group of large spindles were seen in the belly of the inferior oblique muscle, while the polar regions contain few small isolated spindles. The relevance of such high spindle receptor content in these tiny muscles is discussed.

Fetus↗
PubMed1975

The responses of muscle spindles in sheep extraocular muscles.

1. Responses from de-efferented muscle spindles in sheep extraocular muscles have been recorded in the Gasserian ganglion using glass microelectrodes. 2. The afferent fibre conduction velocities ranged from 32 to 106 m/sec and most were intermediate. The distribution was unimodal. 3. The afferent responses to ramp stretches and longitudinal vibration of the muscle could not be divided into two groups, but both the dynamic indices and vibration sensitivities of the afferents increased with their conduction velocities. 4. Injection of suxamethonium did not help to classify afferents with intermediate conduction velocity. 5. It is concluded that the afferents from sheep extraocular muscle spindles form a single population whose properties are correlated with their nerve fibre diameters.

Animals↗
PubMed2006

Classification of muscle spindle afferents innervating the masseter muscle in rats.

Taylor et al. [Taylor, A., Durbaba, R., Rodgers, J.F., 1992a. The classification of afferents from muscle spindles of the jaw-closing muscles of the cat. J Physiol 456, 609-628] developed a method to classify muscle spindle afferents using succinylcholine (Sch) and ramp and hold stretches. They demonstrated that cat jaw muscle spindle afferents show high proportion of intermediate responses to ramp and hold jaw stretch. Together with observations on the responses to Sch their data suggests that the majority of jaw muscle spindle afferents are influenced by a combination of nuclear bag(2) and nuclear chain fibres. Relatively few are influenced solely by nuclear bag(1) fibres. The purpose of this study was to categorize jaw muscle spindle afferent in rodents in response to ramp and hold stretches. Several measures were used to classify spindle afferents including (1) conduction velocity, (2) coefficient of variation (C.V.) of the interspike interval during jaw opening, and (3) the dynamic sensitivity and the initial discharge of spindle afferents before and after succinylcholine infusion (Sch, 100mg/kg, i.v.). Consistent with observations in the cat jaw muscles, the distribution of the conduction velocity and the C.V. of Vmes masseter afferents were unimodal. Therefore, these parameters were of little value in functional classification of spindle innervation. Succinylcholine injection either markedly increased the dynamic sensitivity or produced no change in Vmes afferents. Unlike cat jaw muscle spindle afferents, the effect of Sch on the initial discharge was not clearly separable from those responding or not responding to Sch. These results suggest that rat jaw muscle spindle afferents, have physiological properties that are primarily intermediate in nature and are likely to reflect a predominance of influence from nuclear bag(2) and chain fibres. However, the distinction between bag(2) and chain fibres influences is not as clearly defined in the rat compared to the cat.

Action Potentials↗
PubMed1990

Histochemical profile of muscle spindles of rat's sural muscles.

The histochemical profile of intrafusal fibres of muscle spindles and muscle spindle capsule were analysed in normal sural muscles of a rat. Weak activity of oxidative enzymes (NADH diaphorase, succinic dehydrogenase, lactate dehydrogenase) and creatine phosphokinase were found in bag1 and bag2 fibres, but the oxidative enzyme activity was moderate in chain fibres. High phosphorylase activity was demonstrated in bag fibres as well as in chain fibres. No differences could be detected in adenosine desaminase activity between these various intrafusal fibres. In the outer capsule of muscle spindles, high amount of type III collagen and elastin, but only small amount of type I collagen and fibronectin could be observed.

Adenosine Deaminase↗
PubMed1979

Muscle spindle supply to the masticatory muscles in the Japane ermine (Carnivora).

Histological examination of the jaw muscles of the Japanese ermine showed that 4 jaw-closing muscles have 13 muscle spindles on one side of the face. The temporal muscle has 99 muscle spindles, 68 being in the anterior vertical and 31 in the posterior horizontal belly. The masseter muscle has 33 muscle spindles, 23 being in the profound and 10 in the superficial belly. The medial pterygoid muscle has 7 muscle spindles and the zygomaticomandibular muscle contains 4 muscle spindles. The lateral pterygoid and the jaw-opening muscles have no spindles.

Animals↗
PubMed1988

Localization of proprioceptive neurons innervating the muscle spindles of pig extraocular muscles studied by horseradish peroxidase labelling.

Each muscle of the extraocular muscles, containing abundant muscle spindles, was exposed to horseradish peroxidase (HRP) on 8 young pigs (2-month-old, 20-30 kg in body weight, both sexes). The results obtained are follows: The HRP-labelled neurons innervating the superior rectus muscle were always found in a crescent ventro-medio-dorsal fashion in the most medial position of the contralateral oculomotor nucleus. The HRP-labelled cells for the medial rectus muscle appeared close to the superior rectus group in the ipsilateral nucleus. The labelled cells for the inferior rectus muscle appeared in the ventrolateral position of the ipsilateral nucleus and those for the inferior oblique muscle in the area between the medial rectus and inferior rectus muscle groups. The labelled cells for the superior oblique muscle were found in the contralateral trochlear nucleus and those for the lateral rectus muscle bilaterally in the abducens nuclei, predominantly on the ipsilateral side and poorly on the contralateral side. The HRP-labelled cells were composed of large (alpha) and small (gamma) multipolar cells and of bipolar, oval or round (proprioceptive) cells, all intermingled together within the nucleus. The bipolar cells have been also identified in the 3 nuclei by means of Nissl staining technique. On this basis, they should be considered as the proprioceptive neurons. In the shrew-moles, the cell bodies of the proprioceptive neurons innervating the snout muscle spindles have been found close to the ipsilateral glossopharyngeal ganglion and those of the somatic sensory neurons in the ipsilateral trigeminal ganglion. In the pigs, no HRP-labelled cells were found in the trigeminal mesencephalic tract nucleus, but the HRP-labelled cells were found in the ipsilateral trigeminal and the superior cervical sympathetic ganglia. From the results, it could be emphasized that the proprioceptive neurons innervating the pig extraocular muscle spindles are located within the nuclei of the IIIrd, IVth and VIth cranial nerves.

Animals↗
PubMed2001

Scanning electron microscopic study of muscle spindles in the tenuissimus muscle of the Chinese hamster: with reference to the outer capsule, inner capsule and fusimotor endings.

The outer capsule, inner capsule and fusimotor endings of muscle spindles in the tenuissimus muscle of mature Chinese hamsters were examined by scanning electron microscopy (SEM). The thin and long tenuissimus muscle was transversely cut into several segments, and the segments were longitudinally or obliquely cut with a razor blade to mechanically remove the spindle sheath (outer capsule). These specimens were treated with 8 N HCl at 60 degrees C to isolate the muscle spindles and clearly expose the internal structures such as the inner capsule and fusimotor endings innervating intrafusal muscle fibers. The spindle sheath was about 1 mm long and at the equator about 50 microm in diameter. Within the outer capsule, cells of the inner capsule in the equatorial region were polygonal in shape, and continuously surrounded the axial bundle like a sleeve. This continuous sheath became sieve-like in the juxta-equatorial region, depending on the twining of thin and flattened cytoplasmic extensions and/or processes of the cells. Owing to the continuous inner capsular sheath in the equatorial region, the arrangement of sensory endings were not visualized under SEM. Fusimotor endings observed in the juxta-equatorial and polar regions consisted of poorly-developed subneural apparatuses with predominantly pit-like and short slit-like junctional folds.

Animals↗
PubMed1987

Developing muscle spindles in the mouse masseter muscle studied by electron microscopy.

The morphogenesis of the muscle spindles of the masseter muscle was investigated by electron microscopy. The mice used in this study were those from the 16-day-old fetuses to the four-day-old young, and the three-month-old adult ICR mice. At the time of observation the formation of the masseter muscle spindle had already started in the 16-day-old fetus. In the 17-day-old fetus, the sensory nerve terminated not only in the myotube but also in the myoblast in which no myofilaments were yet formed. From the observations on the 16-day-old and 17-day-old fetuses, it is suggested that the myotubes of the intrafusal muscle fibers are formed by the fusion of the myocytes already containing the myofilaments. The gamma motor end-plate appeared two days later than the sensory nerve terminal formation in the muscle spindle. The initial inner capsule of the spindle was observed in the four-day-old young. The cell without the myofilaments appeared amidst the cluster of the intrafusal muscle fibers in the three-day-old young. It is considered that this cell may be the origin of the inner capsule cell. The periaxial space formation and the myelination of the masseteric nerve fiber occurred in the four-day-old young. The formation of the postsynaptic folds was observed in the extrafusal muscle fiber at the same stage. Thus, the muscle spindles, nerve fibers and the extrafusal muscle fibers showed a remarkable development at the same time in this early postnatal stage.

Animals↗