Human Muscle Spindles Research Articles

The pathology of the human muscle spindle. A light microscopic, biometric and histochemical study.

A biometric study was made on 810 muscle spindles in 214 muscles. The absence of atrophy of the intra-fusal muscle fibres and the frequency of spindles with focal dilatation of the periaxial space were the prominent features in denervated muscles. Thickening of the spindle capsule without atrophy of the intra-fusal muscle fibres was often seen in dystrophic muscles. The frequency of changes was greatest in cases of myositis. Eleven spindles were studied by histochemical techniques. In one case of denervation atrophy, all the intrafusal muscle fibres had an enzyme pattern similar to the grouping that occurs in extra-fusal fibres during reinnervation. The outer membranes of the thickened spindle capsule, frequent in dystrophic muscles, were 5-Nucleotidase rich an ATPase poor. The inner membrane was ATPase rich and 5-Nucleotidase poor.

Afferent discharge from human muscle spindles in non-contracting muscles. Steady state impulse frequency as a function of joint angle.

AbstractImpulses in single muscle spindle afferents from the antebrachial finger flexor muscles were recorded from the median nerve of waking human subjects. The discharge frequency in the steady state was measured as the metacarpo‐phalangeal joint angles were passively changed in steps. At a comfortable resting position of the hand, less than ten percent of the spindle primaries were discharging. Within intermediate ranges of muscle lengths the discharge frequency of the single units did not exceed 20 impulse per second (ips). The response to joint movements was that expected from muscle stretch and muscle release alone and there was no indication of fusimotor adjustments as a result of joint movement. The frequency of the single units increased linearly with joint extension, the mean sensitivity of the primaries being 0.18 ips per degree which is about 5 times lower than the sensitivity of de‐efferented spindles in cat ankle extensors. The afferent discharge from the secondaries was in most respects very similar to that of the primaries. The low discharge frequency, the low percentage of active units and the low position sensitivity all indicate an insignificant fusimotor outflow to relaxed human hand muscles and a comparatively poor ability of the spindles to measure muscle length under these conditions.

Human muscle spindle discharge during isometric voluntary contractions. Amplitude relations between spindle frequency and torque.

AbstractDuring isometric voluntary contractions, the impulse frequency in muscle spindle afferents was analysed in relation to the contraction intensity in man. Single unit impulses from the finger flexor muscles were recorded with percutaneously inserted tungsten needle electrodes from the median nerve. The spindle frequency increased with the contraction intensity. For very weak contractions the increase was steep but levelled off to attain an average slope of 32.8 ips/Nm at the metacarpo‐phalangeal joint for the primaries and 22.8 ips/Nm for the secondaries when the muscles to a single finger were activated. The close relation between spindle frequency and torque suggests parallel modulations of the skeletomotor and the fusimotor outputs during voluntary contractions. The dominating type of fusimotor outflow was of the static type but clear indications of increased dynamic fusimotor outflow were also seen. Quantitative considerations of the spindle frequency as a function of contraction intensity and as a function of muscle length suggest that the muscle spindles and their central connections do not constitute a very powerful mechanism for holding the muscle at constant length when the load varies.

Distribution of muscle spindles in the human first dorsal interosseus.

AbstractThe problem of accurately locating muscle spindles within the bulk of skeletal muscle has been the major difficulty in histological evaluation of human muscle spindles and in attempts to record their physiological activity. Entire first Dorsal Interossei were taken from full‐term infants, stained in toto by deCastro's silver technique, serially sectioned or squashed, and individual spindles microdissected for study. A model of the muscle with its extrafusal innervation was constructed and the average number of spindles in five muscles was found to be 47 (range 4C–54). The first Dorsal Interosseus muscle is a bi‐pinnate structure divided by a central tendon which inserts on the proximal first phalanx. The spindles within this muscle are nearly equally distributed between the halves. Most of the spindles are concentrated in two well‐defined regions, a lateral, more distal spindle‐rich region and a medial, more proximal, grouping. Each of these two concentrations consists of approximately one‐third of the spindles present, the remaining one‐third being rather uniformly distributed throughout the muscle mass. An idea of the degree of concentration usually seen is illustrated by finding as many as eight spindles present in a 100X field in cross‐section. This density of concentration and apparent consistency of location within the muscle is expected to facilitate procurement of more adequate numbers of spindles at muscle biopsy and to aid the intramuscular recording from human muscle spindles.

Techniques for the demonstration of human muscle spindle innervation in neuromuscular disease

The human muscle spindle has a complex sensory and motor innervation. Methods are described for the study of spindle structure in both normal and pathological muscle obtained at post-mortem examination, and some anatomical details of spindle innervation in normal muscle are illustrated.

Discharge patterns in human muscle spindle afferents during isometric voluntary contractions.

AbstractUnitary nerve impulses were recorded from the median nerve of waking human subjects with percutaneously inserted tungsten electrodes. Activities from 63 muscle spindle endings were studied during isometric voluntary contractions. Three main types of response patterns were encountered: a sustained increase of the discharge, a sustained decrease, and a weak discharge consisting of a few impulses. It was concluded that the sustained increase of the discharge was accounted for by an increase of the fusimotor activity, whereas the sustained decrease was accounted for by mechanical unloading. The weak discharge might be accounted for by either mechanical or fusimotor mechanisms. Fusimotor activation concomitant with the skeletomotor activity could be demonstrated for 81% of the spindle afferents. One particular response pattern was not characteristic for certain endings but many units responded with different patterns depending upon the intensity and spatial extent of the contraction. Analyses of the unitary responses to the contraction of different muscle portions indicated that there was a close spatial correspondence in the muscle between the skeletomotor activity and the fusimotor activity.

Human Muscle Spindle Histochemistry

SEVERAL recent histochemical studies of muscle spindles 1-9 have demonstrated the relative activity of various enzymes and other components in the different types of intrafusal fibers. With a single exception consisting of a brief report 6 these results were based on studies of subhuman species. Since species differences in histochemical reactions of intrafusal fibers have been documented, 1,4,6,7 conclusions drawn from nonhuman studies may be misleading when attempts are made to extrapolate these results to human muscle. The purpose of this report is to describe the histochemistry of the nonnervous portion of normal human muscle spindles and to compare the reactions of intrafusal fibers with those of extrafusal fibers. Material and Methods For obvious reasons muscle tissue suitable for histochemical investigation is difficult to obtain from humans with no evidence of muscle disease. Biopsy specimens used in this study were obtained from the patients described below for the reasons listed.

"Trophic" influences of nerve on muscle.

"Trophic" influences of nerve on muscle.

THE REACTION OF MUSCLE TO DENERVATION

ArticlesTHE REACTION OF MUSCLE TO DENERVATIONSarah S. TowerSarah S. TowerPublished Online:01 Jan 1939https://doi.org/10.1152/physrev.1939.19.1.1MoreSectionsPDF (7 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited BySensory Protection of Rat Muscle Spindles following Peripheral Nerve Injury and ReinnervationPlastic and Reconstructive Surgery, Vol. 124, No. 6BibliographyMotorneuron protection by N-acetyl-cysteine after ventral root avulsion and ventral rhizotomyBritish Journal of Plastic Surgery, Vol. 58, No. 6Skeletal Muscle Denervation Increases Satellite Cell Susceptibility to ApoptosisPlastic and Reconstructive Surgery, Vol. 110, No. 1The Effect of Two Episodes of Denervation and Reinnervation on Skeletal Muscle Contractile FunctionPlastic and Reconstructive Surgery, Vol. 109, No. 1Endocytotic activity of mouse skeletal muscle fibres after long-term denervationJournal of the Neurological Sciences, Vol. 125, No. 2TTX-sensitive and TTX-insensitive sodium channel mRNA transcripts are independently regulated in adult skeletal muscle after denervationNeuron, Vol. 7, No. 3Reinnervation and recovery of mouse soleus muscle after long-term denervationNeuroscience, Vol. 39, No. 1Molecular aspects of the trophic influence of nerve on muscleProgress in Neurobiology, Vol. 21, No. 3β-Adrenergic receptors in innervated and denervated skeletal muscleBiochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 470, No. 1Diazepam blockade of repetitive action potentials in skeletal muscle fibres. A model of its membrane actionBrain Research, Vol. 133, No. 2Changes in chemosensitivity of skeletal muscles as related to endplate formationProgress in Neurobiology, Vol. 6The pathology of the human muscle spindle: Effect of denervationJournal of the Neurological Sciences, Vol. 22, No. 1Ultrastructural changes in the proleg retractor muscles of Galleria mellonella after denervationJournal of Insect Physiology, Vol. 16, No. 10Bibliography on muscle receptors; Their morphology, pathology and physiologyExperimental Neurology, Vol. 18The fine structure of neuromuscular junctions in the segmental muscles of the blowfly larvaJournal of Insect Physiology, Vol. 13, No. 6Blood Flow and Oxygen Consumption in Muscles after Section of Ventral RootsCirculation Research, Vol. 20, No. 5Spontaneous electrical activity of human muscleElectroencephalography and Clinical Neurophysiology, Vol. 20, No. 4Studies on the phrenic nerves and the diaphragm of the dogThe American Journal of Surgery, Vol. 97, No. 6The growth and function of the muscles of mastication in relation to the development of the facial skeleton and of the dentitionAmerican Journal of Orthodontics, Vol. 40, No. 6Synchronization of potentials and response to direct current stimulation in denervated mammalian muscleElectroencephalography and Clinical Neurophysiology, Vol. 3, No. 2THE NATURAL HISTORY OF POLIOMYELITISThe Lancet, Vol. 253, No. 6560THE CLINICAL APPLICATION OF ELECTROMYOGRAPHYThe Lancet, Vol. 241, No. 6234SULPHONAMIDES AND TISSUE-DAMAGEThe Lancet, Vol. 238, No. 6166MUSCLE ATROPHYThe Lancet, Vol. 238, No. 6166 More from this issue > Volume 19Issue 1January 1939Pages 1-48 https://doi.org/10.1152/physrev.1939.19.1.1History Published online 1 January 1939 Published in print 1 January 1939 Metrics