muscle spindles


Summary: Skeletal muscle structures that function as the MECHANORECEPTORS responsible for the stretch or myotactic reflex (REFLEX, STRETCH). They are composed of a bundle of encapsulated SKELETAL MUSCLE FIBERS, i.e., the intrafusal fibers (nuclear bag 1 fibers, nuclear bag 2 fibers, and nuclear chain fibers) innervated by SENSORY NEURONS.

Top Publications

  1. Chen H, Hippenmeyer S, Arber S, Frank E. Development of the monosynaptic stretch reflex circuit. Curr Opin Neurobiol. 2003;13:96-102 pubmed
    ..Finally, neurotrophin 3 released from muscle spindles regulates the strength of sensory-motor connections within the spinal cord postnatally.
  2. Wicke W, Wasicky R, Brugger P, Kaminski S, Lukas J. Histochemical and immunohistochemical study on muscle fibers in human extraocular muscle spindles. Exp Eye Res. 2007;84:670-9 pubmed
    ..Sixteen muscle spindles in human extraocular muscles counted as 'true' spindles revealed 27% nuclear chain fibers [40.1 microm+/-10...
  3. Bombardi C, Grandis A, Chiocchetti R, Bortolami R, Johansson H, Lucchi M. Immunohistochemical localization of alpha(1a)-adrenoreceptors in muscle spindles of rabbit masseter muscle. Tissue Cell. 2006;38:121-5 pubmed
    The expression of alpha(1a)-adrenoreceptors (alpha(1a)-ARs) within the muscle spindles of rabbit masseter muscle was investigated...
  4. Fallon J, Macefield V. Vibration sensitivity of human muscle spindles and Golgi tendon organs. Muscle Nerve. 2007;36:21-9 pubmed
  5. Kucera J, Cooney W, Que A, Szeder V, Stancz Szeder H, Walro J. Formation of supernumerary muscle spindles at the expense of Golgi tendon organs in ER81-deficient mice. Dev Dyn. 2002;223:389-401 pubmed
    ..potentials than stimulation of distal nerves in hindlimbs, a deficit that is paralleled by a paucity of muscle spindles in proximal muscles (Arber et al., 2000)...
  6. Hui K, Kucera J, Henderson J. Differential sensitivity of skeletal and fusimotor neurons to Bcl-2-mediated apoptosis during neuromuscular development. Cell Death Differ. 2008;15:691-9 pubmed
    ..These results demonstrate, for the first time, the connection between Bcl-2 expression, motor neuron survival, and the establishment of different motor populations. ..
  7. Muller K, Ryals J, Feldman E, Wright D. Abnormal muscle spindle innervation and large-fiber neuropathy in diabetic mice. Diabetes. 2008;57:1693-701 pubmed publisher
    ..Large sensory axons innervating muscle spindles provide feedback for balance and gait and, when damaged, can cause altered sensorimotor function...
  8. Beith I, Harrison P. Stretch reflexes in human abdominal muscles. Exp Brain Res. 2004;159:206-13 pubmed
    ..It follows that if the homonymous stretch reflex of abdominal muscles have a monosynaptic component, then a similar monosynaptic pathway activates synergistic motoneurones, not only ipsilaterally but also contralaterally. ..
  9. Gould T, Yonemura S, Oppenheim R, Ohmori S, Enomoto H. The neurotrophic effects of glial cell line-derived neurotrophic factor on spinal motoneurons are restricted to fusimotor subtypes. J Neurosci. 2008;28:2131-46 pubmed publisher
    ..Whereas nearly all hindlimb muscles exhibited normal gross innervation, intrafusal muscle spindles displayed a significant loss of innervation in most but not all muscles at P0...

More Information


  1. Taylor M, Holdeman A, Weltmer S, Ryals J, Wright D. Modulation of muscle spindle innervation by neurotrophin-3 following nerve injury. Exp Neurol. 2005;191:211-22 pubmed
    b>Muscle spindles monitor changes in muscle length and are innervated by groups Ia and II sensory axons as well as gamma motor axons...
  2. Komori T, Gyobu H, Ueno H, Kitamura T, Senba E, Morikawa Y. Expression of kin of irregular chiasm-like 3/mKirre in proprioceptive neurons of the dorsal root ganglia and its interaction with nephrin in muscle spindles. J Comp Neurol. 2008;511:92-108 pubmed publisher
    ..was observed in TrkC-positive nerve fibers around neurotrophin 3 (NT3)-positive intrafusal muscle fibers of muscle spindles at E17.5...
  3. Kim G, Suzuki S, Kanda K. Age-related physiological and morphological changes of muscle spindles in rats. J Physiol. 2007;582:525-38 pubmed
    Age-related physiological and morphological changes of muscle spindles were examined in rats (male Fischer 344/DuCrj: young, 4-13 months; middle-aged, 20-22 months; old, 28-31 months)...
  4. Cordo P, Flores Vieira C, Verschueren S, Inglis J, Gurfinkel V. Position sensitivity of human muscle spindles: single afferent and population representations. J Neurophysiol. 2002;87:1186-95 pubmed
  5. De Doncker L, Picquet F, Petit J, Falempin M. Characterization of spindle afferents in rat soleus muscle using ramp-and-hold and sinusoidal stretches. J Neurophysiol. 2003;89:442-9 pubmed
    The discharge properties of 51 afferents were studied in the rat soleus muscle spindles. Under deep anesthesia using a pentobarbital sodium solution (30 mg/kg), a laminectomy was performed and the right L(4) and L(5) dorsal and ventral ..
  6. Linari M, Bottinelli R, Pellegrino M, Reconditi M, Reggiani C, Lombardi V. The mechanism of the force response to stretch in human skinned muscle fibres with different myosin isoforms. J Physiol. 2004;554:335-52 pubmed
  7. Friese A, Kaltschmidt J, Ladle D, Sigrist M, Jessell T, Arber S. Gamma and alpha motor neurons distinguished by expression of transcription factor Err3. Proc Natl Acad Sci U S A. 2009;106:13588-93 pubmed publisher
    ..Signals from muscle spindles are needed to support the differentiation of Err3(on)/NeuN(off) presumptive gamma motor neurons, whereas ..
  8. Whitehead J, Keller Peck C, Kucera J, Tourtellotte W. Glial cell-line derived neurotrophic factor-dependent fusimotor neuron survival during development. Mech Dev. 2005;122:27-41 pubmed
    ..was decreased, whereas in transgenic mice that overexpress GDNF in muscle, fusimotor innervation to muscle spindles was increased...
  9. Liu J, Willison H, Pedrosa Domellöf F. Immunolocalization of GQ1b and related gangliosides in human extraocular neuromuscular junctions and muscle spindles. Invest Ophthalmol Vis Sci. 2009;50:3226-32 pubmed publisher
    ..anti-GQ1b, -GT1a, and -GD1b antibody binding in human extraocular muscles (EOMs), axial and limb muscles, and muscle spindles and thereby test the hypothesis that their distinctive ganglioside composition provides the molecular basis ..
  10. Leu M, Bellmunt E, Schwander M, Farinas I, Brenner H, Muller U. Erbb2 regulates neuromuscular synapse formation and is essential for muscle spindle development. Development. 2003;130:2291-301 pubmed
    ..However, functional spindles never develop. Taken together, our data suggest that Erbb2 signaling regulates the formation of both neuromuscular synapses and muscle spindles.
  11. Shneider N, Mentis G, Schustak J, O Donovan M. Functionally reduced sensorimotor connections form with normal specificity despite abnormal muscle spindle development: the role of spindle-derived neurotrophin 3. J Neurosci. 2009;29:4719-35 pubmed publisher
    ..muscle spindle afferents and spinal motor neurons are believed to be regulated by factors originating from muscle spindles. Here, we find that the connections form with appropriate specificity in mice with abnormal spindle ..
  12. Rosant C, Nagel M, Perot C. Aging affects passive stiffness and spindle function of the rat soleus muscle. Exp Gerontol. 2007;42:301-8 pubmed
    ..The contralateral muscle was used to count muscle spindles and spindle fibers (ATPase staining) and immunostained to identify MyHC isoforms...
  13. Winarakwong L, Muramoto T, Soma K, Takano Y. Age-related changes and the possible adaptability of rat jaw muscle spindles: immunohistochemical and fine structural studies. Arch Histol Cytol. 2004;67:227-40 pubmed
    Afferent signals from jaw muscle spindles contribute to the feedback mechanism that regulates mastication...
  14. Chen H, Tourtellotte W, Frank E. Muscle spindle-derived neurotrophin 3 regulates synaptic connectivity between muscle sensory and motor neurons. J Neurosci. 2002;22:3512-9 pubmed
    Ia afferents induce the formation of muscle spindles prenatally and maintain them postnatally...
  15. Rossi A, Mammucari C, Argentini C, Reggiani C, Schiaffino S. Two novel/ancient myosins in mammalian skeletal muscles: MYH14/7b and MYH15 are expressed in extraocular muscles and muscle spindles. J Physiol. 2010;588:353-64 pubmed publisher
    ..only in a minor fibre population in EO muscles, corresponding to slow-tonic fibres, and in bag fibres of muscle spindles. MYH15 protein is present in most fibres of the orbital layer of EO muscles and in the extracapsular region ..
  16. Birznieks I, Burton A, Macefield V. The effects of experimental muscle and skin pain on the static stretch sensitivity of human muscle spindles in relaxed leg muscles. J Physiol. 2008;586:2713-23 pubmed publisher
    Animal studies have shown that noxious inputs onto gamma-motoneurons can cause an increase in the activity of muscle spindles, and it has been proposed that this causes a fusimotor-driven increase in muscle stiffness that is believed to ..
  17. Macefield V, Sverrisdottir Y, Wallin B. Resting discharge of human muscle spindles is not modulated by increases in sympathetic drive. J Physiol. 2003;551:1005-11 pubmed
    There is evidence in experimental animals that, in addition to receiving fusimotor drive, muscle spindles are subject to modulation by the sympathetic nervous system...
  18. Simon A, Shenton F, Hunter I, Banks R, Bewick G. Amiloride-sensitive channels are a major contributor to mechanotransduction in mammalian muscle spindles. J Physiol. 2010;588:171-85 pubmed publisher
    ..are a major contributor to mechanosensory transduction in primary mechanosensory afferents, using adult rat muscle spindles as a model system...
  19. Hippenmeyer S, Shneider N, Birchmeier C, Burden S, Jessell T, Arber S. A role for neuregulin1 signaling in muscle spindle differentiation. Neuron. 2002;36:1035-49 pubmed
    ..One example of such an interaction is the influence of proprioceptive sensory axons on the differentiation of muscle spindles. We have monitored the expression of three transcription factors, Egr3, Pea3, and Erm, that delineate early ..
  20. Vrieseling E, Arber S. Target-induced transcriptional control of dendritic patterning and connectivity in motor neurons by the ETS gene Pea3. Cell. 2006;127:1439-52 pubmed
    ..These findings suggest that target-induced transcriptional programs control MN dendrite orientation and play a crucial role in the establishment of sensory-motor connections in the spinal cord. ..
  21. Jacobson C, Duggan D, Fischbach G. Neuregulin induces the expression of transcription factors and myosin heavy chains typical of muscle spindles in cultured human muscle. Proc Natl Acad Sci U S A. 2004;101:12218-23 pubmed
    ..Taken together, these results indicate that not only can NRG induce the expression of a transcription factor key to spindle fiber development (Egr3), but that a portion of this developmental process can be replicated in vitro. ..
  22. Elsohemy A, Butler R, Bain J, Fahnestock M. Sensory protection of rat muscle spindles following peripheral nerve injury and reinnervation. Plast Reconstr Surg. 2009;124:1860-8 pubmed publisher
    ..denervation results in irreversible muscle fiber atrophy, connective tissue hyperplasia, and deterioration of muscle spindles, specialized sensory receptors necessary for proper skeletal muscle function...
  23. Wang Z, Li L, Frank E. The role of muscle spindles in the development of the monosynaptic stretch reflex. J Neurophysiol. 2012;108:83-90 pubmed publisher
    Muscle sensory axons induce the development of specialized intrafusal muscle fibers in muscle spindles during development, but the role that the intrafusal fibers may play in the development of the central projections of these Ia sensory ..
  24. Andrechek E, Hardy W, Girgis Gabardo A, Perry R, Butler R, Graham F, et al. ErbB2 is required for muscle spindle and myoblast cell survival. Mol Cell Biol. 2002;22:4714-22 pubmed
    ..This resulted in viable mice with a progressive defect in proprioception due to loss of muscle spindles. Interestingly, a partial reduction of ErbB2 levels also reduced the number of muscle spindles...
  25. Stelzer J, Larsson L, Fitzsimons D, Moss R. Activation dependence of stretch activation in mouse skinned myocardium: implications for ventricular function. J Gen Physiol. 2006;127:95-107 pubmed
    ..Such a mechanism would contribute to increased systolic ejection in response to increased delivery of activator Ca2+ during excitation-contraction coupling. ..
  26. Alexander C, Harrison P. The bilateral reflex control of the trapezius muscle in humans. Exp Brain Res. 2002;142:418-24 pubmed
    ..These results imply that muscle spindle afferents from the ipsilateral trapezius monosynaptically activate motoneurones contralaterally. ..
  27. Romanovsky D, Moseley A, Mrak R, Taylor M, Dobretsov M. Phylogenetic preservation of alpha3 Na+,K+-ATPase distribution in vertebrate peripheral nervous systems. J Comp Neurol. 2007;500:1106-16 pubmed
    The alpha(3) isoform of Na(+),K(+)-ATPase is uniquely expressed in afferent and efferent neurons innervating muscle spindles in the peripheral nervous system (PNS) of adult rats, but the distribution pattern of this isoform in other ..
  28. Cheret C, Willem M, Fricker F, Wende H, Wulf Goldenberg A, Tahirovic S, et al. Bace1 and Neuregulin-1 cooperate to control formation and maintenance of muscle spindles. EMBO J. 2013;32:2015-28 pubmed publisher IgNrg1 signal strength in vivo results in increasingly severe deficits in formation and maturation of muscle spindles, a proprioceptive organ critical for muscle coordination...
  29. Haftel V, Bichler E, Nichols T, Pinter M, Cope T. Movement reduces the dynamic response of muscle spindle afferents and motoneuron synaptic potentials in rat. J Neurophysiol. 2004;91:2164-71 pubmed
    ..of muscle contraction is the history dependence observed under some conditions in the response properties of muscle spindles. The present study was designed to test one report that in successive trials of muscle stretch-release, ..
  30. Triantafyllou A. Immunohistochemical characterization of capsular cells in neuromuscular spindles of the neck. J Oral Pathol Med. 2007;36:501-4 pubmed
    ..Cells resembling perineurial cells and endoneurial fibroblasts, and basement membrane rich in collagen type IV comprise the capsules of neuromuscular spindles. ..
  31. Fischer M, Schafer S. Effects of changes in pH on the afferent impulse activity of isolated cat muscle spindles. Brain Res. 2005;1043:163-78 pubmed
    ..H(+), lactate and CO(2) might also affect the receptor in the fatiguing muscle, the impulse activity of muscle spindles isolated from the cat tenuissimus muscle was characterized under varying degrees of extracellular pH, thus ..
  32. Banks R, Hulliger M, Saed H, Stacey M. A comparative analysis of the encapsulated end-organs of mammalian skeletal muscles and of their sensory nerve endings. J Anat. 2009;214:859-87 pubmed publisher
    ..the existence of a gradual proximo-distal decline in the overall average size of the afferent complement of muscle spindles from axial through hind limb to intrinsic foot muscles, but with considerable muscle-specific variability...
  33. Herndon C, Ankenbruck N, Lester B, Bailey J, Fromm L. Neuregulin1 signaling targets SRF and CREB and activates the muscle spindle-specific gene Egr3 through a composite SRF-CREB-binding site. Exp Cell Res. 2013;319:718-30 pubmed publisher
    b>Muscle spindles are sensory receptors embedded within muscle that detect changes in muscle length...
  34. Mameli O, Stanzani S, Russo A, Pellitteri R, Spatuzza M, Caria M, et al. Hypoglossal nucleus projections to the rat masseter muscle. Brain Res. 2009;1283:34-40 pubmed publisher
    ..also spread into the masseter branch of the trigeminal nerve to target the polar portions of the masseter muscle spindles. Retrograde double labelling, performed by injecting Dil into the pad and True Blue into the ipsilateral ..
  35. Thunberg J, Ljubisavljevic M, Djupsjöbacka M, Johansson H. Effects on the fusimotor-muscle spindle system induced by intramuscular injections of hypertonic saline. Exp Brain Res. 2002;142:319-26 pubmed
    ..Predominantly static fusimotor neurones were activated. The possible role of the fusimotor-muscle spindle system in altered motor control during experimentally induced muscle pain is discussed. ..
  36. Cao D, Pickar J, Ge W, Ianuzzi A, Khalsa P. Position sensitivity of feline paraspinal muscle spindles to vertebral movement in the lumbar spine. J Neurophysiol. 2009;101:1722-9 pubmed publisher
    b>Muscle spindles contribute to sensorimotor control by supplying feedback regarding muscle length and consequently information about joint position...
  37. Fischer M, Schafer S. Effects of the calcium antagonist nifedipine on the afferent impulse activity of isolated cat muscle spindles. Brain Res. 2002;954:256-76 pubmed
    The impulse activity of muscle spindles isolated from the cat tenuissimus muscle was investigated under varying concentrations of the L-type calcium channel blocker nifedipine...
  38. Berdah S, De Troyer A. Contribution of spindle reflexes to post-inspiratory activity in the canine external intercostal muscles. J Physiol. 2001;534:873-80 pubmed activity than the parasternal intercostal muscles and are more abundantly supplied with muscle spindles. In the present study, the hypothesis was tested that spindle afferent inputs play a major role in ..
  39. Tourtellotte W, Keller Peck C, Milbrandt J, Kucera J. The transcription factor Egr3 modulates sensory axon-myotube interactions during muscle spindle morphogenesis. Dev Biol. 2001;232:388-99 pubmed
    ..We conclude that Egr3 has an essential role in regulating genes required for the transformation of undifferentiated myotubes into intrafusal fibers, and hence for the phenotypic differentiation of spindles. ..
  40. Pickar J, Wheeler J. Response of muscle proprioceptors to spinal manipulative-like loads in the anesthetized cat. J Manipulative Physiol Ther. 2001;24:2-11 pubmed
    ..The purpose of the present study was to determine whether muscle spindles and Golgi tendon organs in paraspinal muscles respond to a mechanical load whose force-time profile is ..
  41. Ribot Ciscar E, Roll J. Ago-antagonist muscle spindle inputs contribute together to joint movement coding in man. Brain Res. 1998;791:167-76 pubmed
    ..All in all, joint movement perception seems to result from the co-processing by the central nervous system of the multiple spindle feedbacks originating from the whole set of muscles involved in the performance of a movement. ..
  42. Ribot Ciscar E, Rossi Durand C, Roll J. Muscle spindle activity following muscle tendon vibration in man. Neurosci Lett. 1998;258:147-50 pubmed
    ..The results are discussed in the light of previous psychophysiological studies reporting an altered position sense and a development of involuntary muscle contractions in postvibratory periods. ..
  43. Arber S, Ladle D, Lin J, Frank E, Jessell T. ETS gene Er81 controls the formation of functional connections between group Ia sensory afferents and motor neurons. Cell. 2000;101:485-98 pubmed
    ..Er81 mutant mice exhibit a severe motor discoordination, yet the specification of MNs and induction of muscle spindles occurs normally...
  44. Tourtellotte W, Milbrandt J. Sensory ataxia and muscle spindle agenesis in mice lacking the transcription factor Egr3. Nat Genet. 1998;20:87-91 pubmed
    b>Muscle spindles are skeletal muscle sensory organs that provide axial and limb position information (proprioception) to the central nervous system...
  45. Nahirney P, Ovalle W. Distribution of dystrophin and neurofilament protein in muscle spindles of normal and Mdx-dystrophic mice: an immunocytochemical study. Anat Rec. 1993;235:501-10 pubmed
    ..b>Muscle spindles in the soleus of 32-week-old normal and age-matched mdx mice were examined by immunocytochemical methods to ..
  46. Nakajima T, Izumizaki M, Sekihara C, Atsumi T, Homma I. Combined effects of preceding muscle vibration and contraction on the tonic vibration reflex. Exp Brain Res. 2009;192:211-9 pubmed publisher
    ..These results suggest that vibration and contraction work synergistically to develop intrafusal thixotropy. ..
  47. Querfurth H. Action-potential initiation and maintained activity of the isolated frog muscle spindle. Eur J Neurosci. 2006;24:1147-56 pubmed
    ..The experiments show dynamic threshold patterns that control action-potential initiation by the assessment of the actual amplitude of depolarization and its rate of rise. ..
  48. Madhavan S, Shields R. Influence of age on dynamic position sense: evidence using a sequential movement task. Exp Brain Res. 2005;164:18-28 pubmed
    ..Rehabilitative training methods that improve dynamic position sense of the ankles may improve physical function and balance in the elderly. ..
  49. Edman K, Radzyukevich T, Kronborg B. Contractile properties of isolated muscle spindles of the frog. J Physiol. 2002;541:905-16 pubmed
    Force and isotonic shortening velocities were studied (0.6-4.0 degrees C) in isolated single muscle spindles from the anterior tibialis muscle of Rana temporaria using techniques that enabled measurements both from the spindle as a whole ..
  50. Blumer R, Wasicky R, Brugger P, Hoetzenecker W, Wicke W, Lukas J. Number, distribution, and morphologic particularities of encapsulated proprioceptors in pig extraocular muscles. Invest Ophthalmol Vis Sci. 2001;42:3085-94 pubmed
    ..GTOs and muscle spindles were numerous in pig EOMs...
  51. Munteanu S, Strawhorn A, Landorf K, Bird A, Murley G. A weightbearing technique for the measurement of ankle joint dorsiflexion with the knee extended is reliable. J Sci Med Sport. 2009;12:54-9 pubmed
    ..However, the reliability of this measurement technique needs to be interpreted in the context of the purpose for which the measurement is intended. ..
  52. Lackner J, DiZio P. Adaptation to Coriolis force perturbation of movement trajectory; role of proprioceptive and cutaneous somatosensory feedback. Adv Exp Med Biol. 2002;508:69-78 pubmed
  53. Bani D, Bergamini M. Ultrastructural abnormalities of muscle spindles in the rat masseter muscle with malocclusion-induced damage. Histol Histopathol. 2002;17:45-54 pubmed publisher
    ..In the present study, the masseter muscle spindles of the same malocclusion-bearing rats were examined by electron microscopy...