Intrafusal muscleSignaling and behavSensoryAfferentsExtrafusal fibersProprioceptiveNeuronsFusimotorProprioceptionSkeletalInnervatePostnatal developmentCapsuleSensitivityNerveFibresEliminationStretchOnsetStagesAfferentTarget muscleSpeciesResultsControlAlphaReceptorPresenceMakeFormationActivityFactorsStaticIncreaseShow
Intrafusal muscle5
- Muscle spindles are fusiform (spindle-shaped), and the specialized fibers that make up the muscle spindle are called intrafusal muscle fibers. (wikipedia.org)
- The dynamic axons innervate the bag1 intrafusal muscle fibers. (wikipedia.org)
- they make synapses at either or both of the ends of the intrafusal muscle fibers and regulate the sensitivity of the sensory afferents, which are located in the non-contractile central (equatorial) region. (wikipedia.org)
- Upon release of acetylcholine by the active gamma motor neuron, the end portions of the intrafusal muscle fibers contract, thus elongating the non-contractile central portions (see "fusimotor action" schematic below). (wikipedia.org)
- Motor myoneural junctions on frog intrafusal muscle fibers. (xenbase.org)
Signaling and behav1
- Collectively, we present the first evidence that Na V 1.1 is essential for mammalian proprioceptive signaling and behaviors. (elifesciences.org)
Sensory11
- The muscle spindle has both sensory and motor components. (wikipedia.org)
- Sensory information conveyed by primary type Ia sensory fibers which spiral around muscle fibres within the spindle, and secondary type II sensory fibers Activation of muscle fibres within the spindle by up to a dozen gamma motor neurons and to a lesser extent by one or two beta motor neurons[citation needed] Muscle spindles are found within the belly of a skeletal muscle. (wikipedia.org)
- Primary type Ia sensory fibers (large diameter) spiral around all intrafusal muscle fibres, ending near the middle of each fibre. (wikipedia.org)
- Fusimotor neurons are classified as static or dynamic according to the type of muscle fibers they innervate and their effects on the responses of the Ia and II sensory neurons innervating the central, non-contractile part of the muscle spindle. (wikipedia.org)
- When a muscle is stretched, primary type Ia sensory fibers of the muscle spindle respond to both changes in muscle length and velocity and transmit this activity to the spinal cord in the form of changes in the rate of action potentials. (wikipedia.org)
- Likewise, secondary type II sensory fibers respond to muscle length changes (but with a smaller velocity-sensitive component) and transmit this signal to the spinal cord. (wikipedia.org)
- The function of the gamma motor neurons is not to supplement the force of muscle contraction provided by the extrafusal fibers, but to modify the sensitivity of the muscle spindle sensory afferents to stretch. (wikipedia.org)
- Deletion of GDNF expression from muscle spindles results in the selective elimination of γ-MNs with preservation of the spindle and its sensory innervation. (biomedcentral.com)
- At the larval stage 57 (Nieuwkoop and Faber 1967), muscle spindles were first identified primarily by the presence of sensory endings associated with a thin bundle of myotubes, e.g. intrafusal (IF) myotubes which were partly invested by a single cellular layer. (xenbase.org)
- Sensory endings were smaller in size and in number per spindle than those in the adult, forming irregular beaded chains with occasional tubular expansions. (xenbase.org)
- Unique sensory endings in rat muscle spindles. (xenbase.org)
Afferents3
- They increase the firing rate of Ia and II afferents at a given muscle length (see schematic of fusimotor action below). (wikipedia.org)
- This raises the resting potential of the endings, thereby increasing the probability of action potential firing, thus increasing the stretch-sensitivity of the muscle spindle afferents. (wikipedia.org)
- Short and long-term changes in synaptic efficacy occur in vivo at the central synapse between muscle spindle afferents (Ia) and spinal motoneurons ( Mendell, 1984 ). (jneurosci.org)
Extrafusal fibers1
- The reflexly evoked activity in the alpha motor neurons is then transmitted via their efferent axons to the extrafusal fibers of the muscle, which generate force and thereby resist the stretch. (wikipedia.org)
Proprioceptive1
- Muscle spindles provide proprioceptive information required for motor control. (biomedcentral.com)
Neurons10
- The responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, for example, by activating motor neurons via the stretch reflex to resist muscle stretch. (wikipedia.org)
- The motor part of the spindle is provided by motor neurons: up to a dozen gamma motor neurons also known as fusimotor neurons. (wikipedia.org)
- Gamma motor neurons supply only muscle fibres within the spindle, whereas beta motor neurons supply muscle fibres both within and outside of the spindle. (wikipedia.org)
- Activation of the neurons causes a contraction and stiffening of the end parts of the muscle spindle muscle fibers. (wikipedia.org)
- The Ia afferent signals are transmitted monosynaptically to many alpha motor neurons of the receptor-bearing muscle. (wikipedia.org)
- This article provides insight into the importance of a voltage-gated sodium channel in proprioceptors, a group of mechanosensory neurons that target muscle. (elifesciences.org)
- Gamma motor neurons (γ-MNs) selectively innervate muscle spindle intrafusal fibers and regulate their sensitivity to stretch. (biomedcentral.com)
- Fusimotor axons originate either from gamma motor neurons (γ-MNs), which only innervate intrafusal fibers of the muscle spindle, or from alpha motor neurons (α-MNs), which innervate extrafusal muscle and also send a β-skeletofusimotor collateral axon to innervate the muscle spindle [ 2 - 4 ]. (biomedcentral.com)
- Surprisingly, TRN neurons associated with spindles in sleep are also associated with alpha oscillations during attention. (frontiersin.org)
- Spindles are generated by interactions between thalamic reticular nucleus (TRN) neurons and thalamo-cortical relay neurons. (frontiersin.org)
Fusimotor3
- Unlike other mechanoreceptors, the sensitivity of muscle spindles is actively regulated by a specialized fusimotor system. (biomedcentral.com)
- The advantages of a γ-fusimotor system to control spindle sensitivity independently of force-generating extrafusal muscle fibers are not fully understood, nor are the mechanisms that generate the distinct γ- and α-MN subtypes in mammals. (biomedcentral.com)
- Development of muscle spindles deprived of fusimotor innervation. (xenbase.org)
Proprioception1
- Here, we identify a new role for Na V 1.1 in mammalian proprioception. (elifesciences.org)
Skeletal4
- Muscle spindles are stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle. (wikipedia.org)
- Fine structure of skeletal muscle. (xenbase.org)
- Skeletal muscles-which enable animals to move-are made up of large elongated muscle cells that span the entire length of the muscle. (elifesciences.org)
- Skeletal muscle fibre formation requires a coordinated programme of morphological and biochemical changes in the differentiating cells. (elifesciences.org)
Innervate1
- They constitute a distinct subpopulation that differs in morphology, physiology and connectivity from α-MNs, which innervate extrafusal muscle fibers and exert force. (biomedcentral.com)
Postnatal development2
- With these markers of γ-MN identity, we show after conditional elimination of GDNF from muscle spindles that the survival of γ-MNs is selectively dependent on spindle-derived GDNF during the first 2 weeks of postnatal development. (biomedcentral.com)
- Morphogenesis of rat muscle spindles after nerve lesion during early postnatal development. (xenbase.org)
Capsule2
- Muscle spindles have a capsule of connective tissue, and run parallel to the extrafusal muscle fibers. (wikipedia.org)
- Histological and histochemical observations on the capsule of the muscle spindle in normal and denervated muscle. (xenbase.org)
Sensitivity2
- This allows for continuous control of the mechanical sensitivity of spindles over the wide range of lengths and velocities that occur during normal motor behaviors [ 1 ]. (biomedcentral.com)
- Phylogenetically, γ-MNs are best developed in mammals, whereas lower vertebrates (for example, amphibians) use a β-skeletofusimotor system alone to control the sensitivity of their muscle spindles. (biomedcentral.com)
Nerve1
- Synaptic efficacy at the rat Ia-motoneuron synapse has been reported to increase in vivo , within 3 d of sectioning a single muscle nerve ( Miyata and Yasuda, 1988 ). (jneurosci.org)
Fibres2
- These activate the muscle fibres within the spindle. (wikipedia.org)
- identified a new member of the MAP family that is produced in myoblasts as soon as they start to form muscle fibres, and named it oMAP4. (elifesciences.org)
Elimination1
- Irreversible elimination of muscle receptors. (xenbase.org)
Stretch1
- This suggests that while a combination of Piezo2 and other Na V isoforms is sufficient to elicit activity in response to transient stimuli, Na V 1.1 is required for transmission of receptor potentials generated during sustained muscle stretch. (elifesciences.org)
Onset1
- These bursts are sleep spindles, an important characteristic of sleep onset. (scholarpedia.org)
Stages1
- Stages in the development of cat muscle spindles. (xenbase.org)
Afferent2
- The Ia afferent signal is also transmitted polysynaptically through interneurons (Ia inhibitory interneurons), which inhibit alpha motorneurons of antagonist muscles, causing them to relax. (wikipedia.org)
- Furthermore, these results suggest that the probability of transmitter release at this synapse is regulated by either afferent activity and/or trophic communication with the target muscle. (jneurosci.org)
Target muscle1
- GFP display structural and synaptic features of γ-MNs and are selectively lost in mutants lacking target muscle spindles. (biomedcentral.com)
Species1
- Importantly, and in all species, the EMG shows the complete loss of muscle tone (i.e., atonia) that is a characteristic of REM sleep. (scholarpedia.org)
Results2
- Loss of muscle spindles also results in the downregulation of Gfrα1 expression in some large diameter MNs, suggesting that spindle-derived factors may also influence populations of α-MNs with β-skeletofusimotor collaterals. (biomedcentral.com)
- The results were compared with the formative process of mammalian spindles. (xenbase.org)
Control1
- Therefore, the next challenge is to understand how other processes-such as the selective stabilisation of some microtubules and the movement of cell materials along the microtubules-cooperate to control muscle fibre formation. (elifesciences.org)
Alpha1
- Surprisingly, not only did we find that spindle-generating TRN circuits engage in attentional processing, but we also discover that this engagement involves alpha oscillations, a waking rhythm with computational properties similar to spindles. (frontiersin.org)
Receptor1
- Using this knowledge we characterized genetic strategies to label developing γ-MNs based on GDNF receptor expression, showed their strict dependence for survival on muscle spindle-derived GDNF and generated an animal model in which γ-MNs are selectively lost. (biomedcentral.com)
Presence2
- The presence of spindles is marked by the arrows during Stage 2. (scholarpedia.org)
- Stage 2 is notable for the presence of spindles, which are waxing and waning bursts of frequencies in the sigma band. (scholarpedia.org)
Make2
- Cells called myoblasts elongate and fuse together at their tips to make the muscle cells. (elifesciences.org)
- The microtubules in cells that make smaller amounts of this protein were more disorganised, and these cells were unable to fuse with each other to form muscle cells. (elifesciences.org)
Formation2
- The initial formation of muscle spindles was studied with electron microscopy using the toe muscle of Xenopus laevis. (xenbase.org)
- The microtubule cytoskeleton is critical for muscle cell differentiation and undergoes reorganisation into an array of paraxial microtubules, which serves as template for contractile sarcomere formation. (elifesciences.org)
Activity1
- During this state, the EOG can show gradual rolling eye movements and there is low or minimal muscle activity. (scholarpedia.org)
Factors1
- Second, axotomy eliminates access to trophic factors supplied by the muscle. (jneurosci.org)
Static1
- Muscle spindles are composed of 5-14 muscle fibers, of which there are three types: dynamic nuclear bag fibers (bag1 fibers), static nuclear bag fibers (bag2 fibers), and nuclear chain fibers. (wikipedia.org)
Increase1
- Postnatal increase of intrafusal fibers in the rat muscle spindle. (xenbase.org)
Show1
- The experiments show that the filaments progressively become more ordered as the myoblasts develop into muscle cells. (elifesciences.org)