Evidence that the secondary as well as the primary endings of the muscle spindles may be responsible for the tonic stretch reflex of the decerebrate cat

The quantitative interrelation between stretch, tension and position in space was studied in decerebrate cats. The tension produced by the isolated M. triceps brachii was recorded by means of strain gauges. It was found that the tension increment, produced by a particular stretch, increases as the preparation is turned from the prone to the supine position around its longitudinal axis. The proportion between the tensions produced by a series of two or more different stretches, however, stays constant under these conditions. It was shown, furthermore, that the effect of a change in position upon the degree of rigidity—i.e., the difference between the tensions in the prone and in the supine positions—is the greater the greater the initial stretch. A quantitative analysis of the results disclosed that the vestibular factor and the proprioceptive factor are related in a multiplicative manner. These experiments show that the vestibular apparatus and the muscle spindles exert their influence not in an isolated and independent, but a quantitatively interdependent manner. The results of the present work together with the findings of other authors (Granit) give strength to the argument that the vestibular apparatus controls the stretch reflex activity in an indirect manner, i.e., over the ‘by-pass’ of the gamma-efferents.

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The effects of vibration-induced altered stretch reflex sensitivity on maximal motor unit firing properties

Journal of Neurophysiology ◽

10.1152/jn.00326.2018 ◽

2019 ◽

Vol 121 (6) ◽

pp. 2215-2221 ◽

Cited By ~ 3

Author(s):

Alejandra Barrera-Curiel ◽

Ryan J. Colquhoun ◽

Jesus A. Hernandez-Sarabia ◽

Jason M. DeFreitas

Keyword(s):

Motor Unit ◽

Muscle Spindle ◽

Stretch Reflex ◽

Muscle Spindles ◽

Motor Unit Action Potential ◽

Firing Rates ◽

Motor Unit Firing ◽

Firing Properties ◽

Spindle Function ◽

Voluntary Strength

It is well known that muscle spindles have a monosynaptic, excitatory connection with α-motoneurons. However, the influence of muscle spindles on human motor unit behavior during maximal efforts remains untested. It has also been shown that muscle spindle function, as assessed by peripheral reflexes, can be systematically manipulated with muscle vibration. Therefore, the purpose of this study was to analyze the effects of brief and prolonged vibration on maximal motor unit firing properties. A crossover design was used, in which each of the 24 participants performed one to three maximal knee extensions under three separate conditions: 1) control, 2) brief vibration that was applied during the contraction, and 3) after prolonged vibration that was applied for ~20 min before the contraction. Multichannel EMG was recorded from the vastus lateralis during each contraction and was decomposed into its constituent motor unit action potential trains. Surprisingly, an approximate 9% reduction in maximal voluntary strength was observed not only after prolonged vibration but also during brief vibration. In addition, both vibration conditions had a large, significant effect on firing rates (a decrease in the rates) and a small to moderate, nonsignificant effect on recruitment thresholds (a small increase in the thresholds). Therefore, vibration had a detrimental influence on both maximal voluntary strength and motor unit firing properties, which we propose is due to altered function of the stretch reflex pathway. NEW & NOTEWORTHY We used vibration to alter muscle spindle function and examined the vibration’s influence on maximal motor unit properties. We discovered that vibration had a detrimental influence on motor unit behavior and motor output by decreasing motor unit firing rates, increasing recruitment thresholds, which led to decreased maximal strength. We believe that understanding the role of muscle spindles during maximal contractions provides a deeper insight into motor control and sensorimotor integration.

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Tilt responses of neurons in the caudal descending nucleus of the decerebrate cat: influence of the caudal cerebellar vermis and of neck receptors

Journal of Neurophysiology ◽

10.1152/jn.1996.75.3.1242 ◽

1996 ◽

Vol 75 (3) ◽

pp. 1242-1249 ◽

Cited By ~ 10

Author(s):

V. J. Wilson ◽

H. Ikegami ◽

R. H. Schor ◽

D. B. Thomson

Keyword(s):

Head Rotation ◽

Muscle Spindles ◽

Vestibular Nuclei ◽

Vestibular Stimulation ◽

Cerebellar Vermis ◽

Neck Muscle ◽

Vestibular Input ◽

Decerebrate Cat ◽

Neck Rotation ◽

Vertical Semicircular Canal

1. In decerebrate cats with intact cerebellums, we studied the responses of neurons in the caudal areas of the vestibular nuclei to natural vestibular stimulation in vertical planes and to neck rotation. The activity of most neurons was recorded in the caudal half of the descending nucleus. 2. One goal of our experiments was to compare the dynamic and spatial properties of responses to sinusoidal vestibular stimulation with those seen in previous experiments in which the caudal cerebellar vermis, including the nodulus and uvula, was removed. This part of the cerebellum receives vestibular input and projects to the caudal areas of the vestibular nuclei, suggesting that it could influence responses to stimulation of the labyrinth. 3. As in our previous experiments, most neurons could be classified as receiving predominant input either from the otoliths or from one vertical semicircular canal. When mean gain and phase and response vector orientations were compared, there were no obvious differences between the behavior of neurons in the partially decerebellate preparation and the one with the cerebellum intact, demonstrating that in the decerebrate cat the nodulus and uvula have little or no influence on the processing of vertical vestibular input in this region of the vestibular nuclei. 4. Only 23 of 74 (31%) of neurons tested responded to neck rotation. This contrasts with the much larger fractions that respond to this stimulus in Deiters' nucleus and in the rostral descending nucleus. We also recorded from neurons near the vestibular nuclei, mainly in the external cuneate nucleus. All of them (9 of 9) responded to neck rotation. 5. Responses to neck rotation also differed in their dynamics from those found more rostrally in the vestibular nuclei. Dynamics of more rostral neurons resemble those of neck muscle spindles, as do those of external cuneate neurons. The dynamics of caudal vestibular neurons, on the other hand, have a steeper gain slope and more advanced phases than do those of neurons in the more rostral vestibular nuclei. This suggests the possibility of involvement of additional receptors in the production of these responses. 6. In the more rostral vestibular nuclei, responses to vestibular and neck rotation are most often antagonistic, so that head rotation results in little or no response. This is not the case in the caudal areas of the vestibular nuclei, where less than half the neurons tested displayed antagonistic behavior. Further experiments are required to put the neck projection to the caudal vestibular nuclei in a functional context.

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Mechanical analysis of heterogenic inhibition between soleus muscle and the pretibial flexors in the cat

Journal of Neurophysiology ◽

10.1152/jn.1991.66.4.1139 ◽

1991 ◽

Vol 66 (4) ◽

pp. 1139-1155 ◽

Cited By ~ 26

Author(s):

T. R. Nichols ◽

D. Koffler-Smulevitz

Keyword(s):

Stretch Reflex ◽

Metatarsophalangeal Joint ◽

Reciprocal Inhibition ◽

Mechanical Analysis ◽

Initial State ◽

Stretch Reflexes ◽

Decerebrate Cat ◽

Intravenous Injections ◽

Activation Level ◽

Length Changes

1. The role of proprioceptive pathways linking the direct antagonists soleus (S) and tibialis anterior (TA) muscles in governing the mechanical properties of the ankle joint were studied in the decerebrate cat. Actions of these heterogenic pathways were compared with those between S and extensor digitorum longus (EDL), a muscle that also acts at the metatarsophalangeal joint. These neurally mediated interactions between S and either TA or EDL were studied by applying controlled length changes to the isolated tendons of pairs of these muscles and recording the resulting changes in force. The muscles were activated with the use of electrically evoked crossed-extension reflexes, flexion reflexes, and brain stem stimulation. 2. Heterogenic inhibition from TA or EDL onto S was well developed whether S was initially quiescent or activated by a crossed-extension reflex. The inhibition persisted for the duration of the stretch of TA or EDL. During a crossed-extension reflex, TA did not generate background force, but brief stretch reflexes could be obtained. During flexion reflexes, stretch reflexes in S were usually abolished, and heterogenic inhibition from S to TA was weak or absent. 3. The strength of the heterogenic inhibition onto S was dependent on the initial length and activation level of TA and EDL. Changes in flexor length or activation level per se did not alter the background force or strength of the stretch reflex in S. Even taking into account the variation of strength of inhibition with the initial state of the muscle of origin, the strength of the inhibition was stronger from TA to S than the other way around. 4. The contributions of heterogenic inhibition from TA and EDL to S were independent in the sense that these components summed linearly with each other and with the autogenic reflex in S. In addition, the magnitude of the inhibition from TA to S was proportional to the amplitude of stretch for low to intermediate levels of initial force in S. The inhibition appeared to affect the mechanical responses of S essentially as rapidly as the stretch reflex in this muscle. 5. The heterogenic inhibition from TA to S was reduced or abolished by intravenous injections of strychnine but unaffected by injections of picrotoxin or bicuculline. These results, together with the observation that the inhibition sums linearly with the stretch reflex, suggest that the mechanism of this heterogenic inhibition is glycinergic and postsynaptic and, therefore, may include Ia-disynaptic reciprocal inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

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Sympathetic outflow enhances the stretch reflex response in the relaxed soleus muscle in humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.00955.2004 ◽

2005 ◽

Vol 98 (4) ◽

pp. 1366-1370 ◽

Cited By ~ 16

Author(s):

Nis Hjortskov ◽

Jørgen Skotte ◽

Christian Hye-Knudsen ◽

Nils Fallentin

Keyword(s):

Soleus Muscle ◽

Stretch Reflex ◽

Mental Arithmetic ◽

Muscle Spindles ◽

Short Latency ◽

Reflex Response ◽

Sympathetic Outflow ◽

Direct Influence ◽

Handgrip Exercise ◽

Sympathetic Nervous

Animal experiments suggest that an increase in sympathetic outflow can depress muscle spindle sensitivity and thus modulate the stretch reflex response. The results are, however, controversial, and human studies have failed to demonstrate a direct influence of the sympathetic nervous system on the sensitivity of muscle spindles. We studied the effect of increased sympathetic outflow on the short-latency stretch reflex in the soleus muscle evoked by tapping the Achilles tendon. Nine subjects performed three maneuvers causing a sustained activation of sympathetic outflow to the leg: 3 min of static handgrip exercise at 30% of maximal voluntary contraction, followed by 3 min of posthandgrip ischemia, and finally during a 3-min mental arithmetic task. Electromyography was measured from the soleus muscle with bipolar surface electrodes during the Achilles tendon tapping, and beat-to-beat changes in heart rate and mean arterial blood pressure were monitored continuously. Mean arterial pressure was significantly elevated during all three maneuvers, whereas heart rate was significantly elevated during static handgrip exercise and mental arithmetic but not during posthandgrip ischemia. The peak-to-peak amplitude of the short-latency stretch reflex was significantly increased during mental arithmetic ( P < 0.05), static handgrip exercise ( P < 0.001), and posthandgrip ischemia ( P < 0.005). When expressed in percent change from rest, the mean peak-to-peak amplitude increased by 111 (SD 100)% during mental arithmetic, by 160 (SD 103)% during static handgrip exercise, and by 90 (SD 67)% during posthandgrip ischemia. The study clearly indicates a facilitation of the short-latency stretch reflex during increased sympathetic outflow. We note that the enhanced stretch reflex responses observed in relaxed muscles in the absence of skeletomotor activity support the idea that the sympathetic nervous system can exert a direct influence on the human muscle spindles.

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The effects of cold-induced muscle spindle secondary activity on monosynaptic and stretch reflexes in the decerebrate cat

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y79-093 ◽

1979 ◽

Vol 57 (6) ◽

pp. 606-614 ◽

Cited By ~ 4

Author(s):

C. E. Chapman ◽

W. J. Michalski ◽

J. J. Séguin

Keyword(s):

Muscle Spindle ◽

Stretch Reflex ◽

Synergistic Effects ◽

Medial Gastrocnemius ◽

Monosynaptic Reflex ◽

Lateral Gastrocnemius ◽

Stretch Reflexes ◽

Decerebrate Cat ◽

Muscle Cooling ◽

Decerebrate Cats

The effects of muscle spindle secondary ending activity on the stretch reflex were studied in unanesthetized decerebrate cats. Activation of secondary endings was accomplished by reducing the muscle temperature. This has been shown to cause a sustained asynchronous discharge from secondary endings. Cooling of the medial gastrocnemius or lateral gastrocnemius–soleus muscles caused an increase in the phasic and tonic components of their stretch reflexes. Cooling of the relaxed medial gastrocnemius muscle caused similar increases in the components of the stretch reflex of the synergistic lateral gastrocnemius–soleus muscle and an increase in its monosynaptic reflex. It was concluded that the facilitatory autogenetic and synergistic effects of muscle cooling on the stretch and monosynaptic reflexes were brought about by activity in group II afferents from muscle spindle secondary endings and could not be ascribed to any other type of muscle receptor. These results support the concept of an excitatory role for the secondary endings of the muscle spindle in the stretch reflex of the decerebrate cat.

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Damping Actions of the Neuromuscular System With Inertial Loads: Soleus Muscle of the Decerebrate Cat

Journal of Neurophysiology ◽

10.1152/jn.2000.83.2.652 ◽

2000 ◽

Vol 83 (2) ◽

pp. 652-658 ◽

Cited By ~ 23

Author(s):

David C. Lin ◽

W. Zev Rymer

Keyword(s):

Energy Dissipation ◽

Linear System ◽

Soleus Muscle ◽

Stretch Reflex ◽

Directional Asymmetry ◽

Reflex Response ◽

Neuromuscular System ◽

Damping Properties ◽

Kinetic Measurements ◽

Decerebrate Cat

A transient perturbation applied to a limb held in a given posture can induce oscillations. To restore the initial posture, the neuromuscular system must provide damping, which is the dissipation of the mechanical energy imparted by such a perturbation. Despite their importance, damping properties of the neuromuscular system have been poorly characterized. Accordingly, this paper describes the damping characteristics of the neuromuscular system interacting with inertial loads. To quantitatively examine damping, we coupled simulated inertial loads to surgically isolated, reflexively active soleus muscles in decerebrate cats. A simulated force impulse was applied to the load, causing a muscle stretch, which elicited a reflex response. The resulting deviation from the initial position gave rise to oscillations, which decayed progressively. Damping provided by the neuromuscular system was then calculated from the load kinetics. To help interpret our experimental results, we compared our kinetic measurements with those of an analogous linear viscoelastic system and found that the experimental damping properties differed in two respects. First, the amount of damping was greater for large oscillation amplitudes than for small (damping is independent of amplitude in a linear system). Second, plots of force against length during the induced movements showed that damping was greater for shortening than lengthening movements, reflecting greater effective viscosity during shortening. This again is different from the behavior of a linear system, in which damping effects would be symmetrical. This asymmetric and nonlinear damping behavior appears to be related to both the intrinsic nonlinear mechanical properties of the soleus muscle and to stretch reflex properties. The muscle nonlinearities include a change in muscle force-generating capacity induced by forced lengthening, akin to muscle yield, and the nonlinear force-velocity property of muscle, which is different for lengthening versus shortening. Stretch reflex responses are also known to be asymmetric and amplitude dependent. The finding that damping is greater for larger amplitude motion represents a form of automatic gain adjustment to a larger perturbation. In contrast, because of reduced damping at small amplitudes, smaller oscillations would tend to persist, perhaps contributing to normal or “physiological” tremor. This lack of damping for small amplitudes may represent an acceptable compromise for postural regulation in that there is substantial damping for larger movements, where energy dissipation is more critical. Finally, the directional asymmetry in energy dissipation provided by muscle and reflex properties must be reflected in the neural mechanisms for a stable posture.

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