Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Reflex, Stretch”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources
PubMed1992

Stretch reflex of quadriceps femoris and its relation to rigidity in Parkinson's disease.

Much evidence suggests that parkinsonian rigidity is due to hyperactivity of a reflex arc. While tendon jerk and H reflex are not modified in Parkinson's disease (PD), the long-latency component of stretch reflex (LLR) shows an increased size in PD. It has been proposed that this modification could account for rigidity. We studied in 14 PD patients and 8 normal subjects the stretch reflex of the quadriceps femoris. The muscle was stretched by a torque motor in two experimental sets: at rest and with voluntary background activity. Latency, duration and size of the reflex were compared in two groups; correlation between size of the reflex and rigidity was investigated. A lower threshold for the reflex was found in PD patients in trials at rest, and LLR showed increased size and duration in trials with background activity. No clear relationships between these data and rigidity were demonstrated.

Adult↗
PubMed1979

Participation of the stretch reflex in human physiological tremor.

Microneurographic studies were made of normal human muscle spindle afferent activity to evaluate the role played by these endings, and by the segmental stretch reflex, in various types of physiological tremor. Primary endings are sufficiently sensitive to respond to the minute tremulous movements normally seen in contracting muscles. Human muscle spindle endings appear to possess the same non-linear sensitivity to small stretches as has been reported for cat muscle spindles. The findings also support the notion that the segmental stretch reflex plays an important role in enhanced physiological tremor, in so far as it tends to synchronize the motor outflow in such a way as to produce rhythmical contractions properly timed to reinforce the mechanical resonant properties of muscle spindle endings, the stretch reflex also serves to damp the larger oscillations of finger or hand which result from a brisk tap or muscle twitch. There is no evidence for alpha-gamma co-activation in these enhanced physiological tremors.

Afferent Pathways↗
PubMedDate not supplied

Adaptation of the short latency component of the stretch reflex plays only a minor role in compensating for muscle fatigue induced by spontaneous hopping in humans.

The influence of fatigue on the stretch reflex evoked in ankle extensor muscles by hopping was investigated in six healthy men. The men hopped on a force platform, at spontaneous frequency and amplitude, until they were unable to maintain the initial frequency or amplitude of the jumps. This task was done with the knees flexing normally during ground contact or under instructions to straighten the knees. Surface electromyograms (EMG) of soleus (SO), gastrocnemius medialis (GM), and tibialis anterior (TA) muscles were recorded simultaneously with the vertical component of the ground reaction force. Spectrum analysis of the EMG recorded during isometric tests performed immediately before and after the fatiguing hopping task demonstrated the existence of fatigue in SO and GM and often in TA. The stretch reflex was studied during the first and last ten jumps of every hopping series. The long-latency components of the reflex were too variable to be analysed. Whatever the hopping condition, latency and amplitude of the short latency component were not significantly modified by fatigue. Fatigue enhanced the occurrence of this reflex component in SO only. These data suggest that in fatiguing submaximal hopping, the neuromuscular system does not fundamentally change its stiffness regulation before the endurance time has been reached.

Adaptation, Physiological↗
PubMed1984

Recruitment order of motoneurons in stretch reflexes is highly correlated with their axonal conduction velocity.

Motor units of soleus and medial gastrocnemius (MG) muscles were studied in pairs during stretch reflexes in the decerebrate cat to determine the relation between their recruitment orders and axonal conduction velocities. In 97% of soleus pairs, the motor unit with the lower axonal conduction velocity was recruited first. Since the soleus is a homogeneous muscle in the cat, differences in motor-unit type are, therefore, not a sine qua non for orderly recruitment nor is recruitment random within homogeneous populations of motor units, as recently proposed (28). In the medial gastrocnemius, a heterogeneous muscle, the same high correlation (97%) between recruitment sequence and conduction velocity was observed. Thus, the factors that determine recruitment order in heterogeneous muscles are as closely correlated with axonal diameter as they are in homogeneous muscles. Comparison of axonal conduction velocities in our sample of MG units with those in three samples of type-identified MG units studied by other investigators also suggests that motor-unit type is not the critical factor controlling the sequence of activation in heterogeneous muscles. It is concluded that the combined effects of all presynaptic and postsynaptic factors that determine susceptibility to discharge in motoneurons during stretch reflexes are strictly correlated with their axonal conduction velocities, as predicted by the size principle.

Animals↗
PubMed1981

Reliability and efficacy of the long-latency stretch reflex in the human thumb.

1. The amount of positional compensation afforded by the long-latency reflex in the flexor pollicis longus has been investigated in ten normal human subjects. 2. The interphalangeal joint of the thumb was extended by between 2 and 40 degrees at up to 900 deg/s by suddenly increasing the standing force applied to the lever against which the subject was pressing with the pad of the thumb. 3. Electromyographic (e.m.g.) responses at spinal-latency were very small or absent for stretches of this magnitude. The long-latency stretch reflex produced an average positional correction of about 50% for disturbances in the range of 5-25 degrees. The response began to saturate for disturbances of greater than 25 degrees. 4. The e.m.g. response was pulsatile, lasting only some 50 ms, even during continuously increasing disturbances; frequently it terminated despite a remaining positional error. 5. There was a large variation from subject to subject in the average amount of positional correction provided by the stretch reflex. Examination of single responses to the same stretch in individual subjects showed an even greater variation from trial to trial. 6. Variation in the compensation produced by the long-latency stretch reflex from trial to trial could not be explained by the slight variation in size or maximum velocity of the individual stretches.

Adult↗
PubMed1982

Effects of muscle length on an increased stretch reflex in children with cerebral palsy.

No inhibitory influence of length on the increased stretch reflex was found in the internal gastrocnemius muscle of 19 cerebral palsied children. A facilitory influence of length was found in at least five patients in which quantitative data were obtained. These results were compared with previous data on a facilitory influence in the hamstrings and inhibitory influence in quadriceps muscles.

Cerebral Palsy↗
PubMed1975

Participation of mono- and polysynaptic transmission during tonic activation of the stretch reflex arcs.

Through intracellular observations of the cat spinal motoneuron both mono- and polysynaptic reflex arcs were shown to participate in repetitive activation of stretch reflex. Experiments were performed on 25 cats anesthetized by intraperitoneal (i.p.) injection of 3 cc/kg of a mixture of 1% chloralose and 10% urethane. Driving of the motoneuronal discharges accomplished by electric stimulation (16-100 Hz) of the gastrocnemius lateralis and medialis nerves. Repeated electric stimulation of muscle nerves elicited monosynaptic "vibratory" EPSPs and a polysynaptic "augmenting" EPSP in the motoneuron. The firing of the motoneuron occurred when a temporal summation of the "vibratory" EPSPs was sufficiently obtained. The discharge frequency of motoneuron, MNf, was expressed as a product of electrostimulus frequency, Sf, and reciprocal of an integer, n, i.e. MNf=(1/n)Sf. An increase in the stimulus intensity resulted in a dimimution of the vibratory EPSP and a remarkable increase of n. This was assumed to be due to an inhibitory process produced by the Group II fibers. The minimum value of integer n was always a determinant factor for the maximum value of MNf which was referred to as the "preferred" frequency of the motoneuron. Long-lasting electric stimulation of muscle nerves was followed by a more remarkable recruitment of the augmenting EPSP which made the motoneuron attain its critical threshold of firing. Motoneuronal spikes elicited by such a large augmenting EPSP were not locked to the Ia impulses. Unlocked spikes were observed only in a later stage of electric stimulation of Ia fibers.

Animals↗
PubMed1972

Muscle afferent potential ('A-wave') in the surface electromyogram of a phasic stretch reflex in normal humans.

The experiments reported in this paper tested the hypothesis that the afferent potential elicited by a tendon tap in an isometrically recorded phasic stretch reflex can be detected in the surface EMG of normal humans when appropriate techniques are used. These techniques involved (1) training the subjects to relax mentally and physically so that the EMG was silent before and immediately after the diphasic MAP which reflects a highly synchronous discharge of afferent impulses from low threshold muscle stretch receptors after a tendon tap, and (2) using a data retrieval computer to summate stimulus-locked potentials in the EMG over a series of 16 samples using taps of uniform peak force and duration on the Achilles tendon to elicit the tendon jerk in the calf muscles. A discrete, diphasic potential (`A-wave') was recorded from EMG electrodes placed on the surface of the skin over the medial gastrocnemius muscle. The `A-wave' afferent potential had the opposite polarity to the corresponding efferent MAP. Under control conditions of relaxation the `A-wave' had a latency after the onset of the tap of 2 msec, the peak to peak amplitude was of the order of 5 μV and the duration was in the range of 6 to 10 msec. Further experiments were conducted to show that the `A-wave' (1) was not an artefact of the instrumentation used, (2) had a threshold at low intensities of stimulation, and (3) could be reliably augmented by using a Jendrassik manoeuvre compared with the potential observed during control (relaxation) conditions. The results support the conclusion that the `A-wave' emanates from the pool of muscle spindles which discharges impulses along group Ia nerve fibres in response to the phasic stretch stimulus because the primary ending of the spindles is known to initiate the stretch reflex and the spindles can be sensitized by fusimotor impulses so that their threshold is lowered as a result of a Jendrassik manoeuvre. The finding has important implications for the investigation of the fusimotor system in intact man.

Achilles Tendon↗
PubMed1994

Medium latency stretch reflexes in young-onset Parkinson's disease and MPTP-induced parkinsonism.

It is still unclear why components of the phasic stretch reflex are increased in Parkinson's disease (PD). To study the role of aging, we assessed medium latency (ML) stretch reflexes in 19 Parkinson patients (8 with young-onset PD, 11 with late-onset PD) and 23 normal subjects (10 young, 13 old). To assess the contribution of supraspinal dopaminergic influences, we also studied 5 young parkinsonian patients with a selective central dopamine deficiency induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). ML responses were recorded from the medial gastrocnemius muscle which was stretched by 4 degrees toe-up rotations of a platform upon which subjects were standing. ML responses were significantly enhanced in late-onset patients compared with older controls. In contrast, ML responses did not differ between young-onset patients and young controls. This observation could be attributed to the significantly different influence of age on ML-amplitudes in patients and controls. Thus, ML-amplitudes declined with age in controls, whereas they increased with age in PD possibly because older patients were more severely affected than younger patients. Thus, the difference between young-onset and late-onset PD seems to be related to the opposite effects of increasing age and disease severity in patients and controls. ML-amplitudes did not differ between patients with MPTP-induced parkinsonism, patients with young-onset PD and controls, suggesting that supraspinal dopaminergic systems are not critically involved in control of ML responses. This result also indicates that the severity effect in PD may be related to disruption of non-dopaminergic pathways which occurs in late-onset, but not young-onset patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Nitrergic proprioceptive afferents originating from quadriceps femoris muscle are related to monosynaptic Ia-motoneuron stretch reflex circuit in the dog.

1. The aim of the present study was to examine the occurrence of the neuronal nitric oxide synthase immunoreactivity in the stretch reflex circuit pertaining to the quadriceps femoris muscle in the dog. 2. Immunohistochemical processing for neuronal nitric oxide synthase and histochemical staining for nicotinamide adenine dinucleotide phosphate diaphorase were used to demonstrate the presence of neuronal nitric oxide synthase in the proprioceptive afferents issuing in the quadriceps femoris muscle. The retrograde tracer Fluorogold injected into the quadriceps femoris muscle was used to detect the proprioceptive afferents and their entry into the L5 and L6 dorsal root ganglia. 3. A noticeable number of medium-sized intensely nitric oxide synthase immunolabelled somata (1000-2000 microm(2) square area) was found in control animals in the dorsolateral part of L5 and L6 dorsal root ganglia along with large-caliber intraganglionic nitric oxide synthase immunolabelled fibers, presumed to be Ia axons. Before entering the dorsal funiculus the large-caliber nitric oxide synthase immunolabelled fibers of the L5 and L6 dorsal roots formed a massive medial bundle, which upon entering the dorsal root entry zone reached the dorsolateral part of the dorsal funiculus and were distributed here in a funnel-shaped fashion. The largest nitric oxide synthase immunolabelled fibers, 8.0-9.2 microm in diameter, remained close to the dorsal horn, while medium-sized fibers were seen dispersed across the medial portion of the dorsal funiculus. Single, considerably tapered nitric oxide synthase immunolabelled fibers, 2.2-4.6 microm in diameter, were seen to proceed in ventrolateral direction until they reached the mediobasal portion of the dorsal horn and the medial part of lamina VII. In lamina IX, only short fragments of nitric oxide synthase immunoreactive fibers and their terminal ramifications could be seen. Nitric oxide synthase immunolabelled terminals varying greatly in size were identified in control material at the base of the dorsal horn, in the vicinity of motoneurons ventrally and ventrolaterally in L5 and L6 segments and in Clarke's column of L3 and L4 segments. Injections of the retrograde tracer Fluorogold into the quadriceps femoris muscle and cut femoral nerve, combined with nitric oxide synthase immunohistochemistry of the L5 and L6 dorsal root ganglia, confirmed the existence of a number of medium-sized nitric oxide synthase immunoreactive and Fluorogold-fluorescent somata presumed to be proprioceptive Ia neurons (1000-2000 microm(2) square area) in the dorsolateral part of both dorsal root ganglia. L5 and L6 dorsal rhizotomy caused a marked depletion of nitric oxide synthase immunoreactivity in the medial bundle of the L5 and L6 dorsal roots and in the dorsal funiculus of L5 and L6 segments. 4. The analysis of control material and the degeneration of the large- and medium-caliber nitric oxide synthase immunoreactive Ia fibers in the dorsal funiculus of L5 and L6 segments confirmed the presence of nitric oxide synthase in the afferent limb of the monosynaptic Ia-motoneuron stretch reflex circuit related to the quadriceps femoris muscle.

Animals↗
PubMed2003

Effects of TMJ anesthesia and jaw gape on jaw-stretch reflexes in humans.

OBJECTIVE: To study the roles of afferent sensory inputs in the temporomandibular joint (TMJ) and of muscle length in the modulation of the jaw-stretch reflex in humans. METHODS: Reflexes were evoked in both the masseter and temporalis muscles under standardized conditions in 11 young women. The study was performed in two sessions; experimental conditions were jaw gape and injection of local anesthetics. For jaw gape, 4, 14, and 24 mm were used in random order. One milliliter TMJ injections (carbocaine, 10 mg/ml, versus isotonic saline, 0.9%) were given in a randomized, double blind manner. When a participant received carbocaine during the first session, isotonic saline was injected during the second one. A total of 480 reflexes were evoked in every participant. RESULTS: No significant differences were found between carbocaine and isotonic saline. ANOVA and post hoc paired t tests did show, however, a significant effect of jaw gape for the left masseter and anterior temporalis muscles, with the 14 mm gape having the highest amplitude. CONCLUSIONS: Blocking the afferent sensory input (including the mechanoreceptors) from the TMJ seems to have no influence on the sensitivity of the human jaw-stretch reflex. Instead, muscle spindles are the most likely receptors to be responsible for the reflex modulation that was observed in the present study.

Adult↗
PubMed1989

Effects of eperisone-HCl on the stretch reflex in anesthetized cats.

The effect of eperisone-HCl on the spinal stretch reflex was investigated in cats anesthetized with urethane-chloralose. The reflex activity, elicited by muscle stretches, was recorded from the split ventral root and analyzed using a cross-correlation histogram between the motoneuronal spikes and muscle stretches. Eperisone-HCl was intravenously applied at a dose of 5 mg/kg. It was found that eperisone weakly inhibited the reflex activity of tonic motoneurons (approximately 30%), and that of the phasic ones was either moderately (approximately 70%) or completely (100%) inhibited by eperisone. The cross-correlation analysis suggested that the membrane potentials of both tonic and phasic motoneurons are equally lowered by eperisone or that monosynaptic transmission from primary afferents of muscle spindles to motoneurons is inhibited by eperisone.

Anesthesia↗
PubMed1986

Adaptive plasticity in primate spinal stretch reflex: persistence.

Monkeys can gradually change the amplitude of the wholly segmental, largely monosynaptic, spinal stretch reflex (SSR) when confronted by a task requiring such change (15-19). Change develops over months and may reverse and redevelop at similarly slow rates. We investigated the persistence of SSR amplitude change over nonperformance periods of up to 38 days. Eight animals with chronic EMG electrodes learned to maintain elbow angle and a given level of biceps background EMG against constant extension torque. At random times, a brief additional extension torque pulse elicited the biceps SSR. In the control mode, reward always followed. Under the SSR increase or SSR decrease mode, reward occurred only if the absolute value of biceps EMG in the SSR interval was above or below a set value. Animals completed 3,000-6,000 trials/day over data-collection periods of 2-17 mo. Animals worked first under the control mode for up to 60 days and then under the SSR increase or SSR decrease mode for up to 274 days. Mode was switched once or twice more (SSR increase to SSR decrease or vice versa) over subsequent months. Animals responded to each SSR increase or SSR decrease mode exposure with gradual mode-appropriate change in SSR amplitude. Mode exposures were interrupted by gaps in performance of 10-38 days. Gaps produced transient 10- to 15% decreases in SSR amplitude under the control mode. This nonspecific decrease disappeared over the first week of postgap performance. Under the control mode, gaps had no other effects on SSR amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1980

Multi-loop representation of the segmental muscle stretch reflex. Its risk of instability.

The multi-channel system of the segmental muscle stretch reflex arc is modelled as an arrangement of two or three parallel "component" loops coupled to each other at spinal and at muscle level. Such a model is thought to be more realistic than the usually adopted representation of the stretch reflex as a single negative feedback loop. Anatomical and physiological data were taken from the literature for an extensive simulation of the compound system with special reference to the problem of its stability. Particular emphasis was put on the question of which kind of central (spinal) connectivity is appropriate to best reduce the risk for instability which arises easily in certain system configurations. This paper describes the system and presents simple introductory computations apt to demonstrate the problems the physiological system has to cope with.

Animals↗
PubMed2000

Differential angle-dependent modulation of the long-latency stretch reflex responses in elbow flexion synergists.

We determined the effect of elbow joint angle on the short-(M1) and long-latency stretch reflex (M2 and M3) responses of the elbow flexion synergists, the brachioradialis (BR), and the biceps brachii (BB), during weak isometric elbow flexion tasks. The elbow joint angle was 35,75 and 115 degrees (full-extension angle was 0 degrees ), and the muscle contraction level was 0,3 and 6% of maximum voluntary contraction (MVC) of the BR. In BR, the M1, M2 and M3 responses were significantly greater at 75 and 115 degrees than at 35 degrees. On the other hand, in BB, the M2 response was significantly greater at 35 degrees than at 75 and 115 degrees, while the M1 and M3 responses were not significantly different among the elbow joint angles. These results indicated that the stretch reflex responses of BR might be dependent on the changes of muscle length in stretch stimulus, while the M2 response of BB might not be dependent on the actual stimulus intensity. Therefore, we concluded that the M2 of BB might be modulated selectively by a higher reflex center in accordance with relationships of the mechanical advantages between synergistic muscles.

Adult↗
PubMed2005

Jaw stretch reflexes in children.

The substantial morphological transformations that occur during human development present the nervous system with a considerable challenge in terms of motor control. Variability of skilled motor performance is a hallmark of a developing system. In adults, the jaw stretch reflex contributes to the functional stability of the jaw. We have investigated the response properties of the jaw stretch reflex in two groups of young children and a group of young adults. Response latencies increased with development, and all age groups produced stimulus-magnitude-dependent increases in reflex gain and resulting biting force. Reflex gain was largest for the older children (9-10 years), yet net increases in resulting biting force were comparable across age groups. These data and earlier experiments suggest that oral sensorimotor pathways mature throughout childhood in concert with the continued acquisition of complex motor skills.

Adult↗
PubMed1985

Development of the monosynaptic stretch reflex in the rat: an in vitro study.

The properties and development of the stretch reflex pathway were investigated in new-born and fetal rats using the isolated spinal cord-hind limb preparation. Muscle afferent discharge was elicited by small stretch of the triceps surae muscle in the new-born rat and in the fetus. It appeared as early as embryonic day 18.5. Ramp-and-hold stretch elicited only phasic discharges in most afferent fibres. A phasic reflex response was evoked in the triceps surae muscle by brief or ramp-and-hold stretch of the muscle in the new-born rat. The threshold stretch required for evoking the reflex response was close to that for eliciting the afferent discharge. A reflex response in the triceps surae muscle was also evoked by electrical stimulation of the triceps surae muscle nerve or the sciatic nerve in the new-born rat. Excitatory post-synaptic potentials (e.p.s.p.s) in the triceps surae motoneurones were evoked by stimulation of the muscle nerve in the new-born rat. The amplitude of the e.p.s.p.s was large enough to generate spike potentials. Homonymous e.p.s.p.s were significantly larger than heteronymous e.p.s.p.s. The amplitudes of the e.p.s.p.s were very susceptible to the rate of stimulus repetition. At a stimulus frequency of 10 Hz they were depressed to less than 10% of the control value. Presynaptic impulses evoked by stimulation of afferents in the muscle nerve appear in the motor nucleus less than 1.0 ms before the onset of synaptically evoked field potentials. The interval between the arrival of impulses evoked by dorsal root stimulation and the onset of e.p.s.p.s in motoneurones was 0.56 +/- 0.16 ms, indicating monosynaptic transmission from the primary afferents to the motoneurones. In the fetus, a reflex response in the triceps surae muscle was observed following a small stretch of the muscle (or electrical stimulation of the sciatic nerve) in all preparations at embryonic day 20.5 and in about half of those examined at embryonic day 19.5. Neither stimulation evoked a reflex response at embryonic day 18.5. Latencies of the reflex responses evoked by muscle stretch or by nerve stimulation were similar to those in the new-born rat. It is concluded that the monosynaptically evoked stretch reflex response in the triceps surae muscle first appear at embryonic day 19.5. Natural and electrical stimulation of the plantar skin evoked a reflex response with long latencies in flexor muscles. Such a cutaneous reflex was first present at embryonic day 17.5, two days earlier than the onset of the stretch reflex.

Action Potentials↗
PubMed1999

Widespread short-latency stretch reflexes and their modulation during stumbling over obstacles.

The present study investigated whether short-latency stretch reflexes are present during human stumbling reactions. While subjects walked on a treadmill, the forward sway of the foot was unexpectedly obstructed with an obstacle. All subjects showed reflex responses with average latencies of 34-42 ms in both the upper and the lower leg flexors and extensors of the obstructed leg. The amplitudes of these responses depended on the phase in the step cycle and were not strictly related to either the background activity of the corresponding muscles or variations in the perturbation. Hence, mechanisms at a premotoneuronal level might play a role in the active phase-dependent control of these responses. The coactivation of antagonists as well as the lack of obvious kinesiologic consequences following the responses suggest that the short-latency responses may generate joint stiffness. This may be a first line of defense in preparing for the functional reaction, which is generated by longer latency responses, in order to take appropriate action concerning the obstacle.

Adult↗