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At least 145 records · Page 8Linked to original sources

PubMed1987

Difference in electromyographic response of finger flexion muscles between tonic vibration reflex and finger flexion reflex induced by finger tip vibration.

Vibratory stimulus applied to the skin of the finger tip induced flexion reflex in that finger. By using the cross-correlation function, characteristics of this reflex were compared to those of tonic vibration reflex (TVR). In the cross-correlogram between unitary electromyogram (EMG) activity in the muscle flexor digitorum superficialis and vibratory stimulus with random frequency, one mode was seen in TVR, and two modes in finger flexion reflex. The secondary mode was significantly wider than the primary mode. Thus it may originate from skin mechanoreceptors and manifest via a reflex center involving a long loop.

Adult↗

PubMed1993

Flexion reflexes following anterolateral cordotomy in man: dissociation between pain sensation and nociceptive reflex RIII.

Nociceptive flexion reflexes (RIII response) of the lower limbs were recorded after unilateral cervico-thoracic anterolateral cordotomy (ALC) in 7 patients. Pre-operative recordings were also obtained in 1 patient and follow-up observations in 3 patients. Flexion reflexes ipsilateral to cordotomy remained normal after surgery. Conversely, responses contralateral to the cordotomy exhibited two consistent postoperative changes: first, the RIII reflex was always dissociated from subjective pain, i.e., it appeared in the absence of any pain sensation, and, second, the RIII was depressed in the limb contralateral to ALC in 5 of 7 patients. RIII attenuation ranged from slight reduction to total abolition, and proved to be reversible in 2 of 3 patients tested during the follow-up. The reappearance of withdrawal reflexes was never accompanied by a recovery of pain sensation in the stimulated limb. We conclude that the dissociation between flexion reflexes and pain sensation, which was evidenced even in case of depressed RIII responses, should be attributable to the surgical lesion of spinothalamic fibers. Dissociation between RIII and subjective pain is a landmark indicating a lesion of the spinothalamic fibers, and may be used for the clinical assessment of spinothalamic dysfunction. Conversely, RIII depression after ALC does not depend upon the surgical lesion to the spinothalamic axons, but may be secondary to interruption of ascending spinoreticular fibers in the anterolateral quadrant, and/or of descending excitatory axons in the ventral cord.

Adult↗

PubMed2006

Placebo controlled utility and feasibility study of the H-reflex and flexor reflex in spastic children treated with intrathecal baclofen.

OBJECTIVE: To evaluate feasibility and utility of the soleus H-reflex and tibialis anterior flexor reflex (FR) in identifying spinal cord neuronal response to intrathecal baclofen (ITB) in children with severe spastic cerebral palsy. METHODS: During a randomized, double-blind, placebo-controlled dose-escalation test treatment, maximum H amplitude/maximum M amplitude (H/M ratio) and FR parameters were bilaterally recorded at baseline and 2-3 h after intrathecal bolus administration of placebo and increasing doses of baclofen until both an improvement in the individual treatment goal(s) and a one-point reduction on the Ashworth scale were observed. RESULTS: Electrophysiological data of 14 children were studied. The H-reflex was feasible in 13 children, the FR threshold area in 9 and the FR, elicited with supramaximal stimulation, in only one child. After ITB, the H/M ratio significantly decreased (left: 0.67+/-0.47 to 0.15+/-0.18, P=0.005; right: 0.55+/-0.32 to 0.14+/-0.19, P=0.002) without placebo effect. FR threshold area after ITB, only decreased significantly in children not taking oral baclofen (left: 146+/-53 to 41+/-54 mV ms, P=0.000; right: 156+/-80 to 66+/-48 mV ms, P=0.002). CONCLUSIONS: This is the first randomized, double-blind, placebo-controlled dose-escalation study in spastic children demonstrating the soleus H-reflex to be a feasible and objective measure to quantify the decreasing motoneuron excitability in response to ITB bolus administration. Only in children not taking oral baclofen, FR threshold area can also be used as an objective outcome measure, yet feasibility is limited. SIGNIFICANCE: We suggest introducing the H-reflex as the electrophysiological gold standard for the evaluation of the effect of ITB in spastic children.

Adolescent↗

PubMed2000

Contribution of TTX-resistant C-fibres and Adelta-fibres to nociceptive flexor-reflex and non-flexor-reflex pathways in cats.

The contribution of Adelta-fibres and C-fibres activated by noxious heat stimulation of the central pad of the foot to nociceptive spinal flexor reflex pathways (FRA-type) and to nociceptive excitatory reflex pathways to foot extensors (non-FRA type) was investigated in high spinal cats. A-fibres were completely blocked by tetrodotoxin (TTX), leaving C-fibre conduction intact. Thus, effects persisting after TTX were attributed to nociceptive C-fibres while the contribution of nociceptive Adelta-fibres was defined by the difference between those effects and the control effects before TTX. The initial action of noxious stimulation on both types of reflex action was mediated predominantly by Adelta-fibres, while the later action was mainly mediated by C-fibres. In two (out of seven) experiments Adelta-fibres exerted a significant inhibitory influence on the C-fibre action in FRA pathways, but such an inhibitory interaction between the two fibre groups was absent in the non-FRA reflex pathways. The technique of TTX application at the peripheral nerve proved to be a reliable method for a long-lasting selective investigation of C-fibre effects. The results revealed that both Adelta- and C-fibres contributed to nociceptive FRA and non-FRA reflex pathways.

Animals↗

PubMed1983

The Bezold-Jarisch reflex revisited: clinical implications of inhibitory reflexes originating in the heart.

The concept of depressor reflexes originating in the heart was introduced by von Bezold in 1867 and was later revived by Jarisch. The Bezold-Jarisch reflex originates in cardiac sensory receptors with nonmyelinated vagal afferent pathways. The left ventricle, particularly the inferoposterior wall, is a principal location for these sensory receptors. Stimulation of these inhibitory cardiac receptors by stretch, chemical substances or drugs increases parasympathetic activity and inhibits sympathetic activity. These effects promote reflex bradycardia, vasodilation and hypotension (Bezold-Jarisch reflex) and also modulate renin release and vasopressin secretion. Conversely, decreases in the activity of these inhibitory sensory receptors reflexly increase sympathetic activity, vascular resistance, plasma renin activity and vasopressin. Long regarded as pharmacologic curiosities, it is now clear that reflexes originating in these inhibitory cardiac sensory receptors are important to the pathophysiology of many cardiovascular disorders. This paper reviews the role of inhibitory cardiac sensory receptors in several clinical states including 1) bradycardia, hypotension and gastrointestinal disorders with inferoposterior myocardial ischemia and infarction, 2) bradycardia and hypotension during coronary arteriography, 3) exertional syncope in aortic stenosis, 4) vasovagal syncope, 5) neurohumoral excitation in chronic heart failure, and 6) the therapeutic effects of digitalis.

Animals↗

PubMed2003

Study of the role of the second defecation reflex: anorectal excitatory reflex in the pathogenesis of constipation.

BACKGROUND: Previous studies have shown that anal distension caused rectal contraction, an action mediated through the anorectal excitatory reflex. Anal anesthetization aborted rectal contraction and rectal evacuation was induced by excessive straining. We investigated the hypothesis that inhibition or absence of the anorectal excitatory reflex could lead to constipation. METHODS: We studied 18 patients (mean age +/- SD: 40.6 +/- 5.8 years, 14 women) with rectal inertia, 14 (41.7 +/- 6.6 years, 12 women) with puborectalis paradoxical syndrome, and 10 healthy volunteers (37.9 +/- 4.8 years, 8 women). The rectum was filled with normal saline until urge and then evacuated; residual fluid was calculated. The anal and rectal pressure response to anal balloon distension in increments of 2 mL of saline was recorded by a two-channel microtip catheter. RESULTS: In the healthy volunteers, saline was evacuated as a continuous stream without straining except occasionally at the start of evacuation; no residual fluid was encountered. Anal balloon distension effected notable rectal pressure increase. In rectal inertia patients, evacuation occurred in small fluid gushes produced with excessive straining; residual fluid of large volume was collected. Anal balloon distension up to 10 mL produced no notable rectal pressure changes. The patients with PPS failed to evacuate more than a few mL of fluid despite excessive straining; the volume of residual fluid was considerable. Anal balloon distension caused a notable rectal pressure rise. The results were reproducible. CONCLUSIONS: These results suggest that the defecation reflexes (rectoanal and anorectal) are absent in rectal inertia patients and this presumably denotes a neurogenic disorder. The anorectal reflex is active in puborectalis paradoxical syndrome, but the rectoanal reflex is not, indicating a possible myogenic defect in the puborectalis muscle.

Adult↗

PubMed2001

Rectal inhibition by inferior rectal nerve stimulation in dogs: recognition of a new reflex--the 'voluntary anorectal inhibition reflex'.

OBJECTIVE: The effect of inferior rectal nerve (IRN) stimulation on the rectum was studied, postulating that nerve stimulation might inhibit rectal contractility and could thus be used in the management of defecation disorders. METHOD: The IRN was exposed through a para-anal incision in 12 dogs (18.2 +/- 3.3 SD kg, seven male, five female) and a cuff-type electrode was applied to the nerve. A balloon introduced into the rectum was filled with saline in increments of 5 ml. The rectal and rectal neck (anal canal) pressures, and the electromyographic (EMG) activity of the external anal sphincter (EAS) and Internal anal sphincter (IAS) were recorded until the balloon was expelled to the exterior. The test was repeated until the expulsion volume was reached, and the IRN was stimulated (pulse width 200 mu/s, charge density 2 to 6 microCi/cm2 per phase). The test was performed again following individual anaesthetization of the EAS and the IAS. RESULTS: At a mean rectal distending volume of 38.3 +/- 2.3 ml, the rectal pressure increased (P < 0.01), rectal neck pressure declined (P < 0.01), the EAS and IAS EMGs disappeared, and the balloon was expelled. IRN stimulation at a distending volume of 38.3 +/- 2.3 ml increased the EMG activity of the EAS, whereas the rectal pressure and IAS EMG did not change (P > 0.05) and the balloon was not expelled. With IRN stimulation at the distending volume of 38.3 +/- 2.3 ml while the EAS was anaesthetized, the rectal pressure increased (P < 0.01), rectal neck pressure diminished, IAS EMG activity disappeared, and the balloon was expelled. Upon repetition of IRN stimulation during anaesthetization of the IAS, the rectal pressure remained high and the balloon was not expelled. CONCLUSION: It is suggested that the EAS produces continence by a twofold action. The EAS prevents IAS relaxation on rectal contraction, with a resulting rectal relaxation. A reflex relationship is postulated to exist between failure of the IAS to relax and rectal relaxation. We call this reflex relationship 'voluntary anorectal inhibition reflex'. Secondly, the EAS mechanically compresses the rectal neck. It seems that contraction of the EAS, which is a striated muscle, mechanically occludes the rectal neck for a few seconds--enough for the rectum to relax in a reflex manner as an effect of the voluntary anorectal inhibition reflex.

Animals↗

PubMed2002

Development of a quantitative reflex hammer for measurement of tendon stretch reflex.

Quantification of tendon stretch reflex requires precise measurement of the tapping force of a reflex hammer. A quantitative reflex (QR) hammer consisting of two cut rubber pieces from a generic rubber reflex hammer and a uniaxial force transducer was constructed. Finite element stress analyses were conducted to estimate the natural frequency characteristics of the hammer and to find the stress distributions during the impact. Pendulum impact testing was conducted at four different heights to assess the calibration linearity and repeatability of the measurement. The QR hammer had a fundamental natural frequency of 515 Hz and showed minimal displacement and stress at the tip from the finite element simulation of the impact. The QR hammer also provided reliable and repeatable measurements as demonstrated with high coefficients of determination, exceeding 0.994 and small coefficients of variations, less than 4%. The calibration linearity was 0.64% compared with the reference force platform measurement. The QR hammer demonstrated sufficient accuracy and reliability for precise clinical assessment of tendon stretch reflexes.

Calibration↗

PubMed1977

Effects of postural changes of the upper limb on reflex transmission in the lower limb. Cervicolumbar reflex interactions in man.

The influence of passive changes in upper limb position on the excitability of three myotatic arc reflexes (soleus, quadriceps, and biceps femoris) of the lower limb has been explored on 42 volunteers. The results indicate that the excitability of the three myotatic arcs can be influenced at a distance by postural modifications of the upper limb. When the ipsilateral upper limb is forwards or the contralateral backwards, a facilitation of both soleus and quadriceps tendon reflexes is observed while the biceps femoris reflexes are reduced. This pattern of facilitation and inhibition is reversed when the ipsilateral upper limb is backwards or the contralateral forwards. The facilitations as well as inhibitions of proximal myotatic arc reflexes are quantitatively more marked than that of the soleus reflex. Facilitation and inhibition are not linearly related to the angle of the arm with the trunk. Effects begin at a considerable angle, become maximal at 45 degrees, and progressively disappear for greater values. It is suggested that the distinct pattern of facilitation and inhibition which is exerted in reciprocal fashion on extensor and flexor motor nuclei might depend on the long propriospinal neurones connecting cervical and lumbar enlargements.

Achilles Tendon↗

PubMed1994

Reflex effects of lung inflation on tracheomotor tone observed during apnea produced by the Hering-Breuer reflex.

Reflex effects of static pressure lung inflation (SLI) on tracheomotor tone (TT) were studied during apnea produced by the Hering-Breuer expiratory-facilitatory reflex. Anesthetized dogs were placed on cardiopulmonary bypass, and diaphragm electromyogram was used as an indicator of central nervous system inspiratory output. Tracheomotor tone (TT) was reflexly produced by chemoreceptor stimulation. The volume and frequency of the ventilator [phasic lung inflation (PLI)] were adjusted to produce nearly a maximum reflex decrease in TT. The increase in TT observed while PLI was withheld (0 mmHg tracheal pressure) for 1-2 min was used as the control response. SLIs were interspersed among sets of PLIs. Although SLI produced apnea, TT returned toward the control TT recorded during 0 mmHg tracheal pressure. TT observed during apnea was reflexly sensitive to further increases in SLI and to changes in chemoreceptor stimulation, which also affected the time course of the tracheomotor responses. These results suggest that the reflex decrease in TT produced by SLI and the Hering-Breuer expiratory-facilitatory reflex are mediated by different central mechanisms but may be from the same or different pulmonary receptors.

Air Pressure↗

PubMed1978

Studies on the mechanism of reflex vasodilatation. The cholinergic component in the baroreceptorial reflex in the dog.

This study was designed to investigate whether the cholinergic system is involved in the genesis of the reflex vasodilatation which follows the systemic hypertension induced by fast intravenous injection of norepinephrine in the dog. Accordingly, in 7 dogs the gracilis muscle was isolated and perfused and the reflex evoked. The analysis of the integrated areas of vasodilatation after atropine pretreatment showed a significant decrease of the reflex response in the perfused circulation. In fact, the mean value of the integrated areas of vasodilatation which was 66 +/- 8 mm Hg/min in the control condition, was reduced to 45 +/- 4 mm Hg/min after administration of atropine in the gracilis artery; meanwhile the integrated areas of systemic hypertension did not show any change. Phentolamine intra-arterial administration completely abolished the reflex. These results suggest the existence of a cholinergic component in the reflex vasodilatation induced by transitory baroreceptorial stimulation.

Animals↗

PubMed1991

Straining urethral reflex: description of a reflex and its clinical significance. Preliminary report.

The present communication describes a reflex, which I call 'straining urethral reflex', and discusses its clinical significance. The study was performed on 17 healthy volunteers with a mean age of 39.6 years. The intrarectal pressure (representative of the intra-abdominal pressure) was measured by means of a balloon-tipped catheter introduced into the rectum and connected to a pressure transducer. A concentric needle electrode was introduced into the external urethral sphincter. The subject was asked to strain, and the urethral sphincter electromyographic activity and the intrarectal pressure were recorded. Two types of straining were investigated: sudden and slow. The procedure was repeated in 10 subjects after urethral sphincter infiltration with xylocaine or saline. On sudden straining, the external urethral sphincter contracted. The anesthetized sphincter did not respond, while the saline-infiltrated sphincter responded to sudden straining. Slow sustained straining did not evoke the reflex response. The latency of the reflex was calculated. The external urethral sphincter contraction on sudden straining guards against the involuntary opening of the vesical neck and urinary leak under stress conditions of a sudden increase in the intra-abdominal pressure. The reflex may prove significant in the diagnosis of micturition control disorders. It can thus be included as an investigative tool in urologic practice.

Adult↗

PubMed1994

Amount of asymmetry in grasp reflex depends on the grasp reflex of the left hand in human neonates.

Grasp-reflex strengths from right and left hands were measured in 33 human neonates. There was no significant correlation between right minus left grasp-reflex strength and grasp-reflex strength from the right hand. The grasp-reflex strength of the left hand was negatively linearly correlated with the right minus left grasp-reflex strength. It was suggested that the right brain may be the main determinant for the motor asymmetry in hands.

Brain↗

PubMed1992

[Reflex control of laryngeal functions in the cat: the effect of vibratory stimuli of the laryngeal mucosa on the laryngeal reflex].

To investigate the effect of vibratory stimuli of the subglottic mucosa on the laryngeal reflex, experiments were performed on cats anesthetized with intraperitoneal injection of a mixture of urethane and chloralose. The external branch of the superior laryngeal nerve was cut, while the internal branch of the superior laryngeal nerve (ISLN) was mounted on stimulating electrodes. Electromyograms (EMG) were recorded from the contralateral thyreoarytenoid (TA), posterior cricoarytenoid (PCA), lateral cricoarytenoid (LCA), and cricothyreoid (CT) muscles. When the ISLN was electrically stimulated, the laryngeal reflex was induced. Short latency (early) and long latency (late) responses were observed in TA, PCA, LCA, and CT. Then, vibratory stimuli were applied to the surface of the subglottic mucosa. Vibratory frequencies used in this study were varied stepwise from 100 Hz to 400 Hz, with the amplitude adjusted at 20 microns. Vibratory stimuli had no effect on early responses but did, however, exert a facilitatory effect on late responses of TA and LCA in the transitional phase from inspiration to expiration and on late responses of PCA in the inspiratory phase. After denervation of ISLN, the vibratory effect on late responses disappeared completely. No significant vibratory effect was observed on CT in any respiratory phase. These results suggest that vibratory stimuli applied to the surface of the subglottic mucosa reflexively facilitate the laryngeal reflex and that ISLN afferents and respiratory drive modulate the laryngeal reflex.

Animals↗

PubMed1991

Dilatation and closing anal reflexes. Description and clinical significance of new reflexes: preliminary report.

The present communication describes new reflexes which are called 'dilatation and closing anal reflexes', and discusses their clinical significance. The study comprised 21 healthy volunteers and 15 incontinent patients (7 with partial fecal incontinence and 8 with urinary stress incontinence). The technique comprised the introduction into the rectal neck of a balloon-tipped catheter. The balloon was inflated with air in increments of 10 ml up to 50 ml, and the EMG response of the external and urethral sphincters to balloon inflation and deflation was recorded. A new device called 'switch inflation' apparatus was used to inflate the balloon simultaneously with switching of the EMG apparatus. Rapid rectal neck inflation and deflation evoked external anal and urethral sphincter contraction. Slow and gradual inflation or deflation did not initiate the response. The anesthetized external anal sphincter did not respond to the stimulus, while the saline-infiltrated sphincter responded. The latency of the reflexes was recorded. In fecal incontinent patients, the external anal sphincter, on rapid rectal neck inflation or deflation, showed lower EMG activity and longer latency than in normal volunteers; the external urethral sphincter responded as in normal volunteers. In urinary stress incontinent patients, the external anal sphincter responded normally for both rectal neck inflation and deflation. The external urethral sphincter showed lower EMG activity and prolonged latency than normal on rectal neck inflation; it did not respond to deflation. The dilatation and closing reflexes seem to play a role in fecal and urinary continence as well as in fecal sampling. Detectable changes in latency or amplitude of the evoked response indicate a defect in the reflex pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

[Generalized nocifensor reflexes--II. A modified reflex pattern caused by functional disorders of the thalamus].

In the past, clinically relevant diagnostic procedures using nocifensive reflexes have been restricted mainly to ascertaining the functional status of the efferent or afferent portion of the reflex arc. The method described here, which evoked global nocifensive reflexes, permits differentiated conclusions to be drawn regarding possible supraspinal influences on nocifension. The reflex patterns yielded by the procedure can provide information regarding the functional status of the formatio reticularis, which is subject to modulatory influences of the pallidostriatum and thalamus. The results show that specific, pathohistologically confirmed lesions of the thalamus de-inhibit the formatio reticularis for motor reticulospinal activity and that this is reflected in the nocifensive pattern. Thus, the nocifensive reflex on the contralateral side to the thalamic process is stronger and has a shorter latent time than that on the clinically healthy side. This phenomenon has so far been confirmed on all patients with an impaired thalamus function.

Humans↗

PubMed1990

Impaired arterial baroreceptor reflex and cardiopulmonary vagal reflex in conscious spontaneously hypertensive rats.

The activity of baroreceptor reflexes and cardiopulmonary reflexes was examined in conscious spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) rats. The baroreceptor heart rate reflex, elicited by phenylephrine- and nitroprusside-induced changes in blood pressure, had a reduced range and lower heart rate plateau in SHR than in WKY rats, which suggests impaired vagal control of the heart rate in SHR. Cardiopulmonary receptor reflex activity was assessed by intravenous injections of phenyldiguanide which evoke the Bezold-Jarisch reflex. Phenyldiguanide elicited dose-dependent bradycardic and hypotensive responses in WKY rats, but these were significantly attenuated in SHR. This is the first demonstration of impaired Bezold-Jarisch responses in conscious SHR and provides evidence of both impaired vagally mediated arterial baroreceptor activity and impaired cardiopulmonary receptor activity in this rat strain.

Animals↗

PubMed1990

[Elimination of the obturator reflex as a specific indication for dilute solutions of etidocaine. A study of the suitability of a local anesthetic for reflex elimination in the 3-in-1 block technic].

Direct stimulation of the obturator nerve by the electroresectoscope during transurethral resection of tumors in lateral bladder regions is possible under regional or general anaesthesia without muscle relaxation. The resulting obturator reflex may lead to perforation of the bladder. Two different regional techniques can be used to interrupt the obturator reflex arc: (1) separate block of the obturator nerve; or (2) the "3-in-1 block" (Winnie). In the present study elimination of the obturator reflex was carried out by "3-in-1 block" with diluted solutions of etidocaine in 55 cases. Venous plasma levels of etidocaine were measured in 9 patients after application of etidocaine 0.5% (unilateral 30 ml and bilateral 60 ml). Samples were taken 10, 20, 30, 40, 60, and 120 min after the "3-in-1 block". RESULTS. The "3-in-1 block" with diluted etidocaine produced excellent motor block of the obturator nerve. Clinical side effects did not occur. Plasma peak levels reached 2.2 micrograms/ml; the protein binding rate was 85%-95%. DISCUSSION. Elimination of the obturator reflex is the only specific motor nerve block in anesthesia. Diluted etidocaine solutions seem to be adequate: irrespective the technique used for eliminating the reflex, diluted etidocaine produces a good effect and permits a dosage reduction compared with other local anesthetics. It is possible to block the obturator nerve bilaterally by "3-in-1 block" or unilaterally by "3-in-1 block" in combination with epidural analgesia within the recommended dose limits.

Acetanilides↗