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thigh horizontal and foot supported on the floor. Move the foot inward toward you so that the heel is off the floor and the ball of the foot supports the weight of the leg. When the weights and angles are correctly adjusted, an oscillation will start in the muscle of the calf with a frequency of about six to eight per second and an amplitude of about half an inch at the knee. This oscillation is called
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Balance is a partly involuntary and unconscious business, dependent on "spinal reflexes." When provided with appropriate context, these reflexes go into oscillation that is called "clonus," a phenomenon that is familiar to everybody and which is easily produced. (While sitting, place the leg with
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likely due to their common physiological origins. Some consider clonus as simply an extended outcome of spasticity. Although closely linked, clonus is not seen in all patients with spasticity. Clonus tends to not be present with spasticity in patients with significantly increased
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injury). This lack of inhibition biases neurons to a net excitatory state, therefore increasing total signal conduction. Signaling delay is present due to an increased nerve conduction time. Long delays are primarily due to long reflex pathways, which are common in
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The self re-excitation of hyperactive stretch reflexes theory involves a repetitive contract-relax cycle in the affected muscle, which creates oscillatory movements in the affected limb. In order for self re-excitation to exist, both an increase in
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in neurophysiology and is a recurrent series of patellar reflexes, generated in a feedback circuit. The effect of each contraction is fed back as a modification of tension to the calf muscle. This change of tension triggers the next patellar
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Although the two proposed mechanisms are very different in and are still debated, some studies now propose the potential of both mechanisms co-existing to create clonus. It is thought that the
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Clonus is most commonly found at the ankle, specifically with a dorsiflexion/plantarflexion movement (up and down). Some case studies have also reported clonus in the finger, toe, and
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muscle. Subsequent beating of the foot will result, however only a sustained clonus (5 beats or more) is considered abnormal. Clonus can also be tested in the
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Clonus, with respect to the presence of a central oscillator, functions on the theory that when the central oscillator is turned on by a
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Hilder, Joseph M.; Zev W. Rymer (September 1999). "A Stimulation Study of Reflex
Instability in Spasticity: Origins of Clonus".
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tracts found in distal muscle groups. Clonus is commonly seen in the ankle but may exist in other distal structures as well.
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excitability is likely accomplished by alterations to the net inhibition of neurons occurring as a result of injury to the
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would be more readily conducted, and thus turn on this central oscillator. This theory is still being investigated.
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of clonus beats have been found to be directly proportional to the length of the reflex pathway it is found in.
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Douglas, Wallace M.; Bruce H Ross; Christine K. Thomas (Aug 25, 2005). "Motor unit behaviour during clonus".
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In the text, Bateson goes on to describe induction of clonus as a key element of
Balinese ritual.
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on average, and may last a few seconds to several minutes depending on the patient's condition.
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is tested by rapidly flexing the foot into dorsiflexion (upward), inducing a stretch to the
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pathway may be stimulated first, and through its events, cause a decreased
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involving descending motor pathways, and in many cases is accompanied by
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pathology), clonus causes large motions that are usually initiated by a
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735:(1st ed.). New York: Cornelia & Michael Bessie. p. 85.
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Set of involuntary and rhythmic muscular contractions and relaxations
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drugs, where clonus strongly predicts imminent serotonin toxicity (
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in the ankle (as opposed to the typical up and down motion).
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described the induction of clonus in healthy people:
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A Sacred Unity: Further Steps To An
Ecology of Mind
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682:Anthony, J; Damasceno, A; Ojjii, D (2016-05-18).
504:IEEE Transactions on Rehabilitation Engineering
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290:event, it will continue to rhythmically excite
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92:conditions, particularly associated with
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604:Weisenburg, Theodore H (November 1903).
172:Clonus is typically seen in people with
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410:Gregory Bateson, A Sacred Unity, p. 85
649:Journal of Nervous and Mental Disease
610:Journal of Nervous and Mental Disease
388:Voluntary Induction in Healthy People
242:signal delay are required. Increased
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212:, such as after ingestion of potent
606:"Triceps, Biceps and Finger Clonus"
345:Clonus results due to an increased
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115:. Studies have shown clonus beat
779:Dr. Gilman on Serotonin Toxicity
688:Cardiovascular Journal of Africa
661:10.1097/00005053-190205000-00002
622:10.1097/00005053-190311000-00003
430:Generalized tonic–clonic seizure
198:generalized tonic–clonic seizure
784:Video about Clonus at the ankle
570:10.1152/japplphysiol.00649.2005
643:Mitchell, John K. (May 1902).
384:(knee cap), towards the toes.
325:Clonus tends to co-exist with
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294:, therefore creating clonus.
119:to range from three to eight
274:structures like the ankle.
248:central nervous system (CNS)
229:Hyperactive stretch reflexes
80:is a set of involuntary and
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731:Bateson, Gregory (1991).
32:Parts: The Clonus Horror
380:by rapidly pushing the
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349:excitation (decreased
190:hepatic encephalopathy
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321:Clonus and spasticity
210:adverse drug reaction
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445:Tetanic contractions
208:. It can also be an
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335:spinal cord injury
282:Central oscillator
218:serotonin syndrome
192:. It can occur in
186:spinal cord damage
182:multiple sclerosis
109:lower motor neuron
94:upper motor neuron
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30:For the film, see
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86:contractions
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73:Ankle clonus
340:muscle tone
256:spinal cord
798:Categories
451:References
327:spasticity
288:peripheral
101:spasticity
669:145648718
630:143749312
556:CiteSeerX
425:Myoclonus
364:Diagnosis
354:threshold
307:threshold
276:Frequency
224:Mechanism
206:eclampsia
133:laterally
117:frequency
84:muscular
54:Neurology
49:Specialty
718:27213858
578:16099891
524:10498378
419:See also
408:—
405:reflex.)
305:current
303:synaptic
194:epilepsy
151:knee cap
82:rhythmic
709:4928160
586:8598394
382:patella
268:muscles
147:Patella
97:lesions
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440:Tetany
402:clonus
358:reflex
331:stroke
272:distal
264:joints
261:distal
252:stroke
178:stroke
113:reflex
78:Clonus
43:Clonus
665:S2CID
626:S2CID
582:S2CID
378:knees
370:ankle
240:nerve
168:Cause
127:Signs
737:ISBN
714:PMID
574:PMID
520:PMID
333:and
266:and
204:and
188:and
704:PMC
696:doi
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