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Clonus is a set of involuntary and rhythmic muscular contractions and relaxations. Clonus is a sign of certain neurological conditions, particularly associated with upper motor neuron lesions involving descending motor pathways, and in many cases is accompanied by spasticity (another form of hyperexcitability). [ 1 ]
clonus: always abnormal The clasp-knife response is a stretch reflex with a rapid decrease in resistance when attempting to flex a joint. It is one of the ...
Clonus results due to an increased motor neuron excitation (decreased action potential threshold) and is common in muscles with long conduction delays, such as the long reflex tracts found in distal muscle groups. [7] Clonus is commonly seen in the ankle but may exist in other distal structures as well, such as the knee or spine. [8]
exaggerated deep tendon reflexes including spasticity, and clonus (a series of involuntary rapid muscle contractions) Such signs are collectively termed the "upper motor neuron syndrome". Affected muscles typically show multiple signs, with severity depending on the degree of damage and other factors that influence motor control. In ...
Myoclonus is a brief, involuntary, irregular (lacking rhythm) twitching of a muscle, a joint, or a group of muscles, different from clonus, which is rhythmic or regular. Myoclonus (myo-"muscle", clonus "spasm") describes a medical sign and, generally, is not a diagnosis of a disease.
[15] [41] During pregnancy brisk or hyperactive reflexes are common, however, ankle clonus is a sign of neuromuscular irritability that usually reflects severe pre-eclampsia and also can precede eclampsia. [93] Magnesium sulfate is used to prevent convulsions in cases of severe pre-eclampsia.
Asterixis (more colloquially referred to as flapping tremor) is not actually a tremor, but rather a negative myoclonus.This movement disorder is characterized by an inability to maintain a position, which is demonstrated by jerking movements of the outstretched hands when bent upward at the wrist (which can be similar to a bird flapping its wings, hence the name "flapping tremor").
Many organisms, including aspen trees, reproduce by cloning, often creating large groups of organisms with the same DNA.One example depicted here is quaking aspen.. Cloning is the process of producing individual organisms with identical genomes, either by natural or artificial means.