jitter (redirected from jittery)

jitter

Imaging Low amplitude irregularities in echo location on an ultrasound display, attributed to electronic noise, mechanical disturbances, and other variables Neurophysiology Muscle jitter The normal electric variability–'chaos'–measured by single-fiber EMG–in the interval between 2 action potentials of successive discharges of the same single muscle fiber in the same motor unit; jitter is characterized as instability in subcomponents of motor unit action potentials, and is due to the variation in the synaptic delay at the branch points in the distal axon and at the neuromuscular junction; like fiber density, jitter is ↑ in neuropathic conditions–motor neuron diseases–eg, myasthenia gravis, is accompanied by denervation and reinnervation, and attributed to inefficient transmission of impulses in recent neural collaterals, or due to blocking–abnormal neuromuscular transmission; it is normal or near-normal in myopathic disease See Fiber density, Single-fiber electromyography PsychologyJitters, see there.