Effects of changes in intracellular action potential on potentials recorded by single-fiber, macro, and belly-tendon electrodes.
Some myopathies are accompanied by abnormal calcium homeostasis. Electromyography (EMG) in such patients shows signs of normal or myopathic EMG when detected by a single-fiber electrode and abnormally increased values in macro EMG. As calcium accumulation might be accompanied by changes in intracellular action potential (IAP) and muscle-fiber propagation velocity, we simulated the effects of such changes on motor unit potentials (MUPs) recorded by different kinds of electrodes. We found that: (1) the requirements for what potential can be accepted as a single-fiber action potential (SFAP) are too rigorous; (2) macro MUP amplitude can increase while SFAP amplitude can decrease when there is an increase in the spatial length of IAP spike; and (3) changes in the second phase of a belly-tendon-detected MUP or M wave could be used for noninvasive detection of increased IAP depolarizing (negative) after-potential.
Centre of Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 105, Sofia 1113, Bulgaria. tosho@clbme.bas.bg
Todor I
TI
Arabadzhiev
George V
GV
Dimitrov
Vichren E
VE
Chakarov
Alexander G
AG
Dimitrov
Nonna A
NA
Dimitrova
D000200:Action Potentials / Q000502:physiology*; D000465:Algorithms; D002118:Calcium / Q000378:metabolism; D004566:Electrodes; D004576:Electromyography; D004594:Electrophysiology; D005110:Extracellular Space / Q000502:physiology; D006801:Humans; D009045:Motor Endplate / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000502:physiology*; D013132:Spinocerebellar Degenerations / Q000503:physiopathology; D013710:Tendons / Q000502:physiology*
D002118:Calcium