Biomaterial Database

Extracellular potentials of myelinated and demyelinated human motor nerve fibres. 2003

D I Stephanova, and M Daskalova

Institute of Biophysics, Bulgarian Academy of Sciences, Acad. G. Bontchev Street, B1, 21, Sofia, 1113, Bulgaria. dsteph@iph.bio.bas.bg

The extracellular potentials of myelinated and demyelinated human motor nerve fibres in an unbounded volume conductor are studied. Using our previous double-cable models of normal and demyelinated human fibres, the spatial and temporal intracellular potentials are calculated in the cases of point polarization and adaptation of the fibres. The intracellular potentials are then used as input to a line source model that allows to calculate the corresponding spatial and temporal extracellular potentials at various radial distances in the surrounding volume conductor. Four fibre demyelinations (termed as internodal focal\systematic and paranodal focal\systematic demyelinations, respectively) are studied. In all investigated cases, the radial decline of the peak-to-peak amplitude of the extracellular potential depends on the radial distance of the field point and increases with the increase of the distance. The results are consistent with the interpretation that the considerably different spatial and temporal distributions of the extracellular potentials depend not only on the cable properties of the fibres, but on the methods of fibre stimulation. In the case of fibre adaptation, the temporal extracellular potentials in the normal and demyelinated cases correspond well with electromyograms (EMGs) from healthy subjects and patients with demyelinated disorders as reported in the literature. Simulation results indicate that the models used are rather promising tools in studying the main properties of compound action potentials in patients with demyelinated disorders which up till now have not been sufficiently well understood.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D008959	Models, Neurological	Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Neurologic Models,Model, Neurological,Neurologic Model,Neurological Model,Neurological Models,Model, Neurologic,Models, Neurologic
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009413	Nerve Fibers, Myelinated	A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.	A Fibers,B Fibers,Fiber, Myelinated Nerve,Fibers, Myelinated Nerve,Myelinated Nerve Fiber,Myelinated Nerve Fibers,Nerve Fiber, Myelinated
D011930	Reaction Time	The time from the onset of a stimulus until a response is observed.	Response Latency,Response Speed,Response Time,Latency, Response,Reaction Times,Response Latencies,Response Times,Speed, Response,Speeds, Response
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D005110	Extracellular Space	Interstitial space between cells, occupied by INTERSTITIAL FLUID as well as amorphous and fibrous substances. For organisms with a CELL WALL, the extracellular space includes everything outside of the CELL MEMBRANE including the PERIPLASM and the cell wall.	Intercellular Space,Extracellular Spaces,Intercellular Spaces,Space, Extracellular,Space, Intercellular,Spaces, Extracellular,Spaces, Intercellular
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D042541	Intracellular Space	The area within CELLS.	Subcellular Space,Intracellular Spaces,Space, Intracellular,Space, Subcellular,Spaces, Intracellular,Spaces, Subcellular,Subcellular Spaces
D036421	Nerve Fibers, Unmyelinated	A class of nerve fibers as defined by their nerve sheath arrangement. The AXONS of the unmyelinated nerve fibers are small in diameter and usually several are surrounded by a single MYELIN SHEATH. They conduct low-velocity impulses, and represent the majority of peripheral sensory and autonomic fibers, but are also found in the BRAIN and SPINAL CORD.	C Fibers,C Fiber,Nerve Fiber, Unmyelinated,Unmyelinated Nerve Fiber,Unmyelinated Nerve Fibers