Relative conduction velocity

Fig 3 - Effects of cf-limonene concentration and exposure duration on relative conduction velocity in MGF (reproduced from 11 by permission, copyright Academic Press, 1990) ... 

Action potentials, self-propagating. Action potentials of smooth muscle differ from the typical nerve action potential in at least three ways. First, the depolarization phases of nearly all smooth muscle action potentials are due to an increase in calcium rather than sodium conductance. Consequently, the rates of rise of smooth action potentials are slow, and the durations are long relative to most neural action potentials. Second, smooth muscle action potentials arise from membrane that is autonomously active and tonically modulated by autonomic neurotransmitters. Therefore, conduction velocities and action potential shapes are labile. Finally, smooth muscle action potentials spread along bundles of myocytes which are interconnected in three dimensions. Therefore the actual spatial patterns of spreading of the action potential vary. 

Type Ic drugs profoundly slow conduction velocity while leaving refractoriness relatively unaltered. Although effective for both ventricular and supraventricular arrhythmias, their use for ventricular arrhythmias has been limited by the risk of proarrhythmia. 

In contractile experiments the time from the stimulation of the nerve to the CMAP recorded in muscle provides an estimate of NCV. The length of the nerve from the stimulating electrode to the muscle can simply be measured and divided by the time. However, the time recorded in this way includes the delay for synaptic transmission, which may be increased in models with synaptic defects. If this is a concern or if the only parameter desired is NCV, then the measurement can be obtained non-invasively with a relatively simple setup (e.g., (3)). Using the sciatic nerve, NCV can be calculated by measuring the latency of compound motor action potentials recorded in the muscle of a rear paw. Action potentials are produced by subcutaneous stimulation at two separate sites proximal stimulation at the sciatic notch and distally at the ankle. NCV is then calculated by using the two latencies and conduction distance. Decreases in nerve conduction velocity most often reflect defects in myelination, but may also be the result of changes in internodal distance, decreased axon diameters, or altered excitability. 

Mouritzen C. V. and Andersen M. N. (1966) Mechanisms of ventricular fibrillation during hypothermia relative changes in myocardial refractory period and conduction velocity. J. Thorac. Cardiovasc. Surg. 51, 585-589. 

People with untreated diabetes have high plasma concentrations of free inositol, and high urinary excretion of inositol, associated with relatively low intracellular concentrations of inositol, suggesting that elevated plasma glucose may inhihit the uptake of inositol. There is some evidence that impaired nerve conduction velocity in diahetic neuropathy is associated with low intracellular concentrations of inositol and that inositol supplements improve nerve conduction velocity. However, high intracellular concentrations of inositol also impair nerve conduction velocity, and supplements may have a deleterious effect. 

In nonmyelinated neurons, the conduction velocity of an action potential Is roughly proportional to the diameter of the axon, because a thicker axon will have a greater number of ions that can diffuse. The human brain Is packed with relatively small, myelinated neurons. If the neurons In the... 

The described method of calculation is suitable for flows with relatively low velocities, where there is heat transfer due to conduction. At high gas velocities, the flow in the cooling tubes is turbulent, and so heat transfer occurs basically as a result of extensive cross-mixing of the flow, which averages out the temperature across the cross-section of the tube. 

Environment Chemical definition Circumstance Type, chemistry, concentration, phase, conductivity Velocity, thin layer in equilibrium with relative humidity, wetting and drying, heat transfer boiling, wear and fretting, deposits... 

We propose that in nerve conduction velocity studies, a ratio between relative slowness of conduction velocity and relatively good or excellent amplitude (our "V/A ratio") could potentially be useful for determining early slo-wing of conduction. However, we have not yet formalized this proposed ratio and the relevant normal values thereof. 

Virtually no part of the body is immune from the effects of lead. Lead in the body dismpts energy metabolism at the cellular level, interferes with neural cell function in the brain, disrupts the formation of heme and in the nervous system, inhibits communication and decreases nerve conduction velocity. Even at relatively low exposures, lead s neurotoxic effects can cause decreased intelligence, short-term memory loss, reading under-achievement, impairment of visual-motor function, loss of auditory memory, poor percepmal integration, poor classroom behavior, and impaired reaction time. 

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