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Axonal Polyneuropathy changes in EMG

EMG/NCV section Learn about the Brain Learn about nerves Nerve Fibers conduction which carry sensory impulses described in detail Video below.

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Conduction along a NerveFiber

Okay so we just talked about conduction in an unnerve fiber In nerve fibers, the depolarized Node of Ranvier triggers an increase in the permeability of the sodium ion channels (and thus depolarization) in the adjacent Node of Ranvier.

Above we see a the cells are wrapped around central nerves, they are oligodendrocytes. If they;re wrapped around the peripharal Nerves they're called Schwaan cells.In either case there are these gaps called Nodes of Ranvier The only place these potassium or sodium ions can enter or leave are from these spaces that are unmyelinated Sodiums come in and potassiums going out just like a an unmymelinated nerve fiber, except this signal seems to jump from one node to the next. This is called saltatory conduction. has nothing to do with salt but it comes from the latin word saltaire which means to jump orleap.

Due to this skipping, saltaory conduction is up to 50 times faster than conduction through the fastest unaxons because they don't have to travel throughout every single space before moving to thenext.

So in essence, the action potential is generated only at the nodes The cell membrane below the myelin sheaths hardly have any sodium channels and are therefore not excitable anyway Since the ionic currents are restricted to the nodes of Ranvier in the axons, this minimizes disturbances in the Na concentration gradients which reduces the energy costs of the Na+/K+-ATP pump that have to restore ionic balance.

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Key words : action, potential, nerve, membrane, depolarizes, negative, electron;