Membrane Effects of Neurotoxic Chemicals
The most characteristic feature of the nerve membrane is its electrical excitability. The basis for excitation lies in the ionic concentration gradients across the membrane (low sodium and high potassium at the inside, high sodium and low potassium at the outside), in combination with the selective permeability characteristics of the membrane for these ions. The ion gradients which are maintained by the sodium/potassium pump, result in an electrical polarization of the nerve membrane; the potential at the inside being negative by 60–80 mV with respect to the outside. A nervous impulse is brought about by a rapid, transient increase in the permeability of the membrane for sodium, resulting in an inward sodium current, followed by an increase in the potassium permeability, resulting in an outward potassium current. As a result, the membrane potential temporarily reverses sign and an action potential is conducted along the nerve fibre.
KeywordsSodium Channel Potassium Channel Pyrethroid Insecticide Excitable Membrane Scorpion Toxin
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